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Sample records for schottky effect

  1. Hybrid graphene/silicon Schottky photodiode with intrinsic gating effect

    Science.gov (United States)

    Di Bartolomeo, Antonio; Luongo, Giuseppe; Giubileo, Filippo; Funicello, Nicola; Niu, Gang; Schroeder, Thomas; Lisker, Marco; Lupina, Grzegorz

    2017-06-01

    We propose a hybrid device consisting of a graphene/silicon (Gr/Si) Schottky diode in parallel with a Gr/SiO2/Si capacitor for high-performance photodetection. The device, fabricated by transfer of commercial graphene on low-doped n-type Si substrate, achieves a photoresponse as high as 3 \\text{A} {{\\text{W}}-1} and a normalized detectivity higher than 3.5× {{10}12} \\text{cm} \\text{H}{{\\text{z}}1/2} {{\\text{W}}-1} in the visible range. It exhibits a photocurrent exceeding the forward current because photo-generated minority carriers, accumulated at Si/SiO2 interface of the Gr/SiO2/Si capacitor, diffuse to the Gr/Si junction. We show that the same mechanism, when due to thermally generated carriers, although usually neglected or disregarded, causes the increased leakage often measured in Gr/Si heterojunctions. We perform extensive I-V and C-V characterization at different temperatures and we measure a zero-bias Schottky barrier height of 0.52 eV at room temperature, as well as an effective Richardson constant A **  =  4× {{10}-5} \\text{A} \\text{c}{{\\text{m}}-2} {{\\text{K}}-2} and an ideality factor n≈ 3.6 , explained by a thin (<1 nm) oxide layer at the Gr/Si interface.

  2. Interlayer coupling effects on Schottky barrier in the arsenene-graphene van der Waals heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Congxin, E-mail: xiacongxin@htu.edu.cn; Xue, Bin; Wang, Tianxing; Peng, Yuting [Department of Physic, Henan Normal University, Xinxiang 453007 (China); Jia, Yu [School of Physics and Engineering, Zhengzhou University, Zhengzhou 450052 (China)

    2015-11-09

    The electronic characteristics of arsenene-graphene van der Waals (vdW) heterostructures are studied by using first-principles methods. The results show that a linear Dirac-like dispersion relation around the Fermi level can be quite well preserved in the vdW heterostructures. Moreover, the p-type Schottky barrier (0.18 eV) to n-type Schottky barrier (0.31 eV) transition occurs when the interlayer distance increases from 2.8 to 4.5 Å, which indicates that the Schottky barrier can be tuned effectively by the interlayer distance in the vdW heterostructures.

  3. Effects of sputtering power Schottky metal layers on rectifying performance of Mo-SiC Schottky contacts

    Science.gov (United States)

    Lee, Seula; Lee, Jinseon; You, Sslimsearom; Kyoung, Sinsu; Kim, Kyung Hwan

    2016-01-01

    In this study, Schottky barrier diodes based on silicon carbide with various levels of Schottky metal layer input power were prepared and characterized. In this structure, molybdenum and aluminum were employed as the Schottky metal and top electrode, respectively. Schottky metal layers were deposited with input power ranging from 30 to 210 W. Schottky metal layers and top electrodes were deposited with a thickness of 3000 Å. The Schottky barrier heights, series resistances, and ideality factor were calculated from current-voltage (I-V) curves obtained using the Cheung-Cheung and Norde methods. All deposition processes were conducted using a facing targets sputtering system. Turn on voltage was minimized when the input power was 90 W, at which point electrical characteristics were observed to have properties superior to those at other levels of input power.

  4. Effect of temperature and post-deposition annealing on Schottky barrier characterization of Bromoindium phthalocyanine/aluminum interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Azim-Araghi, M.E.; Sahebi, R., E-mail: ramezan.sahebi@yahoo.com

    2014-01-15

    To investigate DC electrical properties and Schottky barrier characterization between BrInPc/Al interfaces, some thin films of BrInPc in sandwich form were prepared with Al electrodes. J–V characterization showed ohmic behavior at lower voltages upto 0.3 V followed by Schottky emission conduction mechanism at higher voltages. In the Schottky region two different slopes in the plot of ln (J) against V{sup 1/2} were observed and two different values of Schottky barrier height was determined for these regions. To investigate the effect of temperature on Schottky barrier behavior between BrInPc and aluminum interface, we studied the J–V characteristics of devices at the temperature range of 298–373 K. By increasing the temperature, the width of Schottky depletion region decreased and the Schottky barrier height increased, and at temperatures higher than 333 K the dominant conduction mechanism changed to Poole–Frenkel type. For annealed samples at 373 K and 423 K, the Schottky barrier height increased as the result of thermal annealing and increasing annealing temperature. The width of the Schottky depletion region decreased by annealing and increasing the annealing temperature.

  5. Effect of mechanical stress on current-voltage characteristics of thin film polycrystalline diamond Schottky diodes

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, G.; Charlson, E.M.; Charlson, E.J.; Stacy, T.; Meese, J.M. (Department of Electrical and Computer Engineering, University of Missouri, Columbia, Missouri 65211 (United States)); Popovici, G.; Prelas, M. (Department of Nuclear Engineering, University of Missouri, Columbia, Missouri 65211 (United States))

    1993-02-15

    Schottky diodes utilized for mechanical stress effect studies were fabricated using aluminum contacts to polycrystalline diamond thin films grown by a hot-filament-assisted chemical vapor deposition process. Compressive stress was found to have a large effect on the forward biased current-voltage characteristics of the diode, whereas the effect on the reverse biased characteristics was relatively small. This stress effect on the forward biased diamond Schottky diode was attributed to piezojunction and piezoresistance effects that dominated the diode current-voltage characteristics in the small and large bias regions, respectively. At a large constant forward bias current, a good linear relationship between output voltage and applied force was observed for force of less than 10 N, as predicted by the piezoresistance effect. The measured force sensitivity of the diode was as high as 0.75 V/N at 1 mA forward bias. Compared to either silicon or germanium junction diodes and tunnel diodes, polycrystalline diamond Schottky diodes not only are very stress sensitive but also have good linearity. This study shows polycrystalline diamond Schottky diodes have potential as mechanical sensors.

  6. Utilizing Schottky barriers to suppress short-channel effects in organic transistors

    Science.gov (United States)

    Fernández, Anton F.; Zojer, Karin

    2017-10-01

    Transistors with short channel lengths exhibit profound deviations from the ideally expected behavior. One of the undesired short-channel effects is an enlarged OFF current that is associated with a premature turn on of the transistor. We present an efficient approach to suppress the OFF current, defined as the current at zero gate source bias, in short-channel organic transistors. We employ two-dimensional device simulations based on the drift-diffusion model to demonstrate that intentionally incorporating a Schottky barrier for injection enhances the ON-OFF ratio in both staggered and coplanar transistor architectures. The Schottky barrier is identified to directly counteract the origin of enlarged OFF currents: Short channels promote a drain-induced barrier lowering. The latter permits unhindered injection of charges even at reverse gate-source bias. An additional Schottky barrier hampers injection for such points of operations. We explain how it is possible to find the Schottky barrier of the smallest height necessary to exactly compensate for the premature turn on. This approach offers a substantial enhancement of the ON-OFF ratio. We show that this roots in the fact that such optimal barrier heights offer an excellent compromise between an OFF current diminished by orders of magnitude and an only slightly reduced ON current.

  7. Multiple Schottky Barrier-Limited Field-Effect Transistors on a Single Silicon Nanowire with an Intrinsic Doping Gradient.

    Science.gov (United States)

    Barreda, Jorge L; Keiper, Timothy D; Zhang, Mei; Xiong, Peng

    2017-04-05

    In comparison to conventional (channel-limited) field-effect transistors (FETs), Schottky barrier-limited FETs possess some unique characteristics which make them attractive candidates for some electronic and sensing applications. Consequently, modulation of the nano Schottky barrier at a metal-semiconductor interface promises higher performance for chemical and biomolecular sensor applications when compared to conventional FETs with ohmic contacts. However, the fabrication and optimization of devices with a combination of ideal ohmic and Schottky contacts as the source and drain, respectively, present many challenges. We address this issue by utilizing Si nanowires (NWs) synthesized by a chemical vapor deposition process which yields a pronounced doping gradient along the length of the NWs. Devices with a series of metal contacts on a single Si NW are fabricated in a single lithography and metallization process. The graded doping profile of the NW is manifested in monotonic increases in the channel and junction resistances and variation of the nature of the contacts from ohmic to Schottky of increasing effective barrier height along the NW. Hence multiple single Schottky junction-limited FETs with extreme asymmetry and high reproducibility are obtained on an individual NW. A definitive correlation between increasing Schottky barrier height and enhanced gate modulation is revealed. Having access to systematically varying Schottky barrier contacts on the same NW device provides an ideal platform for identifying optimal device characteristics for sensing and electronic applications.

  8. Novel field-effect schottky barrier transistors based on graphene-MoS 2 heterojunctions

    KAUST Repository

    Tian, He

    2014-08-11

    Recently, two-dimensional materials such as molybdenum disulphide (MoS 2) have been demonstrated to realize field effect transistors (FET) with a large current on-off ratio. However, the carrier mobility in backgate MoS2 FET is rather low (typically 0.5-20 cm2/V.s). Here, we report a novel field-effect Schottky barrier transistors (FESBT) based on graphene-MoS2 heterojunction (GMH), where the characteristics of high mobility from graphene and high on-off ratio from MoS2 are properly balanced in the novel transistors. Large modulation on the device current (on/off ratio of 105) is achieved by adjusting the backgate (through 300 nm SiO2) voltage to modulate the graphene-MoS2 Schottky barrier. Moreover, the field effective mobility of the FESBT is up to 58.7 cm2/V.s. Our theoretical analysis shows that if the thickness of oxide is further reduced, a subthreshold swing (SS) of 40 mV/decade can be maintained within three orders of drain current at room temperature. This provides an opportunity to overcome the limitation of 60 mV/decade for conventional CMOS devices. The FESBT implemented with a high on-off ratio, a relatively high mobility and a low subthreshold promises low-voltage and low-power applications for future electronics.

  9. Evaluation of Polarization Effects of e(-) Collection Schottky CdTe Medipix3RX Hybrid Pixel Detector

    OpenAIRE

    Astromskas, V; Gimenez, EN; Lohstroh, A; Tartoni, N

    2016-01-01

    This paper focuses on the evaluation of operational conditions such as temperature, exposure time and flux on the polarization of a Schottky electron collection CdTe detector. A Schottky e- collection CdTe Medipix3RX hybrid pixel detector was developed as a part of the CALIPSO-HIZPAD2 EU project. The 128 ×128 pixel matrix and 0.75 mm thick CdTe sensor bump-bonded to Medipix3RX readout chips enabled the study of the polarization effects. Single and quad module Medipix3RX chips were used which ...

  10. A study of lateral Schottky contacts in WSe2 and MoS2 field effect transistors using scanning photocurrent microscopy

    Science.gov (United States)

    Yi, Ya; Wu, Changming; Liu, Hongchao; Zeng, Jiali; He, Hongtao; Wang, Jiannong

    2015-09-01

    Schottky contacts, formed at metal/semiconductor interfaces, always have a large impact on the performance of field-effect transistors (FETs). Here, we report the experimental studies of Schottky contacts in two-dimensional (2D) transition metal dichalcogenide (TMDC) FET devices. We use scanning photocurrent microscopy (SPCM) to directly probe the spatial distribution of the in-plane lateral Schottky depletion regions at the metal/2D-TMDC interfaces. The laser incident position dependent and the gate voltage tunable polarity and magnitude of the short-circuit photocurrent reveal the existence of the in-plane Schottky depletion region laterally extending away from the metal contact edges along the channel. This lateral depletion region length is estimated to be around several microns and can be effectively tuned by the gate and drain-source biases. Our results solidify the importance of lateral Schottky depletion regions in the photoresponse of 2D TMDC optoelectronic devices.Schottky contacts, formed at metal/semiconductor interfaces, always have a large impact on the performance of field-effect transistors (FETs). Here, we report the experimental studies of Schottky contacts in two-dimensional (2D) transition metal dichalcogenide (TMDC) FET devices. We use scanning photocurrent microscopy (SPCM) to directly probe the spatial distribution of the in-plane lateral Schottky depletion regions at the metal/2D-TMDC interfaces. The laser incident position dependent and the gate voltage tunable polarity and magnitude of the short-circuit photocurrent reveal the existence of the in-plane Schottky depletion region laterally extending away from the metal contact edges along the channel. This lateral depletion region length is estimated to be around several microns and can be effectively tuned by the gate and drain-source biases. Our results solidify the importance of lateral Schottky depletion regions in the photoresponse of 2D TMDC optoelectronic devices. Electronic

  11. Monolayer borophene electrode for effective elimination of both the Schottky barrier and strong electric field effect

    Science.gov (United States)

    Liu, L. Z.; Xiong, S. J.; Wu, X. L.

    2016-08-01

    The formation of Schottky barriers between 2D semiconductors and traditional metallic electrodes has greatly limited the application of 2D semiconductors in nanoelectronic and optoelectronic devices. In this study, metallic borophene was used as a substitute for the traditional noble metal electrode to contact with the 2D semiconductor. Theoretical calculations demonstrated that no Schottky barrier exists in the borophene/2D semiconductor heterostructure. The contact remains ohmic even with a strong electric field applied. This finding provides a way to construct 2D electronic devices and sensors with greatly enhanced performance.

  12. Monolayer borophene electrode for effective elimination of both the Schottky barrier and strong electric field effect

    Energy Technology Data Exchange (ETDEWEB)

    Liu, L. Z., E-mail: lzliu@nju.edu.cn, E-mail: hkxlwu@nju.edu.cn; Xiong, S. J.; Wu, X. L., E-mail: lzliu@nju.edu.cn, E-mail: hkxlwu@nju.edu.cn [Key Laboratory of Modern Acoustics, MOE, Institute of Acoustics and Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China)

    2016-08-08

    The formation of Schottky barriers between 2D semiconductors and traditional metallic electrodes has greatly limited the application of 2D semiconductors in nanoelectronic and optoelectronic devices. In this study, metallic borophene was used as a substitute for the traditional noble metal electrode to contact with the 2D semiconductor. Theoretical calculations demonstrated that no Schottky barrier exists in the borophene/2D semiconductor heterostructure. The contact remains ohmic even with a strong electric field applied. This finding provides a way to construct 2D electronic devices and sensors with greatly enhanced performance.

  13. Local irradiation effects of one-dimensional ZnO based self-powered asymmetric Schottky barrier UV photodetector

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yaxue [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Qi, Junjie, E-mail: junjieqi@ustb.edu.cn [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Biswas, Chandan [Department of Electrical Engineering, University of California Los Angeles, California 90095 (United States); Li, Feng; Zhang, Kui; Li, Xin [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Zhang, Yue, E-mail: yuezhang@ustb.edu.cn [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Key Laboratory of New Energy Materials and Technologies, University of Science and Technology Beijing, Beijing 100083 (China)

    2015-09-15

    A self-powered metal-semiconductor-metal (MSM) UV photodetector was successfully fabricated based on Ag/ZnO/Au structure with asymmetric Schottky barriers. This exhibits excellent performance compared to many previous studies. Very high photo-to-dark current ratio (approximately 10{sup 5}–10{sup 6}) was demonstrated without applying any external bias, and very fast switching time of less than 30 ms was observed during the investigation. Opposite photocurrent direction was generated by irradiating different Schottky diodes in the fabricated photodetector. Furthermore, the device performance was optimized by largely irradiating both the ZnO microwire (MW) junctions. Schottky barrier effect theory and O{sub 2} adsorption–desorption theories were used to investigate the phenomenon. The device has potential applications in self-powered UV detection field and can be used as electrical power source for electronic, optoelectronic and mechanical devices. - Highlights: • A self-powered Schottky barrier UV photodetector based on 1-D ZnO is fabricated. • For the first time we investigate the local irradiation effects of UV detector. • Irradiating both the junctions and ZnO can optimize the performance of the device.

  14. Effect of cooling on the efficiency of Schottky varactor frequency multipliers at millimeter waves

    Science.gov (United States)

    Louhi, Jyrki; Raiesanen, Antti; Erickson, Neal

    1992-01-01

    The efficiency of the Schottky diode multiplier can be increased by cooling the diode to 77 K. The main reason for better efficiency is the increased mobility of the free carriers. Because of that the series resistance decreases and a few dB higher efficiency can be expected at low input power levels. At high output frequencies and at high power levels, the current saturation decreases the efficiency of the multiplication. When the diode is cooled the maximum current of the diode increases and much more output power can be expected. There are also slight changes in the I-V characteristic and in the diode junction capacitance, but they have a negligible effect on the efficiency of the multiplier.

  15. Inhomogeneous barrier height effect on the current-voltage characteristics of an Au/n-InP Schottky diode

    Science.gov (United States)

    Zeghdar, Kamal; Dehimi, Lakhdar; Saadoune, Achour; Sengouga, Nouredine

    2015-12-01

    We report the current-voltage (I-V) characteristics of the Schottky diode (Au/n-InP) as a function of temperature. The SILVACO-TCAD numerical simulator is used to calculate the I-V characteristic in the temperature range of 280-400 K. This is to study the effect of temperature on the I-V curves and assess the main parameters that characterize the Schottky diode such as the ideality factor, the height of the barrier and the series resistance. The I-V characteristics are analyzed on the basis of standard thermionic emission (TE) theory and the inhomogeneous barrier heights (BHs) assuming a Gaussian distribution. It is shown that the ideality factor decreases while the barrier height increases with increasing temperature, on the basis of TE theory. Furthermore, the homogeneous BH value of approximately 0.524 eV for the device has been obtained from the linear relationship between the temperature-dependent experimentally effective BHs and ideality factors. The modified Richardson plot, according to the inhomogeneity of the BHs, has a good linearity over the temperature range. The evaluated Richardson constant A* was 10.32 A·cm-2·K-2, which is close to the theoretical value of 9.4 A·cm-2·K-2 for n-InP. The temperature dependence of the I-V characteristics of the Au/n-InP Schottky diode have been successfully explained on the basis of the thermionic emission (TE) mechanism with a Gaussian distribution of the Schottky barrier heights (SBHs). Simulated I-V characteristics are in good agreement with the measurements [Korucu D, Mammadov T S. J Optoelectronics Advanced Materials, 2012, 14: 41]. The barrier height obtained using Gaussian Schottky barrier distribution is 0.52 eV, which is about half the band gap of InP.

  16. Annealing effects on electrical, structural, and surface morphological properties of Ir/n-InGaN Schottky structures

    Energy Technology Data Exchange (ETDEWEB)

    Reddy, V. Rajagopal; Padma, R.; Reddy, M.S.P. [Department of Physics, Sri Venkateswara University, Tirupati (India); Choi, C.J. [School of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center (SPRC), Chonbuk National University, Jeonju (Korea, Republic of)

    2012-10-15

    The effects of thermal annealing on electrical and structural characteristics of iridium (Ir) Schottky contacts to n-type InGaN have been studied using current-voltage (I-V), capacitance-voltage (C-V), secondary ion mass spectrometer (SIMS), and X-ray diffraction (XRD) measurements. Measurements showed that the Schottky barrier height (SBH) of as-deposited sample is 0.79 eV (I-V) and 1.07 eV (C-V). It is observed that the barrier height increases to 0.85 eV (I-V) and 1.21 eV (C-V) after annealing at 300 C for 1 min in N{sub 2} ambient. However, it is found that the SBH slightly decreases when the contacts are annealed at 400 and 500 C and the corresponding values are 0.84 eV (I-V), 1.17 eV (C-V) for 400 C and 0.80 eV (I-V), 1.11 eV (C-V) for 500 C, respectively. Using Cheung's functions, the barrier height ({Phi}{sub b}), ideality factor (n), and series resistance (R{sub s}) are also calculated. From the above results, it is clear that the optimum annealing temperature for Ir Schottky contact is 300 C. SIMS and XRD results shows that the formation of gallide phases at Ir/n-InGaN interfaces could be the reason for variation in the SBHs upon annealing at elevated temperatures. Atomic force microscopy (AFM) results show that the overall surface morphology of Ir Schottky contacts on n-InGaN stays reasonably smooth. These results make Ir Schottky contacts attractive for high-temperature device applications. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. Single-Event Effect Testing of the Cree C4D40120D Commercial 1200V Silicon Carbide Schottky Diode

    Science.gov (United States)

    Lauenstein, J.-M.; Casey, M. C.; Wilcox, E. P.; Kim, Hak; Topper, A. D.

    2014-01-01

    This study was undertaken to determine the single event effect (SEE) susceptibility of the commercial silicon carbide 1200V Schottky diode manufactured by Cree, Inc. Heavy-ion testing was conducted at the Texas A&M University Cyclotron Single Event Effects Test Facility (TAMU). Its purpose was to evaluate this device as a candidate for use in the Solar-Electric Propulsion flight project.

  18. Exploring New Mechanisms for Effective Antimicrobial Materials: Electric Contact-Killing Based on Multiple Schottky Barriers.

    Science.gov (United States)

    de Lucas-Gil, Eva; Reinosa, Julián J; Neuhaus, Kerstin; Vera-Londono, Liliana; Martín-González, Marisol; Fernández, José F; Rubio-Marcos, Fernando

    2017-08-09

    The increasing threat of multidrug-resistance organisms is a cause for worldwide concern. Progressively microorganisms become resistant to commonly used antibiotics, which are a healthcare challenge. Thus, the discovery of new antimicrobial agents or new mechanisms different from those used is necessary. Here, we report an effective and selective antimicrobial activity of microstructured ZnO (Ms-ZnO) agent through the design of a novel star-shaped morphology, resulting in modulation of surface charge orientation. Specifically, we find that Ms-ZnO particles are composed of platelet stacked structure, which generates multiple Schottky barriers due to the misalignment of crystallographic orientations. We also demonstrated that this effect allows negative charge accumulation in localized regions of the structure to act as "charged domain walls", thereby improving the antimicrobial effectiveness by electric discharging effect. We use a combination of field emission scanning electron microscopy (FE-SEM), SEM-cathodoluminescence imaging, and Kelvin probe force microscopy (KPFM) to determine that the antimicrobial activity is a result of microbial membrane physical damage caused by direct contact with the Ms-ZnO agent. It is important to point out that Ms-ZnO does not use the photocatalysis or the Zn 2+ released as the main antimicrobial mechanism, so consequently this material would show low toxicity and robust stability. This approach opens new possibilities to understand both the physical interactions role as main antimicrobial mechanisms and insight into the coupled role of hierarchical morphologies and surface functionality on the antimicrobial activity.

  19. CdSe Nanowire-Based Flexible Devices: Schottky Diodes, Metal-Semiconductor Field-Effect Transistors, and Inverters.

    Science.gov (United States)

    Jin, Weifeng; Zhang, Kun; Gao, Zhiwei; Li, Yanping; Yao, Li; Wang, Yilun; Dai, Lun

    2015-06-24

    Novel CdSe nanowire (NW)-based flexible devices, including Schottky diodes, metal-semiconductor field-effect transistors (MESFETs), and inverters, have been fabricated and investigated. The turn-on voltage of a typical Schottky diode is about 0.7 V, and the rectification ratio is larger than 1 × 10(7). The threshold voltage, on/off current ratio, subthreshold swing, and peak transconductance of a typical MESFET are about -0.3 V, 4 × 10(5), 78 mV/dec, and 2.7 μS, respectively. The inverter, constructed with two MESFETs, exhibits clear inverting behavior with the gain to be about 28, 34, and 38, at the supply voltages (V(DD)) of 3, 5, and 7 V, respectively. The inverter also shows good dynamic behavior. The rising and falling times of the output signals are about 0.18 and 0.09 ms, respectively, under 1000 Hz square wave signals input. The performances of the flexible devices are stable and reliable under different bending conditions. Our work demonstrates these flexible NW-based Schottky diodes, MESFETs, and inverters are promising candidate components for future portable transparent nanoelectronic devices.

  20. The Effect of Bilayer Graphene Nanoribbon Geometry on Schottky-Barrier Diode Performance

    Directory of Open Access Journals (Sweden)

    Meisam Rahmani

    2013-01-01

    Full Text Available Bilayer graphene nanoribbon is a promising material with outstanding physical and electrical properties that offers a wide range of opportunities for advanced applications in future nanoelectronics. In this study, the application of bilayer graphene nanoribbon in schottky-barrier diode is explored due to its different stacking arrangements. In other words, bilayer graphene nanoribbon schottky-barrier diode is proposed as a result of contact between a semiconductor (AB stacking and metal (AA stacking layers. To this end, an analytical model joint with numerical solution of carrier concentration for bilayer graphene nanoribbon in the degenerate and nondegenerate regimes is presented. Moreover, to determine the proposed diode performance, the carrier concentration model is adopted to derive the current-voltage characteristic of the device. The simulated results indicate a strong bilayer graphene nanoribbon geometry and temperature dependence of current-voltage characteristic showing that the forward current of the diode rises by increasing of width. In addition, the lower value of turn-on voltage appears as the more temperature increases. Finally, comparative study indicates that the proposed diode has a better performance compared to the silicon schottky diode, graphene nanoribbon homo-junction contact, and graphene-silicon schottky diode in terms of electrical parameters such as turn-on voltage and forward current.

  1. Non-invasively improving the Schottky barriers of metal-MoS2 interfaces: effects of atomic vacancies in a BN buffer layer.

    Science.gov (United States)

    Su, Jie; Feng, Liping; Liu, Siyang; Liu, Zhengtang

    2017-08-09

    Using first-principles calculations within density functional theory, vacancies in the BN buffer layer have been predicted to improve the Schottky barrier of the metal-MoS2 interface without deteriorating the intrinsic properties of the MoS2 layer. Here, the effects of concentrations, sizes and types of vacancies on the contact properties of metal/BN-MoS2 sandwich interfaces are comparatively studied. The results show that vacancies in the BN buffer layer not only don't deteriorate the charge scatterings and electronic properties of the MoS2 layer at the metal/BN-MoS2 interface, but also improve the charge density and contact resistance between the metal surface and the BN layer. Although these vacancies have a negligible influence on the Fermi level pinning effect of the metal/BN-MoS2 interface, both N-vacancies and B-vacancies significantly change the position of the Fermi level of the metal/BN-MoS2 interface and then tune the Schottky barriers. Moreover, the Schottky barriers of metal/BN-MoS2 interfaces can decrease at first with the increasing concentrations and sizes of vacancies. When the concentration of vacancies increases to 4%, the Schottky barriers of metal/BN-MoS2 interfaces can reduce to the minimum value. The lowest n-type and p-type Schottky barriers of Au/BN-MoS2 and Pt/BN-MoS2 interfaces can reduce to -0.16 and 0.28 eV, respectively. However, the Schottky barriers are deteriorated when the sizes and concentrations of vacancies continue to increase because vacancies with large sizes and concentrations obviously change the interfacial structures of metal/BN-MoS2 interfaces and disarrange the directions of interface dipoles. The predictions in this work provide a non-invasive method to achieve high performance metal-MoS2 interfaces with low Schottky barriers.

  2. Effect of gating and pressure on the electronic transport properties of crossed nanotube junctions: formation of a Schottky barrier

    Energy Technology Data Exchange (ETDEWEB)

    Havu, P; Hashemi, M J; Kaukonen, M; Nieminen, R M [Department of Applied Physics, Aalto University, PO Box 11100, FI-00076 Aalto (Finland); Seppaelae, E T [Nokia Research Center, Itaemerenkatu 11-13, FI-00180 Helsinki (Finland)

    2011-03-23

    The electronic transport properties of crossed carbon nanotube junctions are investigated using ab initio methods. The optimal atomic structures and the intertube distances of the junctions are obtained using van der Waals corrected density functional theory. The effect of gating on the intertube conductance of the junctions is explored, showing the charge accumulation to the nanotube contact and the charge depletion region at the metal-semiconductor Schottky contact. Finally, it is shown how the conductance of the junctions under the gate voltage is affected by pressure applied to the nanotube film. (fast track communication)

  3. Sputtered Gold as an Effective Schottky Gate for Strained Si/SiGe Nanostructures

    Science.gov (United States)

    Scott, Gavin; Xiao, Ming; Croke, Ed; Yablonovitch, Eli; Jiang, Hongwen

    2007-03-01

    Metallization of Schottky surface gates by sputtering Au on strained Si/SiGe heterojunctions enables the depletion of the two dimensional electron gas (2DEG) at a relatively small voltage while maintaining an extremely low level of leakage current. A fabrication process has been developed to enable the formation of sub-micron Au electrodes sputtered onto Si/SiGe without the need of a wetting layer.

  4. Effect of thermal treatment on the characteristics of iridium Schottky barrier diodes on n-Ge (1 0 0)

    Energy Technology Data Exchange (ETDEWEB)

    Chawanda, A., E-mail: albert.chawanda@up.ac.za [Department of Physics, University of Pretoria, 0002 (South Africa); Department of Physics, Midlands State University, Bag 9055, Gweru (Zimbabwe); Coelho, S.M.M.; Auret, F.D.; Mtangi, W. [Department of Physics, University of Pretoria, 0002 (South Africa); Nyamhere, C. [Department of Physics, Nelson Mandela Metropolitan University, Box 77000, Port Elizabeth 6031 (South Africa); Nel, J.M.; Diale, M. [Department of Physics, University of Pretoria, 0002 (South Africa)

    2012-02-05

    Highlights: Black-Right-Pointing-Pointer Ir/n-Ge (1 0 0) Schottky diodes were characterized using I-V, C-V and SEM techniques under various annealing conditions. Black-Right-Pointing-Pointer The variation of the electrical and structural properties can be due to effects phase transformation during annealing. Black-Right-Pointing-Pointer Thermal stability of these diodes is maintained up to 500 Degree-Sign C anneal. Black-Right-Pointing-Pointer SEM results depicts that the onset temperature for agglomeration in 20 nm Ir/n-Ge (1 0 0) system occurs between 600 and 700 Degree-Sign C. - Abstract: Iridium (Ir) Schottky barrier diodes were deposited on bulk grown (1 0 0) Sb-doped n-type germanium by using the electron beam deposition system. Electrical characterization of these contacts using current-voltage (I-V) and capacitance-voltage (C-V) measurements was performed under various annealing conditions. The variation of the electrical properties of these Schottky diodes can be attributed to combined effects of interfacial reaction and phase transformation during the annealing process. Thermal stability of the Ir/n-Ge (1 0 0) was observed up to annealing temperature of 500 Degree-Sign C. Furthermore, structural characterization of these samples was performed by using a scanning electron microscopy (SEM) at different annealing temperatures. Results have also revealed that the onset temperature for agglomeration in a 20 nm Ir/n-Ge (1 0 0) system occurs between 600 and 700 Degree-Sign C.

  5. Effects of Annealing on Electrical Characteristics and Current Transport Mechanisms of the Y/ p-GaN Schottky Diode

    Science.gov (United States)

    Reddy, V. Rajagopal; Asha, B.; Choi, Chel-Jong

    2016-07-01

    This study investigates the effects of annealing on the electrical properties and current transport mechanism of Y/ p-GaN Schottky barrier diodes (SBDs). We found no significant change in the surface morphology of the Y Schottky contacts during the annealing process. The Schottky barrier height (SBH) of the as-deposited Y/ p-GaN SBD was estimated to be 0.95 eV ( I- V)/1.19 eV ( C- V). The SBH increased upon annealing at 400°C and 500°C, and then decreased slightly with annealing at 600°C. Thus the maximum SBH of the Y/ p-GaN SBD was achieved at 500°C, with values of 1.01 eV ( I- V)/1.29 eV ( C- V). In addition, the SBH values were estimated by Cheung's, Norde, and Ψs- V plots and were found to be in good agreement with one another. Series resistance ( R S) values were also calculated by I- V, Cheung's, and Norde functions at different annealing temperatures, with results showing a decrease in the interface state density of the SBD with annealing at 500°C, followed by a slight increase upon annealing at 600°C. The forward-bias current transport mechanism of SBD was investigated by the log I-log V plot at different annealing temperatures. Our investigations revealed that the Poole-Frenkel emission mechanism dominated the reverse leakage current in Y/ p-GaN SBD at all annealing temperatures.

  6. The TiO(2) nanoparticle effect on the performance of a conducting polymer Schottky diode.

    Science.gov (United States)

    Yoo, K H; Kang, K S; Chen, Y; Han, K J; Kim, Jaehwan

    2008-12-17

    Among the conjugate polymers, poly(3,4-ethylenedioxythiophene):poly (styrenesulfonate) (PEDOT:PSS) has been paid a great deal of attention for various application fields. The absorption intensity of the whole UV-visible range increases linearly, as the concentration of PEDOT:PSS increases. When a small amount of TiO(2) nanoparticles are dispersed in the PEDOT:PSS solution, the absorption in the visible range normally increases, but the UV range absorption (TiO(2) absorption area) is greatly depressed as the concentration of PEDOT:PSS increases. Various weight ratios of TiO(2) nanoparticles in PEDOT:PSS were prepared. The TiO(2)/PEDOT:PSS solution was spin-coated onto the Al electrode and thermally treated to remove water molecules and densify the film. These thermal processes generated nanocracks and nanoholes on the surface of the TiO(2)/PEDOT:PSS film. As the heating temperature increased, wider and longer nanocracks were generated. These nanocracks and nanoholes can be removed by subsequent coating and heating processes. Schottky diodes were fabricated using four different concentrations of TiO(2)-PEDOT:PSS solution. The forward current increased nearly two orders of magnitude by doping approximately 1% of TiO(2) nanoparticles in PEDOT:PSS. Increasing the TiO(2) nanoparticles in the PEDOT:PSS matrix, the forward current was continuously enhanced. The enhancement of forward current is nearly four orders of magnitude with respect to the pristine PEDOT:PSS Schottky diode. The possible conduction mechanisms were examined by using various plotting and curve-fitting methods including a space-charge-limited conduction mechanism [Ln(J) versus Ln(V)], Schottky emission mechanism [Ln(J) versus E(1/2)], and Poole-Frenkel emission mechanism [Ln(J/V) versus E(1/2)]. The plot of Ln(J) versus Ln(V) shows a linear relationship, implying that the major conduction mechanism is SCLC. As the concentration of TiO(2) increased, the conduction mechanism slightly detracted from the

  7. Evaluation of Polarization Effects of e- Collection Schottky CdTe Medipix3RX Hybrid Pixel Detector

    Science.gov (United States)

    Astromskas, Vytautas; Gimenez, Eva N.; Lohstroh, Annika; Tartoni, Nicola

    2016-02-01

    This paper focuses on the evaluation of operational conditions such as temperature, exposure time and flux on the polarization of a Schottky electron collection CdTe detector. A Schottky e- collection CdTe Medipix3RX hybrid pixel detector was developed as a part of the CALIPSO-HIZPAD2 EU project. The 128 ×128 pixel matrix and 0.75 mm thick CdTe sensor bump-bonded to Medipix3RX readout chips enabled the study of the polarization effects. Single and quad module Medipix3RX chips were used which had 128 ×128 and 256 ×256 pixel matrices, respectively. This study reports the sensor-level and pixel-level polarization effects of the detector obtained from a laboratory X-ray source. We report that the sensor-level polarization is highly dependent on temperature, flux and exposure time. Furthermore, the study of pixel-level polarization effects led to identification of a new type of pixel behaviour that is characterised by three distinct phases and, thus, named “tri-phase” (3-P) pixels. The 3-P pixels were the dominant cause of degradation of the flat-field image uniformity under high flux operation. A new method of identifying the optimum operational conditions that utilises a criterion related to the 3-P pixels is proposed. A generated optimum operational conditions chart under the new method is reported. The criterion is used for bias voltage reset depolarization of the detector. The method successfully represented the dependency of polarization on temperature, flux and exposure time and was reproducible for multiple sensors. Operating the detector under the 3-P pixel criterion resulted in the total efficiency not falling below 95%.

  8. Schottky effect in the i -Zn-Ag-Sc-Tm icosahedral quasicrystal and its 1/1 Zn-Sc-Tm approximant

    Science.gov (United States)

    Jazbec, S.; Kashimoto, S.; Koželj, P.; Vrtnik, S.; Jagodič, M.; Jagličić, Z.; Dolinšek, J.

    2016-02-01

    The analysis of low-temperature specific heat of rare-earth (RE)-containing quasicrystals and periodic approximants and consequent interpretation of their electronic properties in the T →0 limit is frequently hampered by the Schottky effect, where crystalline electric fields lift the degeneracy of the RE-ion Hund's rule ground state and introduce additional contribution to the specific heat. In this paper we study the low-temperature specific heat of a thulium-containing i -Zn-Ag-Sc-Tm icosahedral quasicrystal and its 1/1 Zn-Sc-Tm approximant, both being classified as "Schottky" systems. We have derived the crystal-field Hamiltonian for pentagonal symmetry of the crystalline electric field, pertinent to the class of Tsai-type icosahedral quasicrystals and their approximants, where the RE ions are located on fivefold axes of the icosahedral atomic cluster. Using the leading term of this Hamiltonian, we have calculated analytically the Schottky specific heat in the presence of an external magnetic field and made comparison to the experimental specific heat of the investigated quasicrystal and approximant. When the low-temperature specific heat C is analyzed in a C /T versus T2 scale (as it is customarily done for metallic specimens), the Schottky specific heat yields an upturn in the T →0 limit that cannot be easily distinguished from a similar upturn produced by the electron-electron interactions in exchange-enhanced systems and strongly correlated systems. Our results show that extraction of the electronic properties of RE-containing quasicrystals from their low-temperature specific heat may be uncertain in the presence of the Schottky effect.

  9. Effects of oxide layers and metals on photoelectric and optical properties of Schottky barrier photodetector

    Energy Technology Data Exchange (ETDEWEB)

    Mohamad, W.F. [College of Engineering, Al Isra' University, P.O. Box 22 and 33, Al Isra University Post Office, Amman 11622 (Jordan); Abou Hajar, A. [College of Engineering, Aleppo University, Aleppo (Syrian Arab Republic); Saleh, A.N. [College of Engineering, Mosul University, Mosul (Iraq)

    2006-08-15

    Recently, a lot of attention has been paid to Schottky barrier photo detectors due to their promising properties and easy of fabrication. Many samples of SB devices prepared by thermal deposition under high vacuum are studied in this research. Different types and thicknesses of oxides were deposited on silicon substrate. Metals of different types and thicknesses were deposited on top of oxides. Variation of photogenerated current, responsivity, quantum efficiency and detectivity as a function of incident light wavelength were measured. It was found that the shape of the curves has two maxima, one was around 500nm and the other was around 700nm. Ni (100)-SiO{sub 2}-Si structure shows the maximum responsivity at 550nm and it is equal to 400mA/W. When comparison was made between devices of different metals, the nickel layer device showed high responsivity at visible region while the aluminum layer device showed high responsivity at near infrared region. Finally, the aluminum layer device showed detectivity higher than nickel layer device. The maximum detectivity of aluminum device was 6.4x10{sup 10}cm/HzW. (author)

  10. The effect of annealing temperature on the electrical characterization of Co/n type GaP Schottky diode

    Energy Technology Data Exchange (ETDEWEB)

    Orak, İ., E-mail: ikramorak@gmail.com [Vocational School of Health Services, Bingöl University, 12000 Bingöl (Turkey); Ejderha, K. [Vocational School of Technical Sciences, Bingöl University, 12000 Bingöl (Turkey); Sönmez, E. [Department of Physics, Kazim Karabekir Education Faculty, Atatürk University, Erzurum 25240 (Turkey); Alanyalıoğlu, M. [Faculty of Science, Department of Chemistry, 25240 Erzurum (Turkey); Turut, A. [Faculty of Sciences, Department of Engineering Physics, Istanbul Medeniyet University, 34730 Istanbul (Turkey)

    2015-01-15

    The Co/n-GaP nano-Schottky diodes have been fabricated to investigate effect of annealing temperature on the characteristics of the device. DC Magnetron sputtering technique has been used for Co metallic contact. The samples have been annealed for three minutes at 400 °C and 600 °C. XRD analyzes of the devices subjected to thermal annealing process have been investigated. Surface images have been taken with atomic force microscopy (AFM) in order to examine the morphology of the surface of the metal layer before and after the annealing the sample. The current–voltage (I–V) measurements taken at room temperature have shown that the ideality factor and series resistance decrease with the increasing annealing temperature. The ideality factor was found to be 1.02 for sample annealed at 400 °C. Before and after annealing, depending on the temperature measurement, the capacitance–frequency (C–f), and conductance–frequency (G–f) have been measured, and graphs have been plotted.

  11. Schottky-barrier heights of single-crystal NiSi2 on Si(111): The effect of a surface p-n junction

    Science.gov (United States)

    Tung, R. T.; Ng, K. K.; Gibson, J. M.; Levi, A. F. J.

    1986-05-01

    Current-voltage, capacitance-voltage, and activation-energy measurements obtained for epitaxial nickel silicides grown on Si(111) have exposed the importance of the temperature used to flash-evaporate oxide off the surface prior to metal deposition. Near-ideal behavior is found for Schottky barriers grown on substrates cleaned at ~820 °C in ultrahigh vacuum. The Fermi-level positions at the interfaces of single-crystal type-A and type-B NiSi2 are shown to differ by greater than 100 meV. Transmission electron microscopy demonstrated the epitaxial perfection of these silicide layers. At a cleaning temperature of 1050 °C, the apparent Schottky-barrier heights increased substantially for substrates with a doping concentration of ND less than approximately 1015 cm-3. This increase is due to the conversion of the n-type semiconductor surface region to p type during the 1050 °C anneal. The presence of this p-n junction results in a high apparent Schottky-barrier height (>~0.75 eV) which no longer bears an immediate relationship to the interface Fermi-level position. Recent discrepancies reported by different groups concerning the barrier heights of NiSi2 on Si(111) are attributed to this effect.

  12. Low Contact Resistivity with Low Silicide/p+-Silicon Schottky Barrier for High-Performance p-Channel Metal-Oxide-Silicon Field Effect Transistors

    Science.gov (United States)

    Tanaka, Hiroaki; Isogai, Tatsunori; Goto, Tetsuya; Teramoto, Akinobu; Sugawa, Shigetoshi; Ohmi, Tadahiro

    2010-04-01

    A current drivability improvement of p-channel metal-oxide-silicon field effect transistors (MOSFETs) is necessary for the performance enhancement of complementary metal-oxide-semiconductor (CMOS) circuits. In this paper, we present the key technology for fabricating indispensable CMOS circuits with a small Schottky barrier height and a low contact resistance for p-type silicon using Pd2Si. We fabricated a Pd2Si gate Schottky barrier diode and a Kelvin pattern on silicon. The measured Schottky barrier height is 0.29 eV for p-type silicon. We also realized a very low contact resistivity of 3.7 ×10-9 Ω cm2 for the p+ region of silicon. The p-channel MOSFET with Pd2Si source/drain contacts realized a good characteristic, that is, a small off current. The technology developed in this work involves silicide formation for source/drain contacts of p-channel MOSFETs, which is expected to realize the performance enhancement of MOSFETs.

  13. Schottky barrier MOSFET systems and fabrication thereof

    Science.gov (United States)

    Welch, J.D.

    1997-09-02

    (MOS) device systems-utilizing Schottky barrier source and drain to channel region junctions are disclosed. Experimentally derived results which demonstrate operation of fabricated N-channel and P-channel Schottky barrier (MOSFET) devices, and of fabricated single devices with operational characteristics similar to (CMOS) and to a non-latching (SRC) are reported. Use of essentially non-rectifying Schottky barriers in (MOS) structures involving highly doped and the like and intrinsic semiconductor to allow non-rectifying interconnection of, and electrical accessing of device regions is also disclosed. Insulator effected low leakage current device geometries and fabrication procedures therefore are taught. Selective electrical interconnection of drain to drain, source to drain, or source to source, of N-channel and/or P-channel Schottky barrier (MOSFET) devices formed on P-type, N-type and Intrinsic semiconductor allows realization of Schottky Barrier (CMOS), (MOSFET) with (MOSFET) load, balanced differential (MOSFET) device systems and inverting and non-inverting single devices with operating characteristics similar to (CMOS), which devices can be utilized in modulation, as well as in voltage controlled switching and effecting a direction of rectification. 89 figs.

  14. The effect of high temperatures on the electrical characteristics of Au/n-GaAs Schottky diodes

    Science.gov (United States)

    Tunhuma, S. M.; Auret, F. D.; Legodi, M. J.; Diale, M.

    2016-01-01

    In this study, the current-voltage (I-V) and capacitance-voltage (C-V) characteristics of Au/n-GaAs Schottky diodes have been measured over a wide temperature range, 80-480 K. The diodes were rectifying throughout the range and showed good thermal stability. Room temperature values for the ideality factor, I-V barrier height and C-V barrier height were found to be n=1.10, ϕIV=0.85 eV and ϕCV=0.96 eV, respectively. ϕIV increases and n decreases with an increase in temperature. We investigated the effect of elevated temperatures on the barrier height and ideality factor by measuring the diodes at a high temperature (annealing mode) then immediately afterwards measuring at room temperature (post annealing mode). The measurements indicate I-V characteristics that degrade permanently above 300 K. Permanent changes to the C-V characteristics were observed only above 400 K. We also noted a discrepancy in the C-V barrier height and carrier concentration between 340 and 400 K, which we attribute to the influence of the EL2 defect (positioned 0.83 eV below the conduction band minima) on the free carrier density. Consequently, we were able to fit the ϕCV versus temperature curve into two regions with temperature coefficients -6.9×10-4 eV/K and -2.2×10-4 eV/K above and below 400 K.

  15. The effects of localized tail states on charge transport mechanisms in amorphous zinc tin oxide Schottky diodes

    Science.gov (United States)

    Son, Youngbae; Peterson, Rebecca L.

    2017-12-01

    Temperature-dependent current–voltage measurements were performed on vertical Schottky diodes made with solution-processed amorphous zinc tin oxide (a-ZTO) semiconductor and palladium rectifying contacts. Above 260 K, forward bias electron transport occurs via thermionic emission over an inhomogeneous, voltage-dependent Schottky barrier with {\\bar{φ }}b0 = 0.72 eV, σ 0 = 0.12 eV, and A* = 44 A cm‑2 K‑2, where {\\bar{φ }}b0 and {σ }0 are the mean potential barrier and its standard deviation at zero bias, respectively, and A* is Richardson’s constant. For large currents, the series ohmic resistance of the bulk semiconductor dominates. At temperatures below 260 K, less carriers are excited from localized states below the conduction band edge, and space-charge-limited current (SCLC) dominates. The exponential tail density of states parameters extracted for a-ZTO are g tc = 1.34 × 1019 cm‑3 eV‑1 and kT t = 26 meV. The intermediate tail state density in a-ZTO, less than that of amorphous silicon and greater than that of amorphous indium gallium zinc oxide, allows for experimental observation of a temperature-dependent transition of bulk charge transport mechanisms in strong forward bias from semiconductor-like ohmic conduction near room temperature to insulator-like SCLC at lower temperatures. In reverse bias, the same tail states lead to modified Poole–Frenkel emission, reducing the leakage current. The frequency response of a half-wave rectifier and diode impedance spectroscopy confirm that the Schottky diode cut-off frequency is above 1 MHz.

  16. Destructive Single-Event Failures in Schottky Diodes

    Science.gov (United States)

    Casey, Megan C.; Lauenstein, Jean-Marie; Gigliuto, Robert A.; Wilcox, Edward P.; Phan, Anthony M.; Kim, Hak; Chen, Dakai; LaBel, Kenneth A.

    2014-01-01

    This presentation contains test results for destructive failures in DC-DC converters. We have shown that Schottky diodes are susceptible to destructive single-event effects. Future work will be completed to identify parameter that determines diode susceptibility.

  17. Fabrication of high performance field-effect transistors and practical Schottky contacts using hydrothermal ZnO nanowires.

    Science.gov (United States)

    Opoku, Charles; Dahiya, Abhishek Singh; Oshman, Christopher; Daumont, Christophe; Cayrel, Frederic; Poulin-Vittrant, Guylaine; Alquier, Daniel; Camara, Nicolas

    2015-09-04

    The production of large quantities of single crystalline semiconducting ZnO nanowires (NWs) at low cost can offer practical solutions to realizing several novel electronic/optoelectronic and sensor applications on an industrial scale. The present work demonstrates high-density single crystalline NWs synthesized by a multiple cycle hydrothermal process at ∼100 °C. The high carrier concentration in such ZnO NWs is greatly suppressed by a simple low cost thermal annealing step in ambient air at ∼450 °C. Single ZnO NW FETs incorporating these modified NWs are characterized, revealing strong metal work function-dependent charge transport, unobtainable with as-grown hydrothermal ZnO NWs. Single ZnO NW FETs with Al as source and drain (s/d) contacts show excellent performance metrics, including low off-state currents (fA range), high on/off ratio (10(5)-10(7)), steep subthreshold slope (V-s). Modified ZnO NWs with platinum s/d contacts demonstrate excellent Schottky transport characteristics, markedly different from a reference ZnO NW device with Al contacts. This included abrupt reverse bias current-voltage saturation characteristics and positive temperature coefficient (∼0.18 eV to 0.13 eV). This work is envisaged to benefit many areas of hydrothermal ZnO NW research, such as NW FETs, piezoelectric energy recovery, piezotronics and Schottky diodes.

  18. Hydrogen Production on Ag-Pd/TiO2 Bimetallic Catalysts: Is there a Combined Effect of Surface Plasmon Resonance with Schottky Mechanism on the Photo-Catalytic Activity?

    KAUST Repository

    Nadeem, Muhammad A.

    2017-03-28

    Despite many observations that plasmonics can enhance photocatalytic reactions, their relative role in the overall reaction rate is not thoroughly investigated. Here we report that silver nanoparticles contribution in the reaction rate by its plasmonic effect is negligible when compared to that of Pd (Schottky effect). To conduct the study a series of Ag−Pd/TiO2 catalysts have been prepared, characterized and tested for H2 production from water in the presence of an organic sacrificial agent. Pd was chosen as a standard high work function metal needed for the Schottky junction to pump away electrons from the conduction band of the semiconductor and Ag (whose work function is ca. 1 eV lower than that of Pd) for its high plasmonic resonance response at the edge of the bandgap of TiO2. While H2 production rates showed linear dependency on plasmonic response of Ag in the Pd−Ag series, the system performed less than that of pure Pd. In other words, the plasmonic contribution of Ag in the Ag−Pd/TiO2 catalyst for hydrogen production, while confirmed using different excitation energies, is small. Therefore, the “possible” synergistic effect of plasmonic (in the case of Ag) and Schottky-mechanism (in the case of Pd) is minor when compared to that of Schottky-effect alone.

  19. Supersensitive, Fast-Response Nanowire Sensors by Using Schottky Contacts

    KAUST Repository

    Hu, Youfan

    2010-05-31

    A Schottky barrier can be formed at the interface between a metal electrode and a semiconductor. The current passing through the metal-semiconductor contact is mainly controlled by the barrier height and barrier width. In conventional nanodevices, Schottky contacts are usually avoided in order to enhance the contribution made by the nanowires or nanotubes to the detected signal. We present a key idea of using the Schottky contact to achieve supersensitive and fast response nanowire-based nanosensors. We have illustrated this idea on several platforms: UV sensors, biosensors, and gas sensors. The gigantic enhancement in sensitivity of up to 5 orders of magnitude shows that an effective usage of the Schottky contact can be very beneficial to the sensitivity of nanosensors. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Effect of high energy electron irradiation on low frequency noise in 4H-SiC Schottky diodes

    Science.gov (United States)

    Kozlovski, V. V.; Lebedev, A. A.; Levinshtein, M. E.; Rumyantsev, S. L.; Palmour, J. W.

    2017-03-01

    The low-frequency noise in high voltage Ni/4H-SiC Schottky diodes irradiated with high energy (0.9 MeV) electrons was studied in the frequency range from 1 Hz to 50 kHz, temperature interval 295-410 K, and irradiation dose Φ from 0.2 × 1016 cm-2 to 7 × 1016 cm-2. The noise amplitude was found monotonically increasing with the irradiation dose. With the irradiation dose increase, the noise spectra on the linear part of the current voltage characteristic transform from the 1/f noise to the generation recombination noise of at least two trap levels. One of these levels can be classified as Z1/2 with the capture cross section determined from the noise measurements to be ˜10-15 cm2.

  1. Schottky Barriers in Bilayer Phosphorene Transistors.

    Science.gov (United States)

    Pan, Yuanyuan; Dan, Yang; Wang, Yangyang; Ye, Meng; Zhang, Han; Quhe, Ruge; Zhang, Xiuying; Li, Jingzhen; Guo, Wanlin; Yang, Li; Lu, Jing

    2017-04-12

    It is unreliable to evaluate the Schottky barrier height (SBH) in monolayer (ML) 2D material field effect transistors (FETs) with strongly interacted electrode from the work function approximation (WFA) because of existence of the Fermi-level pinning. Here, we report the first systematical study of bilayer (BL) phosphorene FETs in contact with a series of metals with a wide work function range (Al, Ag, Cu, Au, Cr, Ti, Ni, and Pd) by using both ab initio electronic band calculations and quantum transport simulation (QTS). Different from only one type of Schottky barrier (SB) identified in the ML phosphorene FETs, two types of SBs are identified in BL phosphorene FETs: the vertical SB between the metallized and the intact phosphorene layer, whose height is determined from the energy band analysis (EBA); the lateral SB between the metallized and the channel BL phosphorene, whose height is determined from the QTS. The vertical SBHs show a better consistency with the lateral SBHs of the ML phosphorene FETs from the QTS compared than that of the popular WFA. Therefore, we develop a better and more general method than the WFA to estimate the lateral SBHs of ML semiconductor transistors with strongly interacted electrodes based on the EBA for its BL counterpart. In terms of the QTS, n-type lateral Schottky contacts are formed between BL phosphorene and Cr, Al, and Cu electrodes with electron SBH of 0.27, 0.31, and 0.32 eV, respectively, while p-type lateral Schottky contacts are formed between BL phosphorene and Pd, Ti, Ni, Ag, and Au electrodes with hole SBH of 0.11, 0.18, 0.19, 0.20, and 0.21 eV, respectively. The theoretical polarity and SBHs are in good agreement with available experiments. Our study provides an insight into the BL phosphorene-metal interfaces that are crucial for designing the BL phosphorene device.

  2. ALD TiO2 thin film as dielectric for Al/p-Si Schottky diode

    Indian Academy of Sciences (India)

    The – curves in the reverse direction are taken and interpreted via both Schottky and Poole–Frenkel effects. Schottky effect was found to be dominant in the reverse direction. In addition, the capacitance–voltage (–) and conductance–voltage (/–) characteristics of diode were investigated at different frequencies ...

  3. Hybrid functional versus quasiparticle calculations for the Schottky barrier and effective work function at TiN/HfO2 interface

    Science.gov (United States)

    Oh, Young Jun; Lee, Alex Taekyung; Noh, Hyeon-Kyun; Chang, K. J.

    2013-02-01

    We investigate the Schottky barrier and effective work function (EWF) at TiN/HfO2 interface through density functional calculations. For different interfaces that consist of either Ti-O or N-Hf interface bonds, the intrinsic metal-induced gap states are nearly independent of the interface structure, with similar decay lengths into the oxide. Due to the weak Fermi-level pinning, the EWF is more sensitive to the extrinsic effect of interface bonding. As N-rich interface bonds are replaced by O-rich bonds, the EWF decreases by up to 0.36 eV, which is attributed to the formation of opposing interface dipoles. To improve the band gap and EWF, we perform both hybrid functional and quasiparticle (QP) calculations. In the GW0 approximation, in which the Green's function is self-consistently calculated by updating only QP energies and the full frequency-dependent dielectric function is used, the agreement of the EWF with experiment is greatly improved, while QP calculations at the G0W0 level or using the plasmon-pole dielectric function tend to overestimate the EWF. In the self-consistent GW approach, in which both QP energies and wave functions are updated in iterations, the band gap is overestimated, resulting in the lower EWF. On the other hand, the EWF is severely underestimated with the hybrid functional because of the larger shift of the valence band edge level of HfO2.

  4. Transformation of polycrystalline tungsten to monocrystalline tungsten W(100) and its potential application in Schottky emitters

    NARCIS (Netherlands)

    Dokania, A.K.; Hendrikx, R.; Kruit, P.

    2009-01-01

    The electron sources in electron microscopes and electron lithography machines often consist of small diameter W(100) wires, etched to form a sharp tip. The electron emission is facilitated by the Schottky effect, thus the name Schottky emitter. The authors are investigating the feasibility of

  5. Gigantic Enhancement in Sensitivity Using Schottky Contacted Nanowire Nanosensor

    KAUST Repository

    Wei, Te-Yu

    2009-12-09

    A new single nanowire based nanosensor is demonstrated for illustrating its ultrahigh sensitivity for gas sensing. The device is composed of a single ZnO nanowire mounted on Pt electrodes with one end in Ohmic contact and the other end in Schottky contact. The Schottky contact functions as a "gate" that controls the current flowing through the entire system. By tuning the Schottky barrier height through the responsive variation of the surface chemisorbed gases and the amplification role played by the nanowire to Schottky barrier effect, an ultrahigh sensitivity of 32 000% was achieved using the Schottky contacted device operated in reverse bias mode at 275 °C for detection of 400 ppm CO, which is 4 orders of magnitude higher than that obtained using an Ohmic contact device under the same conditions. In addition, the response time and reset time have been shortened by a factor of 7. The methodology and principle illustrated in the paper present a new sensing mechanism that can be readily and extensively applied to other gas sensing systems. © 2009 American Chemical Society.

  6. Recrystallization effects of swift heavy {sup 209}Bi ions irradiation on electrical degradation in 4H-SiC Schottky barrier diode

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Zhimei; Ma, Yao; Gong, Min [Key Laboratory for Microelectronics, College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China); Key Laboratory of Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064 (China); Li, Yun [Key Laboratory for Microelectronics, College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China); Huang, Mingmin [Key Laboratory for Microelectronics, College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China); Key Laboratory of Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064 (China); Gao, Bo [Key Laboratory for Microelectronics, College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China); Zhao, Xin, E-mail: zhaoxin1234@scu.edu.cn [Key Laboratory for Microelectronics, College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China)

    2017-06-15

    In this paper, the phenomenon that the recrystallization effects of swift heavy {sup 209}Bi ions irradiation can partially recovery damage with more than 1 × 10{sup 10} ions/cm{sup 2} is investigated by the degradation of the electrical characteristics of 4H-SiC Schottky barrier diode (SBD) with swift heavy ion irradiation. Deep level transient spectroscopy (DLTS) and Current-Voltage (I-V) measurements clearly indicated that E{sub 0.62} defect induced by swift heavy ion irradiation, which was a recombination center, could result in the increase of reverse leakage current (I{sub R}) at fluence less than 1 × 10{sup 9} ions/cm{sup 2} and the recovery of I{sub R} at fluence more than 1 × 10{sup 10} ions/cm{sup 2} in 4H-SiC SBD. The variation tendency of I{sub R} is consisted with the change of E{sub 0.62} defect. Furthermore, it is reasonable explanation that the damage or defect formed at low fluence in SiC may be recovered by further swift heavy ion irradiation with high fluence, which is due to the melting with the ion tracks of the amorphous zones through a thermal spike and subsequent epitaxial recrystallization initiated from the neighboring crystalline regions.

  7. Fullerene-based Schottky-junction organic solar cells: a brief review

    Science.gov (United States)

    Sutty, Sibi; Williams, Graeme; Aziz, Hany

    2014-01-01

    Recent advances in fullerene-based Schottky organic solar cells (OSCs) are presented, with a focus on the current understanding of device physics. Fullerene-based Schottky OSCs attain high open-circuit voltages due to the n-type Schottky junction formed between fullerene and an adjacent high work function anode. Small concentrations of donor material doped into the fullerene matrix serve as efficient exciton dissociation and hole transport agents that can substantially bolster short-circuit currents and fill factors. As a consequence, fullerene-based Schottky OSCs have been demonstrated to provide some of the highest-performance vacuum-deposited small molecule OSCs, with power conversion efficiencies up to 8.1%. Fullerene-based Schottky OSCs constructed using different donor materials and varying cathode buffer layers, as studied by a number of different research groups, are presented. To elucidate the differences between Schottky OSCs and more traditional bulk-heterojunction OSCs, we discuss the photophysics of fullerenes, the role of the donor material, and charge transport in low donor concentration active layers. Fullerene-based Schottky OSCs possess considerable advantages because they can reach high efficiencies with a simple structure using readily available and cost-effective materials. The impact and applicability of the Schottky device architecture on the field of organic photovoltaics at large are discussed.

  8. Nitrogen-Doped Carbon Activated in Situ by Embedded Nickel through the Mott-Schottky Effect for the Oxygen Reduction Reaction.

    Science.gov (United States)

    Chen, Teng; Guo, Siqi; Yang, Jie; Xu, Yida; Sun, Jie; Wei, Dali; Chen, Zhaoxu; Zhao, Bin; Ding, Weiping

    2017-09-14

    The development of low-cost non-precious-metal electrocatalysts with high activity and stability in the oxygen reduction reaction (ORR) remains a great challenge. Heteroatom-doped carbon materials are receiving increased attention in research as effective catalysts. However, the uncontrolled doping of heteroatoms into a carbon matrix tends to inhibit the activity of a catalyst. Here, the in situ activation of a uniquely structured nitrogen-doped carbon/Ni composite catalyst for the ORR is demonstrated. This well-designed catalyst is composed of a nitrogen-doped carbon shell and embedded metallic nickel. The embedded Ni nanoparticles, dispersed on stable alumina with a high specific surface area for protecting them from agglomeration and in an unambiguous composite structure, are electron-donating and are shielded by the nitrogen-doped carbon from oxidation/dissolution in harsh environments. The electronic structure of the nitrogen-doped carbon shell is modulated by the transfer of electrons at the interface of nitrogen-doped carbon-Ni heterojunctions owing to the Mott-Schottky effect. The electrochemically active surface area result implies that the active sites do not relate to Ni directly and the enhanced catalytic activity mainly arises from the modulation of nitrogen-doped carbon by nickel. XPS and theoretical calculations suggest that the donated electrons are transferred to pyridinic N primarily, which ought to enhance the catalytic activity intrinsically. Benefiting from these transferred electrons, the half-wave potential of the nitrogen-doped carbon/Ni composite catalyst is 94 mV positively shifted compared to the Ni-free sample. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Semi-insulating GaAs-based Schottky contacts in the role of detectors of ionising radiation: An effect of the interface treatment

    CERN Document Server

    Ivanco, J; Darmo, J; Krempasky, M; Besse, I; Senderak, R

    1999-01-01

    It is generally agreed that the substrate material quality plays a key role in the performance of back-to-back detectors of ionising radiation based on semi-insulating (SI) material. The aim of this paper is to evaluate usually overlooked problem, namely the influence of the Schottky contact preparation on detector performance. We report on different approaches to modify and control the quality of the metal/SI GaAs interface via a treatment of the SI-GaAs surface by means of low-temperature hydrogen plasma and wet etching. The measured electrical and detecting properties of such structures display a strong dependence on the history and the way the GaAs surface is treated prior to the metal evaporation. We point out, therefore, that the semiconductor surface treatment before the Schottky metallization plays a role of comparable importance to the influence of the SI-GaAs substrate properties on detector performances. (author)

  10. Temperature dependent current-voltage characteristics of Au/n-Si Schottky barrier diodes and the effect of transition metal oxides as an interface layer

    Science.gov (United States)

    Mahato, Somnath; Puigdollers, Joaquim

    2018-02-01

    Temperature dependent current-voltage (I‒V) characteristics of Au/n-type silicon (n-Si) Schottky barrier diodes have been investigated. Three transition metal oxides (TMO) are used as an interface layer between gold and silicon. The basic Schottky diode parameters such as ideality factor (n), barrier height (ϕb 0) and series resistance (Rs) are calculated and successfully explained by the thermionic emission (TE) theory. It has been found that ideality factor decreased and barrier height increased with increased of temperature. The conventional Richardson plot of ln(I0/T2) vs. 1000/T is determined the activation energy (Ea) and Richardson constant (A*). Whereas value of 'A*' is much smaller than the known theoretical value of n-type Si. The temperature dependent I-V characteristics obtained the mean value of barrier height (ϕb 0 bar) and standard deviation (σs) from the linear plot of ϕap vs. 1000/T. From the modified Richardson plot of ln(I0/T2) ˗ (qσ)2/2(kT)2 vs. 1000/T gives Richardson constant and homogeneous barrier height of Schottky diodes. Main observation in this present work is the barrier height and ideality factor shows a considerable change but the series resistance value exhibits negligible change due to TMO as an interface layer.

  11. Effects of 5.4 MeV alpha-particle irradiation on the electrical properties of nickel Schottky diodes on 4H–SiC

    Energy Technology Data Exchange (ETDEWEB)

    Omotoso, E. [Department of Physics, University of Pretoria, Private Bag X20, Hatfield 0028 (South Africa); Department of Physics, Obafemi Awolowo University, Ile-Ife 220005 (Nigeria); Meyer, W.E.; Auret, F.D.; Paradzah, A.T.; Diale, M.; Coelho, S.M.M.; Janse van Rensburg, P.J.; Ngoepe, P.N.M. [Department of Physics, University of Pretoria, Private Bag X20, Hatfield 0028 (South Africa)

    2015-12-15

    Current–voltage, capacitance–voltage and conventional deep level transient spectroscopy at temperature ranges from 40 to 300 K have been employed to study the influence of alpha-particle irradiation from an {sup 241}Am source on Ni/4H–SiC Schottky contacts. The nickel Schottky barrier diodes were resistively evaporated on n-type 4H–SiC samples of doping density of 7.1 × 10{sup 15} cm{sup −3}. It was observed that radiation damage caused an increase in ideality factors of the samples from 1.04 to 1.07, an increase in Schottky barrier height from 1.25 to 1.31 eV, an increase in series resistance from 48 to 270 Ω but a decrease in saturation current density from 55 to 9 × 10{sup −12} A m{sup −2} from I–V plots at 300 K. The free carrier concentration of the sample decreased slightly after irradiation. Conventional DLTS showed peaks due to four deep levels for as-grown and five deep levels after irradiation. The Richardson constant, as determined from a modified Richardson plot assuming a Gaussian distribution of barrier heights for the as-grown and irradiated samples were 133 and 151 A cm{sup −2} K{sup −2}, respectively. These values are similar to literature values.

  12. A nanoscale pn junction in series with tunable Schottky barriers

    Science.gov (United States)

    Aspitarte, Lee; McCulley, Daniel R.; Minot, Ethan D.

    2017-10-01

    PN junctions in nanoscale materials are of interest for a range of technologies including photodetectors, solar cells, and light-emitting diodes. However, Schottky barriers at the interface between metal contacts and the nanomaterial are often unavoidable. The effect of metal-semiconductor interfaces on the behavior of nanoscale diodes must be understood, both to extract the characteristics of the pn junction, and to understand the overall characteristics of the final device. Here, we study the current-voltage characteristics of diodes that are formed in fully suspended carbon nanotubes (CNTs). We utilize tunable Schottky barrier heights at the CNT-metal interface to elucidate the role of the Schottky barriers on the device characteristics. We develop a quantitative model to show how a variety of device characteristics can arise from apparently similar devices. Using our model we extract key parameters of the Schottky barriers and the pn junction, and predict the overall I-V characteristics of the device. Our equivalent circuit model is relevant to a variety of nanomaterial-based diode devices that are currently under investigation.

  13. Analysis and simulation of nonlinearity and effects of spontaneous emission in Schottky-junction-based plasmonic amplifiers.

    Science.gov (United States)

    Livani, Abdolber Mallah; Kaatuzian, Hassan

    2015-07-01

    An amplifier that operates on surface plasmon polaritons has been analyzed and simulated. Nonlinearity behavior and the spontaneous emission effects of the plasmonic amplifier are investigated in this paper. A rate equations approach has been used in which parameters are derived from simulation results of the plasmonic amplifier (Silvaco/ATLAS). Details on the method of this derivation are included, which were not previously reported. Rate equations are solved numerically by MATLAB codes. These codes verify the Silvaco results. The plasmonic amplifier operates on surface plasmons with a free-space wavelength of 1550 nm. Results show that, even without the effect of spontaneous emission, gain of the plasmonic amplifier saturates in high input levels. Saturation power, which can be used for comparing nonlinearity of different amplifiers, is 2.1 dBm for this amplifier. Amplified spontaneous emission reduces the gain of the amplifiers, which is long. There is an optimum value for the length of the amplifier. For the amplifier of this work, the optimum length for the small signal condition is 265 μm.

  14. Schottky-contact plasmonic rectenna for biosensing

    Science.gov (United States)

    Alavirad, Mohammad; Siadat Mousavi, Saba; Roy, Langis; Berini, Pierre

    2013-10-01

    We propose a plasmonic gold nanodipole array on silicon, forming a Schottky contact thereon, and covered by water. The behavior of this array under normal excitation has been extensively investigated. Trends have been found and confirmed by identification of the mode propagating in nanodipoles and its properties. This device can be used to detect infrared radiation below the bandgap energy of the substrate via internal photoelectric effect (IPE). Also we estimate its responsivity and detection limit. Finally, we assess the potential of the structure for bulk and surface (bio) chemical sensing. Based on modal results an analytical model has been proposed to estimate the sensitivity of the device. Results show a good agreement between numerical and analytical interpretations.

  15. Effect of temperature on the passive state of Alloy 31 in a LiBr solution: Passivation and Mott-Schottky analysis

    OpenAIRE

    Fernández Domene, Ramón Manuel; Blasco-Tamarit, E.; García-García, D.M.; Garcia-Anton, Jose

    2015-01-01

    The passive behaviour of Alloy 31, a highly-alloyed austenitic stainless steel (UNS N08031), has been investigated in a LiBr heavy brine (700 g/l) at different temperatures using potentiostatic polarisation and Mott-Schottky analysis. Cation vacancies have been found to be the dominant defect in the passive films formed on Alloy 31. An increase in temperature enhanced the generation of cation vacancies at the film/solution interface and raised the steady-state passive current density. The den...

  16. The properties of transparent TiO2 films for Schottky photodetector

    Directory of Open Access Journals (Sweden)

    Sung-Ho Park

    2017-08-01

    Full Text Available In this data, the properties of transparent TiO2 film for Schottky photodetector are presented for the research article, entitled as “High-performing transparent photodetectors based on Schottky contacts” (Patel et al., 2017 [1]. The transparent photoelectric device was demonstrated by using various Schottky metals, such as Cu, Mo and Ni. This article mainly shows the optical transmittance of the Ni-transparent Schottky photodetector, analyzed by the energy dispersive spectroscopy and interfacial TEM images for transparency to observe the interface between NiO and TiO2 film. The observation and analyses clearly show that no pinhole formation in the TiO2 film by Ni diffusion. The rapid thermal process is an effective way to form the quality TiO2 film formation without degradation, such as pinholes (Qiu et al., 2015 [2]. This thermal process may apply to form functional metal oxide layers for solar cells and photodetectors.

  17. Schottky Noise and Beam Transfer Functions

    Energy Technology Data Exchange (ETDEWEB)

    Blaskiewicz M.; Blaskiewicz M.

    2016-12-01

    Beam transfer functions (BTF)s encapsulate the stability properties of charged particle beams. In general one excites the beam with a sinusoidal signal and measures the amplitude and phase of the beam response. Most systems are very nearly linear and one can use various Fourier techniques to reduce the number of measurements and/or simulations needed to fully characterize the response. Schottky noise is associated with the finite number of particles in the beam. This signal is always present. Since the Schottky current drives wakefields, the measured Schottky signal is influenced by parasitic impedances.

  18. Tuning of Schottky barrier height of Al/n-Si by electron beam irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Vali, Indudhar Panduranga [Manipal Institute of Technology, Manipal University, Manipal 576104 (India); Shetty, Pramoda Kumara, E-mail: pramod.shetty@manipal.edu [Manipal Institute of Technology, Manipal University, Manipal 576104 (India); Mahesha, M.G. [Manipal Institute of Technology, Manipal University, Manipal 576104 (India); Petwal, V.C.; Dwivedi, Jishnu [Raja Ramanna Centre for Advanced Technology, Department of Atomic Energy, Government of India, Indore 452012 (India); Choudhary, R.J. [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452017 (India)

    2017-06-15

    Highlights: • Tuning of Schottky barrier height has been achieved by electron beam irradiation at different doses on n-Si wafer prior to the fabrication of Schottky contact. • The XPS analyses have shown irradiation induced defects and the formation of several localized chemical states in Si/SiOx interface that influences the Schottky barrier height. • High ideality factor indicates metal-insulator-semiconductor configuration of the Schottky diode and the inhomogeneous nature of the Schottky barrier height. • The modifications in I–V characteristics have been observed as a function of electron dose. This is caused due to changes in the Schottky diode parameters and different transport mechanisms. - Abstract: The effect of electron beam irradiation (EBI) on Al/n-Si Schottky diode has been studied by I–V characterization at room temperature. The behavior of the metal-semiconductor (MS) interface is analyzed by means of variations in the MS contact parameters such as, Schottky barrier height (Φ{sub B}), ideality factor (n) and series resistance (R{sub s}). These parameters were found to depend on the EBI dose having a fixed incident beam of energy 7.5 MeV. At different doses (500, 1000, 1500 kGy) of EBI, the Schottky contacts were prepared and extracted their contact parameters by applying thermionic emission and Cheung models. Remarkably, the tuning of Φ{sub B} was observed as a function of EBI dose. The improved n with increased Φ{sub B} is seen for all the EBI doses. As a consequence of which the thermionic emission is more favored. However, the competing transport mechanisms such as space charge limited emission, tunneling and tunneling through the trap states were ascribed due to n > 1. The analysis of XPS spectra have shown the presence of native oxide and increased radiation induced defect states. The thickness variation in the MS interface contributing to Schottky contact behavior is discussed. This study explains a new technique to tune

  19. Graphene-GaN Schottky Photodiodes Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Integration of graphene as the top metal on GaN Schottky. This will replace platinum, which is 50% transparent at the desired wavelength, with graphene, which has...

  20. Physical based Schottky barrier diode modeling for THz applications

    DEFF Research Database (Denmark)

    Yan, Lei; Krozer, Viktor; Michaelsen, Rasmus Schandorph

    2013-01-01

    temperature. The effects of barrier height lowering, nonlinear resistance from the EPI layer, and hot electron noise are all included for accurate characterization of the Schottky diode. To verify the diode model, measured I-V and C-V characteristics are compared with the simulation results. Due to the lack......In this work, a physical Schottky barrier diode model is presented. The model is based on physical parameters such as anode area, Ohmic contact area, doping profile from epitaxial (EPI) and substrate (SUB) layers, layer thicknesses, barrier height, specific contact resistance, and device...... of measurement data for noise behaviors, simulated noise temperature is compared with the experimental data found from the open literature....

  1. Monte Carlo modelling of Schottky diode for rectenna simulation

    Science.gov (United States)

    Bernuchon, E.; Aniel, F.; Zerounian, N.; Grimault-Jacquin, A. S.

    2017-09-01

    Before designing a detector circuit, the electrical parameters extraction of the Schottky diode is a critical step. This article is based on a Monte-Carlo (MC) solver of the Boltzmann Transport Equation (BTE) including different transport mechanisms at the metal-semiconductor contact such as image force effect or tunneling. The weight of tunneling and thermionic current is quantified according to different degrees of tunneling modelling. The I-V characteristic highlights the dependence of the ideality factor and the current saturation with bias. Harmonic Balance (HB) simulation on a rectifier circuit within Advanced Design System (ADS) software shows that considering non-linear ideality factor and saturation current for the electrical model of the Schottky diode does not seem essential. Indeed, bias independent values extracted in forward regime on I-V curve are sufficient. However, the non-linear series resistance extracted from a small signal analysis (SSA) strongly influences the conversion efficiency at low input powers.

  2. Analytical modeling of trilayer graphene nanoribbon Schottky-barrier FET for high-speed switching applications.

    Science.gov (United States)

    Rahmani, Meisam; Ahmadi, Mohammad Taghi; Abadi, Hediyeh Karimi Feiz; Saeidmanesh, Mehdi; Akbari, Elnaz; Ismail, Razali

    2013-01-30

    Recent development of trilayer graphene nanoribbon Schottky-barrier field-effect transistors (FETs) will be governed by transistor electrostatics and quantum effects that impose scaling limits like those of Si metal-oxide-semiconductor field-effect transistors. The current-voltage characteristic of a Schottky-barrier FET has been studied as a function of physical parameters such as effective mass, graphene nanoribbon length, gate insulator thickness, and electrical parameters such as Schottky barrier height and applied bias voltage. In this paper, the scaling behaviors of a Schottky-barrier FET using trilayer graphene nanoribbon are studied and analytically modeled. A novel analytical method is also presented for describing a switch in a Schottky-contact double-gate trilayer graphene nanoribbon FET. In the proposed model, different stacking arrangements of trilayer graphene nanoribbon are assumed as metal and semiconductor contacts to form a Schottky transistor. Based on this assumption, an analytical model and numerical solution of the junction current-voltage are presented in which the applied bias voltage and channel length dependence characteristics are highlighted. The model is then compared with other types of transistors. The developed model can assist in comprehending experiments involving graphene nanoribbon Schottky-barrier FETs. It is demonstrated that the proposed structure exhibits negligible short-channel effects, an improved on-current, realistic threshold voltage, and opposite subthreshold slope and meets the International Technology Roadmap for Semiconductors near-term guidelines. Finally, the results showed that there is a fast transient between on-off states. In other words, the suggested model can be used as a high-speed switch where the value of subthreshold slope is small and thus leads to less power consumption.

  3. Integration of Plasmonic Effects and Schottky Junctions into Metal-Organic Framework Composites: Steering Charge Flow for Enhanced Visible-Light Photocatalysis.

    Science.gov (United States)

    Xiao, Juan-Ding; Han, Lili; Luo, Jun; Yu, Shu-Hong; Jiang, Hai-Long

    2018-01-22

    A wide range of light absorption and rapid electron-hole separation are desired for efficient photocatalysis. Herein, on the basis of a semiconductor-like metal-organic framework (MOF), a Pt@MOF/Au catalyst with two types of metal-MOF interfaces integrates the surface plasmon resonance excitation of Au nanorods with a Pt-MOF Schottky junction, which not only extends the light absorption of the MOF from the UV to the visible region but also greatly accelerates charge transfer. The spatial separation of Pt and Au particles by the MOF further steers the formation of charge flow and expedites the charge migration. As a result, the Pt@MOF/Au presents an exceptionally high photocatalytic H 2 production rate by water splitting under visible light irradiation, far superior to Pt/MOF/Au, MOF/Au and other counterparts with similar Pt or Au contents, highlighting the important role of each component and the Pt location in the catalyst. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Analysing black phosphorus transistors using an analytic Schottky barrier MOSFET model.

    Science.gov (United States)

    Penumatcha, Ashish V; Salazar, Ramon B; Appenzeller, Joerg

    2015-11-13

    Owing to the difficulties associated with substitutional doping of low-dimensional nanomaterials, most field-effect transistors built from carbon nanotubes, two-dimensional crystals and other low-dimensional channels are Schottky barrier MOSFETs (metal-oxide-semiconductor field-effect transistors). The transmission through a Schottky barrier-MOSFET is dominated by the gate-dependent transmission through the Schottky barriers at the metal-to-channel interfaces. This makes the use of conventional transistor models highly inappropriate and has lead researchers in the past frequently to extract incorrect intrinsic properties, for example, mobility, for many novel nanomaterials. Here we propose a simple modelling approach to quantitatively describe the transfer characteristics of Schottky barrier-MOSFETs from ultra-thin body materials accurately in the device off-state. In particular, after validating the model through the analysis of a set of ultra-thin silicon field-effect transistor data, we have successfully applied our approach to extract Schottky barrier heights for electrons and holes in black phosphorus devices for a large range of body thicknesses.

  5. Transverse Schottky spectra and beam transfer functions of coasting ion beams with space charge

    Energy Technology Data Exchange (ETDEWEB)

    Paret, Stefan

    2010-02-22

    A study of the transverse dynamics of coasting ion beams with moderate space charge is presented in this work. From the dispersion relation with linear space charge, an analytic model describing the impact of space charge on transverse beam transfer functions (BTFs) and the stability limits of a beam is derived. The dielectric function obtained in this way is employed to describe the transverse Schottky spectra with linear space charge as well. The difference between the action of space charge and impedances is highlighted. The setup and the results of an experiment performed in the heavy ion synchrotron SIS-18 at GSI to detect space-charge effects at different beam intensities are explicated. The measured transverse Schottky spectra and BTFs are compared with the linear space-charge model. The stability diagrams constructed from the BTFs are presented. The space-charge parameters evaluated from the Schottky and BTF measurements are compared with estimations based on measured beam parameters. The impact of collective effects on the Schottky and BTF diagnostics is also investigated through numerical simulations. For this purpose the self-field of beams with linear and non-linear transverse density-distributions is computed on a twodimensional grid. The noise of the random particle distribution causes fluctuations of the dipole moment of the beam which produce the Schottky spectrum. BTFs are simulated by exciting the beam with transverse kicks. The simulation results are used to verify the space-charge model. (orig.)

  6. Recent Progress in Ohmic/Schottky-Contacted ZnO Nanowire Sensors

    Directory of Open Access Journals (Sweden)

    Xiaoli Zhao

    2015-01-01

    Full Text Available We review the recent progress of zinc oxide (ZnO nanowire sensors with ohmic-contacted and Schottky-contacted configurations and the enhancement of the performances of Schottky-contacted ZnO NW sensors (SCZNSs by the piezotronic effect. Comparing with the traditional ohmic-contacted ZnO NW sensors (OCZNSs, the SCZNSs have higher sensitivities and faster responses controlled by the barrier height at the metal-semiconductor (M-S interface. The piezotronic effect was applied to tune the Schottky barrier height (SBH with the strain-induced piezoelectric polarization charges at the interface of the M-S contact. The piezotronic effect can thus improve the detection limitation, sensitivity, and response time of the SCZNSs in different applications, such as UV detection, gas and bio/chemical sensing. These piezotronic-enhanced SCZNSs may find potential applications in human-machine interfacing and flexible electronics skin technologies.

  7. Schottky contacts to In2O3

    Directory of Open Access Journals (Sweden)

    H. von Wenckstern

    2014-04-01

    Full Text Available n-type binary compound semiconductors such as InN, InAs, or In2O3 are especial because the branch-point energy or charge neutrality level lies within the conduction band. Their tendency to form a surface electron accumulation layer prevents the formation of rectifying Schottky contacts. Utilizing a reactive sputtering process in an oxygen-containing atmosphere, we demonstrate Schottky barrier diodes on indium oxide thin films with rectifying properties being sufficient for space charge layer spectroscopy. Conventional non-reactive sputtering resulted in ohmic contacts. We compare the rectification of Pt, Pd, and Au Schottky contacts on In2O3 and discuss temperature-dependent current-voltage characteristics of Pt/In2O3 in detail. The results substantiate the picture of oxygen vacancies being the source of electrons accumulating at the surface, however, the position of the charge neutrality level and/or the prediction of Schottky barrier heights from it are questioned.

  8. Performance assessment of nanoscale Schottky MOSFET as ...

    Indian Academy of Sciences (India)

    pp. 511–520. Performance assessment of nanoscale Schottky MOSFET as resonant tunnelling device: Non-equilibrium Green's function formalism ... 2School of Electrical and Computer Engineering, University of Tehran, Tehran, Iran. *Corresponding author. E-mail: z.ahangari@iausr.ac.ir. MS received 2 January 2013; ...

  9. Stochastic Cooling with Schottky Band Overlap

    Energy Technology Data Exchange (ETDEWEB)

    Lebedev, Valeri; /Fermilab

    2005-12-01

    Optimal use of stochastic cooling is essential to maximize the antiproton stacking rate for Tevatron Run II. Good understanding and characterization of the cooling is important for the optimization. The paper is devoted to derivation of the Fokker-Planck equations justified in the case of near or full Schottky base overlap for both longitudinal and transverse coolings.

  10. Schottky contacts to In2O3

    Science.gov (United States)

    von Wenckstern, H.; Splith, D.; Schmidt, F.; Grundmann, M.; Bierwagen, O.; Speck, J. S.

    2014-04-01

    n-type binary compound semiconductors such as InN, InAs, or In2O3 are especial because the branch-point energy or charge neutrality level lies within the conduction band. Their tendency to form a surface electron accumulation layer prevents the formation of rectifying Schottky contacts. Utilizing a reactive sputtering process in an oxygen-containing atmosphere, we demonstrate Schottky barrier diodes on indium oxide thin films with rectifying properties being sufficient for space charge layer spectroscopy. Conventional non-reactive sputtering resulted in ohmic contacts. We compare the rectification of Pt, Pd, and Au Schottky contacts on In2O3 and discuss temperature-dependent current-voltage characteristics of Pt/In2O3 in detail. The results substantiate the picture of oxygen vacancies being the source of electrons accumulating at the surface, however, the position of the charge neutrality level and/or the prediction of Schottky barrier heights from it are questioned.

  11. Schottky barrier measurements on individual GaAs nanowires by X-ray photoemission microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Di Mario, Lorenzo [IMM-CNR, via del Fosso del Cavaliere 100, 00133 Rome (Italy); Turchini, Stefano, E-mail: stefano.turchini@cnr.it [ISM-CNR, via del Fosso del Cavaliere 100, 00133 Rome (Italy); Zamborlini, Giovanni; Feyer, Vitaly [Peter Grünberg Institute (PGI-6) and JARA-FIT, Research Center Jülich, 52425 Jülich (Germany); Tian, Lin [IMM-CNR, via del Fosso del Cavaliere 100, 00133 Rome (Italy); Schneider, Claus M. [Peter Grünberg Institute (PGI-6) and JARA-FIT, Research Center Jülich, 52425 Jülich (Germany); Fakultät für Physik and Center for Nanointegration Duisburg-Essen (CENIDE), Universität Duisburg-Essen, D-47048 Duisburg (Germany); Rubini, Silvia [IOM-CNR, TASC Laboratory, Basovizza 34149, Trieste (Italy); Martelli, Faustino, E-mail: faustino.martelli@cnr.it [IMM-CNR, via del Fosso del Cavaliere 100, 00133 Rome (Italy)

    2016-11-15

    Highlights: • The Schottky barrier at the interface between Cu and GaAs nanowires was measured. • Individual nanowires were investigated by X-ray Photoemission Microscopy. • The Schottky barrier at different positions along the nanowire was evaluated. - Abstract: We present measurements of the Schottky barrier height on individual GaAs nanowires by means of x-ray photoelectron emission microscopy (XPEEM). Values of 0.73 and 0.51 eV, averaged over the entire wires, were measured on Cu-covered n-doped and p-doped GaAs nanowires, respectively, in agreement with results obtained on bulk material. Our measurements show that XPEEM can become a feasible and reliable investigation tool of interface formation at the nanoscale and pave the way towards the study of size-dependent effects on semiconductor-based structures.

  12. A low-cost fabrication method for sub-millimeter wave GaAs Schottky diode

    Science.gov (United States)

    Jenabi, Sarvenaz; Deslandes, Dominic; Boone, Francois; Charlebois, Serge A.

    2017-10-01

    In this paper, a submillimeter-wave Schottky diode is designed and simulated. Effect of Schottky layer thickness on cut-off frequency is studied. A novel microfabrication process is proposed and implemented. The presented microfabrication process avoids electron-beam (e-beam) lithography which reduces the cost. Also, this process provides more flexibility in selection of design parameters and allows significant reduction in the device parasitic capacitance. A key feature of the process is that the Schottky contact, the air-bridges, and the transmission lines, are fabricated in a single lift-off step. This process relies on a planarization method that is suitable for trenches of 1-10 μm deep and is tolerant to end-point variations. The fabricated diode is measured and results are compared with simulations. A very good agreement between simulation and measurement results are observed.

  13. Surface Modification on the Sputtering-Deposited ZnO Layer for ZnO-Based Schottky Diode

    Directory of Open Access Journals (Sweden)

    Ren-Hao Chang

    2013-01-01

    Full Text Available We prepare a zinc oxide- (ZnO- based Schottky diode constructed from the transparent cosputtered indium tin oxide- (ITO- ZnO ohmic contact electrode and Ni/Au Schottky metal. After optimizing the ohmic contact property and removing the ion-bombardment damages using dilute HCl etching solution, the dilute hydrogen peroxide (H2O2 and ammonium sulfide (NH42Sx solutions, respectively, are employed to modify the undoped ZnO layer surface. Both of the Schottky barrier heights with the ZnO layer surface treated by these two solutions, evaluated from the current-voltage (I-V and capacitance-voltage (C-V measurements, are remarkably enhanced as compared to the untreated ZnO-based Schottky diode. Through the X-ray photoelectron spectroscopy (XPS and room-temperature photoluminescence (RTPL investigations, the compensation effect as evidence of the increases in the O–H and OZn acceptor defects appearing on the ZnO layer surface after treating by the dilute H2O2 solution is responsible for the improvement of the ZnO-based Schottky diode. By contrast, the enhancement on the Schottky barrier height for the ZnO layer surface treated by using dilute (NH42Sx solution is attributed to both the passivation and compensation effects originating from the formation of the Zn–S chemical bond and VZn acceptors.

  14. Deep traps and temperature effects on the capacitance of p-type Si-doped GaAs Schottky diodes on (2 1 1) and (3 1 1) oriented GaAs substrates

    Science.gov (United States)

    Boumaraf, R.; Sengouga, N.; Mari, R. H.; Meftah, Af.; Aziz, M.; Jameel, Dler; Al Saqri, Noor; Taylor, D.; Henini, M.

    2014-01-01

    The SILVACO-TCAD numerical simulator is used to explain the effect of different types of deep levels on the temperature dependence of the capacitance of p-type Si-doped GaAs Schottky diodes grown on high index GaAs substrates, namely (3 1 1)A and (2 1 1)A oriented GaAs substrates. For the (3 1 1)A diodes, the measured capacitance-temperature characteristics at different reverse biases show a large peak while the (2 1 1)A devices display a much smaller one. This peak is related to the presence of different types of deep levels in the two structures. These deep levels are characterized by the Deep Level Transient Spectroscopy (DLTS) technique. In the (3 1 1)A structure only majority deep levels (hole deep levels) were observed while both majority and minority deep levels were present in the (2 1 1)A diodes. The simulation software, which calculates the capacitance-voltage and the capacitance-temperature characteristics in the absence and presence of different types of deep levels, agrees well with the experimentally observed behavior of the capacitance-temperature properties. A further evidence to confirm that deep levels are responsible for the observed phenomenon is provided by a simulation of the capacitance-temperature characteristics as a function of the ac-signal frequency.

  15. Out-of-plane strain and electric field tunable electronic properties and Schottky contact of graphene/antimonene heterostructure

    Science.gov (United States)

    Phuc, Huynh V.; Hieu, Nguyen N.; Hoi, Bui D.; Phuong, Le T. T.; Hieu, Nguyen V.; Nguyen, Chuong V.

    2017-12-01

    In this paper, the electronic properties of graphene/monolayer antimonene (G/m-Sb) heterostructure have been studied using the density functional theory (DFT). The effects of out-of-plane strain (interlayer coupling) and electric field on the electronic properties and Schottky contact of the G/m-Sb heterostructure are also investigated. The results show that graphene is bound to m-Sb layer by a weak van-der-Waals interaction with the interlayer distance of 3.50 Å and the binding energy per carbon atom of -39.62 meV. We find that the n-type Schottky contact is formed at the G/m-Sb heterostructure with the Schottky barrier height (SBH) of 0.60 eV. By varying the interlayer distance between graphene and the m-Sb layer we can change the n-type and p-type SBH at the G/m-Sb heterostructure. Especially, we find the transformation from n-type to p-type Schottky contact with decreasing the interlayer distance. Furthermore, the SBH and the Schottky contact could be controlled by applying the perpendicular electric field. With the positive electric field, electrons can easily transfer from m-Sb to graphene layer, leading to the transition from n-type to p-type Schottky contact.

  16. Schottky diodes from 2D germanane

    Energy Technology Data Exchange (ETDEWEB)

    Sahoo, Nanda Gopal; Punetha, Vinay Deep [Nanoscience and Nanotechnology Centre, Department of Chemistry, Kumaun University, Nainital, 263001 Uttarakhand (India); Esteves, Richard J; Arachchige, Indika U. [Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284 (United States); Pestov, Dmitry [Nanomaterials Core Characterization Center, Virginia Commonwealth University, Richmond, Virginia 23284 (United States); McLeskey, James T., E-mail: JamesMcLeskey@rmc.edu [Department of Physics, Randolph-Macon College, Ashland, Virginia 23005 (United States)

    2016-07-11

    We report on the fabrication and characterization of a Schottky diode made using 2D germanane (hydrogenated germanene). When compared to germanium, the 2D structure has higher electron mobility, an optimal band-gap, and exceptional stability making germanane an outstanding candidate for a variety of opto-electronic devices. One-atom-thick sheets of hydrogenated puckered germanium atoms have been synthesized from a CaGe{sub 2} framework via intercalation and characterized by XRD, Raman, and FTIR techniques. The material was then used to fabricate Schottky diodes by suspending the germanane in benzonitrile and drop-casting it onto interdigitated metal electrodes. The devices demonstrate significant rectifying behavior and the outstanding potential of this material.

  17. Liaison, Schottky Problem and Invariant Theory

    CERN Document Server

    Alonso, Maria Emilia; Mallavibarrena, Raquel; Sols, Ignacio

    2010-01-01

    This volume is a homage to the memory of the Spanish mathematician Federico Gaeta (1923-2007). Apart from a historical presentation of his life and interaction with the classical Italian school of algebraic geometry, the volume presents surveys and original research papers on the mathematics he studied. Specifically, it is divided into three parts: linkage theory, Schottky problem and invariant theory. On this last topic a hitherto unpublished article by Federico Gaeta is also included.

  18. Revised diode equation for Ideal Graphene-Semiconductor Schottky Junction

    OpenAIRE

    Liang, Shi-Jun; Ang, Lay Kee

    2015-01-01

    In this paper we carry out a theoretical and experimental study of the nature of graphene/semiconductor Schottky contact. We present a simple and parameter-free carrier transport model of graphene/semiconductor Schottky contact derived from quantum statistical theory, which is validated by the quantum Landauer theory and first-principle calculations. The proposed model can well explain experimental results for samples of different types of graphene/semiconductor Schottky contact.

  19. Deforming super Riemann surfaces with gravitinos and super Schottky groups

    Energy Technology Data Exchange (ETDEWEB)

    Playle, Sam [Dipartimento di Fisica, Università di Torino and INFN, Sezione di Torino,Via P. Giuria 1, I-10125 Torino (Italy)

    2016-12-12

    The (super) Schottky uniformization of compact (super) Riemann surfaces is briefly reviewed. Deformations of super Riemann surface by gravitinos and Beltrami parameters are recast in terms of super Schottky group cohomology. It is checked that the super Schottky group formula for the period matrix of a non-split surface matches its expression in terms of a gravitino and Beltrami parameter on a split surface. The relationship between (super) Schottky groups and the construction of surfaces by gluing pairs of punctures is discussed in an appendix.

  20. Admittance of a-Si:H/c-Si Schottky diodes

    Energy Technology Data Exchange (ETDEWEB)

    Gall, S.; Hirschauer, R.; Braeunig, D. [Hahn-Meitner-Inst., Berlin (Germany). Dept. AT; Kolter, M. [Forschungszentrum Juelich (Germany)

    1996-12-31

    Heterojunction devices, based on hydrogenated amorphous silicon (a-Si:H) and single crystalline silicon (c-Si), are likely candidates for high efficiency solar cells. The authors have measured the admittance (conductance and capacitance) of a-Si:H/c-Si heterostructure Schottky diodes as a function of frequency, temperature and voltage in the dark and under spectral illumination (in the wavelength range between {lambda} = 500nm and {lambda} = 1,200nm). Thus, it is possible to observe the activation/deactivation of trapping-detrapping effects within the a-Si:H layer (near the a-SiH/c-Si interface). They have determined the conduction band offset of the a-Si:H/c-Si heterostructure. The spectral behavior of the admittance is dominated by the absorption of light in the c-Si and the valence band offset of the heterojunction. The authors have also developed an equivalent circuit of the a-Si:H/c-Si heterostructure Schottky diode in the dark, which is capable of describing the measured behavior.

  1. CMOS Application of Schottky Source/Drain SOI MOSFET with Shallow Doped Extension

    Science.gov (United States)

    Matsumoto, Sumie; Nishisaka, Mika; Asano, Tanemasa

    2004-04-01

    The silicon-on-insulator metal-oxide-semiconductor field-effect transistor (SOI MOSFET) whose source/drain is composed of Schottky contacts and a shallow-doped extension is investigated. It is demonstrated that the incorporation of the shallow-doped extension into the Schottky source/drain can increase the current drive and reduce the leakage current under reverse bias for both n-channel and p-channel devices. The shallow doping is performed by implanting Sb for n-channel devices, and BF2 or Ga for p-channel devices. The effect of Schottky contacts on the floating body effect (FBE) is investigated by analyzing the lateral bipolar characteristics of these devices. By employing the shallow-doped extension, a complementary MOS (CMOS) of the Schottky source/drain can be fabricated using single metal (cobalt, in this work) silicide. The stability of CMOS operation with the proposed devices under a high supply voltage is demonstrated by comparing it with a conventional pn-junction SOI MOSFET. It is also demonstrated from the characteristics of the CMOS-inverter ring oscillator that the proposed device operates at speeds as high as or even higher than that of the conventional SOI MOSFET.

  2. Tight-binding analysis of current oscillation in nanoscale In0.53Ga0.47As Schottky MOSFET

    Science.gov (United States)

    Ahangari, Zahra; Fathipour, Morteza

    2013-11-01

    A comprehensive study of band structure effect on the quantum transport of nanoscale In0.53Ga0.47As Schottky MOSFET for the implementation of III-V MOSFET with low source/drain series resistance is presented. Rigorous treatment of the full band structure in ultra-thin body MOSFET is employed using sp3d5s* tight-binding approach. Strong transverse confinement increases the energy of subbands and, indeed, the effective Schottky barrier height. Due to enhanced Schottky barriers and at low drain voltages, a double barrier gate modulated potential well is created along the channel that results in source-to-drain confinement of states. As tunnelling is the main current component in this device, longitudinal confinement induces drain current oscillation at low temperatures. Important factors that may affect current oscillation are demonstrated. Current oscillation that alters the normal performance of the device is investigated in nanowire Schottky MOSFET, as well. Additional quantum confinement in nanowire Schottky MOSFET provides higher effective Schottky barrier height than the double gate structure. Accordingly, the drain current oscillation is more apparent in nanowire Schottky MOSFET than in the double gate device and is gradually smoothed out as the gate length shrinks down in ultra-scaled structure. Effect of diffusive scattering on the quantum transport of the device is investigated, too. What is prominent in our result is that the drain current oscillations degrade as the channel mobility is decreased. The results in this paper are paving a way to elucidate the feasibility of this device in the nanoscale regime.

  3. Atomic composition of WC/ and Zr/O-terminated diamond Schottky interfaces close to ideality

    Energy Technology Data Exchange (ETDEWEB)

    Piñero, J.C., E-mail: josecarlos.pinero@uca.es [Dpto. Ciencias de los Materiales, Universidad de Cádiz, Puerto Real, Cádiz,11510 (Spain); Araújo, D. [Dpto. Ciencias de los Materiales, Universidad de Cádiz, Puerto Real, Cádiz,11510 (Spain); Fiori, A. [National Institute for Materials Science, Tsukuba, Ibaraki (Japan); Traoré, A. [Institut Néel, CNRS-UJF, av. des Martyrs, Grenoble,38042 France (France); Villar, M.P. [Dpto. Ciencias de los Materiales, Universidad de Cádiz, Puerto Real, Cádiz,11510 (Spain); Eon, D.; Muret, P.; Pernot, J. [Institut Néel, CNRS-UJF, av. des Martyrs, Grenoble,38042 France (France); Teraji, T. [National Institute for Materials Science, Tsukuba, Ibaraki (Japan)

    2017-02-15

    Highlights: • Metal/O-terminated diamond interfaces are analyzed by a variety of TEM techniques. • Thermal treatment is shown to modify structural and chemical interface properties. • Electrical behavior vs annealing is shown to be related with interface modification. • Interfaces are characterized with atomic resolution to probe inhomogeneities. • Oxide formation and modification is demonstrated in both Schottky diodes. - Abstract: Electrical and nano-structural properties of Zr and WC-based Schottky power diodes are compared and used for investigating oxide-related effects at the diamond/metal interface. Differences in Schottky barrier heights and ideality factors of both structures are shown to be related with the modification of the oxygen-terminated diamond/metal interface configuration. Oxide formation, oxide thickness variations and interfacial oxygen redistribution, associated with thermal treatment are demonstrated. Ideality factors close to ideality (n{sub WC} = 1.02 and n{sub Zr} = 1.16) are obtained after thermal treatment and are shown to be related with the relative oxygen content at the surface (OCR{sub WC} = 3.03 and OCR{sub Zr} = 1.5). Indeed, thermal treatment at higher temperatures is shown to promote an escape of oxygen for the case of the WC diode, while it generates a sharper accumulation of oxygen at the metal/diamond interface for the case of Zr diode. Therefore, the metal-oxygen affinity is shown to be a key parameter to improve diamond-based Schottky diodes.

  4. Analysis of high reverse currents of 4H-SiC Schottky-barrier diodes

    Science.gov (United States)

    Okino, Hiroyuki; Kameshiro, Norifumi; Konishi, Kumiko; Shima, Akio; Yamada, Ren-ichi

    2017-12-01

    Nickel (Ni), titanium (Ti), and molybdenum (Mo) 4H-silicon carbide Schottky-barrier diodes (SiC SBDs) were fabricated and used to investigate the relation between forward and reverse currents. Temperature dependence of reverse current follows a theory that includes tunneling in regard to thermionic emission, namely, temperature dependence is weak at low temperature but strong at high temperatures. On the other hand, the reverse currents of the Ni and Mo SBDs are higher than their respective currents calculated from their Schottky barrier heights (SBHs), whereas the reverse current of the Ti SBD agrees well with that calculated from its SBH. The cause of the high reverse currents was investigated from the viewpoints of low barrier patch, Gaussian distribution of barrier height (GD), thin surface barrier, and electron effective mass. The high reverse current of the Ni and Mo SBDs can be explained not in terms of a low-barrier patch, GD, or thin surface barrier but in terms of small effective masses. Investigation of crystal structures at the Schottky interface revealed a large lattice mismatch between the metals (Ni, Ti, or Mo) and SiC for the Ni and Mo SBDs. The small effective mass is possibly attributed to the large lattice mismatch, which might generate transition layers at the Schottky interface. It is concluded from these results that the lattice constant as well as the work function is an important factor in selecting the metal species as the Schottky metal for wide band-gap SBDs, for which tunneling current dominates reverse current.

  5. Experimental and computational investigation of graphene/SAMs/n-Si Schottky diodes

    Science.gov (United States)

    Aydin, H.; Bacaksiz, C.; Yagmurcukardes, N.; Karakaya, C.; Mermer, O.; Can, M.; Senger, R. T.; Sahin, H.; Selamet, Y.

    2018-01-01

    We have investigated the effect of two different self-assembled monolayers (SAMs) on electrical characteristics of bilayer graphene (BLG)/n-Si Schottky diodes. Novel 4″bis(diphenylamino)-1, 1‧:3″-terphenyl-5‧ carboxylic acids (TPA) and 4,4-di-9H-carbazol-9-yl-1,1‧:3‧1‧-terphenyl-5‧ carboxylic acid (CAR) aromatic SAMs have been used to modify n-Si surfaces. Cyclic voltammetry (CV) and Kelvin probe force microscopy (KPFM) results have been evaluated to verify the modification of n-Si surface. The current-voltage (I-V) characteristics of bare and SAMs modified devices show rectification behaviour verifying a Schottky junction at the interface. The ideality factors (n) from ln(I)-V dependences were determined as 2.13, 1.96 and 2.07 for BLG/n-Si, BLG/TPA/n-Si and BLG/CAR/n-Si Schottky diodes, respectively. In addition, Schottky barrier height (SBH) and series resistance (Rs) of SAMs modified diodes were decreased compared to bare diode due to the formation of a compatible interface between graphene and Si as well as π-π interaction between aromatic SAMs and graphene. The CAR-based device exhibits better diode characteristic compared to the TPA-based device. Computational simulations show that the BLG/CAR system exhibits smaller energy-level-differences than the BLG/TPA, which supports the experimental findings of a lower Schottky barrier and series resistance in BLG/CAR diode.

  6. Effect of asymmetrical double-pockets and gate-drain underlap on Schottky barrier tunneling FET: Ambipolar conduction vs. high frequency performance

    Science.gov (United States)

    Shaker, Ahmed; Ossaimee, Mahmoud; Zekry, A.

    2016-08-01

    In this paper, a proposed structure based on asymmetrical double pockets SB-TFET with gate-drain underlap is presented. 2D extensive modeling and simulation, using Silvaco TCAD, were carried out to study the effect of both underlap length and pockets' doping on the transistor performance. It was found that the underlap from the drain side suppresses the ambipolar conduction and doesn't enhance the high-frequency characteristics. The enhancement of the high-frequency characteristics could be realized by increasing the doping of the drain pocket over the doping of the source pocket. An optimum choice was found which gives the conditions of minimum ambipolar conduction, maximum ON current and maximum cut-off frequency. These enhancements render the device more competitive as a nanometer transistor.

  7. Electric Field Penetration in Au/Nb:SrTiO3 Schottky Junctions Probed by Bias-Dependent Internal Photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Hikita, Y.

    2011-08-15

    Electric field penetration into the metallic side of a Schottky junction is in principle a universal phenomenon, the magnitude of which increases with the semiconductor permittivity. Here, we quantitatively probe this effect using bias-dependent internal photoemission spectroscopy at the Schottky junction between a large dielectric permittivity semiconductor SrTiO{sub 3} and gold. A clear linear reduction of the barrier height with increasing interface electric field was observed, highlighting the importance of field penetration into the gold. The interfacial permittivity of SrTiO{sub 3} at the interface is reduced from the bulk value, reflecting intrinsic suppression at the interface.

  8. Schottky Photodiode Fabricated from Hydrogen-Peroxide-Treated ZnO Nanowires

    Science.gov (United States)

    Lee, Hsin-Yen; Wu, Bin-Kun; Chern, Ming-Yau

    2013-05-01

    An effective, transparent solar-blind Schottky ultraviolet (UV) sensor made of zinc oxide (ZnO) nanowires (NWs) was fabricated by chemical vapor deposition (CVD). Indium-tin oxide (ITO) thin films were deposited by radio frequency (RF) sputtering as Schottky contacts, where the hydrogen peroxide (H2O2) treatment of ZnO NWs played a key role in the rectifying effect. The photodiode showed a fitted barrier height of 0.89 eV, an ideality factor of 1.82, and a rectification behavior of up to three orders of magnitude at a voltage bias between -1 and +1 V. Photoresponse measurement proved a reliable device in the UV region.

  9. Failure Analysis of Heavy-Ion-Irradiated Schottky Diodes

    Science.gov (United States)

    Casey, Megan C.; Lauenstein, Jean-Marie; Wilcox, Edward P.; Topper, Alyson D.; Campola, Michael J.; Label, Kenneth A.

    2017-01-01

    In this work, we use high- and low-magnitude optical microscope images, infrared camera images, and scanning electron microscope images to identify and describe the failure locations in heavy-ion-irradiated Schottky diodes.

  10. Study of Reduced Graphene Oxide for Trench Schottky Diode

    Science.gov (United States)

    Samihah Khairir, Nur; Rofei Mat Hussin, Mohd; Nasir, Iskhandar Md; Mukhter Uz-Zaman, A. S. M.; Fazlida Hanim Abdullah, Wan; Sabirin Zoolfakar, Ahmad

    2015-11-01

    This paper presents the study of reduced Graphene Oxide (RGO) for trench Schottky diode by replacing conventional metal layer that forms schottky contact with a nanostructured carbon thin film via Reduced Graphene Oxide (RGO) technique. The RGO was synthesis by chemical exfoliation in which modified Hummer's method was approached. It was then deposited on the trench schottky pattern substrate by pressurized spray coating. The sample was then characterized by FESEM, Raman Spectroscopy and I-V test. The results of FESEM and Raman showed good characteristics and well deposited nanostructures of RGO flakes. The two-point I-V test showed that the samples have a low turn-on voltage and a higher break-down voltage, which is better than the conventional schottky diode used in the market.

  11. Modeling and Design of a New Flexible Graphene-on-Silicon Schottky Junction Solar Cell

    OpenAIRE

    Francesco Dell’Olio; Michele Palmitessa; Caterina Ciminelli

    2016-01-01

    A new graphene-based flexible solar cell with a power conversion efficiency >10% has been designed. The environmental stability and the low complexity of the fabrication process are the two main advantages of the proposed device with respect to other flexible solar cells. The designed solar cell is a graphene/silicon Schottky junction whose performance has been enhanced by a graphene oxide layer deposited on the graphene sheet. The effect of the graphene oxide is to dope the graphene and t...

  12. Summary of LHC MD:377: Schottky pick-up

    CERN Document Server

    Betz, Michael; Lefevre, Thibaut; CERN. Geneva. ATS Department

    2015-01-01

    The main objective of this MD was to record Schottky spectra under well known machine conditions. In summary, 7 set-points for the chromaticity and 8 for the emittance have been established and Schottky spectra have been recorded for each setting. The data will be used to benchmark and develop different fitting algorithms. This note presents the initial attempt of curve-fitting and discusses its shortcomings.

  13. High performance and transparent multilayer MoS2 transistors: Tuning Schottky barrier characteristics

    Directory of Open Access Journals (Sweden)

    Young Ki Hong

    2016-05-01

    Full Text Available Various strategies and mechanisms have been suggested for investigating a Schottky contact behavior in molybdenum disulfide (MoS2 thin-film transistor (TFT, which are still in much debate and controversy. As one of promising breakthrough for transparent electronics with a high device performance, we have realized MoS2 TFTs with source/drain electrodes consisting of transparent bi-layers of a conducting oxide over a thin film of low work function metal. Intercalation of a low work function metal layer, such as aluminum, between MoS2 and transparent source/drain electrodes makes it possible to optimize the Schottky contact characteristics, resulting in about 24-fold and 3 orders of magnitude enhancement of the field-effect mobility and on-off current ratio, respectively, as well as transmittance of 87.4 % in the visible wavelength range.

  14. Operation regimes and electrical transport of steep slope Schottky Si-FinFETs

    Science.gov (United States)

    Jeon, Dae-Young; Zhang, Jian; Trommer, Jens; Park, So Jeong; Gaillardon, Pierre-Emmanuel; De Micheli, Giovanni; Mikolajick, Thomas; Weber, Walter M.

    2017-02-01

    In the quest for energy efficient circuits, considerable focus has been given to steep slope and polarity-controllable devices, targeting low supply voltages and reduction of transistor count. The recently proposed concept of the three-independent gated Si-FinFETs with Schottky-barriers (SBs) has proven to bring both functionalities even in a single device. However, the complex combination of transport properties including Schottky emission and weak impact ionization as well as the body effect makes the design of such devices challenging. In this work, we perform a deep electrical characterization analysis to visualize and decouple the different operation regimes and electrical properties of the SB Si-FinFETs using a graphical transport map. From these, we give important guidelines for the design of future devices.

  15. Schottky barrier height tuning using P+ DSS for NMOS contact resistance reduction

    Science.gov (United States)

    Khaja, Fareen Adeni; Rao, K. V.; Ni, Chi-Nung; Muthukrishnan, Shankar; Lei, Jianxin; Darlark, Andrew; Peidous, Igor; Brand, Adam; Henry, Todd; Variam, Naushad

    2012-11-01

    Nickel silicide (NiSi) contacts are adopted in advanced CMOS technology nodes as they demonstrate several benefits such as low resistivity, low Si consumption and formation temperature. But a disadvantage of NiSi contacts is that they exhibit high electron Schottky barrier height (SBH), which results in high contact resistance (Rc) and reduces the NMOS drive current. To reduce SBH for NMOS, we used phosphorous (P) ion implantation into NiPt silicide with optimized anneal in order to form dopant segregated Schottky (DSS). Electrical characterization was performed using test structures such as Transmission Line Model, Cross-Bridge Kelvin Resistor, Van der Pauw and diodes to extract Rc and understand the effects of P+ DSS on ΦBn tuning. Material characterization was performed using SIMS, SEM and TEM analysis. We report ˜45% reduction in Rc over reference sample by optimizing ion implantation and anneal conditions (spike RTA, milli-second laser anneals (DSA)).

  16. Vertically grown Ge nanowire Schottky diodes on Si and Ge substrates

    Science.gov (United States)

    Chandra, Nishant; Tracy, Clarence J.; Cho, Jeong-Hyun; Picraux, S. T.; Hathwar, Raghuraj; Goodnick, Stephen M.

    2015-07-01

    The processing and performance of Schottky diodes formed from arrays of vertical Ge nanowires (NWs) grown on Ge and Si substrates are reported. The goal of this work is to investigate CMOS compatible processes for integrating NWs as components of vertically scaled integrated circuits, and elucidate transport in vertical Schottky NWs. Vertical phosphorus (P) doped Ge NWs were grown using vapor-liquid-solid epitaxy, and nickel (Ni)-Ge Schottky contacts were made to the tops of the NWs. Current-voltage (I-V) characteristics were measured for variable ranges of NW diameters and numbers of nanowires in the arrays, and the I-V characteristics were fit using modified thermionic emission theory to extract the barrier height and ideality factor. As grown NWs did not show rectifying behavior due to the presence of heavy P side-wall doping during growth, resulting in a tunnel contact. After sidewall etching using a dilute peroxide solution, rectifying behavior was obtained. Schottky barrier heights of 0.3-0.4 V and ideality factors close to 2 were extracted using thermionic emission theory, although the model does not give an accurate fit across the whole bias range. Attempts to account for enhanced side-wall conduction due to non-uniform P doping profile during growth through a simple shunt resistance improve the fit, but are still insufficient to provide a good fit. Full three-dimensional numerical modeling using Silvaco Atlas indicates that at least part of this effect is due to the presence of fixed charge and acceptor like traps on the NW surface, which leads to effectively high ideality factors.

  17. Schottky diode based on WS2 crossed with PEDOT/PSSA

    Science.gov (United States)

    Ortiz, Deliris; Pinto, Nicholas; Naylor, Carl; Johnson, A. T. Charlie

    An easy technique to fabricate a Schottky diode with WS2 and PEDOT-PSSA under ambient conditions is presented. WS2 is an air stable transition metal dichalcogenide semiconductor. When connected as a field effect transistor, WS2 exhibited n-type behavior with a charge mobility of ~7cm2/V-s on SiO2. PEDOT/PSSA is a conducting polymer that can be electro-spun to form fibers with a conductivity of ~1 S/cm. In this work we fabricated a Schottky diode by crossing a CVD grown monolayer WS2 crystal with a single electro-spun PEDOT/PSSA fiber. The resulting diode characteristics were analyzed assuming the standard thermionic emission model of a Schottky junction. Analysis of the results includes the ideality parameter of 4.75, diode rectification ratio ~10, and a turn on voltage of 1.4V. Efforts to investigate if these parameters are tunable with a back gate will also be presented. This work was supported by NSF-DMR-1523463 and NSF DMR RUI-1360772. ATJ acknowledges support from EFRI 2DARE EFMA-1542879.

  18. Analytical modeling of Schottky tunneling source impact ionization MOSFET with reduced breakdown voltage

    Directory of Open Access Journals (Sweden)

    Sangeeta Singh

    2016-03-01

    Full Text Available In this paper, we have investigated a novel Schottky tunneling source impact ionization MOSFET (STS-IMOS to lower the breakdown voltage of conventional impact ionization MOS (IMOS and developed an analytical model for the same. In STS-IMOS there is an accumulative effect of both impact ionization and source induced barrier tunneling. The silicide source offers very low parasitic resistance, the outcome of which is an increment in voltage drop across the intrinsic region for the same applied bias. This reduces operating voltage and hence, it exhibits a significant reduction in both breakdown and threshold voltage. STS-IMOS shows high immunity against hot electron damage. As a result of this the device reliability increases magnificently. The analytical model for impact ionization current (Iii is developed based on the integration of ionization integral (M. Similarly, to get Schottky tunneling current (ITun expression, Wentzel–Kramers–Brillouin (WKB approximation is employed. Analytical models for threshold voltage and subthreshold slope is optimized against Schottky barrier height (ϕB variation. The expression for the drain current is computed as a function of gate-to-drain bias via integral expression. It is validated by comparing it with the technology computer-aided design (TCAD simulation results as well. In essence, this analytical framework provides the physical background for better understanding of STS-IMOS and its performance estimation.

  19. High Voltage GaN Schottky Rectifiers

    Energy Technology Data Exchange (ETDEWEB)

    CAO,X.A.; CHO,H.; CHU,S.N.G.; CHUO,C.-C.; CHYI,J.-I.; DANG,G.T.; HAN,JUNG; LEE,C.-M.; PEARTON,S.J.; REN,F.; WILSON,R.G.; ZHANG,A.P.

    1999-10-25

    Mesa and planar GaN Schottky diode rectifiers with reverse breakdown voltages (V{sub RB}) up to 550V and >2000V, respectively, have been fabricated. The on-state resistance, R{sub ON}, was 6m{Omega}{center_dot} cm{sup 2} and 0.8{Omega}cm{sup 2}, respectively, producing figure-of-merit values for (V{sub RB}){sup 2}/R{sub ON} in the range 5-48 MW{center_dot}cm{sup -2}. At low biases the reverse leakage current was proportional to the size of the rectifying contact perimeter, while at high biases the current was proportional to the area of this contact. These results suggest that at low reverse biases, the leakage is dominated by the surface component, while at higher biases the bulk component dominates. On-state voltages were 3.5V for the 550V diodes and {ge}15 for the 2kV diodes. Reverse recovery times were <0.2{micro}sec for devices switched from a forward current density of {approx}500A{center_dot}cm{sup -2} to a reverse bias of 100V.

  20. Influence of nanostructure Fe-doped ZnO interlayer on the electrical properties of Au/n-type InP Schottky structure

    Energy Technology Data Exchange (ETDEWEB)

    Padma, R.; Balaram, N.; Reddy, I. Neelakanta; Reddy, V. Rajagopal, E-mail: reddy_vrg@rediffmail.com

    2016-07-01

    The Au/Fe-doped ZnO/n-InP metal/interlayer/semiconductor (MIS) Schottky structure is fabricated with Fe-doped ZnO nanostructure (NS) as an interlayer. The field emission scanning electron microscopy and atomic force microscopy results demonstrated that the surface morphology of the Fe−ZnO NS on n-InP is fairly smooth. The x-ray diffraction results reveal that the average grain size of the Fe−ZnO film is 12.35 nm. The electrical properties of the Au/n-InP metal-semiconductor (MS) and Au/Fe−ZnO NS/n-InP MIS Schottky structures are investigated by current-voltage and capacitance-voltage measurements at room temperature. The Au/Fe−ZnO NS/n-InP MIS Schottky structure has good rectifying ratio with low-leakage current compared to the Au/n-InP MS structure. The barrier height obtained for the MIS structure is higher than those of MS Schottky structure because of the modification of the effective barrier height by the Fe−ZnO NS interlayer. Further, the barrier height, ideality factor and series resistance are determined for the MS and MIS Schottky structures using Norde and Cheung's functions and compared to each other. The estimated interface state density of MIS Schottky structure is lower than that of MS Schottky structure. Experimental results revealed that the Poole-Frenkel emission is the dominant conduction mechanism in the lower bias region whereas Schottky emission is the dominant in the higher bias region for both the Au/n-InP MS and Au/Fe−ZnO NS/n-InP MIS Schottky structures. - Highlights: • Barrier height of Au/n-InP Schottky diode was modified by Fe−ZnO nanostructure interlayer. • MIS structure has a good rectification ratio compared to the MS structure. • The interface state density of MIS structure is lower than that of MS structure. • Poole-Frenkel mechanism is found to dominate in both MS and MIS structure.

  1. Recent Progress in Ohmic/Schottky-Contacted ZnO Nanowire Sensors

    National Research Council Canada - National Science Library

    Zhao, Xiaoli; Zhou, Ranran; Hua, Qilin; Dong, Lin; Yu, Ruomeng; Pan, Caofeng

    2015-01-01

      We review the recent progress of zinc oxide (ZnO) nanowire sensors with ohmic-contacted and Schottky-contacted configurations and the enhancement of the performances of Schottky-contacted ZnO NW sensors (SCZNSs...

  2. Crystal defects observed by the etch-pit method and their effects on Schottky-barrier-diode characteristics on (\\bar{2}01) β-Ga2O3

    Science.gov (United States)

    Kasu, Makoto; Oshima, Takayoshi; Hanada, Kenji; Moribayashi, Tomoya; Hashiguchi, Akihiro; Oishi, Toshiyuki; Koshi, Kimiyoshi; Sasaki, Kohei; Kuramata, Akito; Ueda, Osamu

    2017-09-01

    A pixel array of vertical Schottky-barrier diodes (SBDs) was fabricated and measured on the surface of a (\\bar{2}01) β-Ga2O3 single crystal. Subsequently, etch pits and patterns were observed on the same surface. Three types of etch pits were discovered: (1) a line-shaped etch pattern originating from a void and extending toward the [010] direction, (2) an arrow-shaped etch pit whose arrow’s head faces toward the [102] direction and, (3) a gourd-shaped etch pit whose point head faces toward the [102] direction. Their average densities were estimated to be 5 × 102, 7 × 104, and 9 × 104 cm-2, respectively. We confirmed no clear relationship between the leakage current in SBDs and these crystalline defects. Such results are obtained because threading dislocations run mainly in the [010] growth direction and do not go through the (\\bar{2}01) sample plate.

  3. Modulation of electrical properties in Cu/n-type InP Schottky junctions using oxygen plasma treatment

    Science.gov (United States)

    Kim, Hogyoung; Cho, Yunae; Jung, Chan Yeong; Kim, Se Hyun; Kim, Dong-Wook

    2015-12-01

    Using current-voltage (I-V) measurements, we investigated the effect of oxygen plasma treatment on the temperature-dependent electrical properties of Cu/n-type indium phosphide (InP) Schottky contacts at temperatures in the range 100-300 K. Changes in the electrical parameters were evident below 180 K for the low-plasma-power sample (100 W), which is indicative of the presence of a wider distribution of regions of low barrier height. Modified Richardson plots were used to obtain Richardson constants, which were similar to the theoretical value of 9.4 A cm-2 K-2 for n-type InP. This suggests that, for all the samples, a thermionic emission model including a spatially inhomogeneous Schottky barrier can be used to describe the charge transport phenomena at the metal/semiconductor interface. The voltage dependence of the reverse-bias current revealed that Schottky emission was dominant for the untreated and high-plasma-power (250 W) samples. For the low-plasma-power sample, Poole-Frenkel emission was dominant at low voltages, whereas Schottky emission dominated at higher voltages. Defect states and nonuniformity of the interfacial layer appear to be significant in the reverse-bias charge transport properties of the low-plasma-power sample.

  4. Schottky barrier tuning of the graphene/SnS2 van der Waals heterostructures through electric field

    Science.gov (United States)

    Zhang, Fang; Li, Wei; Ma, Yaqiang; Dai, Xianqi

    2018-03-01

    Combining the electronic structures of two-dimensional monolayers in ultrathin hybrid nanocomposites is expected to display new properties beyond their single components. The effects of external electric field (Eext) on the electronic structures of monolayer SnS2 with graphene hybrid heterobilayers are studied by using the first-principle calculations. It is demonstrated that the intrinsic electronic properties of SnS2 and graphene are quite well preserved due to the weak van der Waals (vdW) interactions. We find that the n-type Schottky contacts with the significantly small Schottky barrier are formed at the graphene/SnS2 interface. In the graphene/SnS2 heterostructure, the vertical Eext can control not only the Schottky barriers (n-type and p-type) but also contact types (Schottky contact or Ohmic contact) at the interface. The present study would open a new avenue for application of ultrathin graphene/SnS2 heterostructures in future nano- and optoelectronics.

  5. High-performance single CdS nanowire (nanobelt) Schottky junction solar cells with Au/graphene Schottky electrodes.

    Science.gov (United States)

    Ye, Yu; Dai, Yu; Dai, Lun; Shi, Zujin; Liu, Nan; Wang, Fei; Fu, Lei; Peng, Ruomin; Wen, Xiaonan; Chen, Zhijian; Liu, Zhongfan; Qin, Guogang

    2010-12-01

    High-performance single CdS nanowire (NW) as well as nanobelt (NB) Schottky junction solar cells were fabricated. Au (5 nm)/graphene combined layers were used as the Schottky contact electrodes to the NWs (NBs). Typical as-fabricated NW solar cell shows excellent photovoltaic behavior with an open circuit voltage of ∼0.15 V, a short circuit current of ∼275.0 pA, and an energy conversion efficiency of up to ∼1.65%. The physical mechanism of the combined Schottky electrode was discussed. We attribute the prominent capability of the devices to the high-performance Schottky combined electrode, which has the merits of low series resistance, high transparency, and good Schottky contact to the CdS NW (NB). Besides, a promising site-controllable patterned graphene transfer method, which has the advantages of economizing graphene material and free from additional etching process, was demonstrated in this work. Our results suggest that semiconductor NWs (NBs) are promising materials for novel solar cells, which have potential application in integrated nano-optoelectronic systems.

  6. Richardson-Schottky transport mechanism in ZnS nanoparticles

    Directory of Open Access Journals (Sweden)

    Hassan Ali

    2016-05-01

    Full Text Available We report the synthesis and electrical transport mechanism in ZnS semiconductor nanoparticles. Temperature dependent direct current transport measurements on the compacts of ZnS have been performed to investigate the transport mechanism for temperature ranging from 300 K to 400 K. High frequency dielectric constant has been used to obtain the theoretical values of Richardson-Schottky and Poole-Frenkel barrier lowering coefficients. Experimental value of the barrier lowering coefficient has been calculated from conductance-voltage characteristics. The experimental value of barrier lowering coefficient βexp lies close to the theoretical value of Richardson-Schottky barrier lowering coefficient βth,RS showing Richardson-Schottky emission has been responsible for conduction in ZnS nanoparticles for the temperature range studied.

  7. Richardson-Schottky transport mechanism in ZnS nanoparticles

    Science.gov (United States)

    Ali, Hassan; Khan, Usman; Rafiq, M. A.; Falak, Attia; Narain, Adeela; Jing, Tang; Xu, Xiulai

    2016-05-01

    We report the synthesis and electrical transport mechanism in ZnS semiconductor nanoparticles. Temperature dependent direct current transport measurements on the compacts of ZnS have been performed to investigate the transport mechanism for temperature ranging from 300 K to 400 K. High frequency dielectric constant has been used to obtain the theoretical values of Richardson-Schottky and Poole-Frenkel barrier lowering coefficients. Experimental value of the barrier lowering coefficient has been calculated from conductance-voltage characteristics. The experimental value of barrier lowering coefficient βexp lies close to the theoretical value of Richardson-Schottky barrier lowering coefficient βth,RS showing Richardson-Schottky emission has been responsible for conduction in ZnS nanoparticles for the temperature range studied.

  8. Spatial inhomogeneous barrier heights at graphene/semiconductor Schottky junctions

    Science.gov (United States)

    Tomer, Dushyant

    Graphene, a semimetal with linear energy dispersion, forms Schottky junction when interfaced with a semiconductor. This dissertation presents temperature dependent current-voltage and scanning tunneling microscopy/spectroscopy (STM/S) measurements performed on graphene Schottky junctions formed with both three and two dimensional semiconductors. To fabricate Schottky junctions, we transfer chemical vapor deposited monolayer graphene onto Si- and C-face SiC, Si, GaAs and MoS2 semiconducting substrates using polymer assisted chemical method. We observe three main type of intrinsic spatial inhomogeneities, graphene ripples, ridges and semiconductor steps in STM imaging that can exist at graphene/semiconductor junctions. Tunneling spectroscopy measurements reveal fluctuations in graphene Dirac point position, which is directly related to the Schottky barrier height. We find a direct correlation of Dirac point variation with the topographic undulations of graphene ripples at the graphene/SiC junction. However, no such correlation is established at graphene/Si and Graphene/GaAs junctions and Dirac point variations are attributed to surface states and trapped charges at the interface. In addition to graphene ripples and ridges, we also observe atomic scale moire patterns at graphene/MoS2 junction due to van der Waals interaction at the interface. Periodic topographic modulations due to moire pattern do not lead to local variation in graphene Dirac point, indicating that moire pattern does not contribute to fluctuations in electronic properties of the heterojunction. We perform temperature dependent current-voltage measurements to investigate the impact of topographic inhomogeneities on electrical properties of the Schottky junctions. We observe temperature dependence in junction parameters, such as Schottky barrier height and ideality factor, for all types of Schottky junctions in forward bias measurements. Standard thermionic emission theory which assumes a perfect

  9. Silver-Rutile Schottky Diode Fabricated on Oxidized Titanium Foil

    Energy Technology Data Exchange (ETDEWEB)

    Rahbarpour, Saeedeh; Purahmad, Mohsen, E-mail: s.rahbarpour@ee.kntu.ac.ir, E-mail: m.purahmad@ee.kntu.ac.ir [Electrical Engineering Department, K.N. Toosi University of Technology, Tehran (Iran, Islamic Republic of)

    2011-02-15

    The fabrication and characterization of a gas sensing Ag-TiO2 Schottky diode are reported. The fabricated Ag-TiO2-Ti structure, formed by sintering silver nanoparticles on the thermally oxidized titanium foil, demonstrated I-V characteristics of a typical Schottky diode at elevated temperatures up to 500 deg. C. The I-V characteristics of these devices strongly depended on the concentration level of the reducing gas contaminants in the surrounding atmosphere. The samples performed like high-barrier Schottky diodes in clean air, while behaved as ohmic contacts in highly reducing atmospheres. Different concentration levels of the examined alcohol vapours could increase the reverse current of the diodes up to 5 orders of magnitude. The measured electronic features of the device were described via an energy band diagram model.

  10. TCAD analysis of graphene silicon Schottky junction solar cell

    Science.gov (United States)

    Kuang, Yawei; Liu, Yushen; Ma, Yulong; Xu, Jing; Yang, Xifeng; Feng, Jinfu

    2015-08-01

    The performance of graphene based Schottky junction solar cell on silicon substrate is studied theoretically by TCAD Silvaco tools. We calculate the current-voltage curves and internal quantum efficiency of this device at different conditions using tow dimensional model. The results show that the power conversion efficiency of Schottky solar cell dependents on the work function of graphene and the physical properties of silicon such as thickness and doping concentration. At higher concentration of 1e17cm-3 for n-type silicon, the dark current got a sharp rise compared with lower doping concentration which implies a convert of electron emission mechanism. The biggest fill factor got at higher phos doping predicts a new direction for higher performance graphene Schottky solar cell design.

  11. Simulation and measurement of the resonant Schottky pickup

    Science.gov (United States)

    Zang, Yong-Dong; Wu, Jun-Xia; Zhao, Tie-Cheng; Zhang, Sheng-Hu; Mao, Rui-Shi; Xu, Hu-Shan; Sun, Zhi-Yu; Ma, Xin-Wen; Tu, Xiao-Lin; Xiao, Guo-Qing; Nolden, F.; Hülsmann, P.; Yu., A. Litvinov; Peschke, C.; Petri, P.; S. Sanjari, M.; Steck, M.

    2011-12-01

    A resonant Schottky pickup with high sensitivity, built by GSI, will be used for nuclear mass and lifetime measurement at CSRe. The basic concepts of Schottky noise signals, a brief introduction of the geometry of the detector, the transient response of the detector, and MAFIA simulated and perturbation measured results of characteristics are presented in this paper. The resonant frequency of the pickup is about 243 MHz and can be slightly changed at a range of 3 MHz. The unloaded quality factor is about 1072 and the shunt impedance is 76 kΩ. The measured results of the characteristics are in agreement with the MAFIA simulations.

  12. Improved performance of Schottky diodes on pendeoepitaxial gallium nitride

    Science.gov (United States)

    Zheleva, T.; Derenge, M.; Ewing, D.; Shah, P.; Jones, K.; Lee, U.; Robins, L.

    2008-09-01

    We designed experiments to investigate the role of dislocation density on the performance of Schottky diodes fabricated on a GaN material grown conventionally and by pendeo-epitaxy. Devices of varying geometries were fabricated on low defect density GaN regions grown selectively via pendeo-epitaxy. In addition, corresponding devices were fabricated on the conventional GaN material with a high density of dislocations. Schottky diodes fabricated on pendeo-material showed nearly two orders of magnitude lower leakage current and displayed improved ideality factor, while diodes built on a conventional material displayed nonideal characteristics.

  13. Novel palladium germanide schottky contact for high performance schottky barrier ge MOSFETs and characterization of its leakage current mechanism.

    Science.gov (United States)

    Oh, Se-Kyung; Shin, Hong-Sik; Kang, Min-Ho; Lee, Ga-Won; Lee, Hi-Deok

    2012-07-01

    The leakage current mechanism of Palladium (Pd) germanide Schottky contact on n-type Ge-on-Si substrate is analyzed in depth. The electric field dependent analysis shows that the dominant leakage current mechanism is the Poole-Frenkel emission due to the existence of deep level traps in the depletion region of the Pd germanide/n-type Ge Schottky diode. The analysis of the dependence of leakage current on temperature also shows that the Poole-Frenkel emission and generation current are the dominant components below 100 degrees C and that the Schottky emission related to thermionic emission of majority carriers over a potential barrier is the main cause of this dominance at high temperature region.

  14. Carbon nanotube Schottky diodes using Ti-Schottky and Pt-ohmic contacts for high frequency applications

    Science.gov (United States)

    Manohara, Harish M.; Wong, Eric W.; Schlecht, Erich; Hunt, Brian D.; Siegel, Peter H.

    2005-01-01

    We have demonstrated Schottky diodes using semiconducting single-walled nanotubes (s-SWNTs) with titanium Schottky and platinum Ohmic contacts for high-frequency applications. The diodes are fabricated using angled evaporation of dissimilar metal contacts over an s-SWNT. The devices demonstrate rectifying behavior with large reverse bias breakdown voltages of greater than 15 V. To decrease the series resistance, multiple SWNTs are grown in parallel in a single device, and the metallic tubes are burnt-out selectively. At low biases these diodes showed ideality factors in the range of 1.5 to 1.9. Modeling of these diodes as direct detectors at room temperature at 2.5 terahertz (THz) frequency indicates noise equivalent powers (NEP) potentially comparable to that of the state-of-the-art gallium arsenide solid-state Schottky diodes, in the range of 10-13 W(square root)xHz.

  15. The electrical characterization and response to hydrogen of Schottky diodes with a resistive metal electrode-rectifying an oversight in Schottky diode investigation

    Energy Technology Data Exchange (ETDEWEB)

    Dawson, P; Feng, L; Penate-Quesada, L [Centre for Nanostructured Media, School of Maths and Physics, Queen' s University of Belfast, Belfast BT7 1NN (United Kingdom); Hill, G [EPSRC National Centre for III-V Technologies, Mappin Street, University ofSheffield, Sheffield S1 3JD (United Kingdom); Mitra, J, E-mail: P.dawson@qub.ac.uk

    2011-03-30

    Schottky-barrier structures with a resistive metal electrode are examined using the 4-point probe method where the probes are connected to the metal electrode only. The observation of a significant decrease in resistance with increasing temperature (over a range of {approx}100 K) in the diode resistance-temperature (R{sub D}-T) characteristic is considered due to charge carrier confinement to the metal electrode at low temperature (high resistance), with the semiconductor progressively opening up as a parallel current carrying channel (low resistance) with increasing temperature due to increasing thermionic emission across the barrier. A simple model is constructed, based on thermionic emission at quasi-zero bias, that generates good fits to the experimental data. The negative differential resistance (NDR) region in the R{sub D}-T characteristic is a general effect and is demonstrated across a broad temperature range for a variety of Schottky structures grown on Si-, GaAs- and InP-substrates. In addition the NDR effect is harnessed in micro-scaled Pd/n-InP devices for the detection of low levels of hydrogen in an ambient atmosphere of nitrogen.

  16. Electrical and structural properties of (Pd/Au) Schottky contact to as grown and rapid thermally annealed GaN grown by MBE

    Energy Technology Data Exchange (ETDEWEB)

    Nirwal, Varun Singh, E-mail: varun.nirwal30@gmail.com; Singh, Joginder; Gautam, Khyati; Peta, Koteswara Rao [Department of Electronic Science, University of Delhi South Campus, Benito Juarez Road, New Delhi-110021 (India)

    2016-05-06

    We studied effect of thermally annealed GaN surface on the electrical and structural properties of (Pd/Au) Schottky contact to Ga-polar GaN grown by molecular beam epitaxy on Si substrate. Current voltage (I-V) measurement was used to study electrical properties while X-ray diffraction (XRD) measurement was used to study structural properties. The Schottky barrier height calculated using I-V characteristics was 0.59 eV for (Pd/Au) Schottky contact on as grown GaN, which increased to 0.73 eV for the Schottky contact fabricated on 700 °C annealed GaN film. The reverse bias leakage current at -1 V was also significantly reduced from 6.42×10{sup −5} A to 7.31×10{sup −7} A after annealing. The value of series resistance (Rs) was extracted from Cheung method and the value of R{sub s} decreased from 373 Ω to 172 Ω after annealing. XRD results revealed the formation of gallide phases at the interface of (Pd/Au) and GaN for annealed sample, which could be the reason for improvement in the electrical properties of Schottky contact after annealing.

  17. Electrical properties of planar AlGaN/GaN Schottky diodes: Role of 2DEG and analysis of non-idealities

    Science.gov (United States)

    Persano, Anna; Pio, Iolanda; Tasco, Vittorianna; Cuscunà, Massimo; Passaseo, Adriana; Cola, Adriano

    2017-04-01

    A detailed study of the electrical properties of planar AlGaN/GaN Schottky diodes is presented, the focus being on the role of the two dimensional electron gas (2DEG) depletion and the diodes non-idealities in different voltage regimes. The 2DEG depletion behavior is inferred from the analysis of capacitance and current measurements with transition from vertical to lateral diode operation occurring at Vpinch-off = 4 V. In particular, the sub-micrometer depletion width, laterally extending from the edge of the Schottky contact under high reverse voltages, is evaluated on the basis of a simple fringe capacitance model. Current transport mechanisms are discussed, investigating the interrelation between 2DEG, Poole-Frenkel effect, and defects. With regard to defects, the role of dislocations in the AlGaN/GaN diode non-idealities, usually interpreted in terms of Schottky barrier inhomogeneities, is critically addressed. Photocurrent spatial mapping under high reverse voltage points out the not uniform electric field distribution around the Schottky contact and highlights the presence of local photo-conductive paths, likely associated with the dislocations near the edge of the Schottky contact.

  18. First principle study on the electronic properties and Schottky contact of graphene adsorbed on MoS2 monolayer under applied out-plane strain

    Science.gov (United States)

    Phuc, Huynh V.; Hieu, Nguyen N.; Hoi, Bui D.; Phuong, Le T. T.; Nguyen, Chuong V.

    2018-02-01

    In the present work, electronic properties and Schottky contact of graphene adsorbed on the MoS2 monolayer under applied out-plane strain are studied using density functional theory calculations. Our calculations show that weak van derpp Waals interactions between graphene and monolayer MoS2 are dominated at the interlayer distance of 3.34 Å and the binding energy per C atom of - 25.1 meV. A narrow band gap of 3.6 meV has opened in G/MoS2 heterointerface, and it can be modulated by the out-plane strain. Furthermore, the Schottky barrier and Schottky contact types in the G/MoS2 heterointerface can be controlled by the out-plane strain. At the equilibrium state (d = 3.34 Å), the intrinsic electronic structure of G/MoS2 heterointerface is well preserved and forms an n-type Schottky barrier of 0.49 eV. When the interlayer distance decreases, the transition from n-type to p-type Schottky contact occurs at d = 2.74 Å. Our studies promote the application of ultrathin G/MoS2 heterointerface in the next-generation nanoelectronic and photonic devices such as van-der-Waals-based field effect transistors.

  19. Silicon Schottky photovoltaic diodes for solar energy conversion

    Science.gov (United States)

    Anderson, W. A.

    1975-01-01

    Various factors in Schottky barrier solar cell fabrication are evaluated in order to improve understanding of the current flow mechanism and to isolate processing variables that improve efficiency. Results of finger design, substrate resistivity, surface finishing and activation energy studies are detailed. An increased fill factor was obtained by baking of the vacuum system to remove moisture.

  20. Enhanced Plasmonic Light Absorption for Silicon Schottky-Barrier Photodetectors

    DEFF Research Database (Denmark)

    Hashemi, Mahdieh; Farzad, Mahmood Hosseini; Mortensen, N. Asger

    2013-01-01

    is transferred into hot carriers near the Schottky barrier. The proposed broadband photodetector with a bi-grating metallic structure on the silicon substrate enables to absorb 76 % of the infrared light in the metal with a 200-nm bandwidth, while staying insensitive to the incident angle. These results pave...

  1. Electrical Properties of Self-Assembled Nano-Schottky Diodes

    Directory of Open Access Journals (Sweden)

    F. Ruffino

    2008-01-01

    Full Text Available A bottom-up methodology to fabricate a nanostructured material by Au nanoclusters on 6H-SiC surface is illustrated. Furthermore, a methodology to control its structural properties by thermal-induced self-organization of the Au nanoclusters is demonstrated. To this aim, the self-organization kinetic mechanisms of Au nanoclusters on SiC surface were experimentally studied by scanning electron microscopy, atomic force microscopy, Rutherford backscattering spectrometry and theoretically modelled by a ripening process. The fabricated nanostructured materials were used to probe, by local conductive atomic force microscopy analyses, the electrical properties of nano-Schottky contact Au nanocluster/SiC. Strong efforts were dedicated to correlate the structural and electrical characteristics: the main observation was the Schottky barrier height dependence of the nano-Schottky contact on the cluster size. Such behavior was interpreted considering the physics of few electron quantum dots merged with the concepts of ballistic transport and thermoionic emission finding a satisfying agreement between the theoretical prediction and the experimental data. The fabricated Au nanocluster/SiC nanocontact is suggested as a prototype of nano-Schottky diode integrable in complex nanoelectronic circuits.

  2. New Schottky-Pickup for COSY-Jülich

    CERN Document Server

    Mohos, I; Dietrich, J; Klehr, F

    2001-01-01

    A new Schottky-pickup for the Cooler Synchrotron COSY at the Forschungszentrum J?lich was developed, tested and installed. The new pickup with four diagonally arranged plates replaces the two 1 m long Schottky-pickups used until now in COSY. The previous ones were removed mainly to gain space for new installations (e.g. rf-cavity, experimental devices), but also to increase the horizontal aperture. The available space for the new pickup is only 0.8 m. The pickup plates can be combined by means of relays to measure either in the horizontal or in the vertical plane. The pickup can also be used either as a sensitive broadband beam position monitor or as a tuneable narrowband pickup for Schottky-noise analysis with ultahigh sensitivity. A new method for resonant tuning of the Schottky-pickups for transversal measurements was developed. The differentially excited resonant circuitry enhances the sensitivity by about a factor of 30. The pickups are also used for dynamical tune measurements (tune meter) in the accele...

  3. Analysis of Heavy Ion Irradiation Induced Thermal Damage in SiC Schottky Diodes

    Science.gov (United States)

    Abbate, C.; Busatto, G.; Cova, P.; Delmonte, N.; Giuliani, F.; Iannuzzo, F.; Sanseverino, A.; Velardi, F.

    2015-02-01

    A study is presented aimed at describing phenomena involved in Single Event Burnout induced by heavy ion irradiation in SiC Schottky diodes. On the basis of experimental data obtained for 79Br irradiation at different energies, electro-thermal FEM is used to demonstrate that the failure is caused by a strong local increase of the semiconductor temperature. With respect to previous studies the temperature dependent thermal material properties were added. The critical ion energy calculated by this model is in agreement with literature experimental results. The substrate doping dependence of the SEE robustness was analyzed, proving the effectiveness of the developed model for device technological improvements.

  4. Surface plasma-enhanced internal photoemission in gallium arsenide Schottky diodes.

    Science.gov (United States)

    Torosian, K M; Karakashian, A S; Teng, Y Y

    1987-07-01

    An aluminum on n-type gallium arsenide Schottky diode with a prism coupler on the front face was illuminated by a p-polarized Nd:YAG laser to excite the surface plasma resonance in the aluminum barrier contact. The internal photoemission current and reflectance were measured simultaneously as a function of the angle of incidence. The excitation of the surface plasma resonance was observed by a dip in the reflectance which occurred at the same angle as a peak in the photoemission current. These effects disappeared in the case of s-polarization. Enhancement in the photoemission current by as much as a factor of 3 was obtained.

  5. Dependence of the Photocurrent of a Schottky-Barrier Solar Cell on the Back Surface Recombination Velocity and Suggestion for a Structure with Improved Performance

    Directory of Open Access Journals (Sweden)

    Avigyan Chatterjee

    2015-01-01

    Full Text Available Though Schottky-barrier solar cells have been studied extensively previously, not much work has been done recently on these cells, because of the fact that conventional p-n junction silicon solar cells have much higher efficiency and have attracted the attention of most of the researchers. However, the Schottky-barrier solar cells have the advantage of simple and economical fabrication process. In this paper, the effect of back surface recombination velocity on the minority carrier distribution and the spectral response of a Schottky-barrier silicon solar cell have been investigated and, based on this study, a new design of the cell with a back surface field has been suggested, which is expected to give much improved performance.

  6. Organic modification of metal / semiconductor Schottky contacts

    Energy Technology Data Exchange (ETDEWEB)

    Mendez Pinzon, H.A.

    2006-07-10

    In the present work a Metal / organic / inorganic semiconductor hybrid heterostructure (Ag / DiMe-PTCDI / GaAs) was built under UHV conditions and characterised in situ. The aim was to investigate the influence of the organic layer in the surface properties of GaAs(100) and in the electrical response of organic-modified Ag / GaAs Schottky diodes. The device was tested by combining surface-sensitive techniques (Photoemission spectroscopy and NEXAFS) with electrical measurements (current-voltage, capacitance-voltage, impedance and charge transient spectroscopies). Core level examination by PES confirms removal of native oxide layers on sulphur passivated (S-GaAs) and hydrogen plasma treated GaAs(100) (H+GaAs) surfaces. Additional deposition of ultrathin layers of DiMe-PTCDI may lead to a reduction of the surface defects density and thereby to an improvement of the electronic properties of GaAs. The energy level alignment through the heterostructure was deduced by combining UPS and I-V measurements. This allows fitting of the I-V characteristics with electron as majority carriers injected over a barrier by thermionic emission as a primary event. For thin organic layers (below 8 nm thickness) several techniques (UPS, I-V, C-V, QTS and AFM) show non homogeneous layer growth, leading to formation of voids. The coverage of the H+GaAs substrate as a function of the nominal thickness of DiMe-PTCDI was assessed via C-V measurements assuming a voltage independent capacitance of the organic layer. The frequency response of the device was evaluated through C-V and impedance measurements in the range 1 kHz-1 MHz. The almost independent behaviour of the capacitance in the measured frequency range confirmed the assumption of a near geometrical capacitor, which was used for modelling the impedance with an equivalent circuit of seven components. From there it was found a predominance of the space charge region impedance, so that A.C. conduction can only takes place through the

  7. Vertical and In-Plane Current Devices Using NbS2/n-MoS2van der Waals Schottky Junction and Graphene Contact.

    Science.gov (United States)

    Shin, Hyung Gon; Yoon, Hyong Seo; Kim, Jin Sung; Kim, Minju; Lim, June Yeong; Yu, Sanghyuck; Park, Ji Hoon; Yi, Yeonjin; Kim, Taekyeong; Jun, Seong Chan; Im, Seongil

    2018-02-08

    A van der Waals (vdW) Schottky junction between two-dimensional (2D) transition metal dichalcogenides (TMDs) is introduced here for both vertical and in-plane current devices: Schottky diodes and metal semiconductor field-effect transistors (MESFETs). The Schottky barrier between conducting NbS 2 and semiconducting n-MoS 2 appeared to be as large as ∼0.5 eV due to their work-function difference. While the Schottky diode shows an ideality factor of 1.8-4.0 with an on-to-off current ratio of 10 3 -10 5 , Schottky-effect MESFET displays little gate hysteresis and an ideal subthreshold swing of 60-80 mV/dec due to low-density traps at the vdW interface. All MESFETs operate with a low threshold gate voltage of -0.5 ∼ -1 V, exhibiting easy saturation. It was also found that the device mobility is significantly dependent on the condition of source/drain (S/D) contact for n-channel MoS 2 . The highest room temperature mobility in MESFET reaches to approximately more than 800 cm 2 /V s with graphene S/D contact. The NbS 2 /n-MoS 2 MESFET with graphene was successfully integrated into an organic piezoelectric touch sensor circuit with green OLED indicator, exploiting its predictable small threshold voltage, while NbS 2 /n-MoS 2 Schottky diodes with graphene were applied to extract doping concentrations in MoS 2 channel.

  8. High-Performance Schottky Diode Gas Sensor Based on the Heterojunction of Three-Dimensional Nanohybrids of Reduced Graphene Oxide-Vertical ZnO Nanorods on an AlGaN/GaN Layer.

    Science.gov (United States)

    Minh Triet, Nguyen; Thai Duy, Le; Hwang, Byeong-Ung; Hanif, Adeela; Siddiqui, Saqib; Park, Kyung-Ho; Cho, Chu-Young; Lee, Nae-Eung

    2017-09-13

    A Schottky diode based on a heterojunction of three-dimensional (3D) nanohybrid materials, formed by hybridizing reduced graphene oxide (RGO) with epitaxial vertical zinc oxide nanorods (ZnO NRs) and Al0.27GaN0.73(∼25 nm)/GaN is presented as a new class of high-performance chemical sensors. The RGO nanosheet layer coated on the ZnO NRs enables the formation of a direct Schottky contact with the AlGaN layer. The sensing results of the Schottky diode with respect to NO2, SO2, and HCHO gases exhibit high sensitivity (0.88-1.88 ppm-1), fast response (∼2 min), and good reproducibility down to 120 ppb concentration levels at room temperature. The sensing mechanism of the Schottky diode can be explained by the effective modulation of the reverse saturation current due to the change in thermionic emission carrier transport caused by ultrasensitive changes in the Schottky barrier of a van der Waals heterostructure between RGO and AlGaN layers upon interaction with gas molecules. Advances in the design of a Schottky diode gas sensor based on the heterojunction of high-mobility two-dimensional electron gas channel and highly responsive 3D-engineered sensing nanomaterials have potential not only for the enhancement of sensitivity and selectivity but also for improving operation capability at room temperature.

  9. A novel physical parameter extraction approach for Schottky diodes

    Science.gov (United States)

    Wang, Hao; Chen, Xing; Xu, Guang-Hui; Huang, Ka-Ma

    2015-07-01

    Parameter extraction is an important step for circuit simulation methods that are based on physical models of semiconductor devices. A novel physical parameter extraction approach for Schottky diodes is proposed in this paper. By employing a set of analytical formulas, this approach extracts all of the necessary physical parameters of the diode chip in a unique way. It then extracts the package parasitic parameters with a curve-fitting method. To validate the proposed approach, a model HSMS-282c commercial Schottky diode is taken as an example. Its physical parameters are extracted and used to simulate the diode’s electrical characteristics. The simulated results based on the extracted parameters are compared with the measurements and a good agreement is obtained, which verifies the feasibility and accuracy of the proposed approach. Project supported by the Joint Fund of the National Natural Science Foundation of China and the China Academy of Engineering Physics (Grant No. U1230112).

  10. Analysis of current transport properties in nonpolar a-plane ZnO-based Schottky diodes

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hogyoung [Seoul National University of Science and Technology, Seoul (Korea, Republic of); Kim, Haeri; Kim, Dongwook [Ewha Womans University, Seoul (Korea, Republic of)

    2014-09-15

    Using current-voltage (I - V) measurements, we investigated the temperature-dependent transport properties in Ag/nonpolar a-plane ZnO Schottky diodes. The bias-dependent ideality factors were altered by the different temperatures and showed a hump at lower temperatures. The series resistance of the diode depended on the temperatures, which was related to the number of free carriers contributing to the series resistance. For high forward bias, the slope m obtained from the lnI - lnV curves decreased with increasing temperature, assuring the space-charge-limited-current (SCLC) model controlled by an exponential distribution of traps. The reverse-biased current transport was associated with the Schottky effect, with a thermally-assisted tunneling for lower voltages and the Poole-Frenkel effect for higher voltages. The density of localized states (N{sub t}) was obtained by applying the theory of SCLC transport, which yielded a N{sub t} value of 8.32 x 10{sup 11} eV{sup -1}cm{sup -3}.

  11. Phase-Defined van der Waals Schottky Junctions with Significantly Enhanced Thermoelectric Properties.

    Science.gov (United States)

    Wang, Qiaoming; Yang, Liangliang; Zhou, Shengwen; Ye, Xianjun; Wang, Zhe; Zhu, Wenguang; McCluskey, Matthew D; Gu, Yi

    2017-07-06

    We demonstrate a van der Waals Schottky junction defined by crystalline phases of multilayer In 2 Se 3 . Besides ideal diode behaviors and the gate-tunable current rectification, the thermoelectric power is significantly enhanced in these junctions by more than three orders of magnitude compared with single-phase multilayer In 2 Se 3 , with the thermoelectric figure-of-merit approaching ∼1 at room temperature. Our results suggest that these significantly improved thermoelectric properties are not due to the 2D quantum confinement effects but instead are a consequence of the Schottky barrier at the junction interface, which leads to hot carrier transport and shifts the balance between thermally and field-driven currents. This "bulk" effect extends the advantages of van der Waals materials beyond the few-layer limit. Adopting such an approach of using energy barriers between van der Waals materials, where the interface states are minimal, is expected to enhance the thermoelectric performance in other 2D materials as well.

  12. Graphene/silicon nanowire Schottky junction for enhanced light harvesting.

    Science.gov (United States)

    Fan, Guifeng; Zhu, Hongwei; Wang, Kunlin; Wei, Jinquan; Li, Xinming; Shu, Qinke; Guo, Ning; Wu, Dehai

    2011-03-01

    Schottky junction solar cells are assembled by directly coating graphene films on n-type silicon nanowire (SiNW) arrays. The graphene/SiNW junction shows enhanced light trapping and faster carrier transport compared to the graphene/planar Si structure. With chemical doping, the SiNW-based solar cells showed energy conversion efficiencies of up to 2.86% at AM1.5 condition, opening a possibility of using graphene/semiconductor nanostructures in photovoltaic application.

  13. Silicide Schottky Contacts to Silicon: Screened Pinning at Defect Levels

    Energy Technology Data Exchange (ETDEWEB)

    Drummond, T.J.

    1999-03-11

    Silicide Schottky contacts can be as large as 0.955 eV (E{sub v} + 0.165 eV) on n-type silicon and as large as 1.05 eV (E{sub c} {minus} 0.07 eV) on p-type silicon. Current models of Schottky barrier formation do not provide a satisfactory explanation of occurrence of this wide variation. A model for understanding Schottky contacts via screened pinning at defect levels is presented. In the present paper it is shown that most transition metal silicides are pinned approximately 0.48 eV above the valence band by interstitial Si clusters. Rare earth disilicides pin close to the divacancy acceptor level 0.41 eV below the conduction band edge while high work function silicides of Ir and Pt pin close to the divacancy donor level 0.21 eV above the valence band edge. Selection of a particular defect pinning level depends strongly on the relative positions of the silicide work function and the defect energy level on an absolute energy scale.

  14. Metal-semiconductor Schottky barrier junctions and their applications

    CERN Document Server

    1984-01-01

    The present-day semiconductor technology would be inconceivable without extensive use of Schottky barrier junctions. In spite of an excellent book by Professor E.H. Rhoderick (1978) dealing with the basic principles of metal­ semiconductor contacts and a few recent review articles, the need for a monograph on "Metal-Semiconductor Schottky Barrier Junctions and Their Applications" has long been felt by students, researchers, and technologists. It was in this context that the idea of publishing such a monograph by Mr. Ellis H. Rosenberg, Senior Editor, Plenum Publishing Corporation, was considered very timely. Due to the numerous and varied applications of Schottky barrier junctions, the task of bringing it out, however, looked difficult in the beginning. After discussions at various levels, it was deemed appropriate to include only those typical applications which were extremely rich in R&D and still posed many challenges so that it could be brought out in the stipulated time frame. Keeping in view the la...

  15. Silver nanowires-templated metal oxide for broadband Schottky photodetector

    Energy Technology Data Exchange (ETDEWEB)

    Patel, Malkeshkumar; Kim, Hong-Sik; Kim, Joondong, E-mail: joonkim@inu.ac.kr [Photoelectric and Energy Device Application Lab (PEDAL) and Department of Electrical Engineering, Incheon National University, 119 Academy Rd. Yeonsu, Incheon 406772 (Korea, Republic of); Park, Hyeong-Ho [Applied Device and Material Lab., Device Technology Division, Korea Advanced Nano Fab Center (KANC), Suwon 443270 (Korea, Republic of)

    2016-04-04

    Silver nanowires (AgNWs)-templated transparent metal oxide layer was applied for Si Schottky junction device, which remarked the record fastest photoresponse of 3.4 μs. Self-operating AgNWs-templated Schottky photodetector showed broad wavelength photodetection with high responsivity (42.4 A W{sup −1}) and detectivity (2.75 × 10{sup 15} Jones). AgNWs-templated indium-tin-oxide (ITO) showed band-to-band excitation due to the internal photoemission, resulting in significant carrier collection performances. Functional metal oxide layer was formed by AgNWs-templated from ITO structure. The grown ITO above AgNWs has a cylindrical shape and acts as a thermal protector of AgNWs for high temperature environment without any deformation. We developed thermal stable AgNWs-templated transparent oxide devices and demonstrated the working mechanism of AgNWs-templated Schottky devices. We may propose the high potential of hybrid transparent layer design for various photoelectric applications, including solar cells.

  16. Towards substrate engineering of graphene-silicon Schottky diode photodetectors.

    Science.gov (United States)

    Selvi, Hakan; Unsuree, Nawapong; Whittaker, Eric; Halsall, Matthew P; Hill, Ernie W; Thomas, Andrew; Parkinson, Patrick; Echtermeyer, Tim J

    2018-02-01

    Graphene-silicon Schottky diode photodetectors possess beneficial properties such as high responsivities and detectivities, broad spectral wavelength operation and high operating speeds. Various routes and architectures have been employed in the past to fabricate devices. Devices are commonly based on the removal of the silicon-oxide layer on the surface of silicon by wet-etching before deposition of graphene on top of silicon to form the graphene-silicon Schottky junction. In this work, we systematically investigate the influence of the interfacial oxide layer, the fabrication technique employed and the silicon substrate on the light detection capabilities of graphene-silicon Schottky diode photodetectors. The properties of devices are investigated over a broad wavelength range from near-UV to short-/mid-infrared radiation, radiation intensities covering over five orders of magnitude as well as the suitability of devices for high speed operation. Results show that the interfacial layer, depending on the required application, is in fact beneficial to enhance the photodetection properties of such devices. Further, we demonstrate the influence of the silicon substrate on the spectral response and operating speed. Fabricated devices operate over a broad spectral wavelength range from the near-UV to the short-/mid-infrared (thermal) wavelength regime, exhibit high photovoltage responses approaching 106 V W-1 and short rise- and fall-times of tens of nanoseconds.

  17. Fluorine plasma treatment induced deep level traps and their effect on current transportation in Al0.83In0.17N/AlN/GaN Schottky barrier diodes

    Science.gov (United States)

    Xiang, Yong; Yu, Tongjun; Ji, Cheng; Cheng, Yutian; Yang, Xuelin; Kang, Xiangning; Shen, Bo; Zhang, Guoyi

    2016-08-01

    The deep level traps and the electrical properties of fluorine plasma treated (F-treated) and non-treated Al0.83In0.17N/AlN/GaN Schottky barrier diodes (SBDs) were investigated by the temperature-dependent current-voltage (I-V) and deep level transient spectroscopy (DLTS) measurements. Three deep level traps were detected in the SBD after F-treatment at ~E c  -  0.17 eV, ~E c  -  0.27 eV and ~E c  -  1.14 eV. One of the deep level traps at ~E c  -  1.14 eV is mainly located in the Al0.83In0.17N barrier layer with a captured cross section (σ) of ~6.50  ×  10-18 cm2. This F-related deep level trap has 3-4 orders of magnitude of the larger σ and ~0.46 eV greater active energy than that of the dislocation-related one at ~E c  -  0.68 eV with σ of ~1.92  ×  10-21 cm2. Meanwhile, the leakage current of F-treated SBD at  -5 V is reduced by ~2 orders of magnitude compared with that of the non-treated one. This leakage current reduction is mainly attributed to the increase of the Poole-Frenkel emission barrier height from ~0.09 eV in non-treated SBD to ~0.46 eV in the F-treated one. It is believed that the main reverse current transportation is the Poole-Frenkel emission from the F-related deep level trap states into the continuum states of the dislocations in F-treated Al0.83In0.17N/AlN/GaN SBD.

  18. New type of Schottky diode-based Cu-Al-Mn-Cr shape memory material films

    Science.gov (United States)

    Aksu Canbay, C.; Dere, A.; Mensah-Darkwa, Kwadwo; Al-Ghamdi, Ahmed; Karagoz Genç, Z.; Gupta, R. K.; Yakuphanoglu, F.

    2016-07-01

    Cr-doped CuAlMn shape memory alloys were produced by arc melting method. The effects of Cr content on microstructure and transformation parameters of were investigated. The alloys were characterized by X-ray analysis, optical microscope observations and differential scanning calorimetry measurements. The grain size of the alloys was decreased by the addition of Cr into CuAlMn alloy system. The martensite transformation temperature was shifted both the lower temperature and higher temperature with the addition of chromium. This change was explained on the basis of the change in the thermodynamics such as enthalpy, entropy and activation energy values. The obtained results indicate that the phase transformation temperatures of the CuAlMn alloy system can be controlled by addition of Cr. We fabricated a Schottky barrier diode and observed that ideality factor and barrier height increase with increasing temperature. The diodes exhibited a thermal sensor behavior. This indicates that Schottky diode-based Cu-Al-Mn-Cr shape memory material films can be used as a sensor in high-temperature measurement applications.

  19. Impact of defect distribution on IrOx/ZnO interface doping and Schottky barriers

    Science.gov (United States)

    Foster, Geoffrey M.; Gao, Hantian; Mackessy, Grace; Hyland, Alana M.; Allen, Martin W.; Wang, Buguo; Look, David C.; Brillson, Leonard J.

    2017-09-01

    We used depth-resolved cathodoluminescence spectroscopy (DRCLS) to measure the nature and spatial distribution of native point defects at Zn- and O-polar ZnO interfaces with iridium oxide (IrOx) and their impact on Schottky barrier formation. IrOx and other metal oxides exhibit higher Schottky barriers than their pure metal counterparts, consistent with wider depletion regions and potentially useful for ohmic contacts to p-type semiconductors. DRCLS with I-V and 1/C2-V barrier height and carrier profile measurements showed high zinc vacancy VZn and CuZn defect densities that compensate free carrier densities, increase depletion widths, and form higher effective barriers than Ir/ZnO contacts. Zn-polar versus O-polar ZnO interfaces with IrOx exhibit 40% higher VZn + CuZn interface segregation and lower carrier densities within a wider depletion region, accounting for the significantly higher (0.89 vs. 0.67 eV) barrier heights. Both the depth of VZn density segregation and the Zn-deficient layer thickness measured microscopically match the depletion width and applied electric fields comparable to spontaneous polarization fields across similar layers displaying analogous defect segregation. These results account for the difference in polarity-dependent segregation due to the electric field-driven diffusion of native defects near ZnO interfaces.

  20. Controllable Schottky barrier in GaSe/graphene heterostructure: the role of interface dipole

    Science.gov (United States)

    Si, Chen; Lin, Zuzhang; Zhou, Jian; Sun, Zhimei

    2017-03-01

    The discoveries of graphene and other related two-dimensional crystals have recently led to a new technology: van der Waals (vdW) heterostructures based on these atomically thin materials. Such a paradigm has been proved promising for a wide range of applications from nanoelectronics to optoelectronics and spintronics. Here, using first-principles calculations, we investigate the electronic structure and interface characteristics of a newly synthesized GaSe/graphene (GaSe/g) vdW heterostructure. We show that the intrinsic electronic properties of GaSe and graphene are both well preserved in the heterostructure, with a Schottky barrier formed at the GaSe/g interface. More interestingly, the band alignment between graphene and GaSe can be effectively modulated by tuning the interfacial distance or applying an external electric filed. This makes the Schottky barrier height (SBH) controllable, which is highly desirable in the electronic and optoelectronic devices based on vdW heterostructures. In particular, the tunability of the interface dipole and potential step is further uncovered to be the underlying mechanism that ensures this controllable tuning of SBH.

  1. High-performance Schottky heterojunction photodetector with directly grown graphene nanowalls as electrodes.

    Science.gov (United States)

    Shen, Jun; Liu, Xiangzhi; Song, Xuefen; Li, Xinming; Wang, Jun; Zhou, Quan; Luo, Shi; Feng, Wenlin; Wei, Xingzhan; Lu, Shirong; Feng, Shuanglong; Du, Chunlei; Wang, Yuefeng; Shi, Haofei; Wei, Dapeng

    2017-05-11

    Schottky heterojunctions based on graphene-silicon structures are promising for high-performance photodetectors. However, existing fabrication processes adopt transferred graphene as electrodes, limiting process compatibility and generating pollution because of the metal catalyst. In this report, photodetectors are fabricated using directly grown graphene nanowalls (GNWs) as electrodes. Due to the metal-free growth process, GNWs-Si heterojunctions with an ultralow measured current noise of 3.1 fA Hz-1/2 are obtained, and the as-prepared photodetectors demonstrate specific detectivities of 5.88 × 1013 cm Hz1/2 W-1 and 2.27 × 1014 cm Hz1/2 W-1 based on the measured and calculated noise current, respectively, under ambient conditions. These are among the highest reported values for planar silicon Schottky photodetectors. In addition, an on/off ratio of 2 × 107, time response of 40 μs, cut-off frequency of 8.5 kHz and responsivity of 0.52 A W-1 are simultaneously realized. The ultralow current noise is attributed to the excellent junction quality with a barrier height of 0.69 eV and an ideal factor of 1.18. Furthermore, obvious infrared photoresponse is observed in blackbody tests, and potential applications based on the photo-thermionic effect are discussed.

  2. Improvement of diode parameters in Al/n-Si Schottky diodes with Coronene interlayer using variation of the illumination intensity

    Science.gov (United States)

    Pakma, Osman; Çavdar, Şükrü; Koralay, Haluk; Tuğluoğlu, Nihat; Faruk Yüksel, Ömer

    2017-12-01

    In present work, Coronene thin films on Si wafer have been deposited by the spin coating method. It has been ultimately produced Al/Coronene/n-Si/In Schottky diode. Current-voltage (I-V) measurements have been used to determine the effect of illumination intensity in the Schottky diodes. The barrier height (ΦB) values increased as ideality factor (n) values decreased with a increase in illumination intensity. The ΦB values have been found to be 0.697 and 0.755 eV at dark and 100 mW/cm2, respectively. The n values have been found to be 2.81 and 2.07 at dark and 100 mW/cm2, respectively. Additionally, the series resistance (Rs) values from modified Norde method and interface state density (Nss) values using current-voltage measurements have been determined. The values of Rs have been found to be 1924 and 5094 Ω at dark and 100 mW/cm2, respectively. The values of Nss have been found to be 4.76 × 1012 and 3.15 × 1012 eV-1 cm-2 at dark and 100 mW/cm2, respectively. The diode parameters are improved by applying the variation of illumination intensity to the formed Schottky diodes.

  3. Monolayer graphene film on ZnO nanorod array for high-performance Schottky junction ultraviolet photodetectors.

    Science.gov (United States)

    Nie, Biao; Hu, Ji-Gang; Luo, Lin-Bao; Xie, Chao; Zeng, Long-Hui; Lv, Peng; Li, Fang-Ze; Jie, Jian-Sheng; Feng, Mei; Wu, Chun-Yan; Yu, Yong-Qiang; Yu, Shu-Hong

    2013-09-09

    A new Schottky junction ultraviolet photodetector (UVPD) is fabricated by coating a free-standing ZnO nanorod (ZnONR) array with a layer of transparent monolayer graphene (MLG) film. The single-crystalline [0001]-oriented ZnONR array has a length of about 8-11 μm, and a diameter of 100∼600 nm. Finite element method (FEM) simulation results show that this novel nanostructure array/MLG heterojunction can trap UV photons effectively within the ZnONRs. By studying the I-V characteristics in the temperature range of 80-300 K, the barrier heights of the MLG film/ZnONR array Schottky barrier are estimated at different temperatures. Interestingly, the heterojunction diode with typical rectifying characteristics exhibits a high sensitivity to UV light illumination and a quick response of millisecond rise time/fall times with excellent reproducibility, whereas it is weakly sensitive to visible light irradiation. It is also observed that this UV photodetector (PD) is capable of monitoring a fast switching light with a frequency as high as 2250 Hz. The generality of the above results suggest that this MLG film/ZnONR array Schottky junction UVPD will have potential application in future optoelectronic devices. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Floating-Gate Manipulated Graphene-Black Phosphorus Heterojunction for Nonvolatile Ambipolar Schottky Junction Memories, Memory Inverter Circuits, and Logic Rectifiers.

    Science.gov (United States)

    Li, Dong; Chen, Mingyuan; Zong, Qijun; Zhang, Zengxing

    2017-10-11

    The Schottky junction is an important unit in electronics and optoelectronics. However, its properties greatly degrade with device miniaturization. The fast development of circuits has fueled a rapid growth in the study of two-dimensional (2D) crystals, which may lead to breakthroughs in the semiconductor industry. Here we report a floating-gate manipulated nonvolatile ambipolar Schottky junction memory from stacked all-2D layers of graphene-BP/h-BN/graphene (BP, black phosphorus; h-BN, hexagonal boron nitride) in a designed floating-gate field-effect Schottky barrier transistor configuration. By manipulating the voltage pulse applied to the control gate, the device exhibits ambipolar characteristics and can be tuned to act as graphene-p-BP or graphene-n-BP junctions with reverse rectification behavior. Moreover, the junction exhibits good storability properties of more than 10 years and is also programmable. On the basis of these characteristics, we further demonstrate the application of the device to dual-mode nonvolatile Schottky junction memories, memory inverter circuits, and logic rectifiers.

  5. Modeling of Schottky Barrier Diode Millimeter-Wave Multipliers at Cryogenic Temperatures

    DEFF Research Database (Denmark)

    Johansen, Tom K.; Rybalko, Oleksandr; Zhurbenko, Vitaliy

    2015-01-01

    We report on the evaluation of Schottky barrier diode GaAs multipliers at cryogenic temperatures. A GaAs Schottky barrier diode model is developed for theoretical estimation of doubler performance. The model is used to predict efficiency of doublers from room to cryogenic temperatures...

  6. ALD TiO2 thin film as dielectric for Al/p-Si Schottky diode

    Indian Academy of Sciences (India)

    It has potential applications such as cataly- sis, sensors, antireflection coating, solar cells and Schottky diodes (Kadoshima et al 2003; Pakma et al 2008, ... conductor (MIS) Schottky diodes have an important role in the integrated device technology (Pakma et al 2008, 2009,. 2011; Kınacı et al 2012; Sönmezo˘glu and Akın ...

  7. Deep-level transient spectroscopy on an amorphous InGaZnO4 Schottky diode

    NARCIS (Netherlands)

    Chasin, A.; Simoen, E.; Bhoolokam, A.; Nag, M.; Genoe, J.; Gielen, G.; Heremans, P.

    2014-01-01

    The first direct measurement is reported of the bulk density of deep states in amorphous IGZO (indium-gallium-zinc oxide) semiconductor by means of deep-level transient spectroscopy (DLTS). The device under test is a Schottky diode of amorphous IGZO semiconductor on a palladium (Pd) Schottky-barrier

  8. Heterodimensional Schottky contacts to modulation-doped heterojunction with application to photodetection

    Science.gov (United States)

    Seddik, Amro Anwar

    The growing technological demand for high speed and compact integrated electronics and Optics is a pressing challenge. Speed and compactness necessitate low power consumption semiconductors with high transport mobility carriers, with potential of ultra large-scale integration of electronic and Optoelectronics circuitry. One avenue to fulfill these requirements is to utilize reduced dimensionality where carriers are spatially confined to less than three-dimensions, causing their energy levels to become quantized and their transport favorably affected. With recent progress in semiconductor growth and processing technologies low dimensionality has become practically realizable, this makes the study of contact properties to these systems increasingly important. In this work we study the contact between a low- dimensional semiconductor structure and a three- dimensional metal and the application of such a contact in photodetection. We theoretically derive the thermionic emission current for Schottky contact to two-dimensional and one-dimensional structures. The derivation underscores the discrete nature of low-dimensional structures and shows that the thermionic emission current is reduced by a factor exponentially proportional to the first quantized energy level. We also propose and formulate, for the first time, a physical phenomenon in two-dimensional structures created by modulation doping of a heterojunction, which is the effect of the cloud of electrons in the small bandgap material on the thermionic emission current. We have named this the electron- electron cloud effect; we show that this interaction increases the effective Schottky barrier height in a fashion counter to the image force lowering mechanism. In order to realize Schottky contact to low-dimensional structures, we have fabricated a novel Heterojunction Metal-Semiconductor-Metal (HMSM) photodetector. Experimental characterization and the general trends of the behavior of the HMSM devices are presented

  9. Schottky barrier diode based on β-Ga2O3 (100) single crystal substrate and its temperature-dependent electrical characteristics

    Science.gov (United States)

    He, Qiming; Mu, Wenxiang; Dong, Hang; Long, Shibing; Jia, Zhitai; Lv, Hangbing; Liu, Qi; Tang, Minghua; Tao, Xutang; Liu, Ming

    2017-02-01

    The Pt/β-Ga2O3 Schottky barrier diode and its temperature-dependent current-voltage characteristics were investigated for power device application. The edge-defined film-fed growth (EFG) technique was utilized to grow the (100)-oriented β-Ga2O3 single crystal substrate that shows good crystal quality characterized by X-ray diffraction and high resolution transmission electron microscope. Ohmic and Schottky electrodes were fabricated by depositing Ti and Pt metals on the two surfaces, respectively. Through the current-voltage (I-V) measurement under different temperature and the thermionic emission modeling, the fabricated Pt/β-Ga2O3 Schottky diode was found to show good performances at room temperature, including rectification ratio of 1010, ideality factor (n) of 1.1, Schottky barrier height (ΦB) of 1.39 eV, threshold voltage (Vbi) of 1.07 V, ON-resistance (RON) of 12.5 mΩ.cm2, forward current density at 2 V (J@2V) of 56 A/cm2, and saturation current density (J0) of 2 × 10-16 A/cm2. The effective donor concentration Nd - Na was calculated to be about 2.3 × 1014 cm3. Good temperature dependent performance was also found in the device. The Schottky barrier height was estimated to be about 1.3 eV-1.39 eV at temperatures ranging from room temperature to 150 °C. With increasing temperature, parameters such as RON and J@2V become better, proving that the diode can work well at high temperature. The EFG grown β-Ga2O3 single crystal is a promising material to be used in the power devices.

  10. Temperature dependent simulation of diamond depleted Schottky PIN diodes

    Science.gov (United States)

    Hathwar, Raghuraj; Dutta, Maitreya; Koeck, Franz A. M.; Nemanich, Robert J.; Chowdhury, Srabanti; Goodnick, Stephen M.

    2016-06-01

    Diamond is considered as an ideal material for high field and high power devices due to its high breakdown field, high lightly doped carrier mobility, and high thermal conductivity. The modeling and simulation of diamond devices are therefore important to predict the performances of diamond based devices. In this context, we use Silvaco® Atlas, a drift-diffusion based commercial software, to model diamond based power devices. The models used in Atlas were modified to account for both variable range and nearest neighbor hopping transport in the impurity bands associated with high activation energies for boron doped and phosphorus doped diamond. The models were fit to experimentally reported resistivity data over a wide range of doping concentrations and temperatures. We compare to recent data on depleted diamond Schottky PIN diodes demonstrating low turn-on voltages and high reverse breakdown voltages, which could be useful for high power rectifying applications due to the low turn-on voltage enabling high forward current densities. Three dimensional simulations of the depleted Schottky PIN diamond devices were performed and the results are verified with experimental data at different operating temperatures

  11. Temperature dependent simulation of diamond depleted Schottky PIN diodes

    Energy Technology Data Exchange (ETDEWEB)

    Hathwar, Raghuraj; Dutta, Maitreya; Chowdhury, Srabanti; Goodnick, Stephen M. [Department of Electrical Engineering, Arizona State University, Tempe, Arizona 85287-8806 (United States); Koeck, Franz A. M.; Nemanich, Robert J. [Department of Physics, Arizona State University, Tempe, Arizona 85287-8806 (United States)

    2016-06-14

    Diamond is considered as an ideal material for high field and high power devices due to its high breakdown field, high lightly doped carrier mobility, and high thermal conductivity. The modeling and simulation of diamond devices are therefore important to predict the performances of diamond based devices. In this context, we use Silvaco{sup ®} Atlas, a drift-diffusion based commercial software, to model diamond based power devices. The models used in Atlas were modified to account for both variable range and nearest neighbor hopping transport in the impurity bands associated with high activation energies for boron doped and phosphorus doped diamond. The models were fit to experimentally reported resistivity data over a wide range of doping concentrations and temperatures. We compare to recent data on depleted diamond Schottky PIN diodes demonstrating low turn-on voltages and high reverse breakdown voltages, which could be useful for high power rectifying applications due to the low turn-on voltage enabling high forward current densities. Three dimensional simulations of the depleted Schottky PIN diamond devices were performed and the results are verified with experimental data at different operating temperatures.

  12. Schottky Barrier Transport for Multiphase Gallium Nitride Nanowire

    Science.gov (United States)

    Hartz, Steven; Xie, Kan; Liu, Zhun; Ayres, Virginia

    2013-03-01

    Our group has shown that gallium nitride nanowires grown by catalyst-free vapor deposition at 850oC have multiple internal crystalline regions that may be zinc blende or wurtzite phase. Stability is enabled by one or more totally coherent (0001)/(111) internal interfaces. Cross-section HRTEM has further demonstrated that, while the transverse nanowire profile appears triangular, it is actually made up of two or more surface orientations corresponding to the multi-phase internal regions. We present results of a transport investigation of these multiphase nanowires within a nanoFET circuit architecture, focusing on injection from the contacts into the nanowires. Experimental results demonstrated that a variety of surface state derived Schottky barriers could be present at the contact-nanowire interfaces. Transport across the Schottky barriers was modeled using a combined thermionic emission-tunnelling approach, leading to information about barrier height, carrier concentrations, and expected temperature behavior. The experimental and theoretical results indicate that with optimal design taking surface and internal structures into account, high current densities can be supported.

  13. Carbon nanotube and CdSe nanobelt Schottky junction solar cells.

    Science.gov (United States)

    Zhang, Luhui; Jia, Yi; Wang, Shanshan; Li, Zhen; Ji, Chunyan; Wei, Jinquan; Zhu, Hongwei; Wang, Kunlin; Wu, Dehai; Shi, Enzheng; Fang, Ying; Cao, Anyuan

    2010-09-08

    Developing nanostructure junctions is a general and effective way for making photovoltaics. We report Schottky junction solar cells by coating carbon nanotube films on individual CdSe nanobelts with open-circuit voltages of 0.5 to 0.6 V and modest power-conversion efficiencies (0.45-0.72%) under AM 1.5G, 100 mW/cm(2) light condition. In our planar device structure, the CdSe nanobelt serves as a flat substrate to sustain a network of nanotubes, while the nanotube film forms Shottky junction with the underlying nanobelt at their interface and also makes a transparent electrode for the device. The nanotube-on-nanobelt solar cells can work either in front (nanotube side) or back (nanobelt side) illumination with stable performance in air. Our results demonstrate a promising way to develop large-area solar cells based on thin films of carbon nanotubes and semiconducting nanostructures.

  14. Modeling and Design of a New Flexible Graphene-on-Silicon Schottky Junction Solar Cell

    Directory of Open Access Journals (Sweden)

    Francesco Dell’Olio

    2016-10-01

    Full Text Available A new graphene-based flexible solar cell with a power conversion efficiency >10% has been designed. The environmental stability and the low complexity of the fabrication process are the two main advantages of the proposed device with respect to other flexible solar cells. The designed solar cell is a graphene/silicon Schottky junction whose performance has been enhanced by a graphene oxide layer deposited on the graphene sheet. The effect of the graphene oxide is to dope the graphene and to act as anti-reflection coating. A silicon dioxide ultrathin layer interposed between the n-Si and the graphene increases the open-circuit voltage of the cell. The solar cell optimization has been achieved through a mathematical model, which has been validated by using experimental data reported in literature. The new flexible photovoltaic device can be integrated in a wide range of microsystems powered by solar energy.

  15. Numerical simulations of the electrical transport characteristics of a Pt/n-GaN Schottky diode

    Science.gov (United States)

    Bouzid, Fayçal; Pezzimenti, Fortunato; Dehimi, Lakhdar; Megherbi, Mohamed L.; Della Corte, Francesco G.

    2017-09-01

    In this paper, using a numerical simulator, we investigated the current-voltage characteristics of a Pt/n-GaN thin Schottky diode on the basis of the thermionic emission (TE) theory in the 300 to 500 K temperature range. During the simulations, the effect of different defect states within the n-GaN bulk with different densities and spatial locations is considered. The results show that the diode ideality factor and the threshold voltage decrease with increasing temperature, while at the same time, the zero-bias Schottky barrier height (Φb0) extracted from the forward current density-voltage (J-V) characteristics increases. The observed behaviors of the ideality factor and zero-bias barrier height are analyzed on the basis of spatial barrier height inhomogeneities at the Pt/GaN interface by assuming a Gaussian distribution (GD). The plot of apparent barrier height (Φb,App) as a function of q/2kT gives a straight line, where the mean zero-bias barrier height (\\overline{Φ \\text{b0}}) and the standard deviation (σ0) are 1.48 eV and 0.047 V, respectively. The plot of the modified activation energy against q/kT gives an almost the same value of \\overline{Φ \\text{b0}} and an effective Richardson constant A* of 28.22 A cm-2 K-2, which is very close to the theoretical value for n-type GaN/Pt contacts. As expected, the presence of defect states with different trap energy levels has a noticeable impact on the device electrical characteristics.

  16. Schottky bipolar I-MOS: An I-MOS with Schottky electrodes and an open-base BJT configuration for reduced operating voltage

    Science.gov (United States)

    Kannan, N.; Kumar, M. Jagadesh

    2017-04-01

    In this paper, we have proposed a novel impact ionization MOS (I-MOS) structure, called the Schottky bipolar I-MOS, with Schottky source and drain electrodes and utilizing the open-base bipolar junction transistor (BJT) configuration for achieving reduction in the operating voltage of the I-MOS transistor. We report, using 2-D simulations, a low operating voltage (∼1.1 V) and a low subthreshold swing (∼3.6 mV/Decade). For the corresponding p-i-n I-MOS, the operating voltage is ∼5.5 V. The operating voltage of the Schottky bipolar I-MOS is the lowest reported operating voltage for silicon based I-MOS transistors. The nearly 80% reduction in the operating voltage of the Schottky bipolar I-MOS makes it suitable for applications requiring low operating voltages. The Schottky bipolar I-MOS is also expected to have an improved reliability over the p-i-n I-MOS since high energy carriers, induced by impact ionization near the drain, do not have to pass under the gate region in the channel. The use of Schottky contacts instead of heavily doped source and drain regions and the low channel doping level reduces the required thermal budget for device fabrication. The low operating voltage, low subthreshold swing and possibly improved reliability of the Schottky bipolar I-MOS, makes it a potential solution for applications where steep subthreshold slope transistors are being explored as alternative to the conventional MOS transistor.

  17. Optimal indium-gallium-nitride Schottky-barrier thin-film solar cells

    Science.gov (United States)

    Anderson, Tom H.; Lakhtakia, Akhlesh; Monk, Peter B.

    2017-08-01

    A two-dimensional model was developed to simulate the optoelectronic characteristics of indium-gallium-nitride (InξGa1-ξN), thin-film, Schottky-barrier-junction solar cells. The solar cell comprises a window designed to reduce the reflection of incident light, Schottky-barrier and ohmic front electrodes, an n-doped InξGa1-ξN wafer, and a metallic periodically corrugated back-reflector (PCBR). The ratio of indium to gallium in the wafer varies periodically in the thickness direction, and thus the optical and electrical constitutive properties of the alloy also vary periodically. This material nonhomogeneity could be physically achieved by varying the fractional composition of indium and gallium during deposition. Empirical models for indium nitride and gallium nitride, combined with Vegard's law, were used to calculate the optical and electrical constitutive properties of the alloy. The periodic nonhomogeneity aids charge separation and, in conjunction with the PCBR, enables incident light to couple to multiple surface plasmon-polariton waves and waveguide modes. The profile of the resulting chargecarrier-generation rate when the solar cell is illuminated by the AM1.5G spectrum was calculated using the rigorous coupled-wave approach. The steady-state drift-diffusion equations were solved using COMSOL, which employs finite-element methods, to calculate the current density as a function of the voltage. Mid-band Shockley- Read-Hall, Auger, and radiative recombination rates were taken to be the dominant methods of recombination. The model was used to study the effects of the solar-cell geometry and the shape of the periodic material nonhomogeneity on efficiency. The solar-cell efficiency was optimized using the differential evolution algorithm.

  18. Electrical characterization of all-epitaxial Fe/GaN(0001) Schottky tunnel contacts

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez-Garrido, Sergio; Ubben, Kai U.; Herfort, Jens; Gao Cunxu; Brandt, Oliver [Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, D-10117 Berlin (Germany)

    2012-07-16

    We analyze the properties of Fe Schottky contacts prepared in situ on n-type GaN(0001) by molecular beam epitaxy. In particular, we investigate the suitability of these epitaxial Fe layers for electrical spin injection. Current-voltage-temperature measurements demonstrate pure field emission for Fe/GaN:Si Schottky diodes with [Si]=5 Multiplication-Sign 10{sup 18} cm{sup -3}. The Schottky barrier height of the clean, epitaxial Fe/GaN interface is determined by both current-voltage-temperature and capacitance-voltage techniques to be (1.47{+-}0.09)eV.

  19. Two-dimensional ferromagnet/semiconductor transition metal dichalcogenide contacts: p-type Schottky barrier and spin-injection control

    KAUST Repository

    Gan, Liyong

    2013-09-26

    We study the ferromagnet/semiconductor contacts formed by transition metal dichalcogenide monolayers, focusing on semiconducting MoS2 and WS2 and ferromagnetic VS2. We investigate the degree of p-type doping and demonstrate tuning of the Schottky barrier height by vertical compressive pressure. An analytical model is presented for the barrier heights that accurately describes the numerical findings and is expected to be of general validity for all transition metal dichalcogenide metal/semiconductor contacts. Furthermore, magnetic proximity effects induce a 100% spin polarization at the Fermi level in the semiconductor where the spin splitting increases up to 0.70 eV for increasing pressure.

  20. Abrupt Schottky Junctions in Al/Ge Nanowire Heterostructures.

    Science.gov (United States)

    Kral, S; Zeiner, C; Stöger-Pollach, M; Bertagnolli, E; den Hertog, M I; Lopez-Haro, M; Robin, E; El Hajraoui, K; Lugstein, A

    2015-07-08

    In this Letter we report on the exploration of axial metal/semiconductor (Al/Ge) nanowire heterostructures with abrupt interfaces. The formation process is enabled by a thermal induced exchange reaction between the vapor-liquid-solid grown Ge nanowire and Al contact pads due to the substantially different diffusion behavior of Ge in Al and vice versa. Temperature-dependent I-V measurements revealed the metallic properties of the crystalline Al nanowire segments with a maximum current carrying capacity of about 0.8 MA/cm(2). Transmission electron microscopy (TEM) characterization has confirmed both the composition and crystalline nature of the pure Al nanowire segments. A very sharp interface between the ⟨111⟩ oriented Ge nanowire and the reacted Al part was observed with a Schottky barrier height of 361 meV. To demonstrate the potential of this approach, a monolithic Al/Ge/Al heterostructure was used to fabricate a novel impact ionization device.

  1. Self assembled silicon nanowire Schottky junction assisted by collagen

    Science.gov (United States)

    Stievenard, Didier; Sahli, Billel; Coffinier, Yannick; Boukherroub, Rabah; Melnyk, Oleg

    2008-03-01

    We present results on self assembled silicon nanowire Schottky junction assisted by collagen fibrous. The collagen is the principle protein of connective human tissues. It presents the double interest to be a low cost biological material with the possibility to be combed as the DNA molecule. First, the collagen was combed on OTS modified surface with gold electrodes. Second, silicon nanowires were grown on silicon substrate by CVD of silane gas (SiH4) at high temperature (500 C) using a vapor-liquid-solid (VLS) process and gold particles as catalysts. In order to increase electrostatic interaction between the collagen and the nanowires, these latters were chemically modified by mercaptopropylmethoxysilane (MPTS), then chemically oxidized. Therefore, the nanowires were transferred from their substrate into water and a drop of it deposited on the surface. Nanowires are only bound to collagen and in particular, in electrode gaps. The formation of spontaneous Schotkty junction is demonstrated by current-voltage characteristics.

  2. Schottky mass- and lifetime-spectrometry of unstable, stored ions

    CERN Document Server

    Bosch, F

    2003-01-01

    GSI is presently the only facility where unstable, highly charged ions far from stability can be produced by in-flight fragmentation and subsequently stored and cooled in an ion storage ring. The mass-to-charge ratio of those stored ions is measured by two complementary methods that have been developed at GSI: Schottky mass-spectrometry, based on the recording of the revolution frequencies of electron-cooled ions, and isochronous mass-spectrometry, applied on short-lived, uncooled ions at the 'transition energy'. Both methods provide a highly efficient, precise and sensitive determination of the nuclear mass of many simultaneously stored ion species. Similarly, the beta lifetimes of stored, unstable nuclei can also be determined. The impact of nuclear masses and lifetimes for both nuclear physics and astrophysics is also addressed.

  3. Diodes Schottky diamant fonctionnant à 200°C

    OpenAIRE

    Monflier, Richard; Isoird, Karine; Cazarré, Alain; Tasselli, Josiane; Servel, Alexandra; ACHARD, Jocelyn; Eon, David

    2015-01-01

    Les caractéristiques courant-tension jusqu'à 200°C de diodes Schottky diamant verticales et pseudo-verticales réalisées dans le cadre du projet DIAMONIX2 sont présentées dans cet article. Sur les différents échantillons testés le taux de fonctionnalité est supérieur à 75%. Pour les diodes verticales la densité de courant atteint 488 A/cm 2 à 200°C, et un courant de fuite < 10-7 A/cm 2 à 50 V. Toutefois, la hauteur de barrière de 1,96 eV et le coefficient d'idéalité de 1,77 sont certainement c...

  4. Diodes Schottky diamant fonctionnant à 200°C

    OpenAIRE

    Monflier, Richard; Isoird, Karine; Cazarre, Alain; Tasselli, Josiane; Servel, Alexandra; ACHARD, Jocelyn; Eon, David; Valdivia Birnbaum, Maria José

    2016-01-01

    International audience; Les caractéristiques courant-tension jusqu'à 200 °C de diodes Schottky diamant verticales et pseudo-verticales réalisées dans le cadre du projet DIAMONIX2 sont présentées dans cet article. Sur les différents échantillons testés le taux de fonctionnalité est supérieur à 75 % et atteint même 100 % pour l'un d'entre eux. Pour les diodes verticales la densité de courant atteint 488 A/cm2 à 200 °C et pour les diodes pseudo-verticales une densité de courant supérieure à 1000...

  5. Graphene-Based Reversible Nano-Switch/Sensor Schottky Diode

    Science.gov (United States)

    Miranda, Felix A.; Meador, Michael A.; Theofylaktos, Onoufrios; Pinto, Nicholas J.; Mueller, Carl H.; Santos-Perez, Javier

    2010-01-01

    This proof-of-concept device consists of a thin film of graphene deposited on an electrodized doped silicon wafer. The graphene film acts as a conductive path between a gold electrode deposited on top of a silicon dioxide layer and the reversible side of the silicon wafer, so as to form a Schottky diode. By virtue of the two-dimensional nature of graphene, this device has extreme sensitivity to different gaseous species, thereby serving as a building block for a volatile species sensor, with the attribute of having reversibility properties. That is, the sensor cycles between active and passive sensing states in response to the presence or absence of the gaseous species.

  6. Nonlinear absorption coefficient and relative refraction index change for an asymmetrical double δ-doped quantum well in GaAs with a Schottky barrier potential

    Energy Technology Data Exchange (ETDEWEB)

    Rojas-Briseño, J.G.; Martínez-Orozco, J.C.; Rodríguez-Vargas, I. [Unidad Académica de Física, Universidad Autónoma de Zacatecas, Calzada Solidaridad esquina con Paseo la Bufa S/N, C.P. 98060, Zacatecas, Zac. (Mexico); Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autónoma del Estado de Morelos, Av. Universidad 1001, CP 62209, Cuernavaca, Morelos (Mexico); Instituto de Física, Universidad de Antioquia, AA 1226, Medellín (Colombia); Duque, C.A., E-mail: cduque@fisica.udea.edu.co [Instituto de Física, Universidad de Antioquia, AA 1226, Medellín (Colombia)

    2013-09-01

    In this work we are reporting the energy level spectrum for a quantum system consisting of an n-type double δ-doped quantum well with a Schottky barrier potential in a Gallium Arsenide matrix. The calculated states are taken as the basis for the evaluation of the linear and third-order nonlinear contributions to the optical absorption coefficient and to the relative refractive index change, making particular use of the asymmetry of the potential profile. These optical properties are then reported as a function of the Schottky barrier height (SBH) and the separation distance between the δ-doped quantum wells. Also, the effects of the application of hydrostatic pressure are studied. The results show that the amplitudes of the resonant peaks are of the same order of magnitude of those obtained in the case of single δ-doped field effect transistors; but tailoring the asymmetry of the confining potential profile allows the control the resonant peak positions.

  7. Internal photoemission for photovoltaic using p-type Schottky barrier: Band structure dependence and theoretical efficiency limits

    Science.gov (United States)

    Shih, Ko-Han; Chang, Yin-Jung

    2018-01-01

    Solar energy conversion via internal photoemission (IPE) across a planar p-type Schottky junction is quantified for aluminum (Al) and copper (Cu) in the framework of direct transitions with non-constant matrix elements. Transition probabilities and k-resolved group velocities are obtained based on pseudo-wavefunction expansions and realistic band structures using the pseudopotential method. The k-resolved number of direct transitions, hole photocurrent density, quantum yield (QY), and the power conversion efficiency (PCE) under AM1.5G solar irradiance are subsequently calculated and analyzed. For Al, the parabolic and "parallel-band" effect along the U-W-K path significantly enhances the transition rate with final energies of holes mainly within 1.41 eV below the Fermi energy. For Cu, d-state hot holes mostly generated near the upper edge of 3d bands dominate the hole photocurrent and are weekly (strongly) dependent on the barrier height (metal film thickness). Hot holes produced in the 4s band behave just oppositely to their d-state counterparts. Non-constant matrix elements are shown to be necessary for calculations of transitions due to time-harmonic perturbation in Cu. Compared with Cu, Al-based IPE in p-type Schottky shows the highest PCE (QY) up to about 0.2673% (5.2410%) at ΦB = 0.95 eV (0.5 eV) and a film thickness of 11 nm (20 nm). It is predicted that metals with relatively dispersionless d bands (such as Cu) in most cases do not outperform metals with photon-accessible parallel bands (such as Al) in photon energy conversion using a planar p-type Schottky junction.

  8. Modélisation compacte des transistors à nanotube de carbone à contacts Schottky et application aux circuits numériques

    OpenAIRE

    Najari, Montassar

    2010-01-01

    This PhD work presents a computationally efficient physics-based compact model for the Schottky barrier (SB) carbon nanotube field-effect transistor (CNTFET). This compact model includes a new analytical formulation of the channel charge, taking into account the influence of the source and drain SBs. Compact model simulation results (I–V characteristic and channel density of charge) as well as Monte Carlo simulation results, which are provided by a recent work, will be given and compared to e...

  9. Carrier transport in reverse-biased graphene/semiconductor Schottky junctions

    OpenAIRE

    Tomer, D.; Rajput, S.; Hudy, L. J.; Li, C. H.; Li, L.

    2015-01-01

    Reverse-biased graphene (Gr)/semiconductor Schottky diodes exhibit much enhanced sensitivity for gas sensing. However, carrier transport across the junctions is not fully understood yet. Here, Gr/SiC, Gr/GaAs and Gr/Si Schottky junctions under reverse-bias are investigated by temperature-dependent current-voltage measurements. A reduction in barrier height with increasing reverse-bias is observed for all junctions, suggesting electric-field enhanced thermionic emission. Further analysis of th...

  10. Simulation of a perfect CVD diamond Schottky diode steep forward current–voltage characteristic

    Energy Technology Data Exchange (ETDEWEB)

    Kukushkin, V.A., E-mail: vakuk@appl.sci-nnov.ru [Institute of Applied Physics of the Russian Academy of Science, 46 Ulyanov St., 603950 Nizhny Novgorod (Russian Federation); Nizhny Novgorod State University named after N.I. Lobachevsky, 23 Gagarin pr., 603950 Nizhny Novgorod (Russian Federation)

    2016-10-01

    The kinetic equation approach to the simulation of the perfect CVD diamond Schottky diode current–voltage characteristic is considered. In result it is shown that the latter has a significantly steeper forward branch than that of perfect devices of such a type on usual semiconductors. It means that CVD diamond-based Schottky diodes have an important potential advantage over analogous devices on conventional materials.

  11. Barrier characteristics of Pt/Ru Schottky contacts on n-type GaN ...

    Indian Academy of Sciences (India)

    voltage (C–V) characteristics of. Ru/Pt/n-GaN Schottky diodes in the temperature range 100–420 K. The calculated values of barrier height and ide- ality factor for the Ru/Pt/n-GaN Schottky diode are 0·73 eV and 1·4 at 420 K, 0·18 eV and 4·2 at 100 K ...

  12. Barrier height enhancement of Ni/GaN Schottky diode using Ru based passivation scheme

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Ashish, E-mail: dr.akmr@gmail.com; Kumar, Mukesh; Singh, R. [Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016 (India); Kaur, Riajeet [Department of Physics, National Institute of Technology, Kurukshetra 136119 (India); Joshi, Amish G. [CSIR - National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi - 110 012 (India); Vinayak, Seema [Solid State Physical Laboratory, Timarpur, Delhi 110054 (India)

    2014-03-31

    Wet chemical passivation of n-GaN surface using Ru based solution has been reported. X-ray photoelectron spectroscopy characterization of the GaN surface revealed removal of surface oxides by the introduction of Ru complex species. Ni/n-GaN Schottky barrier diodes were fabricated on passivated GaN and a remarkable improvement in Schottky barrier height from 0.76 eV to 0.92 eV was observed.

  13. Tuning the Schottky rectification in graphene-hexagonal boron nitride-molybdenum disulfide heterostructure.

    Science.gov (United States)

    Liu, Biao; Zhao, Yu-Qing; Yu, Zhuo-Liang; Wang, Lin-Zhi; Cai, Meng-Qiu

    2017-12-04

    It was still a great challenge to design high performance of rectification characteristic for the rectifier diode. Lately, a new approach was proposed experimentally to tune the Schottky barrier height (SBH) by inserting an ultrathin insulated tunneling layer to form metal-insulator-semiconductor (MIS) heterostructures. However, the electronic properties touching off the high performance of these heterostructures and the possibility of designing more efficient applications for the rectifier diode were not presently clear. In this paper, the structural, electronic and interfacial properties of the novel MIS diode with the graphene/hexagonal boron nitride/monolayer molybdenum disulfide (GBM) heterostructure had been investigated by first-principle calculations. The calculated results showed that the intrinsic properties of graphene and MoS 2 were preserved due to the weak van der Waals contact. The height of interfacial Schottky barrier can be tuned by the different thickness of hBN layers. In addition, the GBM Schottky diode showed more excellent rectification characteristic than that of GM Schottky diode due to the interfacial band bending caused by the epitaxial electric field. Based on the electronic band structure, we analyzed the relationship between the electronic structure and the nature of the Schottky rectifier, and revealed the potential of utilizing GBM Schottky diode for the higher rectification characteristic devices. Copyright © 2017 Elsevier Inc. All rights reserved.

  14. A high speed PE-ALD ZnO Schottky diode rectifier with low interface-state density

    Science.gov (United States)

    Jin, Jidong; Zhang, Jiawei; Shaw, Andrew; Kudina, Valeriya N.; Mitrovic, Ivona Z.; Wrench, Jacqueline S.; Chalker, Paul R.; Balocco, Claudio; Song, Aimin; Hall, Steve

    2018-02-01

    Zinc oxide (ZnO) has recently attracted attention for its potential application to high speed electronics. In this work, a high speed Schottky diode rectifier was fabricated based on a ZnO thin film deposited by plasma-enhanced atomic layer deposition and a PtOx Schottky contact deposited by reactive radio-frequency sputtering. The rectifier shows an ideality factor of 1.31, an effective barrier height of 0.79 eV, a rectification ratio of 1.17  ×  107, and cut-off frequency as high as 550 MHz. Low frequency noise measurements reveal that the rectifier has a low interface-state density of 5.13  ×  1012 cm‑2 eV‑1, and the noise is dominated by the mechanism of a random walk of electrons at the PtO x /ZnO interface. The work shows that the rectifier can be used for both noise sensitive and high frequency electronics applications.

  15. Development of a Schottky CdTe Medipix3RX hybrid photon counting detector with spatial and energy resolving capabilities

    Energy Technology Data Exchange (ETDEWEB)

    Gimenez, E.N., E-mail: Eva.Gimenez@diamond.ac.uk [Diamond Light Source, Harwell Campus, Oxforshire OX11 0DE (United Kingdom); Astromskas, V. [University of Surrey (United Kingdom); Horswell, I.; Omar, D.; Spiers, J.; Tartoni, N. [Diamond Light Source, Harwell Campus, Oxforshire OX11 0DE (United Kingdom)

    2016-07-11

    A multichip CdTe-Medipix3RX detector system was developed in order to bring the advantages of photon-counting detectors to applications in the hard X-ray range of energies. The detector head consisted of 2×2 Medipix3RX ASICs bump-bonded to a 28 mm×28 mm e{sup −} collection Schottky contact CdTe sensor. Schottky CdTe sensors undergo performance degrading polarization which increases with temperature, flux and the longer the HV is applied. Keeping the temperature stable and periodically refreshing the high voltage bias supply was used to minimize the polarization and achieve a stable and reproducible detector response. This leads to good quality images and successful results on the energy resolving capabilities of the system. - Highlights: • A high atomic number (CdTe sensor based) photon-counting detector was developed. • Polarization effects affected the image were minimized by regularly refreshing the bias voltage and stabilizing the temperature. • Good spatial resolution and image quality was achieved following this procedure.

  16. GaN schottky barrier MOSFET using transparent source/drain electrodes for UV-optoelectronic integration

    Science.gov (United States)

    Jung, Byung-Kwon; Lee, Chang-Ju; Kim, Tae-Hyeon; Kim, Dong-Seok; Lee, Myoung-Bok; Lee, Jung-Hee; Hahm, Sung-Ho

    2012-07-01

    We fabricated a normally-off mode n-channel schottky barrier metal oxide semiconductor field effect transistor (SB-MOSFET) with transparent electrodes (ITO, IZO) as source/drain (S/D) contact on a highly resistive GaN layer grown on silicon substrate. Fabricated SB-MOSFET with ITO S/D exhibited as high as 40 mA/mm of maximum drain current and a 12 mS/mm of maximum transconductance with the threshold voltage of 4.2 V, which is far better than that of SB-MOSFET with IZO S/D. The normalized off-current was as low as 10 nA/mm. The UV-visible extinction ratio of a MOSFET type UV-sensor was measured over 130 for VDS = 5 V. ITO was proved as a promising schottky barrier material for GaN MOSFET source and drain not only for the electronic but UV-sensing applications better than IZO for this purpose.

  17. Electronic parameters of high barrier Au/Rhodamine-101/n-Inp Schottky diode with organic Latin-Small-Letter-Dotless-I nterlayer

    Energy Technology Data Exchange (ETDEWEB)

    Guellue, Oe. [Batman University, Faculty of Sciences and Arts, Department of Physics, Batman (Turkey); Aydogan, S., E-mail: saydogan@atauni.edu.tr [Atatuerk University, Faculty of Sciences, Department of Physics, 25240-Erzurum (Turkey); Tueruet, A. [Atatuerk University, Faculty of Sciences, Department of Physics, 25240-Erzurum (Turkey)

    2012-01-01

    In this work, we present that Rhodamine-101 (Rh-101) organic molecules can control the electrical characteristics of conventional Au/n-InP metal-semiconductor contacts. An Au/n-InP Schottky junction with Rh-101 interlayer has been formed by using a simple cast process. A potential barrier height as high as 0.88 eV has been achieved for Au/Rh-101/n-InP Schottky diodes, which have good current-voltage (I-V) characteristics. This good performance is attributed to the effect of formation of interfacial organic thin layer between Au and n-InP. By using capacitance-voltage measurement of the Au/Rh-101/n-InP Schottky diode the diffusion potential and the barrier height have been calculated as 0.78 V and 0.88 eV, respectively. From the I-V measurement of the diode under illumination, short circuit current and open circuit voltage have been extracted as 1.70 {mu}A and 240 mV, respectively.

  18. Transport mechanisms and interface properties of W/ p-InP Schottky diode at room temperature

    Science.gov (United States)

    Sri Silpa, D.; Sreehith, P.; Rajagopal Reddy, V.; Janardhanam, V.

    2016-04-01

    We have investigated the electrical properties and current transport mechanisms of W/ p-InP Schottky diode using current-voltage ( I- V), capacitance-voltage-frequency ( C- V- f) and conductance-frequency ( G- f) techniques at room temperature. The W/ p-InP Schottky diode exhibits a good rectifying behavior. Measurements show that the Schottky barrier height (SBH) and ideality factor of the W/ p-InP Schottky diode are 0.84 eV ( I- V)/0.98 eV ( C- V) and 1.24, respectively. Also, the SBH and series resistance R s of the diode are extracted by Cheung's functions and the values are in good agreement with each other. Ohmic and space charge-limited conduction mechanisms are found to govern the current flow in the W/ p-InP Schottky diode at low and high forward bias conditions, respectively. Experimental results reveal that the Poole-Frenkel mechanism is found to be dominant in the reverse bias region of W/ p-InP Schottky diode. Further, the interface state density N ss and their relaxation times τ of the W/ p-InP Schottky diode are estimated from the forward bias C- f and G- f characteristics and the values are in the range from 1.95 × 1013 eV-1 cm-2 and 3.38 × 10-5 s at (0.81- E V ) eV to 1.78 × 1013 eV-1 cm-2 and 2.78 × 10-6 s at (0.30- E V ) eV, respectively. Both the N ss and τ show an exponential rise with bias from the top of the valance band toward the mid gap.

  19. Alternative current source based Schottky contact with additional electric field

    Science.gov (United States)

    Mamedov, R. K.; Aslanova, A. R.

    2017-07-01

    Additional electric field (AEF) in the Schottky contacts (SC) that covered the peripheral contact region wide and the complete contact region narrow (as TMBS diode) SC. Under the influence of AEF is a redistribution of free electrons produced at certain temperatures of the semiconductor, and is formed the space charge region (SCR). As a result of the superposition of the electric fields SCR and AEF occurs the resulting electric field (REF). The REF is distributed along a straight line perpendicular to the contact surface, so that its intensity (and potential) has a minimum value on the metal surface and the maximum value at a great distance from the metal surface deep into the SCR. Under the influence of AEF as a sided force the metal becomes negative pole and semiconductor - positive pole, therefore, SC with AEF becomes an alternative current source (ACS). The Ni-nSi SC with different diameters (20-1000 μm) under the influence of the AEF as sided force have become ACS with electromotive force in the order of 0.1-1.0 mV, which are generated the electric current in the range of 10-9-10-7 A, flowing through the external resistance 1000 Ohm.

  20. Schottky-contact plasmonic dipole rectenna concept for biosensing.

    Science.gov (United States)

    Alavirad, Mohammad; Mousavi, Saba Siadat; Roy, Langis; Berini, Pierre

    2013-02-25

    Nanoantennas are key optical components for several applications including photodetection and biosensing. Here we present an array of metal nano-dipoles supporting surface plasmon polaritons (SPPs) integrated into a silicon-based Schottky-contact photodetector. Incident photons coupled to the array excite SPPs on the Au nanowires of the antennas which decay by creating "hot" carriers in the metal. The hot carriers may then be injected over the potential barrier at the Au-Si interface resulting in a photocurrent. High responsivities of 100 mA/W and practical minimum detectable powers of -12 dBm should be achievable in the infra-red (1310 nm). The device was then investigated for use as a biosensor by computing its bulk and surface sensitivities. Sensitivities of ∼ 250 nm/RIU (bulk) and ∼ 8 nm/nm (surface) in water are predicted. We identify the mode propagating and resonating along the nanowires of the antennas, we apply a transmission line model to describe the performance of the antennas, and we extract two useful formulas to predict their bulk and surface sensitivities. We prove that the sensitivities of dipoles are much greater than those of similar monopoles and we show that this difference comes from the gap in dipole antennas where electric fields are strongly enhanced.

  1. Investigation of significantly high barrier height in Cu/GaN Schottky diode

    Energy Technology Data Exchange (ETDEWEB)

    Garg, Manjari, E-mail: meghagarg142@gmail.com; Kumar, Ashutosh; Singh, R. [Department of Physics, Indian Institute of Technology, Delhi, Hauz Khas, New Delhi-110016 (India); Nagarajan, S.; Sopanen, M. [Department of Micro and Nanosciences, Aalto University, P.O. Box 13500, FI-00076, Aalto (Finland)

    2016-01-15

    Current-voltage (I-V) measurements combined with analytical calculations have been used to explain mechanisms for forward-bias current flow in Copper (Cu) Schottky diodes fabricated on Gallium Nitride (GaN) epitaxial films. An ideality factor of 1.7 was found at room temperature (RT), which indicated deviation from thermionic emission (TE) mechanism for current flow in the Schottky diode. Instead the current transport was better explained using the thermionic field-emission (TFE) mechanism. A high barrier height of 1.19 eV was obtained at room temperature. X-ray photoelectron spectroscopy (XPS) was used to investigate the plausible reason for observing Schottky barrier height (SBH) that is significantly higher than as predicted by the Schottky-Mott model for Cu/GaN diodes. XPS measurements revealed the presence of an ultrathin cuprous oxide (Cu{sub 2}O) layer at the interface between Cu and GaN. With Cu{sub 2}O acting as a degenerate p-type semiconductor with high work function of 5.36 eV, a high barrier height of 1.19 eV is obtained for the Cu/Cu{sub 2}O/GaN Schottky diode. Moreover, the ideality factor and barrier height were found to be temperature dependent, implying spatial inhomogeneity of barrier height at the metal semiconductor interface.

  2. Investigation of significantly high barrier height in Cu/GaN Schottky diode

    Directory of Open Access Journals (Sweden)

    Manjari Garg

    2016-01-01

    Full Text Available Current-voltage (I-V measurements combined with analytical calculations have been used to explain mechanisms for forward-bias current flow in Copper (Cu Schottky diodes fabricated on Gallium Nitride (GaN epitaxial films. An ideality factor of 1.7 was found at room temperature (RT, which indicated deviation from thermionic emission (TE mechanism for current flow in the Schottky diode. Instead the current transport was better explained using the thermionic field-emission (TFE mechanism. A high barrier height of 1.19 eV was obtained at room temperature. X-ray photoelectron spectroscopy (XPS was used to investigate the plausible reason for observing Schottky barrier height (SBH that is significantly higher than as predicted by the Schottky-Mott model for Cu/GaN diodes. XPS measurements revealed the presence of an ultrathin cuprous oxide (Cu2O layer at the interface between Cu and GaN. With Cu2O acting as a degenerate p-type semiconductor with high work function of 5.36 eV, a high barrier height of 1.19 eV is obtained for the Cu/Cu2O/GaN Schottky diode. Moreover, the ideality factor and barrier height were found to be temperature dependent, implying spatial inhomogeneity of barrier height at the metal semiconductor interface.

  3. Microwave Annealing for NiSiGe Schottky Junction on SiGe P-Channel

    Directory of Open Access Journals (Sweden)

    Yu-Hsien Lin

    2015-11-01

    Full Text Available In this paper, we demonstrated the shallow NiSiGe Schottky junction on the SiGe P-channel by using low-temperature microwave annealing. The NiSiGe/n-Si Schottky junction was formed for the Si-capped/SiGe multi-layer structure on an n-Si substrate (Si/Si0.57Ge0.43/Si through microwave annealing (MWA ranging from 200 to 470 °C for 150 s in N2 ambient. MWA has the advantage of being diffusion-less during activation, having a low-temperature process, have a lower junction leakage current, and having low sheet resistance (Rs and contact resistivity. In our study, a 20 nm NiSiGe Schottky junction was formed by TEM and XRD analysis at MWA 390 °C. The NiSiGe/n-Si Schottky junction exhibits the highest forward/reverse current (ION/IOFF ratio of ~3 × 105. The low temperature MWA is a very promising thermal process technology for NiSiGe Schottky junction manufacturing.

  4. Ambient organic molecular passivation of Si yields near-ideal, Schottky-Mott limited, junctions

    Science.gov (United States)

    Har-Lavan, Rotem; Yaffe, Omer; Joshi, Pranav; Kazaz, Roy; Cohen, Hagai; Cahen, David

    2012-03-01

    We report near-perfect transfer of the electrical properties of oxide-free Si surface, modified by a molecular monolayer, to the interface of a junction made with that modified Si surface. Such behavior is highly unusual for a covalent, narrow bandgap semiconductor, such as Si. Short, ambient atmosphere, room temperature treatment of oxide-free Si(100) in hydroquinone (HQ)/alkyl alcohol solutions, fully passivates the Si surface, while allowing controlled change of the resulting surface potential. The junctions formed, upon contacting such surfaces with Hg, a metal that does not chemically interact with Si, follow the Schottky-Mott model for metal-semiconductor junctions closer than ever for Si-based junctions. Two examples of such ideal behavior are demonstrated: a) Tuning the molecular surface dipole over 400 mV, with only negligible band bending, by changing the alkyl chain length. Because of the excellent passivation this yields junctions with Hg with barrier heights that follow the change in the Si effective electron affinity nearly ideally. b) HQ/ methanol passivation of Si is accompanied by a large surface dipole, which suffices, as interface dipole, to drive the Si into strong inversion as shown experimentally via its photovoltaic effect. With only ˜0.3 nm molecular interlayer between the metal and the Si, our results proves that it is passivation and prevention of metal-semiconductor interactions that allow ideal metal-semiconductor junction behavior, rather than an insulating transport barrier.

  5. Ambient organic molecular passivation of Si yields near-ideal, Schottky-Mott limited, junctions

    Directory of Open Access Journals (Sweden)

    Rotem Har-Lavan

    2012-03-01

    Full Text Available We report near-perfect transfer of the electrical properties of oxide-free Si surface, modified by a molecular monolayer, to the interface of a junction made with that modified Si surface. Such behavior is highly unusual for a covalent, narrow bandgap semiconductor, such as Si. Short, ambient atmosphere, room temperature treatment of oxide-free Si(100 in hydroquinone (HQ/alkyl alcohol solutions, fully passivates the Si surface, while allowing controlled change of the resulting surface potential. The junctions formed, upon contacting such surfaces with Hg, a metal that does not chemically interact with Si, follow the Schottky-Mott model for metal-semiconductor junctions closer than ever for Si-based junctions. Two examples of such ideal behavior are demonstrated: a Tuning the molecular surface dipole over 400 mV, with only negligible band bending, by changing the alkyl chain length. Because of the excellent passivation this yields junctions with Hg with barrier heights that follow the change in the Si effective electron affinity nearly ideally. b HQ/ methanol passivation of Si is accompanied by a large surface dipole, which suffices, as interface dipole, to drive the Si into strong inversion as shown experimentally via its photovoltaic effect. With only ∼0.3 nm molecular interlayer between the metal and the Si, our results proves that it is passivation and prevention of metal-semiconductor interactions that allow ideal metal-semiconductor junction behavior, rather than an insulating transport barrier.

  6. Design of a silicon RCE Schottky photodetector working at 1.55 {mu}m

    Energy Technology Data Exchange (ETDEWEB)

    Casalino, M. [Istituto per la Microelettronica e Microsistemi (IMM), Consiglio Nazionale delle Ricerche, Via P. Castellino, 80131 Naples (Italy); Universita degli studi ' Mediterranea' di Reggio Calabria, Localita Feo di Vito, 89060 Reggio Calabria (Italy); Sirleto, L. [Istituto per la Microelettronica e Microsistemi (IMM), Consiglio Nazionale delle Ricerche, Via P. Castellino, 80131 Naples (Italy)]. E-mail: luigi.sirleto@imm.cnr.it; Moretti, L. [Universita degli studi ' Mediterranea' di Reggio Calabria, Localita Feo di Vito, 89060 Reggio Calabria (Italy); Della Corte, F. [Universita degli studi ' Mediterranea' di Reggio Calabria, Localita Feo di Vito, 89060 Reggio Calabria (Italy); Rendina, I. [Istituto per la Microelettronica e Microsistemi (IMM), Consiglio Nazionale delle Ricerche, Via P. Castellino, 80131 Naples (Italy)

    2006-12-15

    In this paper, the design of a resonant cavity-enhanced (RCE) Schottky photodetector, based on internal photoemission effect and working at 1.55 {mu}m, is presented. In order to estimate the theoretical quantum efficiency we take the advantage of analytical formulation of the internal photoemission effect (Fowler theory), and its extension for thin films, while for the optical analysis of device a numerical method, based on the transfer matrix method, has been implemented. Finally, we complete our design calculating bandwidth and bandwidth-efficiency product. Our numerical results prove that a quantum efficiency of 0.1% is obtained at resonant wavelength (1.55 {mu}m) with a very thin absorbing metal layer (30 nm). Theoretical values of 100 GHz and 100 MHz were obtained, respectively, for the carrier-transit time limited 3-dB bandwidth and bandwidth-efficiency. The proposed photodetector can work at room temperature and its fabrication is completely compatible with standard silicon technology.

  7. On-Chip Power-Combining for High-Power Schottky Diode Based Frequency Multipliers

    Science.gov (United States)

    Siles Perez, Jose Vicente (Inventor); Chattopadhyay, Goutam (Inventor); Lee, Choonsup (Inventor); Schlecht, Erich T. (Inventor); Jung-Kubiak, Cecile D. (Inventor); Mehdi, Imran (Inventor)

    2015-01-01

    A novel MMIC on-chip power-combined frequency multiplier device and a method of fabricating the same, comprising two or more multiplying structures integrated on a single chip, wherein each of the integrated multiplying structures are electrically identical and each of the multiplying structures include one input antenna (E-probe) for receiving an input signal in the millimeter-wave, submillimeter-wave or terahertz frequency range inputted on the chip, a stripline based input matching network electrically connecting the input antennas to two or more Schottky diodes in a balanced configuration, two or more Schottky diodes that are used as nonlinear semiconductor devices to generate harmonics out of the input signal and produce the multiplied output signal, stripline based output matching networks for transmitting the output signal from the Schottky diodes to an output antenna, and an output antenna (E-probe) for transmitting the output signal off the chip into the output waveguide transmission line.

  8. First results from the LHC Schottky Monitor operated with Direct Diode Detection

    CERN Document Server

    Gasior, M

    2012-01-01

    The LHC is equipped with a Schottky diagnostic system based on 4.8 GHz resonant pick-ups. Their signals are processed according to a three-stage down-mixing scheme, working well in most beam conditions. An important exception is the period of energy ramp of proton beams, when the noise floor of the observed beam spectrum increases dramatically and the Schottky sidebands disappear. To study beam spectra in such conditions the signals from the Schottky pick-ups were split and the second half of their power was processed with a copy of the LHC tune measurement electronics, modified for this application. The experimental set-up is based on simple diode detectors followed by signal processing in the kHz range and 24-bit audio ADCs. With such a test system LHC beam spectra were successfully observed. This contribution presents the used hardware and obtained results.

  9. The controlled growth of graphene nanowalls on Si for Schottky photodetector

    Directory of Open Access Journals (Sweden)

    Quan Zhou

    2017-12-01

    Full Text Available Schottky diode with directly-grown graphene on silicon substrate has advantage of clean junction interface, promising for photodetectors with high-speed and low noise. In this report, we carefully studied the influence of growth parameters on the junction quality and photoresponse of graphene nanowalls (GNWs-based Schottky photodetectors. We found that shorter growth time is critical for lower dark current, but at the same time higher photocurrent. The influence of growth parameters was attributed to the defect density of various growth time, which results in different degrees of surface absorption for H2O/O2 molecules and P-type doping level. Raman characterization and vacuum annealing treatment were carried out to confirm the regulation mechanism. Meanwhile, the release of thermal stress also makes the ideality factor η of thinner sample better than the thicker. Our results are important for the response improvement of photodetectors with graphene-Si schottky junction.

  10. Understanding Pt-ZnO:In Schottky nanocontacts by conductive atomic force microscopy

    Science.gov (United States)

    Chirakkara, Saraswathi; Choudhury, Palash Roy; Nanda, K. K.; Krupanidhi, S. B.

    2016-04-01

    Undoped and In doped ZnO (IZO) thin films are grown on Pt coated silicon substrates Pt/Si by pulsed laser deposition to fabricate Pt/ZnO:In Schottky diodes. The Schottky diodes were investigated by conventional two-probe current-voltage (I-V) measurements and by the I-V spectroscopy tool of conductive atomic force microscopy (C-AFM). The large deviation of the ideality factor from unity and the temperature dependent Schottky barrier heights (SBHs) obtained from the conventional method imply the presence of inhomogeneous interfaces. The inhomogeneity of SBHs is confirmed by C-AFM. Interestingly, the I-V curves at different points are found to be different, and the SBHs deduced from the point diodes reveal inhomogeneity at the nanoscale at the metal-semiconductor interface. A reduction in SBH and turn-on voltage along with enhancement in forward current are observed with increasing indium concentration.

  11. Improved Schottky contacts to InGaN alloys by a photoelectrochemical treatment

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Yin; Cai, Qing; Chen, Dunjun; Lu, Hai; Zhang, Rong; Zheng, Youdou [Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093 (China); Yang, Lianhong [Department of Physics, Changji College, Changji, 831100 (China); Xue, Junjun [School of Electronic Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing, 210093 (China)

    2016-04-15

    We report on improved electrical properties of Schottky contacts to InGaN alloys by introducing a photoelectrochemical treatment. The Schottky barrier height determined by a thermionic-field emission model, a dominating forward-current-transport mechanism, increased by 0.15 eV from 1.02 eV for conventional contacts to 1.17 eV for those with photoelectrochemical treatment at room temperature, while the ideality factors is closer to 1 after photoelectrochemical treatment. Furthermore, the reverse leakage mechanism varies from an ohmic transport mechanism at relatively low voltage and space charge-limited current mechanism at relatively high voltage for conventional contacts to Frenkel-Poole emission for improved Schottky contacts, which is attributed to partly removing surface states by the photoelectrochemical treatment. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. Outstanding gas sensing performance of CuO-CNTs nanocomposite based on asymmetrical schottky junctions

    Science.gov (United States)

    Zhao, Yiming; Ikram, Muhammad; Zhang, Jiawei; Kan, Kan; Wu, Hongyuan; Song, Wanzhen; Li, Li; Shi, Keying

    2018-01-01

    To fabricate a high-performance material for sensor devices at room temperature and further improve the synthetic approach of sensing materials, one dimensional (1D) CuO-CNTs nanocomposites were prepared with CNTs and CuO nanorods (NRs) via a facile reflux method. The 1D composite with the molar ratio of CuO and CNTs at 2.4:1 displays excellent gas sensing performance, i.e. the lowest detectable limit of 970 ppb and the short response time of 6 s-97.0 ppm NO2 at room temperature. In the 1D composite, the CNTs part provides a channel to enable effective and fast carrier transport, while the CuO NRs fabricates an asymmetrical schottky contact at the interface between the composites and the Au electrode. The advantage of the synergy of CNTs and CuO which possesses superior conductivity benefits the sensing of our 1D CuO-CNTs composite by providing affluent electrons.

  13. Unbiased continuous wave terahertz photomixer emitters with dis-similar Schottky barriers.

    Science.gov (United States)

    Mohammad-Zamani, Mohammad Javad; Moravvej-Farshi, Mohammad Kazem; Neshat, Mohammad

    2015-07-27

    We are introducing a new bias free CW terahertz photomixer emitter array. Each emitter consists of an asymmetric metal-semiconductor-metal (MSM) that is made of two side by side dis-similar Schottky contacts, on a thin layer of low temperature grown (LTG) GaAs, with barrier heights of difference (ΔΦ(B)) and a finite lateral spacing (s). Simulations show that when an appropriately designed structure is irradiated by two coherent optical beams of different center wavelengths, whose frequency difference (∆f) falls in a desired THz band, the built-in field between the two dis-similar potential barriers can accelerate the photogenerated carriers that are modulated by ∆ω, making each pitch in the array to act as a CW THz emitter, effectively. We also show the permissible values of s and ΔΦ(B) pairs, for which the strengths of the built-in electric field maxima fall below that of the critical of 50 V/μm- i.e., the breakdown limit for the LTG-GaAs layer. Moreover, we calculate the THz radiation power per emitter in an array. Among many potential applications for these bias free THz emitters their use in endoscopic imaging without a need for hazardous external biasing circuitry that reduces the patient health risk, could be the most important one. A hybrid numerical simulation method is used to design an optimum emitter pitch, radiating at 0.5 THz.

  14. Structuring a TiO2-based photonic crystal photocatalyst with Schottky junction for efficient photocatalysis.

    Science.gov (United States)

    Chen, Huan; Chen, Shuo; Quan, Xie; Zhang, Yaobin

    2010-01-01

    Facile and effective approaches were developed to fabricate the inverse TiO2/Pt opals Schottky structures on the Ti substrate. The as-prepared samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and diffuse reflectance UV-vis spectra (DRS), respectively. The results indicate that these samples were of ordered network, which was built by the Pt skeleton frame and the outer TiO2 layer. The TiO2 layer was identified as anatase with the preferential orientation of (101) plane. The experiments of short-circuit photocurrent (SCPC) and photocatalytic degradation of phenol were also conducted under the UV irradiation in order to evaluate the photoactivity of the samples. By tuning the red edge of photonic stop-band overlapping the absorption maximum of anatase (at 360 nm), both the UV absorption and the carrier separation of the samples were improved. The kinetic constant using the optimal inverse TiO2/Pt opals (0.992 h(-1)) was about 1.5 times as great as that of the disordered inverse TiO2/Pt opals (TiO2/Pt-mix) and was 3.3 times as great as that of pristine TiO2 nanocrystalline film (TiO2-nc) on Ti substrate.

  15. Gold nanoparticles deposited on linker-free silicon substrate and embedded in aluminum Schottky contact.

    Science.gov (United States)

    Gorji, Mohammad Saleh; Razak, Khairunisak Abdul; Cheong, Kuan Yew

    2013-10-15

    Given the enormous importance of Au nanoparticles (NPs) deposition on Si substrates as the precursor for various applications, we present an alternative approach to deposit Au NPs on linker-free n- and p-type Si substrates. It is demonstrated that, all conditions being similar, there is a significant difference between densities of the deposited NPs on both substrates. The Zeta-potential and polarity of charges surrounding the hydroxylamine reduced seeded growth Au NPs, are determined by a Zetasizer. To investigate the surface properties of Si substrates, contact angle measurement is performed. Field-emission scanning electron microscope is then utilized to distinguish the NPs density on the substrates. Finally, Al/Si Schottky barrier diodes with embedded Au NPs are fabricated, and their structural and electrical characteristics are further evaluated using an energy-filtered transmission electron microscope and current-voltage measurements, respectively. The results reveal that the density of NPs is significantly higher on n-type Si substrate and consequently has more pronounced effects on the electrical characteristics of the diode. It is concluded that protonation of Si-OH group on Si surface in low pH is responsible for the immobilization of Au NPs, which eventually contributes to the lowering of barrier height and enhances the electrical characteristics. Copyright © 2013 Elsevier Inc. All rights reserved.

  16. Performance Analysis of a Pt/ n-GaN Schottky Barrier UV Detector

    Science.gov (United States)

    Bouzid, F.; Dehimi, L.; Pezzimenti, F.

    2017-11-01

    The electrical and optical characteristics of an n-type gallium nitride (GaN)-based Schottky barrier ultraviolet (UV) detector, where a platinum (Pt) metal layer forms the anode contact, have been evaluated by means of detailed numerical simulations considering a wide range of incident light intensities. By modeling the GaN physical properties, the detector current density-voltage characteristics and spectral responsivity for different (forward and reverse) bias voltages and temperatures are presented, assuming incident optical power ranging from 0.001 W cm-2 to 1 W cm-2. The effect of defect states in the GaN substrate is also investigated. The results show that, at room temperature and under reverse bias voltage of -300 V, the dark current density is in the limit of 2.18 × 10-19 A cm-2. On illumination by a 0.36- μm UV uniform beam with intensity of 1 W cm-2, the photocurrent significantly increased to 2.33 A cm-2 and the detector spectral responsivity reached a maximum value of 0.2 A W-1 at zero bias voltage. Deep acceptor trap states and high temperature strongly affected the spectral responsivity curve in the considered 0.2 μm to 0.4 μm UV spectral range.

  17. Role of interfacial oxide in high-efficiency graphene-silicon Schottky barrier solar cells.

    Science.gov (United States)

    Song, Yi; Li, Xinming; Mackin, Charles; Zhang, Xu; Fang, Wenjing; Palacios, Tomás; Zhu, Hongwei; Kong, Jing

    2015-03-11

    The advent of chemical vapor deposition (CVD) grown graphene has allowed researchers to investigate large area graphene/n-silicon Schottky barrier solar cells. Using chemically doped graphene, efficiencies of nearly 10% can be achieved for devices without antireflective coatings. However, many devices reported in past literature often exhibit a distinctive s-shaped kink in the measured I/V curves under illumination resulting in poor fill factor. This behavior is especially prevalent for devices with pristine (not chemically doped) graphene but can be seen in some cases for doped graphene as well. In this work, we show that the native oxide on the silicon presents a transport barrier for photogenerated holes and causes recombination current, which is responsible for causing the kink. We experimentally verify our hypothesis and propose a simple semiconductor physics model that qualitatively captures the effect. Furthermore, we offer an additional optimization to graphene/n-silicon devices: by choosing the optimal oxide thickness, we can increase the efficiency of our devices to 12.4% after chemical doping and to a new record of 15.6% after applying an antireflective coating.

  18. Au/n-InP Schottky diodes using an Al2O3 interfacial layer grown by atomic layer deposition

    Science.gov (United States)

    Kim, Hogyoung; Kim, Min Soo; Yoon, Seung Yu; Choi, Byung Joon

    2017-02-01

    We investigated the effect of an Al2O3 interfacial layer grown by atomic layer deposition on the electrical properties of Au Schottky contacts to n-type InP. Considering barrier inhomogeneity, modified Richardson plots yielded a Richardson constant of 8.4 and 7.5 Acm-2K-2, respectively, for the sample with and without the Al2O3 interlayer (theoretical value of 9.4 Acm-2K-2 for n-type InP). The dominant reverse current flow for the sample with an Al2O3 interlayer was found to be Poole-Frenkel emission. From capacitance-voltage measurements, it was observed that the capacitance for the sample without the Al2O3 interlayer was frequency dependent. Sputter-induced defects as well as structural defects were passivated effectively with an Al2O3 interlayer.

  19. LARP LHC 4.8 GHz Schottky System Initial Commissioning with Beam

    CERN Document Server

    Pasquinelli, R J; Jones, O R; Jansson, A

    2011-01-01

    The LHC Schottky system consists for four independent 4.8 GHz triple down conversion receivers with associated data acquisition systems. Each system is capable of measuring tune, chromaticity, momentum spread in either horizontal or vertical planes; two systems per beam. The hardware commissioning has taken place during the spring and summer of 2010. With nominal bunch beam currents of 1011 protons, the first incoherent Schottky signals were detected and analyzed. This paper will report on these initial commissioning results. A companion paper will report on the data analysis curve fitting and remote control user interface of the system.

  20. LARP LHC 4.8 GHZ Schottky System Initial Commissioning with Beam

    CERN Document Server

    Pasquinelli, Ralph J.; Jones, O.Rhodri; Caspers, Fritz

    2011-01-01

    The LHC Schottky system consists for four independent 4.8 GHz triple down conversion receivers with associated data acquisition systems. Each system is capable of measuring tune, chromaticity, momentum spread in either horizontal or vertical planes; two systems per beam. The hardware commissioning has taken place from spring through fall of 2010. With nominal bunch beam currents of 1011 protons, the first incoherent Schottky signals were detected and analyzed. This paper will report on these initial commissioning results. A companion paper will report on the data analysis curve fitting and remote control user interface of the system.

  1. Metal contacts in nanocrystalline n-type GaN: Schottky diodes.

    Science.gov (United States)

    Das, S N; Sarangi, S; Sahu, S N; Pal, A K

    2009-04-01

    Contact properties in nanocrystalline n-GaN in thin film form were studied by depositing nanocrystalline films onto aluminium coated fused silica substrates by high pressure sputtering of Si (1 at%) doped GaN target. Schottky diodes were realized with Au, Ni and Pd as top contacts on the nanocrystalline n-GaN films to examine the contact properties of the diodes thus formed. Variation of current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the Schottky diodes were recorded at different temperatures and analyzed in the light of the existing theories.

  2. An improved forward I-V method for nonideal Schottky diodes with high series resistance

    OpenAIRE

    Lien, C.-D.; So, F. C. T.; Nicolet, M. -A.

    1984-01-01

    Two methods are described to obtain the value of the series resistance(R)of a Schottky diode from its forward I-V characteristic. The value of R is then used to plot the curve ln(I) versus V_D (= V - IR)which becomes a straight line even if ln(I) versus V does not. The ideality factor n and the Schottky-barrier height Φ_(B0) of the diode then follow from the standard procedure. The main advantages of the methods are: 1) a linear regression can be used to calculate the value of R, 2) many dat...

  3. Optimized design of 4H-SiC floating junction power Schottky barrier diodes

    Science.gov (United States)

    Hongbin, Pu; Lin, Cao; Zhiming, Chen; Jie, Ren

    2009-04-01

    SiC floating junction Schottky barrier diodes were simulated with software MEDICI 4.0 and their device structures were optimized based on forward and reverse electrical characteristics. Compared with the conventional power Schottky barrier diode, the device structure is featured by a highly doped drift region and embedded floating junction region, which can ensure high breakdown voltage while keeping lower specific on-state resistance, solved the contradiction between forward voltage drop and breakdown voltage. The simulation results show that with optimized structure parameter, the breakdown voltage can reach 4 kV and the specific on-resistance is 8.3 mΩ·cm2.

  4. Schottky contact barrier height enhancement on p-type silicon by wet chemical etching

    Science.gov (United States)

    Adegboyega, G. A.; Poggi, A.; Susi, E.; Castaldini, A.; Cavallini, A.

    1989-04-01

    A wet chemical etch preceding the usual cleaning process has been found to yield Schottky barriers of high values on p-type silicon. This procedure produces a passivated surface layer which has resulted in Al/0-Si Schottky diodes with barrier height of 0.75 eV and ideality factor of 1.15. Measurements have confirmed the presence of electrically active donor-like states in this surface layer. The origin of the donor states is explained in terms of the deactivation of the boron acceptor by the formation of H + B - pairs.

  5. An Ultra-Wideband Schottky Diode Based Envelope Detector for 2.5 Gbps signals

    DEFF Research Database (Denmark)

    Cimoli, Bruno; Valdecasa, Guillermo Silva; Granja, Angel Blanco

    2016-01-01

    In this paper an ultra-wideband (UWB) Schottky diode based envelope detector is reported. The detector consists of an input matching network, a Schottky diode and wideband output filtering network. The output network is tailored to demodulate ultra-wideband amplitude shift keying (ASK) signals up...... to 2.5 Gbps at 6-9 GHz carrier frequency. The detector uses microstrip and surface-mount device (SMD) components and it is fabricated on a Rogers 6002 substrate. Experimental results show error free transmissions up to 2.5 Gbps at an input power level of -11 dBm. The highest measured conversion gain...

  6. Simulation of electrical characteristics of GaN vertical Schottky diodes

    Science.gov (United States)

    Łukasiak, Lidia; Jasiński, Jakub; Jakubowski, Andrzej

    2016-12-01

    Reverse current of GaN vertical Schottky diodes is simulated using Silvaco ATLAS to optimize the geometry for the best performance. Several physical quantities and phenomena, such as carrier mobility and tunneling mechanism are studied to select the most realistic models. Breakdown voltage is qualitatively estimated based on the maximum electric field in the structure.

  7. 5.2% efficient PbS nanocrystal Schottky solar cells

    NARCIS (Netherlands)

    Piliego, Claudia; Protesescu, Loredana; Bisri, Satria Zulkarnaen; Kovalenko, Maksym V.; Loi, Maria Antonietta

    2013-01-01

    The impact of post-synthetic treatments of nanocrystals (NCs) on the performance of Schottky solar cells, where the active PbS nanocrystal layer is sandwiched directly between two electrodes, is investigated. By monitoring the amount of ligands on the surface of the nanocrystals through Fourier

  8. Thermally Stable Silver Nanowires-Embedding Metal Oxide for Schottky Junction Solar Cells.

    Science.gov (United States)

    Kim, Hong-Sik; Patel, Malkeshkumar; Park, Hyeong-Ho; Ray, Abhijit; Jeong, Chaehwan; Kim, Joondong

    2016-04-06

    Thermally stable silver nanowires (AgNWs)-embedding metal oxide was applied for Schottky junction solar cells without an intentional doping process in Si. A large scale (100 mm(2)) Schottky solar cell showed a power conversion efficiency of 6.1% under standard illumination, and 8.3% under diffused illumination conditions which is the highest efficiency for AgNWs-involved Schottky junction Si solar cells. Indium-tin-oxide (ITO)-capped AgNWs showed excellent thermal stability with no deformation at 500 °C. The top ITO layer grew in a cylindrical shape along the AgNWs, forming a teardrop shape. The design of ITO/AgNWs/ITO layers is optically beneficial because the AgNWs generate plasmonic photons, due to the AgNWs. Electrical investigations were performed by Mott-Schottky and impedance spectroscopy to reveal the formation of a single space charge region at the interface between Si and AgNWs-embedding ITO layer. We propose a route to design the thermally stable AgNWs for photoelectric device applications with investigation of the optical and electrical aspects.

  9. Schottky barrier height of MnSb/GaAs(111)B contacts : Influence of interface structure

    NARCIS (Netherlands)

    Manago, T; Miyanishi, S; Akinaga, H; Van Roy, W; Roelfsema, RFB; Sato, T; Tamura, E; Yuasa, S

    2000-01-01

    The Schottky barrier height (SBH) of MnSb(0001)/n-GaAs(111)B diodes was investigated in terms of current-voltage characteristics for three different GaAs surfaces, GaAs (root 19x root 19), GaAs (2x2), and sulfur passivated GaAs. We observed that the SBH and the ideality factor changed significantly

  10. A high-speed Schottky detector for ultra-wideband communications

    DEFF Research Database (Denmark)

    Valdecasa, Guillermo Silva; Cimoli, Bruno; Blanco Granja, Ángel

    2017-01-01

    This letter reviews the design procedure of a high‐speed Schottky video detector for high‐data‐rate communications within the ultra‐wideband (UWB) frequencies. The classic design approach for video detectors is extended with a mixer‐like analysis, which results in a more detailed assessment...

  11. Electron Waveguide Y-branch Switches Controlled by Pt/GaAs Schottky Gates

    Science.gov (United States)

    Forsberg, E.; Hieke, K.

    Electron waveguide Y-branch switches have been fabricated in a GaAs/AlGaAs heterostructure. These are controlled by Pt/GaAs Schottky contacts, which were realized by an in-situ electrochemical process. In this paper we describe the fabrication process as well as present results from conductance measurements in the fabricated devices.

  12. Tuning the Schottky Barrier at the Graphene/MoS2 Interface by Electron Doping

    DEFF Research Database (Denmark)

    Jin, Chengjun; Rasmussen, Filip Anselm; Thygesen, Kristian Sommer

    2015-01-01

    Using ab initio calculations we investigate the energy level alignment at the graphene/MoS2 heterostructure and the use of electron doping as a strategy to lower the Schottky barrier and achieve a low-resistance Ohmic contact. For the neutral heterostructure, density functional theory (DFT...... concentration is shown to be mainly governed by the electrostatic potential resulting from the doping charge....

  13. Summer Student Report 2014: Schottky component qualification and RF filter characterization

    CERN Document Server

    Egidos Plaja, Nuria

    2014-01-01

    This Summer Student project has been developed in BE-BI-QP department under the supervision of Manfred Wendt. Main goals of the task to be performed are the following: 1)\tFilter characterization: the student will get familiar with the Vector Network Analizer (VNA), S-parameter measurement and PSPICE modelling of low-pass filters. 2)\tFilter response matching: an algorithm to compare and classify filter responses into best-matching pairs will be developed. 3)\tSchottky monitor filter qualification: S-parameter and time domain measurements will be carried out with filters related to Schottky monitor and results will be benchmarked. 4)\tSchottky monitor amplifier measurement: noise figure and gain at a given frequency will be measured for a set of Low Noise Amplifiers related to Schottky monitor. -1dB compression point and 3rd order interception point will be measured too for education purposes. For the development of this project, the student will get familiar with RF measure devices (VNA, VSA), theoretical concep...

  14. Quasi-Schottky-Barrier UTBB SOI MOSFET for Low-Power Robust SRAMs

    DEFF Research Database (Denmark)

    Ghanatian, Hamdam; Hosseini, Seyed Ebrahim; Zeinali, Behzad

    2017-01-01

    This paper presents a low-power robust static random access memory (SRAM) using a novel quasi-Schottky-barrier ultrathin body and ultrathin buried oxide (UTBB) silicon-on-insulator (SOI) device. In the proposed device, the drain terminal is highly doped and a metallic source terminal is used. Giv...

  15. Summary of Schottky barrier height data on epitaxially grown n-and p-GaAs

    CSIR Research Space (South Africa)

    Myburg, G

    1998-07-18

    Full Text Available The Schottky barrier height values, as determined by the current–voltage and capacitance–voltage techniques, of 43 metals which were fabricated by following the same cleaning procedure and using the same high-quality organ metallic vapour phase...

  16. Thin-film GaN Schottky diodes formed by epitaxial lift-off

    Science.gov (United States)

    Wang, Jingshan; Youtsey, Chris; McCarthy, Robert; Reddy, Rekha; Allen, Noah; Guido, Louis; Xie, Jinqiao; Beam, Edward; Fay, Patrick

    2017-04-01

    The performance of thin-film GaN Schottky diodes fabricated using a large-area epitaxial lift-off (ELO) process is reported in this work. Comparison of the device characteristics before and after lift-off processing reveals that the Schottky barrier height remains unchanged by the liftoff processing and is consistent with expectations based on metal-semiconductor work function differences, with a barrier height of approximately 1 eV obtained for Ni/Au contacts on n- GaN. However, the leakage current in both reverse and low-forward-bias regimes is found to improve significantly after ELO processing. Likewise, the ideality factor of the Schottky diodes also improves after ELO processing, decreasing from n = 1.12-1.18 before ELO to n = 1.04-1.10 after ELO. A possible explanation for the performance improvement obtained for Schottky diodes after substrate removal by ELO processing is the elimination of leakage paths consisting of vertical leakage along threading dislocations coupled with lateral conduction through the underlying n+ buffer layer that is removed in the ELO process. Epitaxial liftoff with GaN may enable significant improvement in device performance and economics for GaN-based electronics and optoelectronics.

  17. Temperature dependence of current-and capacitance-voltage characteristics of an Au/4H-SiC Schottky diode

    Science.gov (United States)

    Gülnahar, Murat

    2014-12-01

    In this study, the current-voltage (I-V) and capacitance-voltage (C-V) measurements of an Au/4H-SiC Schottky diode are characterized as a function of the temperature in 50-300 K temperature range. The experimental parameters such as ideality factor and apparent barrier height presents to be strongly temperature dependent, that is, the ideality factor increases and the apparent barrier height decreases with decreasing temperature, whereas the barrier height values increase with the temperature for C-V data. Likewise, the Richardson plot deviates at low temperatures. These anomaly behaviors observed for Au/4H-SiC are attributed to Schottky barrier inhomogeneities. The barrier anomaly which relates to interface of Au/4H-SiC is also confirmed by the C-V measurements versus the frequency measured in 300 K and it is interpreted by both Tung's lateral inhomogeneity model and multi-Gaussian distribution approach. The values of the weighting coefficients, standard deviations and mean barrier height are calculated for each distribution region of Au/4H-SiC using the multi-Gaussian distribution approach. In addition, the total effective area of the patches NAe is obtained at separate temperatures and as a result, it is expressed that the low barrier regions influence meaningfully to the current transport at the junction. The homogeneous barrier height value is calculated from the correlation between the ideality factor and barrier height and it is noted that the values of standard deviation from ideality factor versus q/3kT curve are in close agreement with the values obtained from the barrier height versus q/2kT variation. As a result, it can be concluded that the temperature dependent electrical characteristics of Au/4H-SiC can be successfully commented on the basis of the thermionic emission theory with both models.

  18. Free-standing gallium nitride Schottky diode characteristics and stability in a high-temperature environment

    Science.gov (United States)

    O'Mahony, Donagh; Zimmerman, Walter; Steffen, Sinje; Hilgarth, Just; Maaskant, Pleun; Ginige, Ravin; Lewis, Liam; Lambert, Benoit; Corbett, Brian

    2009-12-01

    Schottky diodes have been fabricated using low-resistivity n-type free-standing GaN substrates with a reduced defect density lowly doped n-type epi-layer and an Ni/Ti/Pt/Au Schottky contact metalization. A thermionic field emission current transport mechanism was identified with a Schottky barrier height of about 0.75 eV and a diode ideality of 1.1 measured at 25 °C, both of which increase with measurement temperature up to 200 °C. The diodes were subjected to long-term testing under forward current (1.3 A cm-2) or reverse voltage (-3.5 V) biased storage at 300 °C in N2 for 466 h and were also monitored under non-biased storage conditions for up to 1000 h at 350 °C and 400 °C in N2 or at 300 °C for 1500 h in air. Except for the non-biased storage test at 400 °C, the diodes show <10% drift in ideality and barrier height during the long-term storage tests. For the 400 °C test, there is a significant increase in both barrier height and ideality over a relatively short storage period (48 h). This to be the first reported study on the long-term stability of Schottky diodes on free-standing GaN and while no catastrophic (e.g. thermal runaway) degradation of any of the diodes was observed, it is proposed that optimized thermal annealing of the Ni-based Schottky contact metalization in the temperature range 350-400 °C is necessary for stable long-term operation at high temperature.

  19. Extraction of the Schottky parameters in metal-semiconductor-metal diodes from a single current-voltage measurement

    OpenAIRE

    Nouchi, Ryo

    2014-01-01

    In order to develop a method to extract the parameters of the two inherent Schottky contacts from a single current-voltage (I-V) characteristic curve, the I-V characteristics of metal-semiconductor-metal (MSM) diodes with asymmetric Schottky barrier heights are theoretically investigated using the thermionic emission model. The MSM diode structure is commonly used because an additional MS interface is required for the electrical characterization of MS diodes. A finite charge-injection barrier...

  20. Charge transport mechanisms of graphene/semiconductor Schottky barriers: A theoretical and experimental study

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Haijian; Liu, Zhenghui; Xu, Gengzhao; Shi, Lin; Fan, Yingmin; Yang, Hui [Suzhou Institute of Nano-Tech and Nano-Bionics, CAS, Suzhou 215123 (China); Xu, Ke, E-mail: kxu2006@sinano.ac.cn; Wang, Jianfeng; Ren, Guoqiang [Suzhou Institute of Nano-Tech and Nano-Bionics, CAS, Suzhou 215123 (China); Suzhou Nanowin Science and Technology Co., Ltd., Suzhou 215123 (China)

    2014-01-07

    Graphene has been proposed as a material for semiconductor electronic and optoelectronic devices. Understanding the charge transport mechanisms of graphene/semiconductor Schottky barriers will be crucial for future applications. Here, we report a theoretical model to describe the transport mechanisms at the interface of graphene and semiconductors based on conventional semiconductor Schottky theory and a floating Fermi level of graphene. The contact barrier heights can be estimated through this model and be close to the values obtained from the experiments, which are lower than those of the metal/semiconductor contacts. A detailed analysis reveals that the barrier heights are as the function of the interface separations and dielectric constants, and are influenced by the interfacial states of semiconductors. Our calculations show how this behavior of lowering barrier heights arises from the Fermi level shift of graphene induced by the charge transfer owing to the unique linear electronic structure.

  1. Analysis of the active layer in SI GaAs Schottky diodes

    Energy Technology Data Exchange (ETDEWEB)

    Castaldini, A.; Cavallini, A.; Polenta, L. [Bologna Univ. (Italy). Dipt. di Fisica]|[INFM, Bologna (Italy); Canali, C. [INFM and Dipartimento di Scienze dell`Ingegneria, Universita` di Modena, Via Campi 213/B, Modena (Italy); Nava, F. [INFN and Dipartimento di Fisica, Universita` di Modena, Via Campi 213/A, Modena (Italy)

    1998-06-01

    The behavior of the active region width W of semi-insulating gallium arsenide Schottky diodes versus reverse biasing has been investigated by optical beam induced current and surface potential techniques. It has been found that at low applied voltages, W follows the square root law peculiar to a Schottky barrier while, for a bias higher than 20 V, the active layer increases linearly with the voltage applied. To go deeper into this matter, the spatial distribution of the electric field has been analyzed in a wide range of bias voltages and it has been observed that at high voltages a plateau occurs, followed by a linear decrease down to a quasi-zero value. In terms of space charge distribution this means that there is a box-shaped space charge region moving towards the ohmic contact at increasing bias. (orig.) 21 refs.

  2. A Silicon Nanocrystal Schottky Junction Solar Cell produced from Colloidal Silicon Nanocrystals

    Directory of Open Access Journals (Sweden)

    Liu Chin-Yi

    2010-01-01

    Full Text Available Abstract Solution-processed semiconductors are seen as a promising route to reducing the cost of the photovoltaic device manufacture. We are reporting a single-layer Schottky photovoltaic device that was fabricated by spin-coating intrinsic silicon nanocrystals (Si NCs from colloidal suspension. The thin-film formation process was based on Si NCs without any ligand attachment, exchange, or removal reactions. The Schottky junction device showed a photovoltaic response with a power conversion efficiency of 0.02%, a fill factor of 0.26, short circuit-current density of 0.148 mA/cm2, and open-circuit voltage of 0.51 V.

  3. On-Chip Power-Combining for High-Power Schottky Diode-Based Frequency Multipliers

    Science.gov (United States)

    Chattopadhyay, Goutam; Mehdi, Imran; Schlecht, Erich T.; Lee, Choonsup; Siles, Jose V.; Maestrini, Alain E.; Thomas, Bertrand; Jung, Cecile D.

    2013-01-01

    A 1.6-THz power-combined Schottky frequency tripler was designed to handle approximately 30 mW input power. The design of Schottky-based triplers at this frequency range is mainly constrained by the shrinkage of the waveguide dimensions with frequency and the minimum diode mesa sizes, which limits the maximum number of diodes that can be placed on the chip to no more than two. Hence, multiple-chip power-combined schemes become necessary to increase the power-handling capabilities of high-frequency multipliers. The design presented here overcomes difficulties by performing the power-combining directly on-chip. Four E-probes are located at a single input waveguide in order to equally pump four multiplying structures (featuring two diodes each). The produced output power is then recombined at the output using the same concept.

  4. An improved forward I-V method for nonideal Schottky diodes with high series resistance

    Science.gov (United States)

    Lien, C.-D.; So, F. C. T.; Nicolet, M.-A.

    1984-01-01

    Two methods are described to obtain the value of the series resistance (R) of a Schottky diode from its forward I-V characteristic. The value of R is then used to plot the curve ln(I) versus V sub D (= V - IR) which becomes a straight line even if ln(I) versus V does not. The ideality factor n and the Schottky-barrier height of the diode then follow from the standard procedure. The main advantages of the methods are: (1) a linear regression can be used to calculate the value of R; (2) many data points are used over the whole data range, which raises the accuracy of the results, and (3) the validity of constant R assumption can be checked by the linearity of the ln (I) versus V sub D curve. The methods are illustrated on the experimental data of a real diode.

  5. Model and observations of Schottky-noise suppression in a cold heavy-ion beam.

    Science.gov (United States)

    Danared, H; Källberg, A; Rensfelt, K-G; Simonsson, A

    2002-04-29

    Some years ago it was found at GSI in Darmstadt that the momentum spread of electron-cooled beams of highly charged ions dropped abruptly to very low values when the particle number decreased to 10 000 or less. This has been interpreted as an ordering of the ions, such that they line up after one another in the ring. We report observations of similar transitions at CRYRING, including an accompanying drop in Schottky-noise power. We also introduce a model of the ordered beam from which the Schottky-noise power can be calculated numerically. The good agreement between the model calculation and the experimental data is seen as evidence for a spatial ordering of the ions.

  6. Fabrication of 4H-SiC Schottky barrier diodes with high breakdown voltages

    CERN Document Server

    Kum, B H; Shin, M W; Park, J D

    1999-01-01

    This paper discusses the fabrication and the breakdown characteristics of 4H-SiC Schottky barrier diodes (SBDs). Optimal processing conditions for the ohmic contacts were extracted using the transmission-line method (TLM) and were applied to the device fabrication. The Ti/4H-SiC SBDs with Si sub x B sub y passivation showed a maximum reverse breakdown voltage of 268 V with a forward current density as high as 70 mA/cm sup 2 at a forward voltage of 2 V. The breakdown of the Pt. 4H-SiC SBDs without any passivation occurred at near 110 V. It is concluded that the breakdown enhancement in the Ti/4H-SiC SBDs can be attributed to the passivation; otherwise, excess surface charge near the edge of the Schottky contact would lead to electric fields of sufficient magnitude to cause field emission.

  7. Fabrication of polymer Schottky diode with Al-PANI/MWCNT-Au structure

    Directory of Open Access Journals (Sweden)

    A Hajibadali

    2014-11-01

    Full Text Available In this research, Schottky diode with Al-PANI/MWCNT-Au structure was fabricated using spin coating of composite polymer and physical vapor deposition of metals. For this purpose, a thin layer of gold was coated on glass and then composite of polyaniline/multi-walled carbon nanotube was synthesized and spin-coated on gold layer. Finally, a thin layer of aluminum was coated on polymer layer. The current-voltage characteristics of diode were studied and found that I-V curve is nonlinear and nonsymmetrical, showing rectifying behavior. I-V characteristics plotted on a logarithmic scale for Schottky diode showed two distinct power law regions. At lower voltages, the mechanism follows Ohm’s Law and at higher voltages, the mechanism is consistent with space charge limited conduction (SCLC emission. The parameters extracted from I-V characteristics were also calculated.

  8. Charged particle detection properties of epitaxial 4H-SiC Schottky diodes

    Energy Technology Data Exchange (ETDEWEB)

    Nava, F.; Vanni, P. [Modena Univ. (Italy). Ist. di Fisica; Verzellesi, G. [Modena Univ. (Italy). DSI; Castaldini, A.; Cavallini, A.; Polenta, L. [Bologna Univ. (Italy). Dipt. di Fisica; Nipoti, R.; Donolato, C. [Consiglio Nazionale delle Ricerche, Bologna (Italy). Ist. LAMEL

    2001-07-01

    This work presents measurements of the charge-collection properties of 4H-SiC Schottky diodes under alpha radiation and investigates the influence of native and alpha induced defects on the detector performance. The contribution of the diffusion of minority carriers to the charge collection efficiency is pointed out. Values of 500 ns and 95 {mu}s are inferred for the hole and electron lifetime, respectively. (orig.)

  9. Schottky contact formation on polar and non-polar AlN

    Energy Technology Data Exchange (ETDEWEB)

    Reddy, Pramod; Bryan, Isaac; Bryan, Zachary; Tweedie, James; Kirste, Ronny; Collazo, Ramon; Sitar, Zlatko [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695-7919 (United States)

    2014-11-21

    The interfaces of m- and c-plane AlN with metals of different work functions and electro-negativities were characterized and the Schottky barrier heights were measured. The Schottky barrier height was determined by measuring the valence band maximum (VBM) with respect to the Fermi level at the surface (interface) before (after) metallization. VBM determination included accurate modeling and curve fitting of density of states at the valence band edge with the XPS data. The experimental behavior of the barrier heights could not be explained by the Schottky-Mott model and was modeled using InterFace-Induced Gap States (IFIGS). A slope parameter (S{sub X}) was used to incorporate the density of surface states and is a measure of Fermi level pinning. The experimental barriers followed theoretical predictions with a barrier height at the surface Fermi level (Charge neutrality level (CNL)) of ∼2.1 eV (∼2.7 eV) on m-plane (c-plane) and S{sub X} ∼ 0.36 eV/Miedema unit. Slope parameter much lower than 0.86 implied a surface/interface states dominated behavior with significant Fermi level pinning and the measured barrier heights were close to the CNL. Titanium and zirconium provided the lowest barriers (1.6 eV) with gold providing the highest (2.3 eV) among the metals analyzed on m-plane. It was consistently found that barrier heights decreased from metal polar to non-polar surfaces, in general, due to an increasing CNL. The data indicated that charged IFIGS compensate spontaneous polarization charge. These barrier height and slope parameter measurements provided essential information for designing Schottky diodes and other contact-based devices on AlN.

  10. 5.2% efficient PbS nanocrystal Schottky solar cells

    OpenAIRE

    Piliego, Claudia; Protesescu, Loredana; Bisri, Satria Zulkarnaen; Kovalenko, Maksym V.; Loi, Maria Antonietta

    2013-01-01

    The impact of post-synthetic treatments of nanocrystals (NCs) on the performance of Schottky solar cells, where the active PbS nanocrystal layer is sandwiched directly between two electrodes, is investigated. By monitoring the amount of ligands on the surface of the nanocrystals through Fourier Transform Infrared (FTIR) measurements, we find that optimized processing conditions can lead to high current density and thus to an increase in overall efficiency. Our devices reach an efficiency of 5...

  11. Theory of photoexcited and thermionic emission across a two-dimensional graphene-semiconductor Schottky junction

    OpenAIRE

    Trushin, Maxim

    2017-01-01

    We find that intrinsic graphene provides efficient photocarrier transport across a two-dimensional graphene-semiconductor Schottky junction as a linear response to monochromatic light with excitation energy well below the semiconductor bandgap. The operation mechanism relies both on zero-bias photoexcited and thermionic emission contributing to photoresponsivity, enabled by the extended photocarrier thermalization time in intrinsic graphene. The photoresponsivity rapidly increases with excita...

  12. Schottky-Gated Probe-Free ZnO Nanowire Biosensor

    KAUST Repository

    Yeh, Ping-Hung

    2009-12-28

    (Figure Presented) A nanowire-based nanosensor for detecting biologically and chemically charged molecules that is probe-free and highly sensitive is demonstrated. The device relies on the nonsymmetrical Schottky contact under reverse bias (see figure) and is much more sensitive than the device based on the symmetric ohmic contact. This approach serves as a guideline for designing more practical chemical and biochemical sensors. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA.

  13. Electrical degradation of double-Schottky barrier in ZnO varistors

    Directory of Open Access Journals (Sweden)

    Jinliang He

    2016-03-01

    Full Text Available Researches on electrical degradation of double-Schottky barrier in ZnO varistors are reviewed, aimed at the constitution of a full picture of universal degradation mechanism within the perspective of defect. Recent advances in study of ZnO materials by atomic-scale first-principles calculations are partly included and discussed, which brings to our attention distinct cognition on the native point defects and their profound impact on degradation.

  14. Electrical degradation of double-Schottky barrier in ZnO varistors

    Energy Technology Data Exchange (ETDEWEB)

    He, Jinliang, E-mail: hejl@tsinghua.edu.cn; Cheng, Chenlu; Hu, Jun [The State Key Lab of Power System, Department of Electrical Engineering, Tsinghua University, Beijing 100084 (China)

    2016-03-15

    Researches on electrical degradation of double-Schottky barrier in ZnO varistors are reviewed, aimed at the constitution of a full picture of universal degradation mechanism within the perspective of defect. Recent advances in study of ZnO materials by atomic-scale first-principles calculations are partly included and discussed, which brings to our attention distinct cognition on the native point defects and their profound impact on degradation.

  15. Band structure, band offsets, substitutional doping, and Schottky barriers of bulk and monolayer InSe

    Science.gov (United States)

    Guo, Yuzheng; Robertson, John

    2017-09-01

    We present a detailed study of the electronic structure of the layered semiconductor InSe. We calculate the band structure of the monolayer and bulk material using density functional theory, hybrid functionals, and G W . The band gap of the monolayer InSe is calculated to be 2.4 eV in screened exchange hybrid functional, close to the experimental photoluminescence gap. The electron affinities and band offsets are calculated for vertical stacked-layer heterostructures, and are found to be suitable for tunnel field effect transistors (TFETs) in combination with WS e2 or similar. The valence-band edge of InSe is calculated to lie 5.2 eV below the vacuum level, similar to that for the closed shell systems HfS e2 or SnS e2 . Hence InSe would be suitable to act as a p -type drain in the TFET. The intrinsic defects are calculated. For Se-rich layers, the Se adatom (interstitial) is found to be the most stable defect, whereas for In-rich layers, the Se vacancy is the most stable for the neutral state. Antisites tend to have energies just above those of vacancies. The Se antisite distorts towards a bond-breaking distortion as in the EL2 center of GaAs. Both substitutional donors and acceptors are calculated to be shallow, and effective dopants. They do not reconstruct to form nondoping configurations as occurs in black phosphorus. Finally, the Schottky barriers of metals on InSe are found to be strongly pinned by metal induced gap states (MIGS) at ˜0.5 eV above the valence-band edge. Any interfacial defects would lead to a stronger pinning at a similar energy. Overall, InSe is an effective semiconductor combining the good features of 2D (lack of dangling bonds, etc.) with the good features of 3D (effective doping), which few others achieve.

  16. 670-GHz Schottky Diode-Based Subharmonic Mixer with CPW Circuits and 70-GHz IF

    Science.gov (United States)

    Chattopadhyay, Goutam; Schlecht, Erich T.; Lee, Choonsup; Lin, Robert H.; Gill, John J.; Mehdi, Imran; Sin, Seth; Deal, William; Loi, Kwok K.; Nam, Peta; hide

    2012-01-01

    GaAs-based, sub-harmonically pumped Schottky diode mixers offer a number of advantages for array implementation in a heterodyne receiver system. Since the radio frequency (RF) and local oscillator (LO) signals are far apart, system design becomes much simpler. A proprietary planar GaAs Schottky diode process was developed that results in very low parasitic anodes that have cutoff frequencies in the tens of terahertz. This technology enables robust implementation of monolithic mixer and frequency multiplier circuits well into the terahertz frequency range. Using optical and e-beam lithography, and conventional epitaxial layer design with innovative usage of GaAs membranes and metal beam leads, high-performance terahertz circuits can be designed with high fidelity. All of these mixers use metal waveguide structures for housing. Metal machined structures for RF and LO coupling hamper these mixers to be integrated in multi-pixel heterodyne array receivers for spectroscopic and imaging applications. Moreover, the recent developments of terahertz transistors on InP substrate provide an opportunity, for the first time, to have integrated amplifiers followed by Schottky diode mixers in a heterodyne receiver at these frequencies. Since the amplifiers are developed on a planar architecture to facilitate multi-pixel array implementation, it is quite important to find alternative architecture to waveguide-based mixers.

  17. Reducing the Schottky barrier between few-layer MoTe2 and gold

    Science.gov (United States)

    Qi, Dianyu; Wang, Qixing; Han, Cheng; Jiang, Jizhou; Zheng, Yujie; Chen, Wei; Zhang, Wenjing; Thye Shen Wee, Andrew

    2017-12-01

    Schottky barriers greatly influence the performance of optoelectronic devices. Schottky barriers can be reduced by harnessing the polymorphism of 2D metal transition dichalcogenides, since both semiconducting and metallic phases exist. However, high energy, high temperature or chemicals are normally required for phase transformation, or the processes are complex. In this work, stable low-resistance contacts between few layer MoTe2 flakes and gold electrodes are achieved by a simple thermal annealing treatment at low temperature (200-400 °C). The resulting Schottky barrier height of the annealed MoTe2/Au interface is low (~23 meV). A new Raman A g mode of the 1T‧ metallic phase of MoTe2 on gold electrode is observed, indicating that the low-resistance contact is due to the phase transition of 2H-MoTe2. The gold substrate plays an important role in the transformation, and a higher gold surface roughness increases the transformation rate. With this method, the mobility and ON-state current of the MoTe2 transistor increase by ~3-4 orders of magnitude, the photocurrent of vertically stacked graphene/MoTe2/Au device increases ~300%, and the response time decreases by ~20%.

  18. A novel nanoscaled Schottky barrier based transmission gate and its digital circuit applications

    Science.gov (United States)

    Kumar, Sunil; Loan, Sajad A.; Alamoud, Abdulrahman M.

    2017-04-01

    In this work we propose and simulate a compact nanoscaled transmission gate (TG) employing a single Schottky barrier based transistor in the transmission path and a single transistor based Sajad-Sunil-Schottky (SSS) device as an inverter. Therefore, just two transistors are employed to realize a complete transmission gate which normally consumes four transistors in the conventional technology. The transistors used to realize the transmission path and the SSS inverter in the proposed TG are the double gate Schottky barrier devices, employing stacks of two metal silicides, platinum silicide (PtSi) and erbium silicide (ErSi). It has been observed that the realization of the TG gate by the proposed technology has resulted into a compact structure, with reduced component count, junctions, interconnections and regions in comparison to the conventional technology. The further focus of this work is on the application part of the proposed technology. So for the first time, the proposed technology has been used to realize various combinational circuits, like a two input AND gate, a 2:1 multiplexer and a two input XOR circuits. It has been observed that the transistor count has got reduced by half in a TG, two input AND gate, 2:1 multiplexer and in a two input XOR gate. Therefore, a significant reduction in transistor count and area requirement can be achieved by using the proposed technology. The proposed technology can be also used to perform the compact realization of other combinational and sequential circuitry in future.

  19. Mo1-xWxSe2-Based Schottky Junction Photovoltaic Cells.

    Science.gov (United States)

    Yi, Sum-Gyun; Kim, Sung Hyun; Park, Sungjin; Oh, Donggun; Choi, Hwan Young; Lee, Nara; Choi, Young Jai; Yoo, Kyung-Hwa

    2016-12-14

    We developed Schottky junction photovoltaic cells based on multilayer Mo1-xWxSe2 with x = 0, 0.5, and 1. To generate built-in potentials, Pd and Al were used as the source and drain electrodes in a lateral structure, and Pd and graphene were used as the bottom and top electrodes in a vertical structure. These devices exhibited gate-tunable diode-like current rectification and photovoltaic responses. Mo0.5W0.5Se2 Schottky diodes with Pd and Al electrodes exhibited higher photovoltaic efficiency than MoSe2 and WSe2 devices with Pd and Al electrodes, likely because of the greater adjusted band alignment in Mo0.5W0.5Se2 devices. Furthermore, we showed that Mo0.5W0.5Se2-based vertical Schottky diodes yield a power conversion efficiency of ∼16% under 532 nm light and ∼13% under a standard air mass 1.5 spectrum, demonstrating their remarkable potential for photovoltaic applications.

  20. Schottky junctions studied using Korringa-Kohn-Rostoker nonequilibrium Green's function method

    Science.gov (United States)

    Akai, Hisazumi; Ogura, Masako

    A scheme that combines the non-equilibrium Green's function method with the Korringa-Kohn-Rostoker (KKR) Green's function method is proposed. The method is different from many previous attempts in that it uses the exact Green's function whose spectrum is not bound within a finite energy range, and hence, provides sound basis for quantitative discussions. The scheme is applied to the Schottky junctions composed of an Al/GaN/Al trilayer. Schottky contacts formed in metal/semiconductor junctions play an important role in semiconductor devices and integrated circuits. They have been intensively investigated for several decades not only for possible application to electronic devices but also for gaining a fundamental understanding of the Schottky barrier formation. Our results show that the Schottly barrier is formed between an undoped GaN and Al interface. The transport property of this system under various finite bias voltages is calculated. It is shown that the asymmetric behavior of electron transport against the direction of bias voltage occurs in this system, confirming the feature of rectification. The present study was partly supported by Grant-in-Aid No. 22104012, MEXT, Japan, the Alexander von Humboldt Foundation, and by the Elements Strategy Initiative Project under the auspice of MEXT, Japan.

  1. Ambipolar MoS2 Transistors by Nanoscale Tailoring of Schottky Barrier Using Oxygen Plasma Functionalization.

    Science.gov (United States)

    Giannazzo, Filippo; Fisichella, Gabriele; Greco, Giuseppe; Di Franco, Salvatore; Deretzis, Ioannis; La Magna, Antonino; Bongiorno, Corrado; Nicotra, Giuseppe; Spinella, Corrado; Scopelliti, Michelangelo; Pignataro, Bruno; Agnello, Simonpietro; Roccaforte, Fabrizio

    2017-07-12

    One of the main challenges to exploit molybdenum disulfide (MoS2) potentialities for the next-generation complementary metal oxide semiconductor (CMOS) technology is the realization of p-type or ambipolar field-effect transistors (FETs). Hole transport in MoS2 FETs is typically hampered by the high Schottky barrier height (SBH) for holes at source/drain contacts, due to the Fermi level pinning close to the conduction band. In this work, we show that the SBH of multilayer MoS2 surface can be tailored at nanoscale using soft O2 plasma treatments. The morphological, chemical, and electrical modifications of MoS2 surface under different plasma conditions were investigated by several microscopic and spectroscopic characterization techniques, including X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), conductive AFM (CAFM), aberration-corrected scanning transmission electron microscopy (STEM), and electron energy loss spectroscopy (EELS). Nanoscale current-voltage mapping by CAFM showed that the SBH maps can be conveniently tuned starting from a narrow SBH distribution (from 0.2 to 0.3 eV) in the case of pristine MoS2 to a broader distribution (from 0.2 to 0.8 eV) after 600 s O2 plasma treatment, which allows both electron and hole injection. This lateral inhomogeneity in the electrical properties was associated with variations of the incorporated oxygen concentration in the MoS2 multilayer surface, as shown by STEM/EELS analyses and confirmed by ab initio density functional theory (DFT) calculations. Back-gated multilayer MoS2 FETs, fabricated by self-aligned deposition of source/drain contacts in the O2 plasma functionalized areas, exhibit ambipolar current transport with on/off current ratio Ion/Ioff ≈ 10(3) and field-effect mobilities of 11.5 and 7.2 cm(2) V(-1) s(-1) for electrons and holes, respectively. The electrical behavior of these novel ambipolar devices is discussed in terms of the peculiar current injection mechanisms in the O2 plasma

  2. Dielectric dipole mitigated Schottky barrier height tuning for contact resistance reduction

    Science.gov (United States)

    Coss, Brian E.

    Contact resistance is increasingly becoming an impediment to continued performance enhancement by scaling for traditional complementary metal oxide semiconductor field effect transistors (CMOSFETS). Solutions to this problem are wanting, and with decreasing con- tact area, demands on the contact properties are escalating. With ever-decreasing contact areas, specific contact resistivity has to be reduced below 1 O-mum2 to 0.1 O-mum 2 in the next 10--15 years. With dopant densities in the source and drain regions nearing the limits of solid solubility, the most likely solution will involve reducing the Schottky barrier height (phi SBH) to near zero. This dissertation focuses on a novel approach to reducing the phiSBH, with the goal of reducing specific contact resistivity. The presence of dipoles at certain oxide interfaces has been revealed by recent research into gate stack scaling. The goal is to utilize these dipoles in a contact, in order to controllably adjust the phi SBH, moving it from its pinned position near the middle of the gap closer to the conduction and/or the valence band edges. To this end, several successful experiments have been conducted. To test the feasibility of controllably adjusting the phiSBH several diodes were fabricated with tantalum nitride (TaN) metal contact and various oxide dipole layers. The ability to adjust the phiSBH to near the conduction and valence band edges is demonstrated, and improved electrical resistance compared with the standard contact metal, NiSi, is demonstrated on n-Si (Chapter 4). Deeper understanding of the dipole formation process, as well as the scalability and maximum phiSBH tuning is explored in extremely thin AlOx/SiO 2 layers using diodes with TaN metal contacts by varying deposition process techniques and parameters. The best layers are found to be extremely thin, but also with large dipole magnitudes, as evidenced by the changes in the phiSBH (Chapter 5). Applications to a real device are explored using a

  3. Performance analyses of Schottky diodes with Au/Pd contacts on n-ZnO thin films as UV detectors

    Science.gov (United States)

    Varma, Tarun; Periasamy, C.; Boolchandani, Dharmendar

    2017-12-01

    In this paper, we report fabrication and performance analyses of UV detectors based on ZnO thin film Schottky diodes with Au and Pd contacts. RF magnetron sputtering technique has been used to deposit the nano-crystalline ZnO thin film, at room temperature. Characterization techniques such as XRD, AFM and SEM provided valuable information related to the micro-structural & optical properties of the thin film. The results show that the prepared thin film has good crystalline orientation and minimal surface roughness, with an optical bandgap of 3.1 eV. I-V and C-V characteristics were evaluated that indicate non-linear behaviour of the diodes with rectification ratios (IF/IR) of 19 and 427, at ± 4 V, for Au/ZnO and Pd/ZnO Schottky diodes, respectively. The fabricated Schottky diodes when exposed to a UV light of 365 nm wavelength, at an applied bias of -2 V, exhibited responsivity of 10.16 and 22.7 A/W, for Au and Pd Schottky contacts, respectively. The Pd based Schottky photo-detectors were found to exhibit better performance with superior values of detectivity and photoconductive gain of 1.95 × 1010 cm Hz0.5/W & 77.18, over those obtained for the Au based detectors which were observed to be 1.23 × 1010 cm Hz0.5/W & 34.5, respectively.

  4. Analytical model of threshold voltage degradation due to localized charges in gate material engineered Schottky barrier cylindrical GAA MOSFETs

    Science.gov (United States)

    Kumar, Manoj; Haldar, Subhasis; Gupta, Mridula; Gupta, R. S.

    2016-10-01

    The threshold voltage degradation due to the hot carrier induced localized charges (LC) is a major reliability concern for nanoscale Schottky barrier (SB) cylindrical gate all around (GAA) metal-oxide-semiconductor field-effect transistors (MOSFETs). The degradation physics of gate material engineered (GME)-SB-GAA MOSFETs due to LC is still unexplored. An explicit threshold voltage degradation model for GME-SB-GAA-MOSFETs with the incorporation of localized charges (N it) is developed. To accurately model the threshold voltage the minimum channel carrier density has been taken into account. The model renders how +/- LC affects the device subthreshold performance. One-dimensional (1D) Poisson’s and 2D Laplace equations have been solved for two different regions (fresh and damaged) with two different gate metal work-functions. LCs are considered at the drain side with low gate metal work-function as N it is more vulnerable towards the drain. For the reduction of carrier mobility degradation, a lightly doped channel has been considered. The proposed model also includes the effect of barrier height lowering at the metal-semiconductor interface. The developed model results have been verified using numerical simulation data obtained by the ATLAS-3D device simulator and excellent agreement is observed between analytical and simulation results.

  5. Hybrid functional and quasiparticle calculations of the Schottky barrier height at TiN/HfO2 interface

    Science.gov (United States)

    Oh, Young Jun; Lee, Alex Taekyung; Noh, Hyeon-Kyun; Chang, K. J.

    2014-03-01

    In high-k/metal gate transistors, it is important to control the metal work function such that it should be close to the valence and conduction band edges of Si in p- and n-channel devices, respectively. The Schottky barrier height (SBH) is affected by composition of metal gate, impurity, and deposition process. In theoretical studies, using the local density functional approximation, the SBH is severely underestimated because of the underestimation of the dielectric band gap. In this work, we perform both hybrid functional and quasiparticle calculations to improve the band gap and effective work function in TiN/HfO2 interface. We consider two types of TiN/HfO2 interface structures, which consist of either Ti-O or N-Hf interface bonds. Depending on the type of interface bonds, the SBH differs by 0.36 eV. In the many-body perturbation theory, the GW0 approach, which employs the self-consistent Green's function and the full frequency-dependent dielectric function, greatly improves the agreement of the SBH with experiments. We discuss the effects of the self-consistency and the plasmon-pole approximation on the SBH. On the other hand, with the hybrid functional, the SBH is overestimated due to the larger downward shift of the valence band edge of HfO2.

  6. Spin beam splitter based on Goos-Haenchen shifts in two-dimensional electron gas modulated by ferromagnetic and Schottky metal stripes

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Mao-Wang; Huang, Xin-Hong; Zhang, Gui-Lin; Chen, Sai-Yan [College of Science, Guilin University of Technology, Guilin 541004 (China)

    2012-11-15

    We present a theoretical study on the spin-dependent Goos-Haenchen (GH) effect in a two-dimensional electron gas modulated by ferromagnetic and Schottky metal (SM) stripes. The GH shifts for spin electron beams across this device are calculated with the help of the stationary phase method. It is shown that the GH shift of spin-up beam is significantly different from that of spin-down beam, i.e., this device shows up a considerable spin polarization effect in GH shifts of electron beams. It also is shown that both magnitude and sign of spin polarization of GH shifts are closely related to the stripe width, the magnetic strength and the gated voltage under SM stripe. These interesting properties not only provide an effective method of spin injection for spintronics application, but also give rise to a tunable spin beam splitter. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. Fabrication and Characterization of n-AlGaAs/GaAs Schottky Diode for Rectenna Device Application

    Energy Technology Data Exchange (ETDEWEB)

    Parimon, Norfarariyanti; Mustafa, Farahiyah; Hashim, Abdul Manaf; Rahman, Shaharin Fadzli Abd; Rahman, Abdul Rahim Abdul [Material Innovations and Nanoelectronics Research Group, Faculty of Electrical Engineering, Universiti Teknologi Malaysia, 81310 Skudai, Johor (Malaysia); Osman, Mohd Nizam, E-mail: manaf@fke.utm.my [Telekom Research and Development, TM Innovation Centre, 63000 Cyberjaya (Malaysia)

    2011-02-15

    Schottky diode was designed and fabricated on n-AlGaAs/GaAs high electron mobility transistor (HEMT) structure for rectenna device application. Rectenna is one of the most potential devices to form the wireless power supply which is really good at converting microwaves to DC. The processing steps used in the fabrication of Schottky diode were the conventional steps used in standard GaAs processing. Current-voltage (I-V) measurements showed that the device had rectifying properties with a barrier height of 0.5468 eV for Ni/Au metallization. The fabricated Schottky diode detected RF signals and the cut-off frequency up to 20 GHz was estimated in direct injection experiments. These preliminary results will provide a breakthrough for the direct integration with antenna towards realization of rectenna device application.

  8. Temperature dependent current transport of Pd/ZnO nanowire Schottky diodes

    Science.gov (United States)

    Gayen, R. N.; Bhattacharyya, S. R.; Jana, P.

    2014-09-01

    Zinc oxide (ZnO) nanowire based Schottky barrier diodes are fabricated by depositing Pd metal contact on top of vertically well-aligned ZnO nanowire arrays. A vertical array of ZnO nanowires on indium tin oxide (ITO) coated glass substrates is synthesized by hybrid wet chemical route. Scanning electron microscopy (SEM), x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) measurement confirm the formation of stoichiometric well-aligned hexagonal (h-ZnO) nanowire arrays with wurtzite structure. Temperature dependent current-voltage (I-V) measurements on palladium-ZnO (Pd/ZnO) nanowire Schottky junctions in the temperature range 303-383 K exhibit excellent rectifying character. From these nonlinear I-V plots, different electrical parameters of diode-like reverse saturation current, barrier height and ideality factor are determined as a function of temperature assuming pure thermionic emission model. The ideality factor is found to decrease while the barrier height increases with the increase in temperature. The series resistance values calculated from Cheung’s functions also show temperature dependency. Such behavior can be attributed to the presence of defects that traps carriers, and barrier height inhomogeneity at the interface of the barrier junction. After barrier height inhomogeneity correction, considering a Gaussian distributed barrier height fluctuation across the Pd/ZnO interface, the estimated values of mean barrier height and modified Richardson constant are more closely matched to the theoretically predicted value for Pd/ZnO Schottky barrier diodes. The variation of density of interface states as a function of interface state energy is also calculated.

  9. Investigation of the electrical parameters of Ag/p-TlGaSeS/C Schottky contacts

    Energy Technology Data Exchange (ETDEWEB)

    Qasrawi, A.F., E-mail: aqasrawi@atilim.edu.tr [Group of Physics, Faculty of Engineering, Atilim University, 06836 Ankara (Turkey); Department of Physics, Arab-American University, Jenin, West Bank, Palestine (Country Unknown); Gasanly, N.M. [Department of Physics, Middle East Technical University, 06800 Ankara (Turkey)

    2012-07-25

    Highlights: Black-Right-Pointing-Pointer Ag/p-TlGaSeS/C Schottky devices are designed and characterized. Black-Right-Pointing-Pointer The device ideality factor and barrier heights are 1.2 and 0.74 eV, respectively. Black-Right-Pointing-Pointer It displayed wide and narrow RF bands at 13.200 and 62.517 kHz, respectively. Black-Right-Pointing-Pointer The relative Q values are found to be 1.4 and of 6.3 Multiplication-Sign 10{sup 4}, respectively. - Abstract: p-type TlGaSeS single crystal was used to fabricate a Schottky device. Silver and carbon metals were used as the Ohmic and Schottky contacts, respectively. The device which displayed wide RF band at 13.200 and narrow band at 62.517 kHz with Q value of 1.4 and of 6.3 Multiplication-Sign 10{sup 4}, respectively, is characterized by means of current (I)-voltage (V), capacitance (C)-voltage characteristics as well as capacitance-frequency (f) characteristics. The device series resistance, ideality factor and barrier height are determined from the I-V curve as 35.8 M{Omega}, 1.2 and 0.74 eV, respectively. The apparent acceptor density and the build in voltage of the device increased with increasing ac signal frequency. The high Q value, observed at 62.517 kHz, indicated a much lower rate of energy loss relative to the stored energy of the device. The energy loss (Q{sup -1}) is much less than 0.001% of the stored value. The device was tested and found to remain at the same mode of resonance for several hours. It never switched or ceased unless it was tuned off.

  10. Improved designs of Si-based quantum wells and Schottky diodes for IR detection

    Energy Technology Data Exchange (ETDEWEB)

    Moeen, M., E-mail: moeen@kth.se [School of Information and Communication Technology, KTH Royal Institute of Technology, Stockholm, 16640, Kista (Sweden); Kolahdouz, M. [School of Electrical and Computer Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Salemi, A.; Abedin, A.; Östling, M. [School of Information and Communication Technology, KTH Royal Institute of Technology, Stockholm, 16640, Kista (Sweden); Radamson, H.H., E-mail: rad@kth.se [School of Information and Communication Technology, KTH Royal Institute of Technology, Stockholm, 16640, Kista (Sweden)

    2016-08-31

    Novel structures of intrinsic or carbon-doped multi quantum wells (MQWs) and intrinsic or carbon-doped Si Schottky diodes (SD), individually or in combination, have been manufactured to detect the infrared (IR) radiation. The carbon concentration in the structures was 5 × 10{sup 20} cm{sup −3} and the MQWs are located in the active part of the IR detector. A Schottky diode was designed and formed as one of the contacts (based on NiSi(C)/TiW) to MQWs where on the other side the structure had an Ohmic contact. The thermal response of the detectors is expressed in terms of temperature coefficient of resistance (TCR) and the quality of the electrical signal is quantified by the signal-to-noise ratio. The noise measurements provide the K{sub 1/f} parameter which is obtained from the power spectrum density. An excellent value of TCR = − 6%/K and K{sub 1/f} = 4.7 × 10{sup −14} was measured for the detectors which consist of the MQWs in series with the SD. These outstanding electrical results indicate a good opportunity to manufacture low cost Si-based IR detectors in the near future. - Highlights: • SiGe (C)/Si(C) multi quantum wells (MQWs) are evaluated to detect IR radiation. • Schottky diodes (SDs), individually or in series with MQWs are also fabricated. • Detectors consisted of MQWs in series with SD show excellent thermal sensing. • The noise values are also extremely low for MQWs in series with SD.

  11. 670 GHz Schottky Diode Based Subharmonic Mixer with CPW Circuits and 70 GHz IF

    Science.gov (United States)

    Chattopadhyay, Goutam (Inventor); Schlecht, Erich T. (Inventor); Lee, Choonsup (Inventor); Lin, Robert H. (Inventor); Gill, John J. (Inventor); Sin, Seth (Inventor); Mehdi, Imran (Inventor)

    2014-01-01

    A coplanar waveguide (CPW) based subharmonic mixer working at 670 GHz using GaAs Schottky diodes. One example of the mixer has a LO input, an RF input and an IF output. Another possible mixer has a LO input, and IF input and an RF output. Each input or output is connected to a coplanar waveguide with a matching network. A pair of antiparallel diodes provides a signal at twice the LO frequency, which is then mixed with a second signal to provide signals having sum and difference frequencies. The output signal of interest is received after passing through a bandpass filter tuned to the frequency range of interest.

  12. Schottky barrier enhancement on n-InP solar cell applications

    DEFF Research Database (Denmark)

    Clausen, Thomas; Leistiko, Otto

    1994-01-01

    It is demonstrated that the Schottky barrier height on n-type InP can be enhanced to values close to the energy bandgap (1.35 eV) by employing a AuZnCr metallization. The process is simple and requires only mild and fast annealing sequences with temperatures not exceeding 500°C. Also, no critical...... epitaxial growth step of junctions is needed, making the process fairly cheap. Thus, prospects for an efficient and simple solar cell device structure for space application purposes based on highly radiant-resistant InP are greatly improved...

  13. Theory of warm ionized gases: equation of state and kinetic Schottky anomaly.

    Science.gov (United States)

    Capolupo, A; Giampaolo, S M; Illuminati, F

    2013-10-01

    Based on accurate Lennard-Jones-type interaction potentials, we derive a closed set of state equations for the description of warm atomic gases in the presence of ionization processes. The specific heat is predicted to exhibit peaks in correspondence to single and multiple ionizations. Such kinetic analog in atomic gases of the Schottky anomaly in solids is enhanced at intermediate and low atomic densities. The case of adiabatic compression of noble gases is analyzed in detail and the implications on sonoluminescence are discussed. In particular, the predicted plasma electron density in a sonoluminescent bubble turns out to be in good agreement with the value measured in recent experiments.

  14. Catalytic-Metal/PdO(sub x)/SiC Schottky-Diode Gas Sensors

    Science.gov (United States)

    Hunter, Gary W.; Xu, Jennifer C.; Lukco, Dorothy

    2006-01-01

    Miniaturized hydrogen- and hydrocarbon-gas sensors, heretofore often consisting of Schottky diodes based on catalytic metal in contact with SiC, can be improved by incorporating palladium oxide (PdOx, where 0 less than or equal to x less than or equal to 1) between the catalytic metal and the SiC. In prior such sensors in which the catalytic metal was the alloy PdCr, diffusion and the consequent formation of oxides and silicides of Pd and Cr during operation at high temperature were observed to cause loss of sensitivity. However, it was also observed that any PdOx layers that formed and remained at PdCr/SiC interfaces acted as barriers to diffusion, preventing further deterioration by preventing the subsequent formation of metal silicides. In the present improvement, the lesson learned from these observations is applied by placing PdOx at the catalytic metal/SiC interfaces in a controlled and uniform manner to form stable diffusion barriers that prevent formation of metal silicides. A major advantage of PdOx over other candidate diffusion-barrier materials is that PdOx is a highly stable oxide that can be incorporated into gas sensor structures by use of deposition techniques that are standard in the semiconductor industry. The PdOx layer can be used in a gas sensor structure for improved sensor stability, while maintaining sensitivity. For example, in proof-of-concept experiments, Pt/PdOx/SiC Schottky-diode gas sensors were fabricated and tested. The fabrication process included controlled sputter deposition of PdOx to a thickness of 50 Angstroms on a 400-m-thick SiC substrate, followed by deposition of Pt to a thickness of 450 Angstroms on the PdOx. The SiC substrate (400 microns in thickness) was patterned with photoresist and a Schottky-diode photomask. A lift-off process completed the definition of the Schottky-diode pattern. The sensors were tested by measuring changes in forward currents at a bias potential of 1 V during exposure to H2 in N2 at temperatures

  15. High performance trench MOS barrier Schottky diode with high-k gate oxide

    Science.gov (United States)

    Zhai, Dong-Yuan; Zhu, Jun; Zhao, Yi; Cai, Yin-Fei; Shi, Yi; Zheng, You-Liao

    2015-07-01

    A novel trench MOS barrier Schottky diode (TMBS) device with a high-k material introduced into the gate insulator is reported, which is named high-k TMBS. By simulation with Medici, it is found that the high-k TMBS can have 19.8% lower leakage current while maintaining the same breakdown voltage and forward turn-on voltage compared with the conventional regular trench TMBS. Project supported by the National Basic Research Program of China (Grant No. 2011CBA00607), the National Natural Science Foundation of China (Grant Nos. 61106089 and 61376097), and the Zhejiang Provincial Natural Science Foundation of China (Grant No. LR14F040001).

  16. Microwave Schottky diagnostic systems for the Fermilab Tevatron, Recycler, and CERN LHC

    CERN Document Server

    Pasquinelli, Ralph J

    2011-01-01

    A means for non-invasive measurement of transverse and longitudinal characteristics of bunched beams in synchrotrons has been developed based on high sensitivity slotted waveguide pickups. The pickups allow for bandwidths exceeding hundreds of MHz while maintaining good beam sensitivity characteristics. Wide bandwidth is essential to allow bunch-by-bunch measurements by means of a fast gate. The Schottky detector system is installed and successfully commissioned in the Fermilab Tevatron, Recycler and CERN LHC synchrotrons. Measurement capabilities include tune, chromaticity, and momentum spread of single or multiple beam bunches in any combination. With appropriate calibrations, emittance can also be measured by integrating the area under the incoherent tune sidebands.

  17. Plasmonic silicon Schottky photodetectors: the physics behind graphene enhanced internal photoemission

    DEFF Research Database (Denmark)

    Levy, Uriel; Grajower, Meir; Gonçalves, P. A. D.

    2017-01-01

    a physical model where surface plasmon polaritons enhance the absorption in a single-layer graphene by enhancing the field along the interface. The relatively long relaxation time in graphene allows for multiple attempts for the carrier to overcome the Schottky barrier and penetrate into the semiconductor......Recent experiments have shown that the plasmonic assisted internal photoemission from a metal to silicon can be significantly enhanced by introducing a monolayer of graphene between the two media. This is despite the limited absorption in a monolayer of undoped graphene (∼πα=2.3%). Here we propose...

  18. Anomalous Schottky Specific Heat and Structural Distortion in Ferromagnetic PrAl2

    Science.gov (United States)

    Pathak, Arjun K.; Paudyal, D.; Mudryk, Y.; Gschneidner, K. A., Jr.; Pecharsky, V. K.

    2013-05-01

    Unique from other rare earth dialuminides, PrAl2 undergoes a cubic to tetragonal distortion below T=30K in a zero magnetic field, but the system recovers its cubic symmetry upon the application of an external magnetic field of 10 kOe via a lifting of the 4f crystal field splitting. The nuclear Schottky specific heat in PrAl2 is anomalously high compared to that of pure Pr metal. First principles calculations reveal that the 4f crystal field splitting in the tetragonally distorted phase of PrAl2 underpins the observed unusual low temperature phenomena.

  19. Microwave Schottky diagnostic systems for the Fermilab Tevatron, Recycler, and CERN Large Hadron Collider

    Directory of Open Access Journals (Sweden)

    Ralph J. Pasquinelli

    2011-07-01

    Full Text Available A means for noninvasive measurement of transverse and longitudinal characteristics of bunched beams in synchrotrons has been developed based on high sensitivity slotted waveguide pickups. The pickups allow for bandwidths exceeding hundreds of MHz while maintaining good beam sensitivity characteristics. Wide bandwidth is essential to allow bunch-by-bunch measurements by means of a fast gate. The Schottky detector system is installed and successfully commissioned in the Fermilab Tevatron, Recycler and CERN LHC synchrotrons. Measurement capabilities include tune, chromaticity, and momentum spread of single or multiple beam bunches in any combination. With appropriate calibrations, emittance can also be measured by integrating the area under the incoherent tune sidebands.

  20. Electrical characteristics and interfacial reactions of rapidly annealed Pt/Ru Schottky contacts on n-type GaN

    Energy Technology Data Exchange (ETDEWEB)

    Reddy, N.N.K.; Rajagopal Reddy, V. [Department of Physics, Sri Venkateswara University, Tirupati (India); Choi, C.J. [School of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center (SPRC), Chonbuk National University, Jeonju (Korea, Republic of)

    2011-07-15

    The electrical properties and interfacial reactions of Pt/Ru Schottky contacts on n-type gallium nitride (GaN) have been investigated as a function of annealing temperature. The calculated Schottky barrier height (SBH) of the as-deposited Pt/Ru Schottky contact is found to be 0.69 eV current-voltage (I-V) and 0.76 eV capacitance-voltage (C-V). Experimental results showed that the SBHs are increased on increasing the annealing temperature. When the contact is annealed at 600 C, a maximum barrier height is obtained and the corresponding values are 0.87 eV (I-V) and 0.99 eV (C-V). The Norde method was also employed to extract the barrier height of Pt/Ru Schottky contacts and the values are 0.70 and 0.86 eV for the samples as-deposited and annealed at 600 C, which are in good agreement with those obtained from the I-V measurement. Shifts of the surface Fermi level are measured with the change in position of the Ga 2p core level peak. Based on the X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) studies, the formation of gallide phases at the Ru/Pt/n-GaN interface could be the reason for the increase in SBH at elevated temperatures. Atomic force microscopy (AFM) results showed that the surface morphology of the Pt/Ru Schottky contact did not change significantly even after annealing at 600 C. These results point out that a Pt/Ru Schottky contact may be a suitable candidate for the fabrication of GaN-based high-temperature device applications. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Barrier height determination on Schottky contacts formed at the back contact-semiconductor interface of degraded solar cells

    Science.gov (United States)

    Misiakos, K.; Lathrop, J. W.

    1984-01-01

    A method is described of determining an equivalent circuit for solar cells which have degraded as a result of the formation of a rectifying Schottky barrier at the back contact. An excellent fit of experimental data has been achieved using SCEPTRE with an equivalent circuit derived from the shape of the measured current voltage characteristics. One key parameter of the Schottky barrier diode, the reverse saturation current, can be used to determine the barrier potential. The barrier potential increases as the cell is stressed with 0.5 volts being a typical experimentally determined value for a degraded cell.

  2. Mg doping of InGaN layers grown by PA-MBE for the fabrication of Schottky barrier photodiodes

    OpenAIRE

    Pereiro, J. (James); Redondo-Cubero, A; Fernandez-Garrido, S.; Rivera, C; Navarro, A.; Muñoz, E; Calleja, E; Gago, R.; Pereiro, Juan

    2010-01-01

    ABSTRACT This work reports on the fabrication of Schottky barrier based Mg-doped (In, Ga)N layers for fluorescence applications. Mg acceptors are used in order to compensate surface and bulk donors that prevent the fabrication of Schottky contacts on unintentionally doped (In, Ga)N layers. Rectifying properties of the contacts exhibited a major improvement when (In, Ga)N:Mg is used. The electrical and optical measurements of the layers showed a hole concentration up to 3?10 19 holes/cm 3 w...

  3. Calculation of the Schottky barrier and current–voltage characteristics of metal–alloy structures based on silicon carbide

    Energy Technology Data Exchange (ETDEWEB)

    Altuhov, V. I., E-mail: altukhovv@mail.ru; Kasyanenko, I. S.; Sankin, A. V. [North Caucasian Federal University, Institute of Service, Tourism and Design (Branch) (Russian Federation); Bilalov, B. A. [Dagestan State Technical University (Russian Federation); Sigov, A. S. [Moscow State Technical University of Radio Engineering, Electronics, and Automation (Russian Federation)

    2016-09-15

    A simple but nonlinear model of the defect density at a metal–semiconductor interface, when a Schottky barrier is formed by surface defects states localized at the interface, is developed. It is shown that taking the nonlinear dependence of the Fermi level on the defect density into account leads to a Schottky barrier increase by 15–25%. The calculated barrier heights are used to analyze the current–voltage characteristics of n-M/p-(SiC){sub 1–x}(AlN){sub x} structures. The results of calculations are compared to experimental data.

  4. Transparent indium-tin oxide/indium-gallium-zinc oxide Schottky diodes formed by gradient oxygen doping

    Science.gov (United States)

    Ho, Szuheng; Yu, Hyeonggeun; So, Franky

    2017-11-01

    Amorphous InGaZnO (a-IGZO) is promising for transparent electronics due to its high carrier mobility and optical transparency. However, most metal/a-IGZO junctions are ohmic due to the Fermi-level pinning at the interface, restricting their device applications. Here, we report that indium-tin oxide/a-IGZO Schottky diodes can be formed by gradient oxygen doping in the a-IGZO layer that would otherwise form an ohmic contact. Making use of back-to-back a-IGZO Schottky junctions, a transparent IGZO permeable metal-base transistor is also demonstrated with a high common-base gain.

  5. Broadband photodetector based on carbon nanotube thin film/single layer graphene Schottky junction

    Science.gov (United States)

    Zhang, Teng-Fei; Li, Zhi-Peng; Wang, Jiu-Zhen; Kong, Wei-Yu; Wu, Guo-An; Zheng, Yu-Zhen; Zhao, Yuan-Wei; Yao, En-Xu; Zhuang, Nai-Xi; Luo, Lin-Bao

    2016-12-01

    In this study, we present a broadband nano-photodetector based on single-layer graphene (SLG)-carbon nanotube thin film (CNTF) Schottky junction. It was found that the as-fabricated device exhibited obvious sensitivity to a wide range of illumination, with peak sensitivity at 600 and 920 nm. In addition, the SLG-CNTF device had a fast response speed (τr = 68 μs, τf = 78 μs) and good reproducibility in a wide range of switching frequencies (50-5400 Hz). The on-off ratio, responsivity, and detectivity of the device were estimated to be 1 × 102, 209 mAW-1 and 4.87 × 1010 cm Hz1/2 W-1, respectively. What is more, other device parameters including linear performance θ and linear dynamic range (LDR) were calculated to be 0.99 and 58.8 dB, respectively, which were relatively better than other carbon nanotube based devices. The totality of the above study signifies that the present SLG-CNTF Schottky junction broadband nano-photodetector may have promising application in future nano-optoelectronic devices and systems.

  6. Temperature dependent electrical characterization of organic Schottky diode based on thick MgPc films

    Science.gov (United States)

    Singh, J.; Sharma, R. K.; Sule, U. S.; Goutam, U. K.; Gupta, Jagannath; Gadkari, S. C.

    2017-07-01

    Magnesium phthalocyanine (MgPc) based Schottky diode on indium tin oxide (ITO) substrate was fabricated by thermal evaporation method. The dark current voltage characteristics of the prepared ITO-MgPc-Al heterojunction Schottky diode were measured at different temperatures. The diode showed the non-ideal rectification behavior under forward and reverse bias conditions with a rectification ratio (RR) of 56 at  ±1 V at room temperature. Under forward bias, thermionic emission and space charge limited conduction (SCLC) were found to be the dominant conduction mechanisms at low (below 0.6 V) and high voltages (above 0.6 V) respectively. Under reverse bias conditions, Poole-Frenkel (field assisted thermal detrapping of carriers) was the dominant conduction mechanism. Three different approaches namely, I-V plots, Norde and Cheung methods were used to determine the diode parameters including ideality factor (n), barrier height (Φb), series resistance (R s) and were compared. SCLC mechanism showed that the trap concentration is 5.52  ×  1022 m-3 and it lies at 0.46 eV above the valence band edge.

  7. Modeling and fabrication of 4H-SiC Schottky junction

    Science.gov (United States)

    Martychowiec, A.; Pedryc, A.; Kociubiński, A.

    2017-08-01

    The rapidly growing demand for electronic devices requires using of alternative semiconductor materials, which could replace conventional silicon. Silicon carbide has been proposed for these harsh environment applications (high temperature, high voltage, high power conditions) because of its wide bandgap, its high temperature operation ability, its excellent thermal and chemical stability, and its high breakdown electric field strength. The Schottky barrier diode (SBD) is known as one of the best refined SiC devices. This paper presents prepared model, simulations and description of technology of 4H-SiC Schottky junction as well as characterization of fabricated structures. The future aim of the application of the structures is an optical detection of an ultraviolet radiation. The model section contains a comparison of two different solutions of SBD's construction. Simulations - as a crucial process of designing electronic devices - have been performed using the ATLAS device of Silvaco TCAD software. As a final result the paper shows I-V characteristics of fabricated diodes.

  8. Waveguide based compact silicon Schottky photodetector with enhanced responsivity in the telecom spectral band.

    Science.gov (United States)

    Goykhman, Ilya; Desiatov, Boris; Khurgin, Jacob; Shappir, Joseph; Levy, Uriel

    2012-12-17

    We experimentally demonstrate an on-chip compact and simple to fabricate silicon Schottky photodetector for telecom wavelengths operating on the basis of internal photoemission process. The device is realized using CMOS compatible approach of local-oxidation of silicon, which enables the realization of the photodetector and low-loss bus photonic waveguide at the same fabrication step. The photodetector demonstrates enhanced internal responsivity of 12.5mA/W for operation wavelength of 1.55µm corresponding to an internal quantum efficiency of 1%, about two orders of magnitude higher than our previously demonstrated results [22]. We attribute this improved detection efficiency to the presence of surface roughness at the boundary between the materials forming the Schottky contact. The combination of enhanced quantum efficiency together with a simple fabrication process provides a promising platform for the realization of all silicon photodetectors and their integration with other nanophotonic and nanoplasmonic structures towards the construction of monolithic silicon opto-electronic circuitry on-chip.

  9. Locally oxidized silicon surface-plasmon Schottky detector for telecom regime.

    Science.gov (United States)

    Goykhman, Ilya; Desiatov, Boris; Khurgin, Jacob; Shappir, Joseph; Levy, Uriel

    2011-06-08

    We experimentally demonstrate an on-chip nanoscale silicon surface-plasmon Schottky photodetector based on internal photoemission process and operating at telecom wavelengths. The device is fabricated using a self-aligned approach of local-oxidation of silicon (LOCOS) on silicon on insulator substrate, which provides compatibility with standard complementary metal-oxide semiconductor technology and enables the realization of the photodetector and low-loss bus photonic waveguide at the same fabrication step. Additionally, LOCOS technique allows avoiding lateral misalignment between the silicon surface and the metal layer to form a nanoscale Schottky contact. The fabricated devices showed enhanced detection capability for shorter wavelengths that is attributed to increased probability of the internal photoemission process. We found the responsivity of the nanodetector to be 0.25 and 13.3 mA/W for incident optical wavelengths of 1.55 and 1.31 μm, respectively. The presented device can be integrated with other nanophotonic and nanoplasmonic structures for the realization of monolithic opto-electronic circuitry on-chip.

  10. Polycrystalline silicon carbide dopant profiles obtained through a scanning nano-Schottky contact

    Energy Technology Data Exchange (ETDEWEB)

    Golt, M. C.; Strawhecker, K. E.; Bratcher, M. S. [U.S. Army Research Laboratory, WMRD, Aberdeen Proving Ground, Maryland 21005 (United States); Shanholtz, E. R. [ORISE, Belcamp, Maryland 21017 (United States)

    2016-07-14

    The unique thermo-electro-mechanical properties of polycrystalline silicon carbide (poly-SiC) make it a desirable candidate for structural and electronic materials for operation in extreme environments. Necessitated by the need to understand how processing additives influence poly-SiC structure and electrical properties, the distribution of lattice defects and impurities across a specimen of hot-pressed 6H poly-SiC processed with p-type additives was visualized with high spatial resolution using a conductive atomic force microscopy approach in which a contact forming a nano-Schottky interface is scanned across the sample. The results reveal very intricate structures within poly-SiC, with each grain having a complex core-rim structure. This complexity results from the influence the additives have on the evolution of the microstructure during processing. It was found that the highest conductivities localized at rims as well as at the interface between the rim and the core. The conductivity of the cores is less than the conductivity of the rims due to a lower concentration of dopant. Analysis of the observed conductivities and current-voltage curves is presented in the context of nano-Schottky contact regimes where the conventional understanding of charge transport to diode operation is no longer valid.

  11. GaAs detectors with an ultra-thin Schottky contact for spectrometry of charged particles

    Energy Technology Data Exchange (ETDEWEB)

    Chernykh, S.V., E-mail: chsv_84@mail.ru [National University of Science and Technology “MISIS”, Moscow (Russian Federation); Research Institute of Experimental and Theoretical Physics, Almaty (Kazakhstan); Chernykh, A.V. [National University of Science and Technology “MISIS”, Moscow (Russian Federation); Didenko, S.I.; Baryshnikov, F.M. [National University of Science and Technology “MISIS”, Moscow (Russian Federation); Research Institute of Experimental and Theoretical Physics, Almaty (Kazakhstan); Burtebayev, N. [Research Institute of Experimental and Theoretical Physics, Almaty (Kazakhstan); Institute of Nuclear Physics, Almaty (Kazakhstan); Britvich, G.I. [Institute of High Energy Physics, Protvino, Moscow region (Russian Federation); Chubenko, A.P. [Research Institute of Experimental and Theoretical Physics, Almaty (Kazakhstan); P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow (Russian Federation); Guly, V.G.; Glybin, Yu.N. [LLC “SNIIP Plus”, Moscow (Russian Federation); Zholdybayev, T.K.; Burtebayeva, J.T.; Nassurlla, M. [Research Institute of Experimental and Theoretical Physics, Almaty (Kazakhstan); Institute of Nuclear Physics, Almaty (Kazakhstan)

    2017-02-11

    For the first time, samples of particle detectors based on high-purity GaAs epilayers with an active area of 25 and 80 mm{sup 2} and an ultra-thin Pt Schottky barrier were fabricated for use in the spectrometry of charged particles and their operating characteristics were studied. The obtained FWHM of 14.2 (for 25 mm{sup 2} detector) and 15.5 keV (for 80 mm{sup 2} detector) on the 5.499 MeV line of {sup 238}Pu is at the level of silicon spectrometric detectors. It was found that the main component that determines the energy resolution of the detector is a fluctuation in the number of collected electron–hole pairs. This allows us to state that the obtained energy resolution is close to the limit for VPE GaAs. - Highlights: • VPE GaAs particle detectors with an active area of 25 and 80 mm{sup 2} were fabricated. • 120 Å ultra-thin Pt Schottky barrier was used as a rectifying contact. • The obtained FWHM of 14.2 keV ({sup 238}Pu) is at the level of Si spectrometric detectors. • Various components of the total energy resolution were analyzed. • It was shown that obtained energy resolution is close to its limit for VPE GaAs.

  12. A sensitive ultraviolet light photodiode based on graphene-on-zinc oxide Schottky junction

    Directory of Open Access Journals (Sweden)

    Zhang Teng-Fei

    2016-11-01

    Full Text Available In this study, we present a simple ultraviolet (UV light photodiode by transferring a layer of graphene film on single-crystal ZnO substrate. The as-fabricated heterojunction exhibited typical rectifying behavior, with a Schottky barrier height of 0.623 eV. Further optoelectronic characterization revealed that the graphene-ZnO Schottky junction photodiode displayed obvious sensitivity to 365-nm light illumination with good reproducibility. The responsivity and photoconductive gain were estimated to be 3×104 A/W and 105, respectively, which were much higher than other ZnO nanostructure-based devices. In addition, it was found that the on/off ratio of the present device can be considerably improved from 2.09 to 12.1, when the device was passivated by a layer of AlOx film. These results suggest that the present simply structured graphene-ZnO UV photodiode may find potential application in future optoelectronic devices.

  13. Temperature-dependent Schottky barrier in high-performance organic solar cells

    Science.gov (United States)

    Li, Hui; He, Dan; Zhou, Qing; Mao, Peng; Cao, Jiamin; Ding, Liming; Wang, Jizheng

    2017-01-01

    Organic solar cells (OSCs) have attracted great attention in the past 30 years, and the power conversion efficiency (PCE) now reaches around 10%, largely owning to the rapid material developments. Meanwhile with the progress in the device performance, more and more interests are turning to understanding the fundamental physics inside the OSCs. In the conventional bulk-heterojunction architecture, only recently it is realized that the blend/cathode Schottky junction serves as the fundamental diode for the photovoltaic function. However, few researches have focused on such junctions, and their physical properties are far from being well-understood. In this paper based on PThBDTP:PC71BM blend, we fabricated OSCs with PCE exceeding 10%, and investigated temperature-dependent behaviors of the junction diodes by various characterization including current-voltage, capacitance-voltage and impedance measurements between 70 to 290 K. We found the Schottky barrier height exhibits large inhomogeneity, which can be described by two sets of Gaussian distributions. PMID:28071700

  14. A sensitive ultraviolet light photodiode based on graphene-on-zinc oxide Schottky junction

    Science.gov (United States)

    Zhang, Teng-Fei; Wu, Guo-An; Wang, Jiu-Zhen; Yu, Yong-Qiang; Zhang, Deng-Yue; Wang, Dan-Dan; Jiang, Jing-Bo; Wang, Jia-Mu; Luo, Lin-Bao

    2017-08-01

    In this study, we present a simple ultraviolet (UV) light photodiode by transferring a layer of graphene film on single-crystal ZnO substrate. The as-fabricated heterojunction exhibited typical rectifying behavior, with a Schottky barrier height of 0.623 eV. Further optoelectronic characterization revealed that the graphene-ZnO Schottky junction photodiode displayed obvious sensitivity to 365-nm light illumination with good reproducibility. The responsivity and photoconductive gain were estimated to be 3×104 A/W and 105, respectively, which were much higher than other ZnO nanostructure-based devices. In addition, it was found that the on/off ratio of the present device can be considerably improved from 2.09 to 12.1, when the device was passivated by a layer of AlOx film. These results suggest that the present simply structured graphene-ZnO UV photodiode may find potential application in future optoelectronic devices.

  15. Low-frequency noise properties in Pt-indium gallium zinc oxide Schottky diodes

    Science.gov (United States)

    Zhang, Jiawei; Zhang, Linqing; Ma, Xiaochen; Wilson, Joshua; Jin, Jidong; Du, Lulu; Xin, Qian; Song, Aimin

    2015-08-01

    The low-frequency noise properties of Pt-indium gallium zinc oxide (IGZO) Schottky diodes at different forward biases are investigated. The IGZO layer and Pt contact were deposited by RF sputtering at room temperature. The diode showed an ideality factor of 1.2 and a barrier height of 0.94 eV. The current noise spectral density exhibited 1/f behavior at low frequencies. The analysis of the current dependency of the noise spectral density revealed that for the as-deposited diode, the noise followed Luo's mobility and diffusivity fluctuation model in the thermionic-emission-limited region and Hooge's empirical theory in the series-resistance-limited region. A low Hooge's constant of 1.4 × 10-9 was found in the space-charge region. In the series-resistance-limited region, the Hooge's constant was 2.2 × 10-5. After annealing, the diode showed degradation in the electrical performance. The interface-trap-induced noise dominated the noise spectrum. By using the random walk model, the interface-trap density was obtained to be 3.6 × 1015 eV-1 cm-2. This work provides a quantitative approach to analyze the properties of Pt-IGZO interfacial layers. These low noise properties are a prerequisite to the use of IGZO Schottky diodes in switch elements in memory devices, photosensors, and mixer diodes.

  16. Zinc Selenide-Based Schottky Barrier Detectors for Ultraviolet-A and Ultraviolet-B Detection

    Directory of Open Access Journals (Sweden)

    V. Naval

    2010-01-01

    Full Text Available Wide-bandgap semiconductors such as zinc selenide (ZnSe have become popular for ultraviolet (UV photodetectors due to their broad UV spectral response. Schottky barrier detectors made of ZnSe in particular have been shown to have both low dark current and high responsivity. This paper presents the results of electrical and optical characterization of UV sensors based on ZnSe/Ni Schottky diodes fabricated using single-crystal ZnSe substrate with integrated UV-A (320–400 nm and UV-B (280–320 nm filters. For comparison, characteristics characterization of an unfiltered detector is also included. The measured photoresponse showed good discrimination between the two spectral bands. The measured responsivities of the UV-A and UV-B detectors were 50 mA/W and 10 mA/W, respectively. A detector without a UV filter showed a maximum responsivity of about 110 mA/W at 375 nm wavelength. The speed of the unfiltered detector was found to be about 300 kHz primarily limited by the RC time constant determined largely by the detector area.

  17. Hot carrier multiplication on graphene/TiO2 Schottky nanodiodes.

    Science.gov (United States)

    Lee, Young Keun; Choi, Hongkyw; Lee, Hyunsoo; Lee, Changhwan; Choi, Jin Sik; Choi, Choon-Gi; Hwang, Euyheon; Park, Jeong Young

    2016-06-08

    Carrier multiplication (i.e. generation of multiple electron-hole pairs from a single high-energy electron, CM) in graphene has been extensively studied both theoretically and experimentally, but direct application of hot carrier multiplication in graphene has not been reported. Here, taking advantage of efficient CM in graphene, we fabricated graphene/TiO2 Schottky nanodiodes and found CM-driven enhancement of quantum efficiency. The unusual photocurrent behavior was observed and directly compared with Fowler's law for photoemission on metals. The Fowler's law exponent for the graphene-based nanodiode is almost twice that of a thin gold film based diode; the graphene-based nanodiode also has a weak dependence on light intensity-both are significant evidence for CM in graphene. Furthermore, doping in graphene significantly modifies the quantum efficiency by changing the Schottky barrier. The CM phenomenon observed on the graphene/TiO2 nanodiodes can lead to intriguing applications of viable graphene-based light harvesting.

  18. Schottky junctions on perovskite single crystals: light-modulated dielectric constant and self-biased photodetection

    KAUST Repository

    Shaikh, Parvez Abdul Ajij

    2016-08-16

    Schottky junctions formed between semiconductors and metal contacts are ubiquitous in modern electronic and optoelectronic devices. Here we report on the physical properties of Schottky-junctions formed on hybrid perovskite CH3NH3PbBr3 single crystals. It is found that light illumination can significantly increase the dielectric constant of perovskite junctions by 2300%. Furthermore, such Pt/perovskite junctions are used to fabricate self-biased photodetectors. A photodetectivity of 1.4 × 1010 Jones is obtained at zero bias, which increases to 7.1 × 1011 Jones at a bias of +3 V, and the photodetectivity remains almost constant in a wide range of light intensity. These devices also exhibit fast responses with a rising time of 70 μs and a falling time of 150 μs. As a result of the high crystal quality and low defect density, such single-crystal photodetectors show stable performance after storage in air for over 45 days. Our results suggest that hybrid perovskite single crystals provide a new platform to develop promising optoelectronic applications. © 2016 The Royal Society of Chemistry.

  19. Large-area silicon nanowire Schottky junction photodetector with tunable absorption and low junction capacitance

    Science.gov (United States)

    Hackett, L. P.; Seyedi, M. A.; Fiorentino, M.; Beausoleil, R. G.

    2017-06-01

    Silicon photodetectors for operation in the near-infrared with a sufficient responsivity and high-speed operation are currently needed as scalable, CMOS compatible components for photonic and communication applications. Photodetectors based on semiconductor nanowire structures with dielectric planarization enable larger active optical areas and higher operating speeds than planar devices due to reduced junction capacitance and enhanced absorption. Here, we report on the fabrication and characterization of a silicon nanowire photodetector with dielectric infilling and a transparent indium tin oxide (ITO) Schottky contact. Optical simulations show that the absorbed power can be confined at the top of the nanowire array, enabling efficient operation in the near-infrared. This is despite the relatively low absorption coefficient for silicon in this wavelength range in addition to the design of the nanowire array to have a low fill factor compared to the bulk material in order to minimize the junction capacitance. The responsivity of this device is  >0.3 A W-1 at a reverse bias of 2 V and the junction capacitance is 8  ±  2 nF cm-2, which are respectively comparable and lower than the values expected for a planar silicon Schottky junction photodetector with a similar active area.

  20. Capacitance-voltage hysteresis of an electrolyte-GaAs Schottky contact associated with field-enhanced trapping of hot electrons

    Science.gov (United States)

    Yamashita, Akiyasu

    1996-09-01

    Electro-optical properties of n-GaAs crystal were studied by using a transparent, electrolyte Schottky contact and the following results were obtained: highly sensitive detection of some critical-point energies in the band structure of GaAs and the Franz-Keldysh shift of the fundamental absorption edge at high electric fields; the observation of a new capacitance-voltage hysteresis effect of the electrolyte-GaAs contact, with a characteristic threshold-field. Details of this hysteresis are presented with related photocapacitance spectra of the contact. In addition, its mechanism is explained by assuming field-enhanced trapping of hot electrons at complex deep-levels and their succeeding charge-state controlled structural transformation.

  1. Roles of lightly doped carbon in the drift layers of vertical n-GaN Schottky diode structures on freestanding GaN substrates

    Science.gov (United States)

    Tanaka, Takeshi; Kaneda, Naoki; Mishima, Tomoyoshi; Kihara, Yuhei; Aoki, Toshichika; Shiojima, Kenji

    2015-04-01

    We studied the roles of lightly doped carbon in a series of n-GaN Schottky diode epitaxial structures on freestanding GaN substrates, and evaluated the effects of the doping on diode performances. A large variation of compensation ratio was observed for carbon doping at (1-2) × 1016 cm-3. A model was proposed to explain this phenomenon, in which a vulnerable balance between donor-type CGa and deep acceptor CN strongly affected the free-carrier generation. Application of Norde plots and reverse biased leakage current in current-voltage measurements suggested provisional optimization for a free-carrier concentration of 8 × 1015 cm-3 to achieve a tradeoff between breakdown voltage and on-resistance of the n-GaN diodes.

  2. Electrical properties and colossal electroresistance of heteroepitaxial SrRuO3/SrTi1-xNbxO3 (0.0002⩽x⩽0.02) Schottky junctions

    Science.gov (United States)

    Fujii, T.; Kawasaki, M.; Sawa, A.; Kawazoe, Y.; Akoh, H.; Tokura, Y.

    2007-04-01

    We investigated the electrical properties of heteroepitaxial oxide Schottky junctions, SrRuO3/SrTi1-xNbxO3 (0.0002⩽x⩽0.02) . The overall features agree with those of a conventional semiconductor Schottky junction, as exemplified by the rectifying current (I) -voltage (V) characteristics with linear logI-V relationship under forward bias and the capacitance (C)-V characteristics with linear 1/C2-V relationship under reverse bias. The x dependence of the junction parameters, such as barrier height, built-in potential, and depletion layer width, can be analyzed by taking into account the band-gap narrowing due to degeneration, as well as the bias-dependent dielectric constant of depleted SrTiO3 . All junctions, except for the most heavily doped (x=0.02) one, show hysteretic I-V characteristics with a colossal electroresistance (CER) effect, where forward (reverse) bias stress reduces (enhances) the junction resistance. The x dependence of the CER effect and the absence of hysteresis in the C-V relationship suggest that the resistance switching in Schottky junctions comes from the change in conductance through additional tunneling paths rather than the change in barrier potential profile. Electron charging in or discharging from a self-trap depending on the bias polarity may account for the nonvolatility of the CER effect. This model is supported by the fact that the CER effect is completely suppressed in interface-engineered junctions with a SrRuO3/2-nm -thick X/SrTi0.99Nb0.01O3 structure, where X is either pristine SrTiO3 or very heavily electron-doped La0.25Sr0.75TiO3 .

  3. Ultra-wideband balanced schottky envelope detector for data communication with high bitrate to carrier frequency ratio

    DEFF Research Database (Denmark)

    Granja, Angel Blanco; Cimoli, Bruno; Rodriguez, Sebastian

    2017-01-01

    filter that rejects the second harmonic spurious from the Schottky diode and a bias tee that selects the optimum rectification point. The manufactured prototype is able to demodulate error free a 4 Gbps amplitude shift keying (ASK) signal at 4 GHz carrier frequency, leading to a record bitrate...

  4. MoB/g-C3 N4 Interface Materials as a Schottky Catalyst to Boost Hydrogen Evolution.

    Science.gov (United States)

    Zhuang, Zechao; Li, Yong; Li, Zilan; Lv, Fan; Lang, Zhiquan; Zhao, Kangning; Zhou, Liang; Moskaleva, Lyudmila; Guo, Shaojun; Mai, Liqiang

    2018-01-08

    Proton adsorption on metallic catalysts is a prerequisite for efficient hydrogen evolution reaction (HER). However, tuning proton adsorption without perturbing metallicity remains a challenge. A Schottky catalyst based on metal-semiconductor junction principles is presented. With metallic MoB, the introduction of n-type semiconductive g-C3 N4 induces a vigorous charge transfer across the MoB/g-C3 N4 Schottky junction, and increases the local electron density in MoB surface, confirmed by multiple spectroscopic techniques. This Schottky catalyst exhibits a superior HER activity with a low Tafel slope of 46 mV dec-1 and a high exchange current density of 17 μA cm-2 , which is far better than that of pristine MoB. First-principle calculations reveal that the Schottky contact dramatically lowers the kinetic barriers of both proton adsorption and reduction coordinates, therefore benefiting surface hydrogen generation. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Wavelength-dependent visible light response in vertically aligned nanohelical TiO2-based Schottky diodes

    Science.gov (United States)

    Kwon, Hyunah; Sung, Ji Ho; Lee, Yuna; Jo, Moon-Ho; Kim, Jong Kyu

    2018-01-01

    Enhancements in photocatalytic performance under visible light have been reported by noble metal functionalization on nanostructured TiO2; however, the non-uniform and discrete distribution of metal nanoparticles on the TiO2 surface makes it difficult to directly clarify the optical and electrical mechanisms. Here, we investigate the light absorption and the charge separation at the metal/TiO2 Schottky junctions by using a unique device architecture with an array of TiO2 nanohelixes (NHs) forming Schottky junctions both with Au-top and Pt-bottom electrodes. Wavelength-dependent photocurrent measurements through the Pt/TiO2 NHs/Au structures revealed that the origin of the visible light absorption and the separation of photogenerated carriers is the internal photoemission at the metal/nanostructured TiO2 Schottky junctions. In addition, a huge persistent photoconductivity was observed by the time-dependent photocurrent measurement, implying a long lifetime of the photogenerated carriers before recombination. We believe that the results help one to understand the role of metal functionalization on TiO2 and hence to enhance the photocatalytic efficiency by utilizing appropriately designed Schottky junctions.

  6. A High Frequency (HF) Inductive Power Transfer Circuit for High Temperature Applications Using SiC Schottky Diodes

    Science.gov (United States)

    Jordan, Jennifer L.; Ponchak, George E.; Spry, David J.; Neudeck, Philip G.

    2018-01-01

    Wireless sensors placed in high temperature environments, such as aircraft engines, are desirable to reduce the mass and complexity of routing wires. While communication with the sensors is straight forward, providing power wirelessly is still a challenge. This paper introduces an inductive wireless power transfer circuit incorporating SiC Schottky diodes and its operation from room temperature (25 C) to 500 C.

  7. Determination of the laterally homogeneous barrier height of palladium Schottky barrier diodes on n-Ge (111)

    CSIR Research Space (South Africa)

    Chawanda, A

    2011-05-01

    Full Text Available .5×1015 cm-3. The Pd Schottky contacts were fabricated by vacuum resistive evaporation. The electrical analysis of the contacts was investigated by means of current–voltage (I–V) and capacitance–voltage (C–V) measurements at a temperature of 296 K...

  8. On the junction physics of Schottky contact of (10, 10) MX2 (MoS2, WS2) nanotube and (10, 10) carbon nanotube (CNT): an atomistic study

    Science.gov (United States)

    Sengupta, Amretashis

    2017-04-01

    Armchair nanotubes of MoS2 and WS2 offer a sizeable band gap, with the advantage of a one dimensional (1D) electronic material, but free from edge roughness and thermodynamic instability of nanoribbons. Use of such semiconducting MX2 (MoS2, WS2) armchair nanotubes (NTs) in conjunction with metallic carbon nanotubes (CNT) can be useful for nanoelectronics and photonics applications. In this work, atomistic simulations of MoS2 NT-CNT and WS2 NT-CNT junctions are carried out to study the physics of such junctions. With density functional theory (DFT) we study the carrier density distribution, effective potential, electron difference density, electron localization function, electrostatic difference potential and projected local density of states of such MX2 NT-CNT 1D junctions. Thereafter the conductance of such a junction under moderate bias is studied with non-equilibrium Green's function (NEGF) method. From the forward bias characteristics simulated from NEGF, we extract diode parameters of the junction. The electrostatic simulations from DFT show the formation of an inhomogeneous Schottky barrier with a tendency towards charge transfer from metal and chalcogen atoms towards the C atoms. For low bias conditions, the ideality factor was calculated to be 1.1322 for MoS2 NT-CNT junction and 1.2526 for the WS2 NT-CNT junction. The Schottky barrier heights displayed significant bias dependent modulation and are calculated to be in the range 0.697-0.664 eV for MoS2 NT-CNT and 0.669-0.610 eV for the WS2 NT-CNT, respectively.

  9. Temperature-dependent electrical parameters and current transport mechanisms of Ru/Ti/ n-InP Schottky diodes

    Science.gov (United States)

    Munikrishna Reddy, Y.; Padmasuvarna, R.; Lakshmi Narasappa, T.; Padma, R.; Rajagopal Reddy, V.

    2015-11-01

    The temperature-dependent electrical properties of Ru/Ti/ n-InP Schottky diodes have been investigated in the temperature range of 120 to 400 K. The estimated barrier heights for the Ru/Ti/ n-InP Schottky barrier diode from the I- V and C- V characteristics vary from 0.24 to 0.73 eV ( I- V) and 0.94 to 0.74 eV ( C- V) and the ideality factor ( n) from 4.65 to 1.80 in the temperature range of 120-400 K. It has been observed that the ideality factor decreases while the barrier height increases with the increase in temperature. The barrier height ( Φ b), ideality factor ( n) and series resistance ( R s) of the Ru/Ti/ n-InP Schottky diode have been also determined using Cheung's and Norde methods. The discrepancy between the barrier heights obtained from the I- V and C- V characteristics is discussed. The interface state densities ( N ss) extracted for the Ru/Ti/ n-InP Schottky diode are in the range of 6.75 × 1013 eV-1 cm-2 ( E c —0.23 eV)-1.09 × 1014 eV-1 cm-2 ( E c —0.17 eV) at 120 K and 1.67 × 1013 eV-1 cm-2 ( E c —0.75 eV)-5.02 × 1013 eV-1 cm-2 ( E c —0.59 eV) at 400 K. It is observed that the interface state density ( N ss) decreases with increase in temperature. Results reveal that the conduction current is dominated by Poole-Frenkel emission in the temperature range from 120 to 320 K and by Schottky emission above 360 K.

  10. High sensitivity Schottky junction diode based on monolithically grown aligned polypyrrole nanofibers: Broad range detection of m-dihydroxybenzene.

    Science.gov (United States)

    Ameen, Sadia; Akhtar, M Shaheer; Seo, Hyung-Kee; Shin, Hyung Shik

    2015-07-30

    Aligned p-type polypyrrole (PPy) nanofibers (NFs) thin film was grown on n-type silicon (100) substrate by an electrochemical technique to fabricate Schottky junction diode for the efficient detection of m-dihydroxybenzene chemical. The highly dense and well aligned PPy NFs with the average diameter (∼150-200 nm) were grown on n-type Si substrate. The formation of aligned PPy NFs was confirmed by elucidating the structural, compositional and the optical properties. The electrochemical behavior of the fabricated Pt/p-aligned PPy NFs/n-silicon Schottky junction diode was evaluated by cyclovoltametry (CV) and current (I)-voltage (V) measurements with the variation of m-dihydroxybenzene concentration in the phosphate buffer solution (PBS). The fabricated Pt/p-aligned PPy NFs/n-silicon Schottky junction diode exhibited the rectifying behavior of I-V curve with the addition of m-dihydroxybenzene chemical, while a weak rectifying I-V behavior was observed without m-dihydroxybenzene chemical. This non-linear I-V behavior suggested the formation of Schottky barrier at the interface of Pt layer and p-aligned PPy NFs/n-silicon thin film layer. By analyzing the I-V characteristics, the fabricated Pt/p-aligned PPy NFs/n-silicon Schottky junction diode displayed reasonably high sensitivity ∼23.67 μAmM(-1)cm(-2), good detection limit of ∼1.51 mM with correlation coefficient (R) of ∼0.9966 and short response time (10 s). Copyright © 2015 Elsevier B.V. All rights reserved.

  11. On the nature of thermal equilibrium point defects in Si: Are the thermal equilibrium point defects in Si crystals Frenkel pairs or Schottky defects?

    Science.gov (United States)

    Suezawa, Masashi; Iijima, Yoshiaki; Yonenaga, Ichiro

    2017-04-01

    Thermal equilibrium point defects (TEPD) are generated as Frenkel pairs or Schottky defects. It is still controversial whether the TEPD in Si are Frenkel or Schottky, which is recalled with the recent experimental finding of their formation energies. After reviews of the Frenkel pair and Schottky defects models, the latter was concluded to be the case since their formation energies determined experimentally are different from each other. This result was applied to calculate the critical ratio of the growth velocity/temperature gradient of the Voronkov model on the grown-in point defects in Si and obtained a different result.

  12. High density Schottky barrier IRCCD sensors for SWIR applications at intermediate temperature

    Science.gov (United States)

    Elabd, H.; Villani, T. S.; Tower, J. R.

    1982-01-01

    Monolithic 32 x 64 and 64 x 1:128 palladium silicide (Pd2Si) interline transfer infrared charge coupled devices (IRCCDs) sensitive in the 1 to 3.5 micron spectral band were developed. This silicon imager exhibits a low response nonuniformity of typically 0.2 to 1.6% rms, and was operated in the temperature range between 40 to 140 K. Spectral response measurements of test Pd2Si p-type Si devices yield quantum efficiencies of 7.9% at 1.25 microns, 5.6% at 1.65 microns 2.2% at 2.22 microns. Improvement in quantum efficiency is expected by optimizing the different structural parameters of the Pd2Si detectors. The spectral response of the Pd2Si detectors fit a modified Fowler emission model. The measured photo-electric barrier height for the Pd2Si detectors is 0.34 eV and the measured quantum efficiency coefficient, C1, is 19%/eV. The dark current level of Pd2Si Schottky barrier focal plane arrays (FPAs) is sufficiently low to enable operation at intermediate temperatures at TV frame rates. Typical dark current level measured at 120 K on the FPA is 2 nA/sq cm. The operating temperature of the Pd2Si FPA is compatible with passive cooler performance. In addition, high density Pd2Si Schottky barrier FPAs are manufactured with high yield and therefore represent an economical approach to short wavelength IR imaging. A Pd2Si Schottky barrier image sensor for push-broom multispectral imaging in the 1.25, 1.65, and 2.22 micron bands is being studied. The sensor will have two line arrays (dual band capability) of 512 detectors each, with 30 micron center-to-center detector spacing. The device will be suitable for chip-to-chip abutment, thus providing the capability to produce large, multiple chip focal planes with contiguous, in-line sensors.

  13. Large area, low capacitance, GaAs nanowire photodetector with a transparent Schottky collecting junction

    Energy Technology Data Exchange (ETDEWEB)

    Seyedi, M. A., E-mail: seyedi@usc.edu; Yao, M.; O' Brien, J.; Dapkus, P. D. [Center for Energy Nanoscience, University of Southern California, Los Angeles, California 90089 (United States); Wang, S. Y. [Center for Energy Nanoscience, University of Southern California, Los Angeles, California 90089 (United States); Nanostructured Energy Conversion Technology and Research (NECTAR), Advanced Studies Laboratories, University of California, Santa Cruz, California 95064, USA and NASA Ames Research Center, Moffett Field, California 94035 (United States)

    2013-12-16

    We present experimental results on a GaAs/Indium-Tin-Oxide Schottky-like heterojunction photodetector based on a nanowire device geometry. By distributing the active detecting area over an array of nanowires, it is possible to achieve large area detection with low capacitance. Devices with bare GaAs and passivated AlGaAs/GaAs nanowires are fabricated to compare the responsivity with and without surface passivation. We are able to achieve responsivity of >0.5A/W and Signal-Noise-Ratio in excess of 7 dB for 2 V applied reverse bias with passivated nanowire devices. Capacitance-voltage measurement yields <5 nF/cm{sup 2}, which shows a strong possibility for high-speed applications with a broad area device.

  14. Untersuchung eines breitbandigen Koaxial-Hohlleiterübergangs für einen Schottky-Strahldiagnosedetektor

    CERN Document Server

    Ehret, M; Wendt, M

    In der vorliegenden Arbeit wurde ein Koaxial-Hohlleiterübergang im Mikrowellenbereich (4.8 GHz) untersucht und verbessert. Diese Kopplung ist eine der Schlüsselstellen des sogenannten „Schottky-Detektors“. Dieser Detektor befindet sich innerhalb des Teilchenbeschleunigers des Large Hadron Colliders am CERN. Während der Arbeit wurden verschiedene Untersuchungen am Detektor durchgeführt und anhand der ermittelten Ergebnisse eine veränderte Kopplerstruktur entwickelt. Diese Struktur wurde zuerst anhand von verschiedenen Modellen in einer elektromagnetischen Feldsimulation überprüft und mit Hilfe verschiedener Algorithmen verifiziert. Im nächsten Schritt wurde ein Testaufbau entwickelt, mit dem eine Überprüfung und eine abschließende Betrachtung der Ergebnisse möglich war. Es konnte gezeigt werden, dass mit der neu entwickelten Struktur die Kopplereigenschaften wesentlich verbessert und die Zielvorgaben sogar deutlich übertroffen wurden.

  15. Upgrade of the LHC Schottky Monitor, Operational Experience and First Results

    CERN Document Server

    Betz, Michael; Lefèvre, Thibaut; Wendt, Manfred

    2016-01-01

    The LHC Schottky system allows the measurement of beam parameters such as tune and chromaticity in an entirely non-invasive way by extracting information from the statistical fluctuations in the incoherent motion of particles. The system was commissioned in 2011 and provided satisfactory beam-parameter measurements during LHC run 1 for lead-ions. However, for protons its usability was substantially limited due to strong interfering signals originating from the coherent motion of the particle bunch. The system has recently been upgraded with optimized travelling-wave pick-ups and an improved 4.8~GHz microwave signal path, with the front-end and the triple down-mixing chain optimized to reduce coherent signals. Design and operational aspects for the complete system are shown and the results from measurements with LHC beams in Run II are presented and discussed.

  16. Hard X-ray detection with a gallium phosphide Schottky diode

    Energy Technology Data Exchange (ETDEWEB)

    Owens, Alan [Science Payload and Advanced Concepts Office, ESA/ESTEC, Postbus 299, 2200AG Noordwijk (Netherlands)], E-mail: aowens@rssd.esa.int; Andersson, S.; Hartog, R. den; Quarati, F. [Science Payload and Advanced Concepts Office, ESA/ESTEC, Postbus 299, 2200AG Noordwijk (Netherlands); Webb, A.; Welter, E. [HASYLAB at DESY, Notkestrasse 85, D-22607 Hamburg (Germany)

    2007-11-01

    We report on the detection of hard X-rays using a GaP Schottky diode at the HASYLAB synchrotron radiation research facility. Exposure to alpha particles from an {sup 214}Am source showed that the device was spectroscopic at room temperature with a FWHM energy resolution of 3.5% at 5.5 MeV. It was also found to be responsive to X-rays in the range 11-100 keV. Although individual energies are not spectrally resolved there is a proportionality of response to increasing X-ray energy. A two-dimensional scan of the sensitive area using a 30x30 {mu}m{sup 2} 30 keV pencil beam showed the spatial response of the detector to be uniform at the few percent level, consistent with statistics.

  17. Review and test of methods for determination of the Schottky diode parameters

    Science.gov (United States)

    Olikh, O. Ya.

    2015-07-01

    This paper deals with the extraction of the Schottky diode parameters from a current-voltage characteristic. 10 analytical methods, 2 numerical methods, and 4 evolutionary algorithms of the series resistance, barrier height, and ideality factor determination are reviewed. The accuracy of the methods is quantified using a wide range of both ideal and noisy synthetic data. In addition, the influencing factors of the parameters extraction accuracy are estimated. The adaptive procedure, which improves the precision of analytical Gromov's method, is suggested. The use of Lambert W function has been shown to reduce the error of parameter extraction by numerical method. Finally, all methods are applied to experimental data. The most reliable and preferred methods are chosen.

  18. Photovoltaic characterization of graphene/silicon Schottky junctions from local and macroscopic perspectives

    Science.gov (United States)

    Hájková, Zdeňka; Ledinský, Martin; Vetushka, Aliaksei; Stuchlík, Jiří; Müller, Martin; Fejfar, Antonín; Bouša, Milan; Kalbáč, Martin; Frank, Otakar

    2017-05-01

    We present Schottky junction solar cell composed of graphene transferred onto hydrogenated amorphous and microcrystalline silicon, a low-cost alternative to well-explored crystalline silicon. We demonstrated sample with open-circuit voltage of 445 mV, a remarkable value for undoped graphene-based solar cell. Photovoltaic characteristics of this sample remained stable over 11 months and could be further improved by doping. The graphene/silicon junctions were characterized by current-voltage curves obtained locally by conductive atomic force microscopy (C-AFM) and macroscopically by standard solar simulator. Very good correlation between both independent measurements proved C-AFM as highly useful tool for photovoltaic characterization on nano- and micrometer scale.

  19. Plasmonic silicon Schottky photodetectors: The physics behind graphene enhanced internal photoemission

    Directory of Open Access Journals (Sweden)

    Uriel Levy

    2017-02-01

    Full Text Available Recent experiments have shown that the plasmonic assisted internal photoemission from a metal to silicon can be significantly enhanced by introducing a monolayer of graphene between the two media. This is despite the limited absorption in a monolayer of undoped graphene ( ∼ π α = 2.3 % . Here we propose a physical model where surface plasmon polaritons enhance the absorption in a single-layer graphene by enhancing the field along the interface. The relatively long relaxation time in graphene allows for multiple attempts for the carrier to overcome the Schottky barrier and penetrate into the semiconductor. Interface disorder is crucial to overcome the momentum mismatch in the internal photoemission process. Our results show that quantum efficiencies in the range of few tens of percent are obtainable under reasonable experimental assumptions. This insight may pave the way for the implementation of compact, high efficiency silicon based detectors for the telecom range and beyond.

  20. An X-band Schottky diode mixer in SiGe technology with tunable Marchand balun

    DEFF Research Database (Denmark)

    Michaelsen, Rasmus Schandorph; Johansen, Tom Keinicke; Tamborg, Kjeld M.

    2017-01-01

    In this paper, we propose a double balanced mixer with a tunable Marchand balun. The circuit is designed in a SiGe BiCMOS process using Schottky diodes. The tunability of the Marchand balun is used to enhance critical parameters for double balanced mixers. The local oscillator-IF isolation can...... be changed from –51 to –60.5 dB by tuning. Similarly, the IIP2 can be improved from 41.3 to 48.7 dBm at 11 GHz, while the input referred 1-dB compression point is kept constant at 8 dBm. The tuning have no influence on conversion loss, which remains at 8.8 dB at a LO power level of 11 dBm at the center...

  1. Ultraviolet Schottky detector based on epitaxial ZnO thin film

    Science.gov (United States)

    Jiang, Dayong; Zhang, Jiying; Lu, Youming; Liu, Kewei; Zhao, Dongxu; Zhang, Zhenzhong; Shen, Dezhen; Fan, Xiwu

    2008-05-01

    In this paper, we have prepared Schottky type ZnO metal-semiconductor-metal (MSM) ultraviolet (UV) detector. The structural, electrical, and optical measurements were carried out. The detector exhibited a peak responsivity of 0.337 A/W at 360 nm and the dark current was about 1 nA under 3 V bias. An ultraviolet-visible rejection ratio was obtained about more than four orders of magnitude from the fabricated detector. The 10-90% rise and fall time were 20 ns and 250 ns, respectively. We proposed that the detector had shown a gain, which was attributed to the trapping of hole carriers at the semiconductor-metal interface.

  2. Stacked mechanical nanogenerator comprising piezoelectric semiconducting nanostructures and Schottky conductive contacts

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhong L [Marietta, GA; Xu, Sheng [Atlanta, GA

    2011-08-23

    An electric power generator includes a first conductive layer, a plurality of semiconducting piezoelectric nanostructures, a second conductive layer and a plurality of conductive nanostructures. The first conductive layer has a first surface from which the semiconducting piezoelectric nanostructures extend. The second conductive layer has a second surface and is parallel to the first conductive layer so that the second surface faces the first surface of the first conductive layer. The conductive nanostructures depend downwardly therefrom. The second conductive layer is spaced apart from the first conductive layer at a distance so that when a force is applied, the semiconducting piezoelectric nanostructures engage the conductive nanostructures so that the piezoelectric nanostructures bend, thereby generating a potential difference across the at semiconducting piezoelectric nanostructures and also thereby forming a Schottky barrier between the semiconducting piezoelectric nanostructures and the conductive nanostructures.

  3. Radiation-resistant photostructure for Schottky diode based on Cr/In2Hg3Te6

    Directory of Open Access Journals (Sweden)

    Ashcheulov A. A.

    2016-05-01

    Full Text Available Ge, Si, InGaAs, GaInAsP photodiodes are used as optical radiation receivers and function in a spectral range of transparency of quartz fiberglass. For the optical systems operated in the increased radioactivity the photodetectors' application on In2Hg3Te6 crystal base characterized by a photosensitivity in the spectral range of 0,5-1,6 mm and also by increased radiation resistance to alpha, beta and gamma radiation is most acceptable. Schottky photodiode structure was designed on the base of this semiconductor formed by a modified floating zone recrystallization technique where the sedimentation effect was leveled. It consists of n-In2Hg3Te6 substrate and deposited by cathode sputtering Cr barrier layer of thickness within a range 10-11 nm choice of Cr is determined by its optimal optical, electric and adhesive features in high quality radiation-resistant photodiode structures manufacturing. Indium and nichrome are used as ohmic contacts. The barrier structures have the contact area of 1,13 mm2 with photo response of 0,6-1,6 mm at the maximal sensitivity 0,43 A/W on the wavelength l,55 mm. Reverse dark current of these structures do not exceed 4 mA at the bias of 1 V (T=295 K, and the potential barrier height is equal to 0,41 eV. The tests of radiation resistance of these structures demonstrated their ability to function at doses of 2⋅108 rem without evident parameters changes. This allows using them in practical aims in the conditions of high radiation.

  4. Response of Ni/4H-SiC Schottky barrier diodes to alpha-particle irradiation at different fluences

    Energy Technology Data Exchange (ETDEWEB)

    Omotoso, E., E-mail: ezekiel.omotoso@up.ac.za [Department of Physics, University of Pretoria, Private Bag X20, Hatfield 0028 (South Africa); Departments of Physics, Obafemi Awolowo University, Ile-Ife 220005 (Nigeria); Meyer, W.E.; Auret, F.D.; Diale, M.; Ngoepe, P.N.M. [Department of Physics, University of Pretoria, Private Bag X20, Hatfield 0028 (South Africa)

    2016-01-01

    Irradiation experiments have been carried out on 1.9×10{sup 16} cm{sup −3} nitrogen-doped 4H-SiC at room temperature using 5.4 MeV alpha-particle irradiation over a fluence ranges from 2.6×10{sup 10} to 9.2×10{sup 11} cm{sup −2}. Current–voltage (I–V), capacitance–voltage (C–V) and deep level transient spectroscopy (DLTS) measurements have been carried out to study the change in characteristics of the devices and free carrier removal rate due to alpha-particle irradiation, respectively. As radiation fluence increases, the ideality factors increased from 1.20 to 1.85 but the Schottky barrier height (SBH{sub I–V}) decreased from 1.47 to 1.34 eV. Free carrier concentration, N{sub d} decreased with increasing fluence from 1.7×10{sup 16} to 1.1×10{sup 16} cm{sup −2} at approximately 0.70 μm depth. The reduction in N{sub d} shows that defects were induced during the irradiation and have effect on compensating the free carrier. The free carrier removal rate was estimated to be 6480±70 cm{sup −1}. Alpha-particle irradiation introduced two electron traps (E{sub 0.39} and E{sub 0.62}), with activation energies of 0.39±0.03 eV and 0.62±0.08 eV, respectively. The E{sub 0.39} as attribute related to silicon or carbon vacancy, while the E{sub 0.62} has the attribute of Z{sub 1}/Z{sub 2}.

  5. Technology CAD of silicided Schottky barrier MOSFET for elevated source-drain engineering

    Energy Technology Data Exchange (ETDEWEB)

    Saha, A.R. [Department of Electronics and ECE, IIT, Kharagpur 721302 (India)]. E-mail: ars.iitkgp@gmail.com; Chattopadhyay, S. [Department of Electronics and ECE, IIT, Kharagpur 721302 (India); School of Electrical, Electronics and Computer Engineering, University of Newcastle, Newcastle upon Tyne (United Kingdom); Bose, C. [Department of Electronics and Telecommunication Engineering, Jadavpur University, Calcutta 700032 (India); Maiti, C.K. [Department of Electronics and ECE, IIT, Kharagpur 721302 (India)

    2005-12-05

    Technology CAD has been used to study the performance of a silicided Schottky barrier (SB) MOSFET with gate, source and drain contacts realized with nickel-silicide. Elevated source-drain structures have been used towards the S/D engineering of CMOS devices. A full process-to-device simulation has been employed to predict the performance of sub-micron SB n-MOSFETs for the first time. A model for the diffusion and alloy growth kinetics has been incorporated in SILVACO-ATLAS and ATHENA to explore the processing and design parameter space for the Ni-silicided MOSFETs. The temperature and concentration dependent diffusion model for NiSi have been developed and necessary material parameters for nickel-silicide and epitaxial-Si have been incorporated through the C-interpreter function. Two-dimensional (2D) process-to-device simulations have also been used to study the dc and ac (RF) performance of silicided Schottky barrier (SB) n-MOSFETs. The extracted sheet resistivity, as a function of annealing temperature of the silicided S/D contacts, is found to be lower than the conventional contacts currently in use. It is also shown that the Technology CAD has the full capability to predict the possible dc and ac performance enhancement of a MOSFET with elevated S/D structures. While the simulated dc performance shows a clear enhancement, the RF analyses show no performance degradation in the cut-off frequency/propagation delay and also improve the ac performance due to the incorporation of silicide contacts in the S/D region.

  6. A high performance charge plasma PN-Schottky collector transistor on silicon-on-insulator

    Science.gov (United States)

    Loan, Sajad A.; Bashir, Faisal; Rafat, M.; Alamoud, Abdul Rehman M.; Abbasi, Shuja A.

    2014-09-01

    In this paper, we propose a new high performance PN-Schottky collector (PN-SC) lateral bipolar junction transistor (BJT) on silicon-on-insulator (SOI). The proposed device addresses the problem of poor speed of conventional lateral PNP-BJT device by using a Schottky collector. Further, it does not use the conventional ways of ion implantation/diffusion to realize n and p type doped region. However, it uses metal electrodes of different work functions to create n and p type charge plasma in an undoped silicon film. The simulation study of the proposed lateral PN-SC bipolar charge plasma transistor on SOI (PN-SC-BCPT) device has shown a significant improvement in current gain (β), cutoff frequency (f T) and switching performance in comparison to conventional PNP-BJT and PNP-bipolar charge plasma transistor (PNP-BCPT) devices. A significantly high β is obtained in the proposed PN-SC-BCPT (˜2100) in comparison to PNP-BCPT (˜1450) and the conventional BJT (˜9) devices, respectively. It has been observed that there is 89.56% and 153.5% increase in f T for the proposed PN-SC-BCPT device (2.18 GHz) in comparison to conventional PNP-BJT (1.15 GHz) and PNP-BCPT (0.86 GHz) devices, respectively. Further, reductions of 24.6% and 15.4% in switching ON-delay and 66% and 30.76% in switching OFF-delay have been achieved in the proposed device based inverters in comparison to PNP-BCPT and the conventional BJT devices based inverters, respectively. Furthermore, the proposed device does not face doping related issues and the requirement of high temperature processing is absent.

  7. Electrical and noise properties of proton irradiated 4H-SiC Schottky diodes

    Science.gov (United States)

    Kozlovski, V. V.; Lebedev, A. A.; Levinshtein, M. E.; Rumyantsev, S. L.; Palmour, J. W.

    2018-01-01

    The current voltage characteristics and the low-frequency noise in high voltage 4H-SiC junction barrier Schottky diodes irradiated with high energy (15 MeV) protons were studied at different temperatures and irradiation doses Φ from 3 × 1012 cm-2 to 1 × 1014 cm-2. Irradiation led to the increase of the base resistance and the appearance of slow relaxation processes at small, V ≤ 0.2 V, and at rather high, V ≥ 2 V, forward voltages. The characteristic times of these relaxation processes ranged from ˜1 μs to 103 s. The exponential part of the current-voltage characteristic was only weakly affected by irradiation. The temperature dependence of the base resistance changed exponentially with temperature with activation energy Ea ˜ 0.6 eV, indicating that the Z1/2 level plays a dominant role in this process. The temperature increase also led to the increase of the ideality factor from 1.05 at 25 °C to 1.1 at 172 °C. At elevated temperatures and high forward voltages V > 2-4 V, the current voltage characteristics tend to be super-linear. It is concluded that at high voltages, the space charge limited current of majority carriers (electrons) and hole injection from the p-n regions play an important role in the formation of the current voltage characteristic. The frequency dependences of noise spectral density S of proton irradiated Schottky diodes have the unusual form of S ˜ 1/f 0.5.

  8. InGaAs Schottky barrier diode array detectors integrated with broadband antenna (Conference Presentation)

    Science.gov (United States)

    Park, Dong Woo; Lee, Eui Su; Park, Jeong-Woo; Kim, Hyun-Soo; Lee, Il-Min; Park, Kyung Hyun

    2017-02-01

    Terahertz (THz) waves have been actively studied for the applications of astronomy, communications, analytical science and bio-technologies due to their low energy and high frequency. For example, THz systems can carry more information with faster rates than GHz systems. Besides, THz waves can be applied to imaging, sensing, and spectroscopy. Furthermore, THz waves can be used for non-destructive and non-harmful tomography of living objects. In this reasons, Schottky barrier diodes (SBD) have been widely used as a THz detector for their ultrafast carrier transport, high responsivity, high sensitivity, and excellent noise equivalent power. Furthermore, SBD detectors envisage developing THz applications at low cost, excellent capability, and high yield. Since the major concerns in the THz detectors for THz imaging systems are the realizations of the real-time image acquisitions via a reduced acquisition time, rather than the conventional raster scans that obtains an image by pixel-by-pixel acquisitions, a line-scan based systems utilizes an array detector with an 1 × n SBD array is preferable. In this study, we fabricated the InGaAs based SBD array detectors with broadband antennas of log-spiral and square-spiral patterns. To optimize leakage current and ideality factor, the dependence to the doping levels of ohmic and Schottky layers have been investigated. In addition, the dependence to the capacitance and resistance to anode size are also examined as well. As a consequence, the real-time THz imaging with our InGaAs SBD array detector have been successfully obtained.

  9. Self-powered flexible and transparent photovoltaic detectors based on CdSe nanobelt/graphene Schottky junctions

    Science.gov (United States)

    Gao, Zhiwei; Jin, Weifeng; Zhou, Yu; Dai, Yu; Yu, Bin; Liu, Chu; Xu, Wanjin; Li, Yanping; Peng, Hailin; Liu, Zhongfan; Dai, Lun

    2013-05-01

    Flexible and transparent electronic and optoelectronic devices have attracted more and more research interest due to their potential applications in developing portable, wearable, low-cost, and implantable devices. We have fabricated and studied high-performance flexible and transparent CdSe nanobelt (NB)/graphene Schottky junction self-powered photovoltaic detectors for the first time. Under 633 nm light illumination, typical photosensitivity and responsivity of the devices are about 1.2 × 105 and 8.7 A W-1, respectively. Under 3500 Hz switching frequency, the response and recovery times of them are about 70 and 137 μs, respectively, which, to the best of our knowledge, are the best reported values for nanomaterial based Schottky junction photodetectors up to date. The detailed properties of the photodetectors, such as the influences of incident light wavelength and light intensity on the external quantum efficiency and speed, are also investigated. Detailed discussions are made in order to understand the observed phenomena. Our work demonstrates that the self-powered flexible and transparent CdSe NB/graphene Schottky junction photovoltaic detectors have a bright application prospect.Flexible and transparent electronic and optoelectronic devices have attracted more and more research interest due to their potential applications in developing portable, wearable, low-cost, and implantable devices. We have fabricated and studied high-performance flexible and transparent CdSe nanobelt (NB)/graphene Schottky junction self-powered photovoltaic detectors for the first time. Under 633 nm light illumination, typical photosensitivity and responsivity of the devices are about 1.2 × 105 and 8.7 A W-1, respectively. Under 3500 Hz switching frequency, the response and recovery times of them are about 70 and 137 μs, respectively, which, to the best of our knowledge, are the best reported values for nanomaterial based Schottky junction photodetectors up to date. The detailed

  10. Nondestructive imaging of buried interfaces in SiC and GaN Schottky contacts using scanning internal photoemission microscopy

    Science.gov (United States)

    Shiojima, Kenji; Yamamoto, Shingo; Kihara, Yuhei; Mishima, Tomoyoshi

    2015-04-01

    We demonstrate a nondestructive characterization of buried interfaces in metal/wide-bandgap semiconductor contacts by using scanning internal photoemission microscopy. For Ni/n-SiC contacts annealed at temperatures above 400 °C, a reduction of the Schottky barrier height owing to partial interfacial reaction was visualized. In Au/Ni/n-GaN contacts, upon annealing at 400 °C, thermal degradation from a scratch on the dot was observed. Forward current-voltage curves were reproduced by lowering the Schottky barrier height and the area of the reacted regions by using this method. The present imaging method exploits its nondestructive highly sensitive extinction for characterizing the contacts formed on wide-gap materials.

  11. High detectivity visible-blind SiF4 grown epitaxial graphene/SiC Schottky contact bipolar phototransistor

    Science.gov (United States)

    Chava, Venkata S. N.; Barker, Bobby G.; Balachandran, Anusha; Khan, Asif; Simin, G.; Greytak, Andrew B.; Chandrashekhar, M. V. S.

    2017-12-01

    We report the performance of a bipolar epitaxial graphene (EG)/p-SiC/n+-SiC UV phototransistor fabricated with a Schottky (EG)/SiC junction grown using a SiF4 precursor. The phototransistor showed responsivity as high as 25 A/W at 250 nm in the Schottky emitter (SE) mode. The Schottky collector (SC) mode showed a responsivity of 17 A/W at 270 nm with a visible rejection (270 nm:400 nm)>103. The fastest response was seen in the SC-mode, with 10 ms turn-on and 47 ms turn-off, with a noise equivalent power of 2.3 fW at 20 Hz and a specific detectivity of 4.4 × 1013 Jones. The high responsivity is due to internal gain from bipolar action. We observe additional avalanche gain from the device periphery in the SC-mode by scanning photocurrent microscopy but not in the SE-mode. This high-performance visible-blind photodetector is attractive for advanced applications such as flame detection.

  12. Magnetic field induced suppression of the forward bias current in Bi2Se3/Si Schottky barrier diodes

    Science.gov (United States)

    Jin, Haoming; Hebard, Arthur

    Schottky diodes formed by van der Waals bonding between freshly cleaved flakes of the topological insulator Bi2Se3 and doped silicon substrates show electrical characteristics in good agreement with thermionic emission theory. The motivation is to use magnetic fields to modulate the conductance of the topologically protected conducting surface state. This surface state in close proximity to the semiconductor surface may play an important role in determining the nature of the Schottky barrier. Current-voltage (I-V) and capacitance-voltage (C-V) characteristics were obtained for temperatures in the range 50-300 K and magnetic fields, both perpendicular and parallel to the interface, as high as 7 T. The I-V curve shows more than 6 decades linearity on semi-logarithmic plots, allowing extraction of parameters such as ideality (η), zero-voltage Schottky barrier height (SBH), and series resistance (Rs). In forward bias we observe a field-induced decrease in current which becomes increasingly more pronounced at higher voltages and lower temperature, and is found to be correlated with changes in Rs rather than other barrier parameters. A comparison of changes in Rs in both field direction will be made with magnetoresistance in Bi2Se3 transport measurement. The work is supported by NSF through DMR 1305783.

  13. Room temperature current-voltage (I-V) characteristics of Ag/InGaN/n-Si Schottky barrier diode

    Science.gov (United States)

    Erdoğan, Erman; Kundakçı, Mutlu

    2017-02-01

    Metal-semiconductors (MSs) or Schottky barrier diodes (SBDs) have a significant potential in the integrated device technology. In the present paper, electrical characterization of Ag/InGaN/n-Si Schottky diode have been systematically carried out by simple Thermionic method (TE) and Norde function based on the I-V characteristics. Ag ohmic and schottky contacts are deposited on InGaN/n-Si film by thermal evaporation technique under a vacuum pressure of 1×10-5 mbar. Ideality factor, barrier height and series resistance values of this diode are determined from I-V curve. These parameters are calculated by TE and Norde methods and findings are given in a comparetive manner. The results show the consistency for both method and also good agreement with other results obtained in the literature. The value of ideality factor and barrier height have been determined to be 2.84 and 0.78 eV at room temperature using simple TE method. The value of barrier height obtained with Norde method is calculated as 0.79 eV.

  14. Fabrication and characterization of magnetically tunable metal-semiconductor schottky diode using barium hexaferrite thin film on gold

    Science.gov (United States)

    Kaur, Jotinder; Sharma, Vinay; Sharma, Vipul; Veerakumar, V.; Kuanr, Bijoy K.

    2016-05-01

    Barium Hexaferrite (BaM) is an extensively studied magnetic material due to its potential device application. In this paper, we study Schottky junction diodes fabricated using gold and BaM and demonstrate the function of a spintronic device. Gold (50 nm)/silicon substrate was used to grow the BaM thin films (100-150 nm) using pulsed laser deposition. I-V characteristics were measured on the Au/BaM structure sweeping the voltage from ±5 volts. The forward and reverse bias current-voltage curves show diode like rectifying characteristics. The threshold voltage decreases while the output current increases with increase in the applied external magnetic field showing that the I-V characteristics of the BaM based Schottky junction diodes can be tuned by external magnetic field. It is also demonstrated that, the fabricated Schottky diode can be used as a half-wave rectifier, which could operate at high frequencies in the range of 1 MHz compared to the regular p-n junction diodes, which rectify below 10 kHz. In addition, it is found that above 1 MHz, Au/BaM diode can work as a rectifier as well as a capacitor filter, making the average (dc) voltage much larger.

  15. Structural, morphological, optical and electrical properties of Schottky diodes based on CBD deposited ZnO:Cu nanorods

    Science.gov (United States)

    Mwankemwa, Benard S.; Legodi, Matshisa J.; Mlambo, Mbuso; Nel, Jackie M.; Diale, Mmantsae

    2017-07-01

    Undoped and copper doped zinc oxide (ZnO) nanorods have been synthesized by a simple chemical bath deposition (CBD) method at a temperature of 90 °C. Structural, morphological, optical and electrical properties of the synthesized ZnO nanorods were found to be dependent on the Cu doping percentage. X-ray diffraction (XRD) patterns revealed strong diffraction peaks of hexagonal wurtzite of ZnO, and no impurity phases from metallic zinc or copper. Scanning electron microscopy (SEM) images showed changes in diameter and shape of nanorods, where by those doped with 2 at.% and 3 at.% aggregated and became compact. Selected area electron diffraction (SAED) patterns indicates high quality, single crystalline wurtzite structure ZnO and intensities of bright spots varied with copper doping concentration. UV-visible absorption peaks of ZnO red shifted with increasing copper doping concentration. Raman studies demonstrated among others, strong and sharp E2 (low) and E2 (high) optical phonon peaks confirming crystal structure of ZnO. Current-voltage measurements based on the gold/ZnO nanorods/ITO showed good rectifying behavior of the Schottky diode. The predicted Schottky barrier height of 0.60 eV was obtained which is not far from the theoretical Schottky-Mott value of 0.80 eV.

  16. Modification of electrical properties of Au/n-type InP Schottky diode with a high-k Ba0.6Sr0.4TiO3 interlayer

    Science.gov (United States)

    Thapaswini, P. Prabhu; Padma, R.; Balaram, N.; Bindu, B.; Rajagopal Reddy, V.

    2016-05-01

    Au/Ba0.6Sr0.4TiO3 (BST)/n-InP metal/insulator/semiconductor (MIS) Schottky diodes have been analyzed by current-voltage (I-V) and capacitance-voltage (C-V) measurements. The surface morphology of the BST films on InP is fairly smooth. The Au/BST/n-InP MIS Schottky diode shows better rectification ratio and low leakage current compared to the conventional Au/n-InP metal-semiconductor (MS) Schottky diode. Higher barrier height is achieved for the MIS Schottky diode compared to the MS Schottky diode. The Norde and Cheung's methods are employed to determine the barrier height, ideality factor and series resistance. The interface state density (NSS) is determined from the forward bias I-V data for both the MS and MIS Schottky diodes. Results reveal that the NSS of the MIS Schottky diode is lower than that of the MS Schottky diode. The Poole-Frenkel emission is found dominating the reverse current in both Au/n-InP MS and Au/BST/n-InP MIS Schottky diodes, indicating the presence of structural defects and trap levels in the dielectric film.

  17. GaN-based Schottky barrier ultraviolet photodetectors with graded doping on patterned sapphire substrates

    Science.gov (United States)

    Mou, Wenjie; Zhao, Linna; Chen, Leilei; Yan, Dawei; Ma, Huarong; Yang, Guofeng; Gu, Xiaofeng

    2017-07-01

    In this paper, we demonstrate high performance GaN-based Schottky-barrier ultraviolet (UV) photodetectors with graded doping prepared on patterned sapphire substrates. The fabricated devices exhibit an extremely low dark current density of ∼1.3 × 10-8 A/cm2 under -5 V bias, a large UV-to-visible light rejection ratio of ∼4.2 × 103, and a peak external quantum efficiency of ∼50.7% at zero bias. Even in the deeper 250-360 nm range, the average external quantum efficiency still remains ∼40%. From the transient response characteristics, the average rising and falling time constants are estimated ∼115 μs and 120 μs, respectively, showing a good electrical and thermal reliability. The specific detectivities D∗, limited by the thermal equilibrium noise and the low-frequency 1/f noise, are derived ∼5.5 × 1013 cm Hz1/2/W (at 0 V) and ∼2.68 × 1010 cm Hz1/2 W-1 (at -5 V), respectively.

  18. Schottky Barrier Height of Pd/MoS2 Contact by Large Area Photoemission Spectroscopy.

    Science.gov (United States)

    Dong, Hong; Gong, Cheng; Addou, Rafik; McDonnell, Stephen; Azcatl, Angelica; Qin, Xiaoye; Wang, Weichao; Wang, Weihua; Hinkle, Christopher L; Wallace, Robert M

    2017-11-08

    MoS2, as a model transition metal dichalcogenide, is viewed as a potential channel material in future nanoelectronic and optoelectronic devices. Minimizing the contact resistance of the metal/MoS2 junction is critical to realizing the potential of MoS2-based devices. In this work, the Schottky barrier height (SBH) and the band structure of high work function Pd metal on MoS2 have been studied by in situ X-ray photoelectron spectroscopy (XPS). The analytical spot diameter of the XPS spectrometer is about 400 μm, and the XPS signal is proportional to the detection area, so the influence of defect-mediated parallel conduction paths on the SBH does not affect the measurement. The charge redistribution by Pd on MoS2 is detected by XPS characterization, which gives insight into metal contact physics to MoS2 and suggests that interface engineering is necessary to lower the contact resistance for the future generation electronic applications.

  19. Self-assembled H-aggregation induced high performance poly (3-hexylthiophene) Schottky diode

    Science.gov (United States)

    Chaudhary, Vivek; Pandey, Rajiv K.; Prakash, Rajiv; Singh, Arun Kumar

    2017-12-01

    The investigation of size confinement and chain orientation within the microstructure of a polymer thin film is very important for electronic device applications and fundamental research. Here, we present single step methodology for the synthesis of solution-processable poly (3-hexylthiophene) (P3HT) nanofibers via a self-assembly process. The formation of P3HT nanofibers is confirmed by atomic force microscopy. The synthesized nanofibers are characterized by UV-visible absorption, photoluminescence, and Raman spectroscopy. The aggregation type of self-assembled P3HT is studied by both UV-visible absorbance and photoluminescence spectroscopy. The exciton bandwidth in polymer films is calculated by following the Spano's H-aggregate model and found to be 28 meV. Raman spectroscopy is used to identify the various stretching modes present in nanofibers. The structural investigation using grazing angle X-ray diffraction of nanofibers reveals the presence of alkyl chain ordering. We have fabricated organic Schottky diodes with P3HT nanofibers on indium tin oxide (ITO) coated glass with configuration Al/P3HT/ITO, and current density-voltage characteristics are subsequently used for extracting the electronic parameters of the device. We have also discussed the charge transport mechanism at the metal/polymer interface.

  20. Synthesis of Peripherally Tetrasubstituted Phthalocyanines and Their Applications in Schottky Barrier Diodes

    Directory of Open Access Journals (Sweden)

    Semih Gorduk

    2017-01-01

    Full Text Available New metal-free and metallophthalocyanine compounds (Zn, Co, Ni, and Cu were synthesized using 2-hydroxymethyl-1,4-benzodioxan and 4-nitrophthalonitrile compounds. All newly synthesized compounds were characterized by elemental analysis, FT-IR, UV-Vis, 1H-NMR, MALDI-TOF MS, and GC-MS techniques. The applications of synthesized compounds in Schottky barrier diodes were investigated. Ag/Pc/p–Si structures were fabricated and charge transport mechanism in these devices was investigated using dc technique. It was observed from the analysis of the experimental results that the charge transport can be described by Ohmic conduction at low values of the reverse bias. On the other hand, the voltage dependence of the measured current for high values of the applied reverse bias indicated that space charge limited conduction is the dominant mechanism responsible for dc conduction. From the observed voltage dependence of the current density under forward bias conditions, it has been concluded that the charge transport is dominated by Poole-Frenkel emission.

  1. Light-Responsive Ion-Redistribution-Induced Resistive Switching in Hybrid Perovskite Schottky Junctions

    KAUST Repository

    Guan, Xinwei

    2017-11-23

    Hybrid Perovskites have emerged as a class of highly versatile functional materials with applications in solar cells, photodetectors, transistors, and lasers. Recently, there have also been reports on perovskite-based resistive switching (RS) memories, but there remain open questions regarding device stability and switching mechanism. Here, an RS memory based on a high-quality capacitor structure made of an MAPbBr3 (CH3NH3PbBr3) perovskite layer sandwiched between Au and indium tin oxide (ITO) electrodes is reported. Such perovskite devices exhibit reliable RS with an ON/OFF ratio greater than 103, endurance over 103 cycles, and a retention time of 104 s. The analysis suggests that the RS operation hinges on the migration of charged ions, most likely MA vacancies, which reversibly modifies the perovskite bulk transport and the Schottky barrier at the MAPbBr3/ITO interface. Such perovskite memory devices can also be fabricated on flexible polyethylene terephthalate substrates with high bendability and reliability. Furthermore, it is found that reference devices made of another hybrid perovskite MAPbI3 consistently exhibit filament-type switching behavior. This work elucidates the important role of processing-dependent defects in the charge transport of hybrid perovskites and provides insights on the ion-redistribution-based RS in perovskite memory devices.

  2. Optimization of chemical structure of Schottky-type selection diode for crossbar resistive memory.

    Science.gov (United States)

    Kim, Gun Hwan; Lee, Jong Ho; Jeon, Woojin; Song, Seul Ji; Seok, Jun Yeong; Yoon, Jung Ho; Yoon, Kyung Jean; Park, Tae Joo; Hwang, Cheol Seong

    2012-10-24

    The electrical performances of Pt/TiO(2)/Ti/Pt stacked Schottky-type diode (SD) was systematically examined, and this performance is dependent on the chemical structures of the each layer and their interfaces. The Ti layers containing a tolerable amount of oxygen showed metallic electrical conduction characteristics, which was confirmed by sheet resistance measurement with elevating the temperature, transmission line measurement (TLM), and Auger electron spectroscopy (AES) analysis. However, the chemical structure of SD stack and resulting electrical properties were crucially affected by the dissolved oxygen concentration in the Ti layers. The lower oxidation potential of the Ti layer with initially higher oxygen concentration suppressed the oxygen deficiency of the overlying TiO(2) layer induced by consumption of the oxygen from TiO(2) layer. This structure results in the lower reverse current of SDs without significant degradation of forward-state current. Conductive atomic force microscopy (CAFM) analysis showed the current conduction through the local conduction paths in the presented SDs, which guarantees a sufficient forward-current density as a selection device for highly integrated crossbar array resistive memory.

  3. 4H-SiC Schottky diode arrays for X-ray detection

    Energy Technology Data Exchange (ETDEWEB)

    Lioliou, G. [Semiconductor Materials and Devices Laboratory, School of Engineering and Informatics, University of Sussex, Falmer, Brighton BN1 9QT (United Kingdom); Chan, H.K. [School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne NE1 7RU (United Kingdom); Gohil, T. [Semiconductor Materials and Devices Laboratory, School of Engineering and Informatics, University of Sussex, Falmer, Brighton BN1 9QT (United Kingdom); Vassilevski, K.V.; Wright, N.G.; Horsfall, A.B. [School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne NE1 7RU (United Kingdom); Barnett, A.M. [Semiconductor Materials and Devices Laboratory, School of Engineering and Informatics, University of Sussex, Falmer, Brighton BN1 9QT (United Kingdom)

    2016-12-21

    Five SiC Schottky photodiodes for X-ray detection have been electrically characterized at room temperature. One representative diode was also electrically characterized over the temperature range 20°C to 140 °C. The performance at 30 °C of all five X-ray detectors, in both current mode and for photon counting X-ray spectroscopy was investigated. The diodes were fabricated in an array form such that they could be operated as either a 2×2 or 1×3 pixel array. Although the devices showed double barrier heights, high ideality factors and higher than expected leakage current at room temperature (12 nA/cm{sup 2} at an internal electric field of 105 kV/cm), they operated as spectroscopic photon counting soft X-ray detectors uncooled at 30 °C. The measured energy resolution (FWHM at 17.4 keV, Mo Kα) varied from 1.36 to 1.68 keV among different diodes.

  4. Formation and modification of Schottky barriers at the PZT/Pt interface

    Science.gov (United States)

    Chen, Feng; Schafranek, Robert; Wu, Wenbin; Klein, Andreas

    2009-11-01

    A determination of the Schottky barrier height at the interface between ferroelectric Pb(Zr,Ti)O3 thin films and Pt by photoelectron spectroscopy is presented. Stepwise Pt deposition was performed in situ onto a contamination-free Pb(Zr,Ti)O3 thin film surface. The substrate surface is reduced in the course of Pt deposition as evident from the observation of metallic Pb. The Fermi level is found at EF - EVB = 1.6 ± 0.1 eV above the valence band maximum of the as-prepared interface. Annealing of the sample in an oxygen pressure of 0.1 and 1 Pa strongly reduces the amount of metallic Pb and leads to a reduction in the Fermi level position at the interface to EF - EVB = 1.1 ± 0.1 eV. Storage in vacuum at room temperature strongly reduces the interface leading to a significantly higher Fermi level position (EF - EVB = 2.2 ± 0.1 eV). The reduction is attributed to the presence of hydrogen in the residual gas. The change in barrier height might be a severe issue for stable device operation with Pt contacts even at ambient temperatures.

  5. Ambipolarity reduction in DMG asymmetric vacuum dielectric Schottky Barrier GAA MOSFET to improve hot carrier reliability

    Science.gov (United States)

    Kumar, Manoj; Haldar, Subhasis; Gupta, Mridula; Gupta, R. S.

    2017-11-01

    An explicit surface potential and subthreshold current model for novel Dual Metal Gate (DMG) Asymmetric Vacuum (AV) as gate dielectric Schottky Barrier (SB) Cylindrical Gate All Around (CGAA) MOSFET with the incorporation of localized charges (Nf) is developed to provide excellent immunity against threshold voltage (Vth) degradation due to hot carriers. Hot carrier induced Localized Charges (LC) either positive or negative leads to degrade the threshold of the device. The major advantage of the proposed DMG-AV-SB-CGAA MOSFET is that it mitigates the ambipolar behavior thus offering very good on current to off current ratio; and also reduces the electron temperature which leads to less hot carrier generation thus lesser degradation in Vth and improved Hot Carrier reliability. The surface potential is determined for three different regions by solving 1-D Poisson's and 2-D Laplace equation through separation of variable method to facilitate an optimal model for calculating the subthreshold drain current from Si-SiO2 interface boundary. The developed model results are in good agreement with that of ATLAS-TCAD simulation.

  6. Dual-Functional On-Chip AlGaAs/GaAs Schottky Diode for RF Power Detection and Low-Power Rectenna Applications

    Directory of Open Access Journals (Sweden)

    Abdul Manaf Hashim

    2011-08-01

    Full Text Available A Schottky diode has been designed and fabricated on an n-AlGaAs/GaAs high-electron-mobility-transistor (HEMT structure. Current-voltage (I-V measurements show good device rectification, with a Schottky barrier height of 0.4349 eV for Ni/Au metallization. The differences between the Schottky barrier height and the theoretical value (1.443 eV are due to the fabrication process and smaller contact area. The RF signals up to 1 GHz are rectified well by the fabricated Schottky diode and a stable DC output voltage is obtained. The increment ratio of output voltage vs input power is 0.2 V/dBm for all tested frequencies, which is considered good enough for RF power detection. Power conversion efficiency up to 50% is obtained at frequency of 1 GHz and input power of 20 dBm with series connection between diode and load, which also shows the device’s good potential as a rectenna device with further improvement. The fabricated n-AlGaAs/GaAs Schottky diode thus provides a conduit for breakthrough designs for RF power detectors, as well as ultra-low power on-chip rectenna device technology to be integrated in nanosystems.

  7. Dual-functional on-chip AlGaAs/GaAs Schottky diode for RF power detection and low-power rectenna applications.

    Science.gov (United States)

    Hashim, Abdul Manaf; Mustafa, Farahiyah; Rahman, Shaharin Fadzli Abd; Rahman, Abdul Rahim Abdul

    2011-01-01

    A Schottky diode has been designed and fabricated on an n-AlGaAs/GaAs high-electron-mobility-transistor (HEMT) structure. Current-voltage (I-V) measurements show good device rectification, with a Schottky barrier height of 0.4349 eV for Ni/Au metallization. The differences between the Schottky barrier height and the theoretical value (1.443 eV) are due to the fabrication process and smaller contact area. The RF signals up to 1 GHz are rectified well by the fabricated Schottky diode and a stable DC output voltage is obtained. The increment ratio of output voltage vs input power is 0.2 V/dBm for all tested frequencies, which is considered good enough for RF power detection. Power conversion efficiency up to 50% is obtained at frequency of 1 GHz and input power of 20 dBm with series connection between diode and load, which also shows the device's good potential as a rectenna device with further improvement. The fabricated n-AlGaAs/GaAs Schottky diode thus provides a conduit for breakthrough designs for RF power detectors, as well as ultra-low power on-chip rectenna device technology to be integrated in nanosystems.

  8. Schottky barrier height of Ni to β-(AlxGa1-x)2O3 with different compositions grown by plasma-assisted molecular beam epitaxy

    Science.gov (United States)

    Ahmadi, Elaheh; Oshima, Yuichi; Wu, Feng; Speck, James S.

    2017-03-01

    Coherent β-(AlxGa1-x)2O3 films (x = 0, 0.038, 0.084, 0.164) were grown successfully on a Sn-doped β-Ga2O3 (010) substrate using plasma-assisted molecular beam epitaxy. Atom probe tomography, transmission electron microscopy, and high resolution x-ray diffraction were used to verify the alloy composition and high quality of the films. Schottky diodes were then fabricated using Ni as the Schottky metal. Capacitance-voltage measurements revealed a very low (current-voltage (I-V) measurements performed at temperatures varying from 300 K to 500 K on the Schottky diodes. These measurements revealed that the apparent Schottky barrier height could have similar values for different compositions of β-(AlxGa1-x)2O3. We believe this is attributed to the lateral fluctuation in the alloy’s composition. This results in a lateral variation in the barrier height. Therefore, the average Schottky barrier height extracted from I-V measurements could be similar for β-(AlxGa1-x)2O3 films with different compositions.

  9. Atomic nature of the Schottky barrier height formation of the Ag/GaAs(001)-2 × 4 interface: An in-situ synchrotron radiation photoemission study

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Chiu-Ping, E-mail: cpcheng@mail.ncyu.edu.tw [Department of Electrophysics, National Chiayi University, Chiayi, 60004, Taiwan, ROC (China); Chen, Wan-Sin [Department of Electrophysics, National Chiayi University, Chiayi, 60004, Taiwan, ROC (China); National Synchrotron Radiation Research Center, Hsinchu, 30076, Taiwan, ROC (China); Lin, Keng-Yung [Graduate Institute of Applied Physics and Department of Physics, National Taiwan University, Taipei, 10617, Taiwan, ROC (China); Wei, Guo-Jhen; Cheng, Yi-Ting [Department of Electrophysics, National Chiayi University, Chiayi, 60004, Taiwan, ROC (China); Lin, Yen-Hsun; Wan, Hsien-Wen [Graduate Institute of Applied Physics and Department of Physics, National Taiwan University, Taipei, 10617, Taiwan, ROC (China); Pi, Tun-Wen, E-mail: pi@nsrrc.org.tw [National Synchrotron Radiation Research Center, Hsinchu, 30076, Taiwan, ROC (China); Tung, Raymond T. [Department of Physics, Brooklyn College, CUNY, NY 11210 (United States); Kwo, Jueinai, E-mail: raynien@phys.nthu.edu.tw [Department of Physics, National Tsing Hua University, Hsinchu, 30013, Taiwan, ROC (China); Hong, Minghwei, E-mail: mhong@phys.ntu.edu.tw [Graduate Institute of Applied Physics and Department of Physics, National Taiwan University, Taipei, 10617, Taiwan, ROC (China)

    2017-01-30

    Highlights: • The interaction of Ag on a p-type α2 GaAs(001)-2 × 4 surface has been studied. • The dipole formation mechanism of the Ag/GaAs(001)-2 × 4 interface is proposed. • Determination of the SBH prior to metal formation is found. • Inadequacy of the metal-induced gap-state model for explaining the SBH is evident. - Abstract: The Interface of Ag with p-type α2 GaAs(001)-2 × 4 has been studied to further understand the formation mechanism of the Schottky barrier height (SBH). In the initial phase of Ag deposition, high-resolution core-level data show that Ag adatoms effectively passivate the surface As-As dimers without breaking them apart. The Ag(+)-As(−) dipoles are thus generated with a maximal potential energy of 0.26 eV; a SBH of 0.38 eV was measured. Greater Ag coverage causes elemental segregation of As/Ga atoms, reversing the direction of the net dipole. The band bending effect near the interface shows a downward shift of 0.08 eV, and the final SBH is similar to the value as measured at the initial Ag deposition. Both parameters are secured at 0.25 Å of Ag thickness prior to the observation of metallic behavior of Ag. Inadequacy of the metal-induced gap-state model for explaining SBH is evident.

  10. Atomic nature of the Schottky barrier height formation of the Ag/GaAs(001)-2 × 4 interface: An in-situ synchrotron radiation photoemission study

    Science.gov (United States)

    Cheng, Chiu-Ping; Chen, Wan-Sin; Lin, Keng-Yung; Wei, Guo-Jhen; Cheng, Yi-Ting; Lin, Yen-Hsun; Wan, Hsien-Wen; Pi, Tun-Wen; Tung, Raymond T.; Kwo, Jueinai; Hong, Minghwei

    2017-01-01

    The Interface of Ag with p-type α2 GaAs(001)-2 × 4 has been studied to further understand the formation mechanism of the Schottky barrier height (SBH). In the initial phase of Ag deposition, high-resolution core-level data show that Ag adatoms effectively passivate the surface As-As dimers without breaking them apart. The Ag(+)-As(-) dipoles are thus generated with a maximal potential energy of 0.26 eV; a SBH of 0.38 eV was measured. Greater Ag coverage causes elemental segregation of As/Ga atoms, reversing the direction of the net dipole. The band bending effect near the interface shows a downward shift of 0.08 eV, and the final SBH is similar to the value as measured at the initial Ag deposition. Both parameters are secured at 0.25 Å of Ag thickness prior to the observation of metallic behavior of Ag. Inadequacy of the metal-induced gap-state model for explaining SBH is evident.

  11. Optimized hydrogen sensing characteristic of Pd/ZnO nanoparticles based Schottky diode on glass substrate

    Science.gov (United States)

    Chandra, Lalit; Sahu, Praveen Kumar; Dwivedi, R.; Mishra, V. N.

    2017-10-01

    The present work deals with the development of the Pd/ZnO naoparticles based sensor for detection of hydrogen (H2) gas at relatively low temperature (75-110 °C). Pd/ZnO Schottky diode was fabricated by ZnO nanoparticles based thin film on glass substrate using sol-gel spin coating technique. These ZnO nanoparticles have been characterized by x-ray diffraction (XRD), atomic force microscopy (AFM), energy dispersive x-ray spectroscope (EDS), and field emission scanning electron microscope (FE-SEM) which reveals the ZnO film having particles size in the range of ~25 to ~110 nm with ~52.73 nm surface roughness. Gas dependent diode parameters such as barrier height and ideality factor have been evaluated upon exposure of H2 gas concentration in the range from 200-2000 ppm over the temperature range from 75 to 110 °C. The sensitivity of the Pd/ZnO sensor has been studied in terms of change in diode forward current upon exposure to H2 gas. Experimental result shows the optimized sensitivity ~246.22% for H2 concentration of 2000 ppm at temperature 90 °C. The hydrogen sensing mechanism has been explained by surface and subsurface adsorption of H2 molecules on Pd surface; subsequently, dissociation of H2 molecules into H  +  H atoms and diffusion to trap sites (oxygen ions) available on ZnO surface, resulting in formation of dipole moments at Pd/ZnO interface. The variation in the sensitivity, response and recovery time with temperature of Pd/ZnO sensor has also been studied.

  12. Inductively coupled plasma etch damage in (-201) Ga2O3 Schottky diodes

    Science.gov (United States)

    Yang, Jiancheng; Ahn, Shihyun; Ren, F.; Khanna, Rohit; Bevlin, Kristen; Geerpuram, Dwarakanath; Pearton, S. J.; Kuramata, A.

    2017-04-01

    Bulk, single-crystal Ga2O3 was etched in BCl3/Ar inductively coupled plasmas as a function of ion impact energy. For pure Ar, the etch rate (R) was found to increase with ion energy (E) as predicted from a model of ion enhanced sputtering by a collision-cascade process, R ∝(E0.5 - ETH0.5), where the threshold energy for Ga2O3, ETH, was experimentally determined to be ˜75 eV. When BCl3 was added, the complexity of the ion energy distribution precluded, obtaining an equivalent threshold. Electrically active damage introduced during etching was quantified using Schottky barrier height and diode ideality factor measurements obtained by evaporating Ni/Au rectifying contacts through stencil masks onto the etched surfaces. For low etch rate conditions (˜120 Å min-1) at low powers (150 W of the 2 MHz ICP source power and 15 W rf of 13.56 MHz chuck power), there was only a small decrease in reverse breakdown voltage (˜6%), while the barrier height decreased from 1.2 eV to 1.01 eV and the ideality factor increased from 1.00 to 1.06. Under higher etch rate (˜700 Å min-1) and power (400 W ICP and 200 W rf) conditions, the damage was more significant, with the reverse breakdown voltage decreasing by ˜35%, the barrier height was reduced to 0.86 eV, and the ideality factor increased to 1.2. This shows that there is a trade-off between the etch rate and near-surface damage.

  13. An ultra-thin Schottky diode as a transmission particle detector for biological microbeams

    Science.gov (United States)

    Harken, Andrew; Randers-Pehrson, Gerhard; Attinger, Daniel; Brenner, David J.

    2013-01-01

    We fabricated ultrathin metal-semiconductor Schottky diodes for use as transmission particle detectors in the biological microbeam at Columbia University’s Radiological Research Accelerator Facility (RARAF). The RARAF microbeam can deliver a precise dose of ionizing radiation in cell nuclei with sub-micron precision. To ensure an accurate delivery of charged particles, the facility currently uses a commercial charged-particle detector placed after the sample. We present here a transmission detector that will be placed between the particle accelerator and the biological specimen, allowing the irradiation of samples that would otherwise block radiation from reaching a detector behind the sample. Four detectors were fabricated with co-planar gold and aluminum electrodes thermally evaporated onto etched n-type crystalline silicon substrates, with device thicknesses ranging from 8.5 μm – 13.5 μm. We show coincident detections and pulse-height distributions of charged particles in both the transmission detector and the commercial detector above it. Detections are demonstrated at a range of operating conditions, including incoming particle type, count rate, and beam location on the detectors. The 13.5 μm detector is shown to work best to detect 2.7 MeV protons (H+), and the 8.5 μm detector is shown to work best to detect 5.4 MeV alpha particles (4He++). The development of a transmission detector enables a range of new experiments to take place at RARAF on radiation-stopping samples such as thick tissues, targets that need immersion microscopy, and integrated microfluidic devices for handling larger quantities of cells and small organisms. PMID:24058378

  14. Barrier height of Pt–In[sub x]Ga[sub 1−x]N (0≤x≤0.5) nanowire Schottky diodes

    KAUST Repository

    Guo, Wei

    2011-01-01

    The barrier height of Schottky diodes made on Inx Ga 1-x N nanowires have been determined from capacitance-voltage measurements. The nanowires were grown undoped on n-type (001) silicon substrates by plasma-assisted molecular beam epitaxy. The length, diameter and density of the nanowires are ∼1 μm, 20 nm, and 1× 1011 cm-2. The Schottky contact was made on the top surface of the nanowires with Pt after planarizing with parylene. The measured barrier height B varies from 1.4 eV (GaN) to 0.44 eV (In0.5 Ga0.5 N) and agrees well with the ideal barrier heights in the Schottky limit. © 2011 American Institute of Physics.

  15. A low knee voltage and high breakdown voltage of 4H-SiC TSBS employing poly-Si/Ni Schottky scheme

    Science.gov (United States)

    Kim, Dong Young; Seok, Ogyun; Park, Himchan; Bahng, Wook; Kim, Hyoung Woo; Park, Ki Cheol

    2018-02-01

    We report a low knee voltage and high breakdown voltage 4H-SiC TSBS employing poly-Si/Ni dual Schottky contacts. A knee voltage was significantly improved from 0.75 to 0.48 V by utilizing an alternative low work-function material of poly-Si as an anode electrode. Also, reverse breakdown voltage was successfully improved from 901 to 1154 V due to a shrunk low-work-function Schottky region by a proposed self-align etching process between poly-Si and SiC. SiC TSBS with poly-Si/Ni dual Schottky scheme is a suitable structure for high-efficiency rectification and high-voltage blocking operation.

  16. Sub-bandgap response of graphene/SiC Schottky emitter bipolar phototransistor examined by scanning photocurrent microscopy

    Science.gov (United States)

    Barker, Bobby G., Jr.; Chava, Venkata Surya N.; Daniels, Kevin M.; Chandrashekhar, M. V. S.; Greytak, Andrew B.

    2018-01-01

    Graphene layers grown epitaxially on SiC substrates are attractive for a variety of sensing and optoelectronic applications because the graphene acts as a transparent, conductive, and chemically responsive layer that is mated to a wide-bandgap semiconductor with large breakdown voltage. Recent advances in control of epitaxial growth and doping of SiC epilayers have increased the range of electronic device architectures that are accessible with this system. In particular, a recently-introduced Schottky-emitter bipolar phototransistor (SEPT) based on an epitaxial graphene (EG) emitter grown on a p-SiC base epilayer has been found to exhibit a maximum common emitter current gain of 113 and a UV responsivity of 7.1 A W‑1. The behavior of this device, formed on an n +-SiC substrate that serves as the collector, was attributed to a very large minority carrier injection efficiency at the EG/p-SiC Schottky contact. This large minority carrier injection efficiency is in turn related to the large built-in potential found at a EG/p-SiC Schottky junction. The high performance of this device makes it critically important to analyze the sub bandgap visible response of the device, which provides information on impurity states and polytype inclusions in the crystal. Here, we employ scanning photocurrent microscopy (SPCM) with sub-bandgap light as well as a variety of other techniques to clearly demonstrate a localized response based on the graphene transparent electrode and an approximately 1000-fold difference in responsivity between 365 nm and 444 nm excitation. A stacking fault propagating from the substrate/epilayer interface, assigned as a single layer of the 8H-SiC polytype within the 4H-SiC matrix, is found to locally increase the photocurrent substantially. The discovery of this polytype heterojunction opens the potential for further development of heteropolytype devices based on the SEPT architecture.

  17. Barrier Parameters and Current Transport Characteristics of Ti/ p-InP Schottky Junction Modified Using Orange G (OG) Organic Interlayer

    Science.gov (United States)

    Sreenu, K.; Venkata Prasad, C.; Rajagopal Reddy, V.

    2017-10-01

    A Ti/Orange G/ p-InP metal/interlayer/semiconductor (MIS) junction has been prepared with Orange G (OG) organic layer by electron beam evaporation and spin coating processes. The electrical properties of Ti/ p-InP metal/semiconductor (MS) and Ti/OG/ p-InP MIS junctions have been analyzed based on current-voltage ( I- V) and capacitance-voltage ( C- V) characteristics. The MIS junction exhibited higher rectifying behavior than the MS junction. The higher barrier height (BH) of the MIS junction compared with the MS junction indicates effective modification by the OG layer. Also, the BH, ideality factor, shunt resistance, and series resistance were extracted based on the I- V characteristic, Cheung's and Norde's methods, and the ΨS- V plot. The BH evaluated by Cheung's and Norde's methods and the ΨS- V plot was shown to be similar, confirming the reliability and validity of the methods applied. The extracted interface state density ( N SS) of the MIS junction was less than for the MS junction, revealing that the OG organic layer reduced the N SS value. Analysis demonstrated that, in the lower bias region, the reverse current conduction mechanism was dominated by Poole-Frenkel emission for both the MS and MIS junction. Meanwhile, in the higher bias region, Schottky emission governed the reverse current conduction mechanism. The results suggest that such OG layers have potential for use in high-quality electronic devices.

  18. Impact of doping on the performance of p-type Be-doped Al0.29 Ga0.71As Schottky diodes

    Directory of Open Access Journals (Sweden)

    Noorah A. Al-Ahmadi

    2017-06-01

    Full Text Available The effects of changing the acceptors concentration on the electrical characteristics of Au/Ti on Be-doped Al0.29Ga0.71As Schottky contact have been investigated in the temperature range of 100–400 K. Using three devices with three different doping levels, the barrier height (ΦB, ideality factor (n and series resistance (RS for each diode were evaluated using both thermionic emission (TE theory and Cheung's method. Our experimental results showed that the sample with a moderate doping concentration of 3 × 1016 cm-3 has the best performance, including ideality factor of 1.25 and rectification ratio of 2.24 × 103 at room temperature. All samples showed an abnormal behavior of reducing ΦB and increasing n with increase of temperature. This behavior was attributed, in case of low concentration samples, to barrier inhomogeneity and was explained by assuming a Gaussian distribution of barrier heights at the interface. While for the heavily doped sample, such non-ideal manner was ascribed with tunneling through the field emission (FE mechanism.

  19. Improved reverse recovery characteristics of inAlN/GaN schottky barrier diode using a SOI substrate

    Science.gov (United States)

    Chiu, Hsien-Chin; Peng, Li-Yi; Wang, Hsiang-Chun; Kao, Hsuan-Ling; Wang, Hou-Yu; Chyi, Jen-Inn

    2017-10-01

    The low-frequency noise (LFN) and reverse recovery charge characteristics of a six-inch InAlN/AlN/GaN Schottky barrier diode (SBD) on the Si-on-insulator (SOI) substrate were demonstrated and investigated for the first time. Raman spectroscopy indicated that using SOI wafers lowered epitaxial stress. According to the DC and LFN measurements at temperatures ranging from 300 to 450 K, the InAlN/GaN SBD on the SOI substrate showed improved forward and reverse currents and achieved a lower reverse recovery charge, compared with a conventional device.

  20. A fast-neutron detection detector based on fission material and large sensitive 4H silicon carbide Schottky diode detector

    Science.gov (United States)

    Liu, Linyue; Liu, Jinliang; Zhang, Jianfu; Chen, Liang; Zhang, Xianpeng; Zhang, Zhongbing; Ruan, Jinlu; Jin, Peng; Bai, Song; Ouyang, Xiaoping

    2017-12-01

    Silicon carbide radiation detectors are attractive in the measurement of the total numbers of pulsed fast neutrons emitted from nuclear fusion and fission devices because of high neutron-gamma discrimination and good radiation resistance. A fast-neutron detection system was developed based on a large-area 4H-SiC Schottky diode detector and a 235U fission target. Excellent pulse-height spectra of fission fragments induced by mono-energy deuterium-tritium (D-T) fusion neutrons and continuous energy fission neutrons were obtained. The detector is proven to be a good candidate for pulsed fast neutron detection in a complex radiation field.

  1. High Density Schottky Barrier Infrared Charge-Coupled Device (IRCCD) Sensors For Short Wavelength Infrared (SWIR) Applications At Intermediate Temperature

    Science.gov (United States)

    Elabd, H.; Villani, T. S.; Tower, J. R.

    1982-11-01

    Monolithic 32 x 64 and 64 x 128 palladium silicide (Pd2Si) interline transfer IRCCDs sensitive in the 1-3.5 pm spectral band have been developed. This silicon imager exhibits a low response nonuniformity of typically 0.2-1.6% rms, and has been operated in the temperature range between 40-140K. Spectral response measurements of test Pd2Si p-type Si devices yield quantum efficiencies of 7.9% at 1.25 μm, 5.6% at 1.65 μm and 2.2% at 2.22 μm. Improvement in quantum efficiency is expected by optimizing the different structural parameters of the Pd2Si detectors. The spectral response of the Pd2Si detectors fit a modified Fowler emission model. The measured photo-electric barrier height for the Pd2Si detector is ≍0.34 eV and the measured quantum efficiency coefficient, C1, is 19%/eV. The dark current level of Pd2Si Schottky barrier focal plane arrays (FPAs) is sufficiently low to enable operation at intermediate tem-peratures at TV frame rates. Typical dark current level measured at 120K on the FPA is 2 nA/cm2. The Pd2Si Schottky barrier imaging technology has been developed for satellite sensing of earth resources. The operating temperature of the Pd2Si FPA is compatible with passive cooler performance. In addition, high density Pd2Si Schottky barrier FPAs are manufactured with high yield and therefore represent an economical approach to short wavelength IR imaging. A Pd2Si Schottky barrier image sensor for push-broom multispectral imaging in the 1.25, 1.65, and 2.22 μm bands is being studied. The sensor will have two line arrays (dual band capability) of 512 detectors each, with 30 μm center-to-center detector spacing. The device will be suitable for chip-to-chip abutment, thus providing the capability to produce large, multiple chip focal planes with contiguous, in-line sensors.

  2. Manufacturing technology program for high burnout silicon Schottky-barrier mixer diodes for Navy air-to-air avionics

    Science.gov (United States)

    Anand, Y.; Ellis, S.

    1982-02-01

    This report describes the establishment of low cost semiconductor processes to manufacture low-barrier-height high-burnout X-band silicon Schottky barrier diodes in production quantities. These devices are thermal-compression-bonded in a rugged low-cost pill (ODS-119) package. They exhibit an overall low noise figure of 7.0 dB (single side band) at 0.5 mW of local oscillator power level and RF burnout of 12 watts (tau = 1 microsec and 1000 Hz rep. rate). Reliability and ruggedness of the design has been demonstrated by tests taken from MIL.S 19500 F.

  3. Calculation of the intrinsic spectral density of current fluctuations in nanometric Schottky-barrier diodes at terahertz frequencies

    Energy Technology Data Exchange (ETDEWEB)

    Mahi, F.Z. [Science and Technology Institute, University of Bechar, 08000 Bechar (Algeria)], E-mail: fati_zo_mahi2002@yahoo.fr; Helmaoui, A. [Science and Technology Institute, University of Bechar, 08000 Bechar (Algeria); Varani, L. [Institut d' Electronique du Sud (CNRS UMR 5214), Universite Montpellier II, 34095 Montpellier (France); Shiktorov, P.; Starikov, E.; Gruzhinskis, V. [Semiconductor Physics Institute, 01108 Vilnius (Lithuania)

    2008-10-01

    An analytical model for the noise spectrum of nanometric Schottky-barrier diodes (SBD) is developed. The calculated frequency dependence of the spectral density of current fluctuations exhibits resonances in the terahertz domain which are discussed and analyzed as functions of the length of the diode, free carrier concentration, length of the depletion region and applied voltage. A good agreement obtained with direct Monte Carlo simulations of GaAs SBDs operating from barrier-limited to flat-band conditions fully validates the proposed approach.

  4. Structural, electrical, and surface morphological characteristics of rapidly annealed Pt/Ti Schottky contacts to n-type InP

    Energy Technology Data Exchange (ETDEWEB)

    Reddy, V. Rajagopal; Reddy, D. Subba; Naik, S. Sankar [Department of Physics, Sri Venkateswara University, Tirupati (India); Choi, C.J. [School of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center (SPRC), Chonbuk National University, Jeonju (Korea, Republic of)

    2011-10-15

    We have investigated the electrical and structural properties of Pt/Ti metallization scheme on n-type InP as a function of annealing temperature using current-voltage (I-V), capacitance-voltage (C-V), Auger electron spectroscopy (AES), and X-ray diffraction (XRD) measurements. Measurements showed that barrier height of as-deposited Pt/Ti Schottky contact is 0.62 eV (I-V) and 0.76 eV (C-V). Experimental results indicate that high-quality Schottky contact with barrier height and ideality factor of 0.66 eV (I-V), 0.80 eV (C-V), and 1.14 can be achieved after annealing at 400 C for 1 min in N{sub 2} atmosphere. Further, it is observed that the barrier height slightly decreases to 0.55 eV (I-V) and 0.71 eV (C-V) after annealing at 500 C. Norde method is also employed to calculate the barrier height of Pt/Ti Schottky contacts. The obtained values are in good agreement with those obtained by I-V measurements. These results indicate that the optimum annealing temperature for the Pt/Ti Schottky contact is 400 C. According to AES and XRD analysis, the formation of indium phases at the Pt/Ti/n-InP interface could be the reason for the increase of Schottky barrier height (SBH) after annealing at 400 C. Results also showed the formation of phosphide phases at the interface. This may be the reason for the decrease in the barrier height after annealing at 500 C. The AFM results showed that the overall surface morphology of Pt/Ti Schottky contact is reasonably smooth. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Fabrication and characterization of Pd/Cu doped ZnO/Si and Ni/Cu doped ZnO/Si Schottky diodes

    Energy Technology Data Exchange (ETDEWEB)

    Agarwal, Lucky; Singh, Brijesh Kumar; Tripathi, Shweta [Department of Electronics & Communication Engineering, Motilal Nehru National Institute of Technology, Allahabad 211004 (India); Chakrabarti, P., E-mail: pchakrabarti.ece@iitbhu.ac.in [Department of Electronics & Communication Engineering, Motilal Nehru National Institute of Technology, Allahabad 211004 (India); Department of Electronics Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India)

    2016-08-01

    In this paper, fabrication and characterization of copper doped ZnO (Cu doped ZnO) based Schottky devices have been reported. Cu doped ZnO thin films have been deposited on p-Si (100) samples by the sol-gel spin coating method. X-Ray diffraction (XRD) and atomic force microscopy (AFM) studies have been done in order to evaluate the structural and morphological properties of the film. The optical properties of the film have been determined by using variable angle ellipsometry. Further, Seebeck measurement of the deposited Cu doped ZnO film leads to positive Seebeck coefficient confirming the p-type conductivity of the sample. The resistivity and acceptor concentration of the film has also been evaluated using four probe measurement system. Pd and Ni metals have been deposited on separate Cu doped ZnO thin film samples using low cost thermal evaporation method to form Schottky contacts. The electrical characterization of the Schottky diode has been performed by semiconductor device analyzer (SDA). Electrical parameters such as barrier height, ideality factor, reverse saturation current and rectification ratio have also been determined for the as-prepared Schottky diode using conventional thermionic emission model and Cheung's method. - Highlights: • Fabrication of sol-gel derived Cu doped ZnO (p-type) Schottky contact proposed. • The p-type Conductivity of the sample confirmed by Seebeck Measurement. • Pd and Ni deposited on Cu doped ZnO film to form Schottky contacts. • Cu doped ZnO expected to emerge as a potential material for thin film solar cells.

  6. Richardson constant and electrostatics in transfer-free CVD grown few-layer MoS2/graphene barristor with Schottky barrier modulation >0.6eV

    Science.gov (United States)

    Jahangir, Ifat; Uddin, M. Ahsan; Singh, Amol K.; Koley, Goutam; Chandrashekhar, M. V. S.

    2017-10-01

    We demonstrate a large area MoS2/graphene barristor, using a transfer-free method for producing 3-5 monolayer (ML) thick MoS2. The gate-controlled diodes show good rectification, with an ON/OFF ratio of ˜103. The temperature dependent back-gated study reveals Richardson's coefficient to be 80.3 ± 18.4 A/cm2/K and a mean electron effective mass of (0.66 ± 0.15)m0. Capacitance and current based measurements show the effective barrier height to vary over a large range of 0.24-0.91 eV due to incomplete field screening through the thin MoS2. Finally, we show that this barristor shows significant visible photoresponse, scaling with the Schottky barrier height. A response time of ˜10 s suggests that photoconductive gain is present in this device, resulting in high external quantum efficiency.

  7. Energetics and Solvation Effects at the Photoanode/Catalyst Interface: Ohmic Contact versus Schottky Barrier

    Energy Technology Data Exchange (ETDEWEB)

    Ping, Yuan [Joint; Goddard, William A. [Joint; Materials; Galli, Giulia A. [Institute; Argonne National Laboratory, Lemont, Illinois 60439, United States

    2015-04-17

    The design of optimal interfaces between photoelectrodes and catalysts is a key challenge in building photoelectrochemical cells to split water. Iridium,dioxide (IrO2) is an,efficient catalyst for oxygen evolution, stable in acidic conditions, and hence a good candidate, to be. interfaced with photoanodes. Using first-principles quantum mechanical calculations; we investigated the structural and electronic properties of tungsten trioxide (WO3) surfaces interfaced with an IrO2 thin film. We, built a microacopic model of the interface that exhibits a formation energy lower than the surface energy of the most, stable IrO2 surface, in spite of a large lattice Mismatch, and has to impurity states pinning the Fermi.,level. We found that upon full coverage of WO3 by IrO2, the two oxides form undesirable Ohmic contacts. However, our calculatious predicted that if both oxides are partially exposed to water solvent, the relative position of the absorber conduction band and the catalyst Fermi level favors charge transfer to the catalyst and hence water We propose :that, for oxide photoelectrodes interfaced with IrO2, it is advantageous to form tough interfaces with the catalyst, e.g., by depositing nanoparticles, instead of sharp interfaces with thin films.

  8. Planar heterostructures of single-layer transition metal dichalcogenides: Composite structures, Schottky junctions, tunneling barriers, and half metals

    Science.gov (United States)

    Aras, Mehmet; Kılıç, ćetin; Ciraci, S.

    2017-02-01

    Planar composite structures formed from the stripes of transition metal dichalcogenides joined commensurately along their zigzag or armchair edges can attain different states in a two-dimensional (2D), single-layer, such as a half metal, 2D or one-dimensional (1D) nonmagnetic metal and semiconductor. Widening of stripes induces metal-insulator transition through the confinements of electronic states to adjacent stripes, that results in the metal-semiconductor junction with a well-defined band lineup. Linear bending of the band edges of the semiconductor to form a Schottky barrier at the boundary between the metal and semiconductor is revealed. Unexpectedly, strictly 1D metallic states develop in a 2D system along the boundaries between stripes, which pins the Fermi level. Through the δ doping of a narrow metallic stripe one attains a nanowire in the 2D semiconducting sheet or narrow band semiconductor. A diverse combination of constituent stripes in either periodically repeating or finite-size heterostructures can acquire critical fundamental features and offer device capacities, such as Schottky junctions, nanocapacitors, resonant tunneling double barriers, and spin valves. These predictions are obtained from first-principles calculations performed in the framework of density functional theory.

  9. Mg doping of InGaN layers grown by PA-MBE for the fabrication of Schottky barrier photodiodes

    Energy Technology Data Exchange (ETDEWEB)

    Pereiro, J; Redondo-Cubero, A; Fernandez-Garrido, S; Rivera, C; Navarro, A; Munoz, E; Calleja, E [Instituto de Sistemas Optoelectronicos y MicrotecnologIa, Universidad Politecnica de Madrid, E-28040 Madrid (Spain); Gago, R, E-mail: jpereiro@die.upm.e [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones CientIficas, E-28049 Madrid (Spain)

    2010-08-25

    This work reports on the fabrication of Schottky barrier based Mg-doped (In,Ga)N layers for fluorescence applications. Mg acceptors are used in order to compensate surface and bulk donors that prevent the fabrication of Schottky contacts on unintentionally doped (In,Ga)N layers grown by plasma-assisted molecular beam epitaxy (PA-MBE). Rectifying properties of the contacts exhibited a major improvement when (In,Ga)N : Mg was used. The electrical and optical measurements of the layers showed a hole concentration of up to 3 x 10{sup 19} holes cm{sup -3} with a Mg acceptor activation energy of {approx}60 meV. Back-illuminated photodiodes fabricated on 800 nm thick Mg-doped In{sub 0.18}Ga{sub 0.82}N layers exhibited a band pass photo-response with a rejection ratio >10{sup 2} between 420 and 470 nm and peak responsivities of 87 mA W{sup -1} at {approx}470 nm. The suitability of these photodiodes for fluorescence measurements was demonstrated.

  10. Composite Transparent Electrode of Graphene Nanowalls and Silver Nanowires on Micropyramidal Si for High-Efficiency Schottky Junction Solar Cells.

    Science.gov (United States)

    Jiao, Tianpeng; Liu, Jian; Wei, Dapeng; Feng, Yanhui; Song, Xuefen; Shi, Haofei; Jia, Shuming; Sun, Wentao; Du, Chunlei

    2015-09-16

    The conventional graphene-silicon Schottky junction solar cell inevitably involves the graphene growth and transfer process, which results in complicated technology, loss of quality of the graphene, extra cost, and environmental unfriendliness. Moreover, the conventional transfer method is not well suited to conformationally coat graphene on a three-dimensional (3D) silicon surface. Thus, worse interfacial conditions are inevitable. In this work, we directly grow graphene nanowalls (GNWs) onto the micropyramidal silicon (MP) by the plasma-enhanced chemical vapor deposition method. By controlling growth time, the cell exhibits optimal pristine photovoltaic performance of 3.8%. Furthermore, we improve the conductivity of the GNW electrode by introducing the silver nanowire (AgNW) network, which could achieve lower sheet resistance. An efficiency of 6.6% has been obtained for the AgNWs-GNWs-MP solar cell without any chemical doping. Meanwhile, the cell exhibits excellent stability exposed to air. Our studies show a promising way to develop simple-technology, low-cost, high-efficiency, and stable Schottky junction solar cells.

  11. Formation of Schottky-type metal/SrTiO{sub 3} junctions and their resistive properties

    Energy Technology Data Exchange (ETDEWEB)

    Stoecker, Hartmut; Zschornak, Matthias [Technische Universitaet Dresden, Institut fuer Strukturphysik, Dresden (Germany); TU Bergakademie Freiberg, Institut fuer Experimentelle Physik, Freiberg (Germany); Seibt, Juliane; Hanzig, Florian; Wintz, Susi; Abendroth, Barbara; Meyer, Dirk C. [TU Bergakademie Freiberg, Institut fuer Experimentelle Physik, Freiberg (Germany); Kortus, Jens [TU Bergakademie Freiberg, Institut fuer Theoretische Physik, Freiberg (Germany)

    2010-08-15

    Motivated by the successful use of strontium titanate with different doping metals for memory cells on the basis of resistive switching and the recent findings on the major importance of oxygen vacancy redistribution in this compound, the present work shows the possibility of a non-volatile resistance change memory based on vacancy-doped SrTiO{sub 3}. The formation of corresponding metal/SrTiO{sub 3-{delta}} junctions ({delta}>0) in an electric field will be discussed as well as the switching between ohmic and Schottky-type contact behavior. A notable hysteresis in the current-voltage characteristics is used to carry out Write, Read, and Erase operations exemplifying the memory cell properties of such junctions. But whereas the electric field-induced formation of Schottky-type junctions is explainable by oxygen vacancy redistribution, the resistive switching needs to be discussed in terms of vacancies serving as electron trap states at the metal/oxide interface. (orig.)

  12. Estimation of the Necessary Bandwidth of the ELENA Longitudinal Schottky Pick-ups for Operation with Unbunched Beams

    CERN Document Server

    Federmann, S

    2013-01-01

    Schottky measurements are an important element of beam diagnostics. In the recently approved ELENA ring, a dedicated Schottky pick-up for longitudinal measurements is foreseen. This pick-up will be implemented by adapting the AD design which consists of two low-noise beam current transformers — one to cover a high frequency range (0.25 – 30MHz) and the other to cover a low frequency range (0.02 – 3MHz). It is of particular interest as to whether these designs can be used with only a change to the geometry, or if modifications are necessary to cope with the different requirements in ELENA. One important question is whether the frequency range covered by the pick-ups is sufficient. Therefore it is of particular interest to determine the necessary bandwidth for operation in ELENA. The present note is dedicated to this task using the scenario of unbunched beam operation, since in this case the signals are very weak and thus challenge the performance of the pick-up.

  13. Frequency and voltage dependent electrical responses of poly(triarylamine thin film-based organic Schottky diode

    Directory of Open Access Journals (Sweden)

    Mohamad Khairul Anuar

    2017-01-01

    Full Text Available A metal-organic-metal (MOM type Schottky diode based on poly (triarylamine (PTAA thin films has been fabricated by using the spin coating method. Investigation of the frequency dependent conductance-voltage (G-V-f and capacitance-voltage (C-V-f characteristics of the ITO/PTAA/Al MOM type diode were carried out in the frequency range from 12 Hz to 100 kHz using an LCR meter at room temperature. The frequency and bias voltage dependent electrical response were determined by admittance-based measured method in terms of an equivalent circuit model of the parallel combination of resistance and capacitance (RC circuit. Investigation revealed that the conductance is frequency and a bias voltage dependent in which conductance continuous increase as the increasing frequency, respectively. Meanwhile, the capacitance is dependent on frequency up to a certain value of frequency (100 Hz but decreases at high frequency (1 – 10 kHz. The interface state density in the Schottky diode was determined from G-V and C-V characteristics. The interface state density has values almost constant of 2.8 x 1012 eV−1cm−2 with slightly decrease by increasing frequencies. Consequently, both series resistance and interface trap density were found to decrease with increasing frequency. The frequency dependence of the electrical responses is attributed the distribution density of interface states that could follow the alternating current (AC signal.

  14. Frequency and voltage dependent electrical responses of poly(triarylamine) thin film-based organic Schottky diode

    Science.gov (United States)

    Anuar Mohamad, Khairul; Tak Hoh, Hang; Alias, Afishah; Ghosh, Bablu Kumar; Fukuda, Hisashi

    2017-11-01

    A metal-organic-metal (MOM) type Schottky diode based on poly (triarylamine) (PTAA) thin films has been fabricated by using the spin coating method. Investigation of the frequency dependent conductance-voltage (G-V-f) and capacitance-voltage (C-V-f) characteristics of the ITO/PTAA/Al MOM type diode were carried out in the frequency range from 12 Hz to 100 kHz using an LCR meter at room temperature. The frequency and bias voltage dependent electrical response were determined by admittance-based measured method in terms of an equivalent circuit model of the parallel combination of resistance and capacitance (RC circuit). Investigation revealed that the conductance is frequency and a bias voltage dependent in which conductance continuous increase as the increasing frequency, respectively. Meanwhile, the capacitance is dependent on frequency up to a certain value of frequency (100 Hz) but decreases at high frequency (1 - 10 kHz). The interface state density in the Schottky diode was determined from G-V and C-V characteristics. The interface state density has values almost constant of 2.8 x 1012 eV-1cm-2 with slightly decrease by increasing frequencies. Consequently, both series resistance and interface trap density were found to decrease with increasing frequency. The frequency dependence of the electrical responses is attributed the distribution density of interface states that could follow the alternating current (AC) signal.

  15. Optical and carrier transport properties of graphene oxide based crystalline-Si/organic Schottky junction solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Khatri, I.; Tang, Z.; Hiate, T.; Liu, Q.; Ishikawa, R.; Ueno, K.; Shirai, H. [Graduate School of Science and Engineering, Saitama University, Saitama 338-8570 (Japan)

    2013-12-21

    We investigated the graphene oxide (GO) based n-type crystalline silicon (c-Si)/conductive poly(ethylene dioxythiophene):poly(styrenesulfonate)(PEDOT:PSS) Schottky junction devices with optical characterization and carrier transport measurement techniques. The optical transmittance in the UV region decreased markedly for the films with increasing the concentration of GO whereas it increased markedly in the visible-infrared regions. Spectroscopic ellipsometry revealed that the ordinary and extraordinary index of refraction increased with increasing the concentration of GO. The hole mobility also increased from 1.14 for pristine film to 1.85 cm{sup 2}/V s for the 12–15 wt. % GO modified film with no significant increases of carrier concentration. The highest conductivity was found for a 15 wt. % GO modified PEDOT:PSS film: the c-Si/PEDOT:PSS:GO device using this sample exhibited a relatively high power conversion efficiency of 11.04%. In addition, the insertion of a 2–3 nm-thick GO thin layer at the c-Si/PEDOT:PSS interface suppressed the carrier recombination efficiency of dark electron and photo-generated hole at the anode, resulting in the increased photovoltaic performance. This study indicates that the GO can be good candidates for hole transporting layer of c-Si/PEDOT:PSS Schottky junction solar cell.

  16. Answer to comments on “Fabrication and photovoltaic conversion enhancement of graphene/n-Si Schottky barrier solar cells by electrophoretic deposition”

    Science.gov (United States)

    Chen, Leifeng; He, Hong

    2017-04-01

    Here, we reply to comments by Valentic et al. on our paper published in Electrochimica Acta (2014, 130: 279). They commented that Au nanoparticles played the dominant role on the whole cell's performances in our improved graphene/Si solar cell. We argued that our devices are Au-doped graphene/n-Si Schottky barrier devices, not Au nanoparticles (film)/n-Si Schottky barrier devices. During the doping process, most of the Au nanopatricles covered the surfaces of the graphene. Schottky barriers between doped graphene and n-Si dominate the total cells properties. Through doping, by adjusting and tailoring the Fermi level of the graphene, the Fermi level of n-Si can be shifted down in the graphene/Si Schottky barrier cell. They also argued that the instability of our devices were related to variation in series resistance reduced at the beginning due to slightly lowered Fermi level and increased at the end by the self-compensation by deep in-diffusion of Au nanoparticles. But for our fabricated devices, we know that an oxide layer covered the Si surface, which makes it difficult for the Au ions to diffuse into the Si layer, due to the continuous growth of SiO{}2 layer on the Si surface which resulted in series resistance decreasing at first and increasing in the end.

  17. Real-time 2.5 Gbit/s ultra-wideband transmission using a Schottky diode-based envelope detector

    DEFF Research Database (Denmark)

    Rommel, Simon; Cimoli, Bruno; Valdecasa, Guillermo Silva

    2017-01-01

    An experimental demonstration of 2.5 Gbit/s real-time ultra-wideband transmission is presented, using a Schottky diode-based envelope detector fabricated ad-hoc using microstrip technology on a Rogers6002 substrate and surface-mount components. Real-time transmission with a BER below FEC threshold...

  18. The Effect of Metal-Semiconductor Contact on the Transient Photovoltaic Characteristic of HgCdTe PV Detector

    Directory of Open Access Journals (Sweden)

    Haoyang Cui

    2013-01-01

    Full Text Available The transient photovoltaic (PV characteristic of HgCdTe PV array is studied using an ultrafast laser. The photoresponse shows an apparent negative valley first, then it evolves into a positive peak. By employing a combined theoretical model of pn junction and Schottky potential, this photo-response polarity changing curves can be interpreted well. An obvious decreasing of ratio of negative valley to positive peak can be realized by limiting the illumination area of the array electrode. This shows that the photoelectric effect of Schottky barrier at metal-semiconductor (M/S interface is suppressed, which will verify the correctness of the model. The characteristic parameters of transient photo-response induced from p-n junction and Schottky potential are extracted by fitting the response curve utilizing this model. It shows that the negative PV response induced by the Schottky barrier decreases the positive photovoltage generated by the pn junction.

  19. Promising Approach for High-Performance MoS2 Nanodevice: Doping the BN Buffer Layer to Eliminate the Schottky Barriers.

    Science.gov (United States)

    Su, Jie; Feng, Li-Ping; Zheng, Xiaoqi; Hu, Chenlu; Lu, Hongcheng; Liu, Zhengtang

    2017-11-07

    Reducing the Schottky barrier height (SBH) of metal-MoS2 interface with no deteriorating the intrinsic properties of MoS2 channel layer is crucial to realize the high-performance MoS2 nanodevice. To realize this expectation, a promising approach is present in this study by doping the boron nitride (BN) buffer layer between metal electrode and MoS2 channel layer. Results demonstrate that no matter the types of concentrations and dopants the intrinsic electronic structure, low electron effective mass of MoS2 channel layer, and the weak Fermi level pinning effects of metal/BN-MoS2 interfaces are preserved and not deteriorated. More importantly, the n- and p-type SBHs of metal/BN-MoS2 interfaces are significantly reduced by the electron-poor and -rich dopants, respectively, when the doped BN buffer layer spreads all over the nanodevice, which is in contrast to the traditional doping rule. Moreover, both the n- and p-type SBHs are further decreased and even eliminated when the concentrations of dopants increase. The n-type SBH of doped Au/BxN-MoS2 interface and the p-type SBH of doped Pt/BNx-MoS2 interface can be reduced to -0.21 and -0.61 eV by doping with high concentrations of Li and O, respectively. This theoretical work provides an effective and promising method to realize high-performance MoS2 nanodevices with negligible SBHs.

  20. On the junction physics of Schottky contact of (10, 10) MX{sub 2} (MoS{sub 2}, WS{sub 2}) nanotube and (10, 10) carbon nanotube (CNT): an atomistic study

    Energy Technology Data Exchange (ETDEWEB)

    Sengupta, Amretashis [Hanse-Wissenschaftskolleg (HWK), Delmenhorst (Germany); Universitaet Bremen, Bremen Center for Computational Materials Science (BCCMS), Bremen (Germany)

    2017-04-15

    Armchair nanotubes of MoS{sub 2} and WS{sub 2} offer a sizeable band gap, with the advantage of a one dimensional (1D) electronic material, but free from edge roughness and thermodynamic instability of nanoribbons. Use of such semiconducting MX{sub 2} (MoS{sub 2}, WS{sub 2}) armchair nanotubes (NTs) in conjunction with metallic carbon nanotubes (CNT) can be useful for nanoelectronics and photonics applications. In this work, atomistic simulations of MoS{sub 2} NT-CNT and WS{sub 2} NT-CNT junctions are carried out to study the physics of such junctions. With density functional theory (DFT) we study the carrier density distribution, effective potential, electron difference density, electron localization function, electrostatic difference potential and projected local density of states of such MX{sub 2} NT-CNT 1D junctions. Thereafter the conductance of such a junction under moderate bias is studied with non-equilibrium Green's function (NEGF) method. From the forward bias characteristics simulated from NEGF, we extract diode parameters of the junction. The electrostatic simulations from DFT show the formation of an inhomogeneous Schottky barrier with a tendency towards charge transfer from metal and chalcogen atoms towards the C atoms. For low bias conditions, the ideality factor was calculated to be 1.1322 for MoS{sub 2} NT-CNT junction and 1.2526 for the WS{sub 2} NT-CNT junction. The Schottky barrier heights displayed significant bias dependent modulation and are calculated to be in the range 0.697-0.664 eV for MoS{sub 2} NT-CNT and 0.669-0.610 eV for the WS{sub 2} NT-CNT, respectively. (orig.)

  1. Temperature dependent electrical characterisation of Pt/HfO2/n-GaN metal-insulator-semiconductor (MIS Schottky diodes

    Directory of Open Access Journals (Sweden)

    Arjun Shetty

    2015-09-01

    Full Text Available This paper reports an improvement in Pt/n-GaN metal-semiconductor (MS Schottky diode characteristics by the introduction of a layer of HfO2 (5 nm between the metal and semiconductor interface. The resulting Pt/HfO2/n-GaN metal-insulator-semiconductor (MIS Schottky diode showed an increase in rectification ratio from 35.9 to 98.9(@ 2V, increase in barrier height (0.52 eV to 0.63eV and a reduction in ideality factor (2.1 to 1.3 as compared to the MS Schottky. Epitaxial n-type GaN films of thickness 300nm were grown using plasma assisted molecular beam epitaxy (PAMBE. The crystalline and optical qualities of the films were confirmed using high resolution X-ray diffraction and photoluminescence measurements. Metal-semiconductor (Pt/n-GaN and metal-insulator-semiconductor (Pt/HfO2/n-GaN Schottky diodes were fabricated. To gain further understanding of the Pt/HfO2/GaN interface, I-V characterisation was carried out on the MIS Schottky diode over a temperature range of 150 K to 370 K. The barrier height was found to increase (0.3 eV to 0.79 eV and the ideality factor decreased (3.6 to 1.2 with increase in temperature from 150 K to 370 K. This temperature dependence was attributed to the inhomogeneous nature of the contact and the explanation was validated by fitting the experimental data into a Gaussian distribution of barrier heights.

  2. Dislocation-assisted tunnelling of charge carriers across the Schottky barrier on the hydride vapour phase epitaxy grown GaN

    Science.gov (United States)

    Chatterjee, Abhishek; Khamari, Shailesh K.; Dixit, V. K.; Oak, S. M.; Sharma, T. K.

    2015-11-01

    Barrier height and Ideality factor of Ni/n-GaN Schottky diodes are measured by performing temperature dependent current-voltage measurements. The measured value of barrier height is found to be much smaller than the theoretically calculated Schottky-Mott barrier height for the Ni/n-GaN diodes. Furthermore, a high value of ideality factor (>2) is measured at low temperatures. In order to understand these results, we need to consider a double Gaussian distribution of barrier height where the two components are related to the thermionic emission and thermionic filed emission mediated by dislocation-assisted tunnelling of carriers across the Schottky barrier. Thermionic emission is seen to dominate at temperatures higher than 170 K while the dislocation-assisted tunnelling dominates at low temperatures. The value of characteristic tunnelling energy measured from the forward bias current-voltage curves also confirms the dominance of dislocation-assisted tunnelling at low temperatures which is strongly corroborated by the Hall measurements. However, the value of characteristic tunnelling energy for high temperature range cannot be supported by the Hall results. This discrepancy can be eliminated by invoking a two layer model to analyse the Hall data which confirms that the charged dislocations, which reach the sample surface from the layer-substrate interface, provide an alternate path for the transport of carriers. The dislocation-assisted tunnelling of carriers governs the values of Schottky diode parameters at low temperature and the same is responsible for the observed inhomogeneity in the values of barrier height. The present analysis is applicable wherever the charge transport characteristics are severely affected by the presence of a degenerate layer at GaN-Sapphire interface and dislocations lines pierce the Schottky junction to facilitate the tunnelling of carriers.

  3. a 530-590 GHZ Schottky Heterodyne Receiver for High-Resolution Molecular Spectroscopy with Lille's Fast-Scan Fully Solid-State DDS Spectrometer

    Science.gov (United States)

    Pienkina, A.; Margulès, L.; Motiyenko, R. A.; Wiedner, Martina C.; Maestrini, Alain; Defrance, Fabien

    2017-06-01

    Laboratory spectroscopy, especially at THz and mm-wave ranges require the advances in instrumentation techniques to provide high resolution of the recorded spectra with precise frequency measurement that facilitates the mathematical treatment. We report the first implementation of a Schottky heterodyne receiver, operating at room temperature and covering the range between 530 and 590 GHz, for molecular laboratory spectroscopy. A 530-590 GHz non-cryogenic Schottky solid-state receiver was designed at LERMA, Observatoire de Paris and fabricated in partnership with LPN- CNRS (Laboratoire de Photonique et de Nanostructures), and was initially developed for ESA Jupiter Icy Moons Explorer (JUICE), intended to observe Jupiter and its icy moon atmospheres. It is based on a sub-harmonic Schottky diode mixer, designed and fabricated at LERMA-LPN, pumped by a Local Oscillator (LO), consisting of a frequency Amplifier/Multiplier chains (AMCs) from RPG (Radiometer Physics GmBh). The performance of the receiver was demonstrated by absorption spectroscopy of CH_3CH_2CN with Lille's fast-scan DDS spectrometer. A series of test measurements showed the receiver's good sensitivity, stability and frequency accuracy comparable to those of 4K QMC bolometers, thus making room-temperature Schottky receiver a competitive alternative to 4K QMC bolometers to laboratory spectroscopy applications. We will present the first results with such a combination of a compact room temperature Schottky heterodyne receiver and a fast-scan DDS spectrometer. J. Treuttel, L. Gatilova, A. Maestrini et al., 2016, IEEE Trans. Terahertz Science and Tech., 6, 148-155. This work was funded by the French ANR under the Contract No. ANR-13-BS05-0008-02 IMOLABS.

  4. Built-in potential and validity of the Mott-Schottky analysis in organic bulk heterojunction solar cells

    Science.gov (United States)

    Mingebach, M.; Deibel, C.; Dyakonov, V.

    2011-10-01

    We investigated poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl-C61 butyric acid methyl ester bulk heterojunction (BHJ) solar cells by means of pulsed photocurrent, temperature dependent current-voltage, and capacitance-voltage measurements. We show that a direct transfer of Mott-Schottky (MS) analysis from inorganic devices to organic BHJ solar cells is not generally appropriate to determine the built-in potential, since the resulting potential depends on the active layer thickness. Pulsed photocurrent measurements enabled us to directly study the case of quasi-flat bands (QFB) in the bulk of the solar cell. It is well below the built-in potential and differs by diffusion-induced band-bending at the contacts. In contrast to MS analysis, the corresponding potential is independent on the active layer thickness and therefore a better measure for flat band conditions in the bulk of a BHJ solar cell as compared to MS analysis.

  5. InGaAs Schottky barrier diode array detector for a real-time compact terahertz line scanner.

    Science.gov (United States)

    Han, Sang-Pil; Ko, Hyunsung; Park, Jeong-Woo; Kim, Namje; Yoon, Young-Jong; Shin, Jun-Hwan; Kim, Dae Yong; Lee, Dong Hun; Park, Kyung Hyun

    2013-11-04

    We present a terahertz (THz) broadband antenna-integrated 1 × 20 InGaAs Schottky barrier diode (SBD) array detector with an average responsivity of 98.5 V/W at a frequency of 250 GHz, which is measured without attaching external amplifiers and Si lenses, and an average noise equivalent power (NEP) of 106.6 pW/√Hz. The 3-dB bandwidth of the SBD detector is also investigated at approximately 180 GHz. For implementing an array-type SBD detector by a simple fabrication process to achieve a high yield, a structure comprising an SiN(x) layer instead of an air bridge between the anode and the cathode is designed. THz line beam imaging using a Gunn diode emitter with a center frequency of 250 GHz and a 1 × 20 SBD array detector is successfully demonstrated.

  6. Combination of conductive filaments and Schottky behavior in multifunctional Sn1-xCuxO2-δ memristor

    Science.gov (United States)

    Mei, Fang; Shen, Hui; Li, Yang; Li, Liben; Zang, Guozhong; Zhou, Min; Ti, Ruixia; Yang, Dianyuan; Huang, Fengzhen; Lu, Xiaomei; Zhu, Jinsong

    2017-10-01

    Resistive switching behaviors of SnO2 films are largely improved by Cu acceptor doping. At a suitable Cu2+ concentration, a high ON/OFF resistance ratio (104), good endurance (104) and long retention (104 s) are achieved in the Cu/SnO2:Cu/Pt sandwich structure with the modulation of carriers and oxygen vacancies. As a memristor, the resistive switching can be triggered by one pulse or a train of pulses, and the latter mode could simulate the long-term potentiation of biological synapses. Moreover, the multi-resistance states during the reset process demonstrate a combination of abrupt and incremental resistive switching. The peculiar conductive behavior of the devices is considered to result from the cooperation of conductive filaments and Schottky barrier, with the oxygen vacancies serving as the bridge. These studies are significant for higher density storage and cognitive computing in future.

  7. GaN Schottky diodes with single-crystal aluminum barriers grown by plasma-assisted molecular beam epitaxy

    Science.gov (United States)

    Tseng, H. Y.; Yang, W. C.; Lee, P. Y.; Lin, C. W.; Cheng, Kai-Yuan; Hsieh, K. C.; Cheng, K. Y.; Hsu, C.-H.

    2016-08-01

    GaN-based Schottky barrier diodes (SBDs) with single-crystal Al barriers grown by plasma-assisted molecular beam epitaxy are fabricated. Examined using in-situ reflection high-energy electron diffractions, ex-situ high-resolution x-ray diffractions, and high-resolution transmission electron microscopy, it is determined that epitaxial Al grows with its [111] axis coincident with the [0001] axis of the GaN substrate without rotation. In fabricated SBDs, a 0.2 V barrier height enhancement and 2 orders of magnitude reduction in leakage current are observed in single crystal Al/GaN SBDs compared to conventional thermal deposited Al/GaN SBDs. The strain induced piezoelectric field is determined to be the major source of the observed device performance enhancements.

  8. Fabrication and characterization of well-aligned zinc oxide nanowire arrays and their realizations in Schottky-device applications

    Energy Technology Data Exchange (ETDEWEB)

    Wong, Kin Mun; Grote, Fabian; Sun, Hui; Lei, Yong [Institute of Materials Physics, Center for Nanotechnology, University of Muenster (Germany); Wen, Liaoyong; Fang, Yaoguo [Institute of Nanochemistry and Nanobiology, Shanghai University, Shanghai 201800 (China)

    2011-07-01

    Highly ordered arrays of vertical zinc oxide (ZnO) nanowires (NWs) or nanopores were fabricated in our group by first thermal evaporating a thin film of gold on the ultrathin alumina membrane (UTAM). The UTAM was then utilized as a substrate for the growth of the ordered arrays using a chemical vapour deposition (CVD) process. Alternatively, a modified CVD process was also used to fabricate ultra-long ZnO NWs with the length of the nanowire exceeding 100 micrometres. Subsequently, densely packed arrays of ZnO NWs Schottky diodes were synthesized by transferring the long NWs on a substrate using a dry contact printing method and the electrical contacts were made on the NWs with a photolithographic process. The interesting electrical properties of the ZnO NWs, diodes or other metal oxide NWs such as the field emission, electron transport and piezoelectric properties were characterized by current-voltage or by other appropriate measurements.

  9. Initial leakage current paths in the vertical-type GaN-on-GaN Schottky barrier diodes

    Science.gov (United States)

    Sang, Liwen; Ren, Bing; Sumiya, Masatomo; Liao, Meiyong; Koide, Yasuo; Tanaka, Atsushi; Cho, Yujin; Harada, Yoshitomo; Nabatame, Toshihide; Sekiguchi, Takashi; Usami, Shigeyoshi; Honda, Yoshio; Amano, Hiroshi

    2017-09-01

    Electrical characteristics of leakage current paths in vertical-type n-GaN Schottky barrier diodes (SBDs) on free-standing GaN substrates are investigated by using photon emission microscopy (PEM). The PEM mapping shows that the initial failure of the SBD devices at low voltages is due to the leakage current paths from polygonal pits in the GaN epilayers. It is observed that these polygonal pits originate from carbon impurity accumulation to the dislocations with a screw-type component by microstructure analysis. For the SBD without polygonal pits, no initial failure is observed and the first leakage appeals at the edge of electrodes as a result of electric field concentration. The mechanism of leakage at pits is explained in terms of trap assisted tunneling through fitting current-voltage characteristics.

  10. Investigation of diode parameters using I-V and C-V characteristics of In/SiO{sub 2}/p-Si (MIS) Schottky diodes

    Energy Technology Data Exchange (ETDEWEB)

    Yueksel, O.F. [Department of Physics, Faculty of Arts and Science, Selcuk University, Kampus, Konya 42075 (Turkey)], E-mail: fyuksel@selcuk.edu.tr; Selcuk, A.B.; Ocak, S.B. [PK, 14 Etlik, Ankara (Turkey)

    2008-08-01

    A study on interface states density distribution and characteristic parameters of the In/SiO{sub 2}/p-Si (MIS) capacitor has been made. The thickness of the SiO{sub 2} film obtained from the measurement of the corrected capacitance in the strong accumulation region for MIS Schottky diodes was 220 A. The diode parameters from the forward bias I-V characteristics such as ideality factor, series resistance and barrier heights were found to be 1.75, 106-112 {omega} and 0.592 eV, respectively. The energy distribution of the interface state density D{sub it} was determined from the forward bias I-V characteristics by taking into account the bias dependence of the effective barrier height. The interface state density obtained using the I-V characteristics had an exponential growth, with bias towards the top of the valance band, from 9.44x10{sup 13} eV{sup -1} cm{sup -2} in 0.329-E{sub v} eV to 1.11x10{sup 13} eV{sup -1} cm{sup -2} in 0.527-E{sub v} eV at room temperature. Furthermore, the values of interface state density D{sub it} obtained by the Hill-Coleman method from the C-V characteristics range from 52.9x10{sup 13} to 1.11x10{sup 13} eV{sup -1} cm{sup -2} at a frequency range of 30kHz-1 MHz. These values of D{sub it} and R{sub s} were responsible for the non-ideal behaviour of I-V and C-V characteristics.

  11. Schottky junction/ohmic contact behavior of a nanoporous TiO2 thin film photoanode in contact with redox electrolyte solutions

    Directory of Open Access Journals (Sweden)

    Masao Kaneko

    2011-02-01

    Full Text Available The nature and photoelectrochemical reactivity of nanoporous semiconductor electrodes have attracted a great deal of attention. Nanostructured materials have promising capabilities applicable for the construction of various photonic and electronic devices. In this paper, a mesoporous TiO2 thin film photoanode was soaked in an aqueous methanol solution using an O2-reducing Pt-based cathode in contact with atmospheric air on the back side. It was shown from distinct photocurrents in the cyclic voltammogram (CV that the nanosurface of the mesoporous n-TiO2 film forms a Schottky junction with water containing a strong electron donor such as methanol. Formation of a Schottky junction (liquid junction was also proved by Mott–Schottky plots at the mesoporous TiO2 thin film photoanode, and the thickness of the space charge layer was estimated to be very thin, i.e., only 3.1 nm at −0.1 V vs Ag/AgCl. On the other hand, the presence of [Fe(CN6]4− and the absence of methanol brought about ohmic contact behavior on the TiO2 film and exhibited reversible redox waves in the dark due to the [Fe(CN6]4−/3− couple. Further studies showed that multiple Schottky junctions/ohmic contact behavior inducing simultaneously both photocurrent and overlapped reversible redox waves was found in the CV of a nanoporous TiO2 photoanode soaked in an aqueous redox electrolyte solution containing methanol and [Fe(CN6]4−. That is, the TiO2 nanosurface responds to [Fe(CN6]4− to give ohmic redox waves overlapped simultaneously with photocurrents due to the Schottky junction. Additionally, a second step photocurrent generation was observed in the presence of both MeOH and [Fe(CN6]4− around the redox potential of the iron complex. It was suggested that the iron complex forms a second Schottky junction for which the flat band potential (Efb lies near the redox potential of the iron complex.

  12. Observation of silicon carbide Schottky barrier diode under applied reverse bias using atomic force microscopy/Kelvin probe force microscopy/scanning capacitance force microscopy

    Science.gov (United States)

    Uruma, Takeshi; Satoh, Nobuo; Yamamoto, Hidekazu

    2017-08-01

    We have observed a commercial silicon-carbide Schottky barrier diode (SiC-SBD) using our novel analysis system, in which atomic force microscopy (AFM) is combined with both Kelvin probe force microscopy (KFM; for surface-potential measurement) and scanning capacitance force microscopy (SCFM; for differential-capacitance measurement). The results obtained for the SiC-SBD under an applied reverse bias indicate both the scan area in the sample and a peak value of the SCFM signal in the region where the existence of trapped electrons is deduced from the KFM analysis. Thus, our measurement system can be used to examine commercial power devices; however, novel polishing procedures are required in order to investigate the Schottky contact region.

  13. Influence of Schottky contact on the C-V and J-V characteristics of HTM-free perovskite solar cells

    Directory of Open Access Journals (Sweden)

    Huang Y.

    2017-01-01

    Full Text Available The influence of the Schottky contact is studied for hole transport material (HTM free CH3NH3PbI3 perovskite solar cells (PSCs, by using drift-diffusion and small signal models. The basic current-voltage and capacitance-voltage characteristics are simulated in reasonable agreement with experimental data. The build in potential of the finite CH3NH3PbI3 layer is extracted from a Mott-Schottky capacitance analysis. Furthermore, hole collector conductors with work-functions of more than 5.5 eV are proposed as solutions for high efficiency HTM-free CH3NH3PbI3 PSCs.

  14. Evaluation of 320x240 pixel LEC GaAs Schottky barrier X-ray imaging arrays, hybridized to CMOS readout circuit based on charge integration

    CERN Document Server

    Irsigler, R; Alverbro, J; Borglind, J; Froejdh, C; Helander, P; Manolopoulos, S; O'Shea, V; Smith, K

    1999-01-01

    320x240 pixels GaAs Schottky barrier detector arrays were fabricated, hybridized to silicon readout circuits, and subsequently evaluated. The detector chip was based on semi-insulating LEC GaAs material. The square shaped pixel detector elements were of the Schottky barrier type and had a pitch of 38 mu m. The GaAs wafers were thinned down prior to the fabrication of the ohmic back contact. After dicing, the chips were indium bump, flip-chip bonded to CMOS readout circuits based on charge integration, and finally evaluated. A bias voltage between 50 and 100 V was sufficient to operate the detector. Results on I-V characteristics, noise behaviour and response to X-ray radiation are presented. Images of various objects and slit patterns were acquired by using a standard dental imaging X-ray source. The work done was a part of the XIMAGE project financed by the European Community (Brite-Euram). (author)

  15. Electroluminescence from a forward-biased Schottky barrier diode on modulation Si {delta}-doped GaAs/InGaAs/AlGaAs heterostructure

    Energy Technology Data Exchange (ETDEWEB)

    Babinski, Adam; Witczak, P.; Twardowski, A.; Baranowski, J. M.

    2001-06-18

    Electroluminescence (EL) from a forward-biased Schottky barrier diode on modulation Si {delta}-doped pseudomorphic GaAs/InGaAs/AlGaAs heterostructure with high mobility electron gas is investigated in this work. It has been found that the EL from the InGaAs quantum well can be observed at temperatures up to 90 K. The EL line shape depends on the current density, which reflects the filling of the InGaAs channel with electrons. The total integrated EL intensity depends linearly on the current density. We propose that hole diffusion from an inversion layer at the Schottky barrier is responsible for the observed optical recombination with electrons in the InGaAs quantum well. {copyright} 2001 American Institute of Physics.

  16. Junction characteristics of ITO/PANI-ZnS/Ag and ITO/PANI-CdS/Ag Schottky diodes: a comparative study

    Science.gov (United States)

    Dey, S. K.; Baglari, S.; Sarkar, D.

    2016-01-01

    Schottky junctions are constructed by depositing PANI-ZnS and PANI-CdS nanocomposite thin films on ITO electrodes. Current-voltage ( I- V) measurements of these systems are performed as a function of temperature in the range of 313-363 K. These junctions show Schottky diode nature. Various parameters, such as saturation current ( I 0), ideality factor ( n), barrier height ( ∅ 0) and series resistance ( R S), are calculated from diode characteristics relations. These parameters show strong temperature dependence. The values of I 0 and ∅ increase with increasing temperature, whereas the values of n and R S show decreasing trend. A Richardson plot of the data shows nonlinear behaviour with Richardson constant 76 and 45 A cm-2 K-2 for PANI-ZnS and PANI-CdS nanocomposite thin films, respectively.

  17. Reverse blocking characteristics and mechanisms in Schottky-drain AlGaN/GaN HEMT with a drain field plate and floating field plates

    Science.gov (United States)

    Wei, Mao; Wei-Bo, She; Cui, Yang; Jin-Feng, Zhang; Xue-Feng, Zheng; Chong, Wang; Yue, Hao

    2016-01-01

    In this paper, a novel AlGaN/GaN HEMT with a Schottky drain and a compound field plate (SD-CFP HEMT) is presented for the purpose of better reverse blocking capability. The compound field plate (CFP) consists of a drain field plate (DFP) and several floating field plates (FFPs). The physical mechanisms of the CFP to improve the reverse breakdown voltage and to modulate the distributions of channel electric field and potential are investigated by two-dimensional numerical simulations with Silvaco-ATLAS. Compared with the HEMT with a Schottky drain (SD HEMT) and the HEMT with a Schottky drain and a DFP (SD-FP HEMT), the superiorities of SD-CFP HEMT lie in the continuous improvement of the reverse breakdown voltage by increasing the number of FFPs and in the same fabrication procedure as the SD-FP HEMT. Two useful optimization laws for the SD-CFP HEMTs are found and extracted from simulation results. The relationship between the number of the FFPs and the reverse breakdown voltage as well as the FP efficiency in SD-CFP HEMTs are discussed. The results in this paper demonstrate a great potential of CFP for enhancing the reverse blocking ability in AlGaN/GaN HEMT and may be of great value and significance in the design and actual manufacture of SD-CFP HEMTs. Project supported by the National Natural Science Foundation of China (Grant Nos. 61204085, 61334002, 61306017, 61474091, 61574112, and 61574110).

  18. Active and fast charge-state switching of single NV centres in diamond by in-plane Al-Schottky junctions

    Directory of Open Access Journals (Sweden)

    Christoph Schreyvogel

    2016-11-01

    Full Text Available In this paper, we demonstrate an active and fast control of the charge state and hence of the optical and electronic properties of single and near-surface nitrogen-vacancy centres (NV centres in diamond. This active manipulation is achieved by using a two-dimensional Schottky-diode structure from diamond, i.e., by using aluminium as Schottky contact on a hydrogen terminated diamond surface. By changing the applied potential on the Schottky contact, we are able to actively switch single NV centres between all three charge states NV+, NV0 and NV− on a timescale of 10 to 100 ns, corresponding to a switching frequency of 10–100 MHz. This switching frequency is much higher than the hyperfine interaction frequency between an electron spin (of NV− and a nuclear spin (of 15N or 13C for example of 2.66 kHz. This high-frequency charge state switching with a planar diode structure would open the door for many quantum optical applications such as a quantum computer with single NVs for quantum information processing as well as single 13C atoms for long-lifetime storage of quantum information. Furthermore, a control of spectral emission properties of single NVs as a single photon emitters – embedded in photonic structures for example – can be realized which would be vital for quantum communication and cryptography.

  19. Microstructural and electrical properties of Al/n-type Si Schottky diodes with Au-CuPc nanocomposite films as interlayer

    Science.gov (United States)

    Reddy, P. R. Sekhar; Janardhanam, V.; Jyothi, I.; Chang, Han-Soo; Lee, Sung-Nam; Lee, Myung Sun; Reddy, V. Rajagopal; Choi, Chel-Jong

    2017-11-01

    Au-CuPc nanocomposite films were prepared by simultaneous evaporation of Au and CuPc with various Au and CuPc concentrations. Microstructural analysis of Au-CuPc films revealed elongated Au cluster formation from isolated Au nanoclusters with increasing Au concentration associated with coalescence of Au clusters. Au-CuPc films with different compositions were employed as interlayer in Al/n-Si Schottky diode. Barrier height and series resistance of the Al/n-Si Schottky diode with Au-CuPc interlayer decreased with increasing Au concentration. This could be associated with the enhancement of electron tunneling between neighboring clusters due to decrease in spacing of Au clusters and formation of conducting paths through the composite material. Interface state density of the Al/n-Si Schottky diode with Au-CuPc interlayer increased with increasing Au concentration. This might be because the inclusion of metal decreases the crystallinity and crystal size of the polymer matrix accompanied by the formation of local defect sites at the places of metal nucleation.

  20. Flicker noise comparison of direct conversion mixers using Schottky and HBT dioderings in SiGe:C BiCMOS technology

    DEFF Research Database (Denmark)

    Michaelsen, Rasmus Schandorph; Johansen, Tom Keinicke; Tamborg, Kjeld

    2015-01-01

    In this paper, we present flicker noise measurements of two X-band direct conversion mixers implemented in a SiGe:C BiCMOS technology. Both mixers use a ring structure with either Schottky diodes or diode-connected HBTs for double balanced operation. The mixers are packaged in a metal casing on a...... circuit demonstrates a 1/f noise corner frequency around 10 kHz.......In this paper, we present flicker noise measurements of two X-band direct conversion mixers implemented in a SiGe:C BiCMOS technology. Both mixers use a ring structure with either Schottky diodes or diode-connected HBTs for double balanced operation. The mixers are packaged in a metal casing...... on an Arlon 25N substrate to shield the sensitive noise measurement. Conversion loss measurements of both mixers is performed both for on-wafer and packaged versions. The experimental results shows that the Schottky diode mixer exhibits a 1/f noise corner frequency of 250 kHz, while the diode connected HBT...

  1. A high-sensitive ultraviolet photodetector composed of double-layered TiO{sub 2} nanostructure and Au nanoparticles film based on Schottky junction

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Huan; Qin, Pei [School of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou, 510006 (China); Yi, Guobin, E-mail: ygb702@163.com [School of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou, 510006 (China); Zu, Xihong [School of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou, 510006 (China); Zhang, Li, E-mail: zhangli2368@126.com [School of Materials and Energy, Guangdong University of Technology, Guangzhou, 510006 (China); Hong, Wei; Chen, Xudong [School of Chemistry and Chemical Engineering, Sun Yat-Sen (Zhongshan) University, Guangzhou, 510275 (China)

    2017-06-15

    In this study, a Schottky-type ultraviolet (UV) photodetector based on double-layered nanostructured TiO{sub 2}/Au films was fabricated. Double-layered titanium dioxide (TiO{sub 2}) nanostructures composed of one layer of TiO{sub 2} nano-flowers on one layer of TiO{sub 2} nanorods on fluorine-doped tin oxide (FTO) pre-coated glass substrates were synthesized via a convenient hydrothermal method using titanium butoxide and hydrochloric acid as the starting precursor, without involving the use of any other surfactants and catalysts. A granular-shaped thin-layer of Au film using vacuum sputter coating technique was subsequently deposited on TiO{sub 2} for the formation of Schottky-type photodetector. The as-fabricated Schottky device showed various photocurrent responses when irradiated with different wavelength of UV light. This suggests that the newly-developed photodetectors have promising potential for identifying different UV light wavelengths. - Highlights: • A novel double-layered TiO{sub 2} nanostructure was synthesized by a simple method. • An UV photodetector composed of TiO{sub 2} and Au was designed and fabricated. • The preparation method of TiO{sub 2}/Au UV photodetector was simple and convenient. • The UV photodetector based on TiO{sub 2}/Au showed excellent sensitivity to UV light.

  2. Temperature dependent forward current-voltage characteristics of Ni/Au Schottky contacts on AlGaN/GaN heterostructures described by a two diodes model

    Science.gov (United States)

    Greco, Giuseppe; Giannazzo, Filippo; Roccaforte, Fabrizio

    2017-01-01

    This paper reports on the temperature dependence of Ni/Au Schottky contacts on AlGaN/GaN heterostructures. The electrical properties of the Schottky barrier were monitored by means of forward current-voltage (I-V) measurements, while capacitance-voltage measurements were used to determine the properties of the two dimensional electron gas. The forward I-V characteristics of Schottky diodes revealed a strong deviation from the ideal behavior, which could not be explained by a standard thermionic emission model. Thus, the Ni/AlGaN/GaN system has been described by a "two diode model," considering the presence of a second barrier height at the AlGaN/GaN heterojunction. Following this approach, the anomalous I-V curves could be explained and the value of the flat-band barrier height (at zero-electric field) could be correctly determined, thus resulting in good agreement with literature data based on photoemission measurements.

  3. Barrier height modification and mechanism of carrier transport in Ni/in situ grown Si3N4/n-GaN Schottky contacts

    Science.gov (United States)

    Karpov, S. Y.; Zakheim, D. A.; Lundin, W. V.; Sakharov, A. V.; Zavarin, E. E.; Brunkov, P. N.; Lundina, E. Y.; Tsatsulnikov, A. F.

    2018-02-01

    In situ growth of an ultra-thin (up to 2.5 nm) Si3N4 film on the top of n-GaN is shown to reduce remarkably the height of the barrier formed by deposition of Ni-based Schottky contact. The reduction is interpreted in terms of polarization dipole induced at the Si3N4/n-GaN interface and Fermi level pinning at the Ni/Si3N4 interface. Detailed study of temperature-dependent current-voltage characteristics enables identification of the electron transport mechanism in such Schottky diodes under forward bias: thermal/field electron emission over the barrier formed in n-GaN followed by tunneling through the Si3N4 film. At reverse bias and room temperature, the charge transfer is likely controlled by Poole-Frenkel ionization of deep traps in n-GaN. Tunneling exponents at forward and reverse biases and the height of the Ni/Si3N4 Schottky barrier are evaluated experimentally and compared with theoretical predictions.

  4. Characterisation of temperature dependent parameters of multi-quantum well (MQW) Ti/Au/n-AlGaAs/n-GaAs/n-AlGaAs Schottky diodes

    Science.gov (United States)

    Filali, Walid; Sengouga, Nouredine; Oussalah, Slimane; Mari, Riaz H.; Jameel, Dler; Al Saqri, Noor Alhuda; Aziz, Mohsin; Taylor, David; Henini, Mohamed

    2017-11-01

    Forward and reverse current-voltage (Isbnd V) of Ti/Au/n-Al0.33Ga0.67As/n-GaAs/n-Al0.33Ga0.67As multi-quantum well (MQW) Schottky diodes were measured over a range of temperatures from 20 to 400 K by a step of 20 K. The Schottky diodes parameters were then extracted from these characteristics. The Cheung method is used for this purpose, assuming a thermionic conduction mechanism. The extracted ideality factor decrease with increasing temperatures. But their values at low temperatures were found to be unrealistic. In order to explain this uncertainty, three assumptions were explored. Firstly an assumed inhomogeneous barrier height gave better parameters especially the Richardson constant but the ideality factor is still unrealistic at low temperatures. Secondly, by using numerical simulation, it was demonstrated that defects including interface states are not responsible for the apparent unrealistic Schottky diode parameters. The third assumption is the tunnelling mechanism through the barrier in the low temperature range. At these lower temperatures, the tunnelling mechanism was more suitable to explain the extracted parameters values.

  5. Simulation study of a new InGaN p-layer free Schottky based solar cell

    Science.gov (United States)

    Adaine, Abdoulwahab; Ould Saad Hamady, Sidi; Fressengeas, Nicolas

    2016-08-01

    On the road towards next generation high efficiency solar cells, the ternary Indium Gallium Nitride (InGaN) alloy is a good passenger since it allows to cover the whole solar spectrum through the change in its Indium composition. The choice of the main structure of the InGaN solar cell is however crucial. Obtaining a high efficiency requires to improve the light absorption and the photogenerated carriers collection that depend on the layers parameters, including the Indium composition, p- and n-doping, device geometry … Unfortunately, one of the main drawbacks of InGaN is linked to its p-type doping, which is very difficult to realize since it involves complex technological processes that are difficult to master and that highly impact the layer quality. In this paper, the InGaN p-n junction (PN) and p-i-n junction (PIN) based solar cells are numerically studied using the most realistic models, and optimized through mathematically rigorous multivariate optimization approaches. This analysis evidences optimal efficiencies of 17.8% and 19.0% for the PN and PIN structures. It also leads to propose, analyze and optimize p-layer free InGaN Schottky-Based Solar Cells (SBSC): the Schottky structure and a new MIN structure for which the optimal efficiencies are shown to be a little higher than for the conventional structures: respectively 18.2% and 19.8%. The tolerance that is allowed on each parameter for each of the proposed cells has been studied. The new MIN structure is shown to exhibit the widest tolerances on the layers thicknesses and dopings. In addition to its being p-layer free, this is another advantage of the MIN structure since it implies its better reliability. Therefore, these new InGaN SBSC are shown to be alternatives to the conventional structures that allow removing the p-type doping of InGaN while giving photovoltaic (PV) performances at least comparable to the standard multilayers PN or PIN structures.

  6. Thermal annealing behaviour of Pd Schottky contacts on melt-grown single crystal ZnO studied by IV and CV measurements

    Energy Technology Data Exchange (ETDEWEB)

    Mtangi, W., E-mail: wilbert.mtangi@up.ac.za [Department of Physics, University of Pretoria, Private Bag X20, Hatfield 0028 (South Africa); Auret, F.D.; Chawanda, A.; Janse van Rensburg, P.J.; Coelho, S.M.M.; Nel, J.M.; Diale, M.; Schalkwyk, L. van [Department of Physics, University of Pretoria, Private Bag X20, Hatfield 0028 (South Africa); Nyamhere, C. [Department of Physics, P.O. Box 77000, Nelson Mandela Metropolitan University, Port Elizabeth 6031 (South Africa)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Highly rectifying Pd/ZnO contacts have been fabricated. Black-Right-Pointing-Pointer The rectification behaviour decrease with annealing temperature. Black-Right-Pointing-Pointer The surface donor concentration increases with increase in annealing temperature. Black-Right-Pointing-Pointer The depletion layer width at a specific reverse voltage decreases with increase in annealing temperature. - Abstract: Current-voltage (IV) and capacitance-voltage (CV) measurement techniques have successfully been employed to study the effects of annealing highly rectifying Pd/ZnO Schottky contacts. IV results reveal a decrease in the contact quality with increasing annealing temperature as confirmed by a decrease in the zero bias barrier height and an increase in the reverse current measured at -1.5 V. An average barrier height of (0.77 {+-} 0.02) eV has been calculated by assuming pure thermionic emission for the as-deposited material and as (0.56 {+-} 0.03) eV after annealing at 550 Degree-Sign C. The reverse current has been measured as (2.10 {+-} 0.01) Multiplication-Sign 10{sup -10} A for the as-deposited and increases by 5 orders of magnitude after annealing at 550 Degree-Sign C to (1.56 {+-} 0.01) Multiplication-Sign 10{sup -5} A. The depletion layer width measured at -2.0 V has shown a strong dependence on thermal annealing as it decreases from 1.09 {mu}m after annealing at 200 Degree-Sign C to 0.24 {mu}m after annealing at 500 Degree-Sign C, resulting in the modification of the dopant concentration within the depletion region and hence the current flowing through the interface from pure thermionic emission to thermionic field emission with the donor concentrations increasing from 6.90 Multiplication-Sign 10{sup 15} cm{sup -3} at 200 Degree-Sign C to 6.06 Multiplication-Sign 10{sup 16} cm{sup -3} after annealing at 550 Degree-Sign C. This increase in the volume concentration has been explained as an effect of a conductive channel

  7. Non-UV Photoelectric Properties of the Ni/n-Si/N+-SiC Isotype Heterostructure Schottky Barrier Photodiode

    Science.gov (United States)

    Li, Lian-Bi; Chen, Zhi-Ming; Ren, Zhan-Qiang; Gao, Zhan-Jun

    2013-09-01

    The energy-band structure and non-ultraviolet photoelectric properties of a Ni/n-Si/N+-SiC isotype heterostructure Schottky photodiode are simulated by using Silvaco-Atlas. There are energy offsets in the conduction and valance band of the heterojunction, which are about 0.09 eV and 1.79 eV, respectively. The non-UV photodiode with this structure is fabricated on a 6H-SiC(0001) substrate. J—V measurements indicate that the device has good rectifying behavior with a rectification ratio up to 200 at 5 V, and the turn-on voltage is about 0.7 V. Under non-ultraviolet illumination of 0.6 W/cm2, the device demonstrates a significant photoelectric response with a photocurrent density of 2.9 mA/cm2 and an open-circuit voltage of 63.0 mV. Non-ultraviolet operation of the SiC-based photoelectric device is initially realized.

  8. Schottky Diode Applications of the Fast Green FCF Organic Material and the Analyze of Solar Cell Characteristics

    Science.gov (United States)

    Çaldiran, Z.; Aydoğan, Ş.; İncekara, Ü.

    2016-05-01

    In this study, a device applications of organic material Fast Green FCF (C37H34N2Na2O10S3Na2) has been investigated. After chemical cleaning process of boron doped H-Si crystals, Al metal was coated on the one surface of crystals by thermal evaporation and fast green organic materials were coated on other surface of crystals with spin coating method (coating parameters; 800 rpm for 60 s). Finally, Ni metal was coated on Fast Green by sputtering and we obtained the Ni/Fast Green FCF/n-Si/Al Schottky type diode. And then we calculated the basic diode parameters of device with current-voltage (I-V) and capacitance- voltage (C-V) measurements at the room temperature. We calculated the ideality factory (n), barrier height (Φb) of rectifing contact from I-V measurements using thermionic emission methods. Furthermore, we calculated ideality factory (n), barrier height (Φb) and series resistance (Rs) of device using Cheung and Norde functions too. The diffusion potential, barrier height, Fermi energy level and donor concentration have been determined from the linear 1/C2-V curves at reverse bias, at room temperature and various frequencies. Besides we measured the current-voltage (I-V) at under light and analyzed the characteristics of the solar cell device.

  9. A Sheath Collision Model with Thermionic Electron Emission and the Schottky Correction Factor for Work Function of Wall Material

    CERN Document Server

    Pekker, Leonid

    2015-01-01

    This paper proposes a model that expands Godyak's collisional sheath model to the case of hot electrodes (anode or cathode) with thermionic electron emission. In the model, the electrodes are assumed to be made from refractory metals and, consequently, the erosion of the electrodes is small and can be neglected. In the frame of two temperature thermal plasma modeling, this model allows self-consistent calculation of the sheath potential drop, the Schottky correction factor for the work function of the wall material, the thermionic electron current density, and the heat fluxes of the charged particles from the plasma to the wall. The model is applied to the cathode spot at the tungsten cathode in argon. It is shown that the Shottky correction factor plays a crucial role in modeling high-intensity arcs. It is demonstrated that a virtual cathode can be formed in the atmospheric pressure argon plasma at the cathode surface temperature of 4785 K if the cathode current density is sufficiently small. The heat flux t...

  10. Submillimeter wave GaAs Schottky diode application based study and optimization for 0.1-1.5 THz

    Science.gov (United States)

    Jenabi, Sarvenaz; Malekabadi, Ali; Deslandes, Dominic; Boone, Francois; Charlebois, Serge A.

    2017-08-01

    In this paper, a design and optimization method for submillimeter-wave Schottky diode is proposed. Parasitic capacitance is significantly reduced to under 20% of the total capacitance of the diode. The parasitic capacitance value is measured to be 0.6 fF for 1 μm anode radius which increased the cut-off frequency to 1.5 THz. A corresponding microfabrication process that provides higher degrees of freedom for the anode diameter, air-bridge dimensions and distance to the substrate is introduced and implemented. The DC and RF measurements are provided and compared with the simulations. In order to provide a better understanding of the diode behavior, the limiting factors of the cut-off frequency for different applications are studied and compared. For the mixer/multiplier mode, an improved and expanded formulation for calculation of the cut-off frequency is introduced. It is shown that the usable voltage bias range (with acceptable cut-off frequency) is limited by the exponential reduction of junction resistance, Rj , in mixer/multiplier mode.

  11. Interface Electrode Morphology Effect on Carrier Concentration and Trap Defect Density in an Organic Photovoltaic Device.

    Science.gov (United States)

    Kesavan, Arul Varman; Rao, Arun D; Ramamurthy, Praveen C

    2017-08-30

    Formation of Schottky barrier contact (SBC) leads reconstruction of charges at the metal/semiconductor (MS) interface because of the wave function overlap between semiconductor and metal contact. Not only is the Schottky barrier contact formation a signature of the material's work function, but also it is sensitive to the interface trap states, the crystal orientation of the interacting materials, and other interface properties. In this work, the effect of aluminum cathode morphology on the polymer Schottky diode and bulk heterojunction (BHJ) photovoltaic device performance is studied. The electron collecting contacts in Schottky diode and BHJ device have been deposited using aluminum in pellet and nanoparticle forms. Devices fabricated by using Al nanoparticle showed improvement in dark as well as photocurrent density. Significant enhancement in JSC leads to overall improved power conversion efficiency. Enhanced performance in Schottky structured diode and OPV device have been correlated with electrode microstructure and its interface properties such as improved electrically active contact and enhanced charge transport. Electrical conductivity is discussed based on enhanced electrical coherence across organic semiconductor and electrode interface. Therefore, the contribution of electrical enhancement leads to improvement in short-circuit current density (JSC) in BHJ solar cell which is due to reduced trap density. Further, PCE was correlated with the density of interface trap states studied by drive level capacitance profiling technique.

  12. Estimation of power dissipation of a 4H-SiC Schottky barrier diode with a linearly graded doping profile in the drift region

    Directory of Open Access Journals (Sweden)

    Rajneesh Talwar

    2009-09-01

    Full Text Available The aim of this paper is to establish the importance of a linearly graded profile in the drift region of a 4H-SiC Schottky barrier diode (SBD. The power dissipation of the device is found to be considerably lower at any given current density as compared to its value obtained for a uniformly doped drift region. The corresponding values of breakdown voltages obtained are similar to those obtained with uniformly doped wafers of 4H-SiC.

  13. Mass measurement of cooled neutron-deficient bismuth projectile fragments with time-resolved Schottky mass spectrometry at the FRS-ESR facility

    Energy Technology Data Exchange (ETDEWEB)

    Litvinov, Yu.A.; Geissel, H. [Giessen Univ. (Germany); Radon, T. [Gesellschaft fuer Schwerionenforschung mbH, Darmstadt (DE)] [and others

    2005-06-01

    Masses of 582 neutron-deficient nuclides (30{<=}Z{<=}85) were measured with time-resolved Schottky mass spectrometry at the FRS-ESR facility at GSI, 117 were used for calibration. The masses of 71 nuclides were obtained for the first time. A typical mass accuracy of 30 {mu}u was achieved. These data have entered the latest atomic mass evaluation. The mass determination of about 140 additional nuclides was possible via known energies (Q-values) of {alpha}-, {beta}-, or proton decays. The obtained results are compared with the results of other measurements. (orig.)

  14. Highly efficient ZnO/Au Schottky barrier dye-sensitized solar cells: Role of gold nanoparticles on the charge-transfer process

    OpenAIRE

    Tanujjal Bora; Htet H. Kyaw; Soumik Sarkar; Samir K. Pal; Joydeep Dutta

    2011-01-01

    Zinc oxide (ZnO) nanorods decorated with gold (Au) nanoparticles have been synthesized and used to fabricate dye-sensitized solar cells (DSSC). The picosecond-resolved, time-correlated single-photon-count (TCSPC) spectroscopy technique was used to explore the charge-transfer mechanism in the ZnO/Au-nanocomposite DSSC. Due to the formation of the Schottky barrier at the ZnO/Au interface and the higher optical absorptions of the ZnO/Au photoelectrodes arising from the surface plasmon absorption...

  15. Passivity of AISI 321 stainless steel in 0.5 M H2SO4 solution studied by Mott–Schottky analysis in conjunction with the point defect model

    Directory of Open Access Journals (Sweden)

    A. Fattah-alhosseini

    2016-11-01

    Full Text Available The passivity of AISI 321 stainless steel in 0.5 M H2SO4 solution, in the steady-state condition, has been explored using electrochemical impedance spectroscopy (EIS and Mott–Schottky analysis. Based on the Mott–Schottky analysis in conjunction with the point defect model (PDM, it was shown that the calculated donor density decreases exponentially with increasing passive film formation potential. The thickness of the passive film was increased linearly with the formation potential. These observations were consistent with the predictions of the PDM, noting that the point defects within the passive film are metal interstitials, oxygen vacancies, or both.

  16. Electronic Characteristics of Rare Earth Doped GaN Schottky Diodes

    Science.gov (United States)

    2013-03-21

    233U and 235U) and plutonium (239Pu) must fall within the limitations of the detector. These isotopes primarily undergo alpha decay [3, 4], which might...2001). Portal, freight and vehicle monitor performance using scintillating glass fiber detectors for the detection of plutonium in the Illicit...Trafficking Radiation Assessment Program. Journal of Radioanalytical and Nuclear Chemistry , 248, 699–705. [7] McHale, Stephen R. “The Effects of Rare Earth

  17. RF-to-DC Characteristics of Direct Irradiated On-Chip Gallium Arsenide Schottky Diode and Antenna for Application in Proximity Communication System

    Directory of Open Access Journals (Sweden)

    Farahiyah Mustafa

    2014-02-01

    Full Text Available We report the RF-to-DC characteristics of the integrated AlGaAs/GaAs Schottky diode and antenna under the direct injection and irradiation condition. The conversion efficiency up to 80% under direct injection of 1 GHz signal to the diode was achieved. It was found that the reduction of series resistance and parallel connection of diode and load tend to lead to the improvement of RF-to-DC conversion efficiency. Under direct irradiation from antenna-to-antenna method, the output voltage of 35 mV was still obtainable for the distance of 8 cm between both antennas in spite of large mismatch in the resonant frequency between the diode and the connected antenna. Higher output voltage in volt range is expected to be achievable for the well-matching condition. The proposed on-chip AlGaAs/GaAs HEMT Schottky diode and antenna seems to be a promising candidate to be used for application in proximity communication system as a wireless low power source as well as a highly sensitive RF detector.

  18. Surface morphological, electrical and transport properties of rapidly annealed double layers Ru/Cr Schottky structure on n-type InP

    Science.gov (United States)

    Shanthi Latha, K.; Rajagopal Reddy, V.

    2017-07-01

    The electrical and transport properties of a fabricated bilayer Ru/Cr/ n-InP Schottky diode (SD) have been investigated at different annealing temperatures. Atomic force microscopy results have showed that the overall surface morphology of the Ru/Cr/ n-InP SD is fairly smooth at elevated temperatures. High barrier height is achieved for the diode annealed at 300 °C compared to the as-deposited, annealed at 200 and 400 °C diodes. The series resistance and shunt resistance of the Ru/Cr/ n-InP SD are estimated by current-voltage method at different annealing temperatures. The barrier heights and series resistance are also determined by Cheung's and modified Norde functions. The interface state density of the Ru/Cr/ n-InP SD is found to be decreased after annealing at 300 °C and then slightly increased upon annealing at 400 °C. The difference between barrier heights obtained from current-voltage and capacitance-voltage is also discussed. Experimental results have showed that the Poole-Frenkel emission is found to be dominant in the lower bias region whereas Schottky emission is dominant in the higher bias region for the Ru/Cr/ n-InP SDs irrespective of annealing temperatures.

  19. Carrier-transport mechanism of Er-silicide Schottky contacts to strained-silicon-on-insulator and silicon-on-insulator.

    Science.gov (United States)

    Jyothi, I; Janardhanam, V; Kang, Min-Sung; Yun, Hyung-Joong; Lee, Jouhahn; Choi, Chel-Jong

    2014-11-01

    The current-voltage characteristics and the carrier-transport mechanism of the Er-silicide (ErSi1.7) Schottky contacts to strained-silicon-on-insulator (sSOI) and silicon-on-insulator (SOI) were investigated. Barrier heights of 0.74 eV and 0.82 eV were obtained for the sSOI and SOI structures, respectively. The barrier height of the sSOI structure was observed to be lower than that of the SoI structure despite the formation of a Schottky contact using the same metal silicide. The sSOI structure exhibited better rectification and higher current level than the SOI structure, which could be associated with a reduction in the band gap of Si caused by strain. The generation-recombination mechanism was found to be dominant in the forward bias for both structures. Carrier generation along with the Poole-Frenkel mechanism dominated the reverse-biased current in the SOI structure. The saturation tendency of the reverse leakage current in the sSOI structure could be attributed to strain-induced defects at the interface in non-lattice-matched structures.

  20. Highly efficient ZnO/Au Schottky barrier dye-sensitized solar cells: Role of gold nanoparticles on the charge-transfer process

    Science.gov (United States)

    Bora, Tanujjal; Kyaw, Htet H; Sarkar, Soumik; Pal, Samir K

    2011-01-01

    Summary Zinc oxide (ZnO) nanorods decorated with gold (Au) nanoparticles have been synthesized and used to fabricate dye-sensitized solar cells (DSSC). The picosecond-resolved, time-correlated single-photon-count (TCSPC) spectroscopy technique was used to explore the charge-transfer mechanism in the ZnO/Au-nanocomposite DSSC. Due to the formation of the Schottky barrier at the ZnO/Au interface and the higher optical absorptions of the ZnO/Au photoelectrodes arising from the surface plasmon absorption of the Au nanoparticles, enhanced power-conversion efficiency (PCE) of 6.49% for small-area (0.1 cm2) ZnO/Au-nanocomposite DSSC was achieved compared to the 5.34% efficiency of the bare ZnO nanorod DSSC. The TCSPC studies revealed similar dynamics for the charge transfer from dye molecules to ZnO both in the presence and absence of Au nanoparticles. A slower fluorescence decay associated with the electron recombination process, observed in the presence of Au nanoparticles, confirmed the blocking of the electron transfer from ZnO back to the dye or electrolyte by the Schottky barrier formed at the ZnO/Au interface. For large area DSSC (1 cm2), ~130% enhancement in PCE (from 0.50% to 1.16%) was achieved after incorporation of the Au nanoparticles into the ZnO nanorods. PMID:22043457

  1. Highly efficient ZnO/Au Schottky barrier dye-sensitized solar cells: Role of gold nanoparticles on the charge-transfer process

    Directory of Open Access Journals (Sweden)

    Tanujjal Bora

    2011-10-01

    Full Text Available Zinc oxide (ZnO nanorods decorated with gold (Au nanoparticles have been synthesized and used to fabricate dye-sensitized solar cells (DSSC. The picosecond-resolved, time-correlated single-photon-count (TCSPC spectroscopy technique was used to explore the charge-transfer mechanism in the ZnO/Au-nanocomposite DSSC. Due to the formation of the Schottky barrier at the ZnO/Au interface and the higher optical absorptions of the ZnO/Au photoelectrodes arising from the surface plasmon absorption of the Au nanoparticles, enhanced power-conversion efficiency (PCE of 6.49% for small-area (0.1 cm2 ZnO/Au-nanocomposite DSSC was achieved compared to the 5.34% efficiency of the bare ZnO nanorod DSSC. The TCSPC studies revealed similar dynamics for the charge transfer from dye molecules to ZnO both in the presence and absence of Au nanoparticles. A slower fluorescence decay associated with the electron recombination process, observed in the presence of Au nanoparticles, confirmed the blocking of the electron transfer from ZnO back to the dye or electrolyte by the Schottky barrier formed at the ZnO/Au interface. For large area DSSC (1 cm2, ~130% enhancement in PCE (from 0.50% to 1.16% was achieved after incorporation of the Au nanoparticles into the ZnO nanorods.

  2. Sub-microsecond x-ray imaging using hole-collecting Schottky type CdTe with charge-integrating pixel array detectors

    Science.gov (United States)

    Becker, J.; Tate, M. W.; Shanks, K. S.; Philipp, H. T.; Weiss, J. T.; Purohit, P.; Chamberlain, D.; Gruner, S. M.

    2017-06-01

    CdTe is increasingly being used as the x-ray sensing material in imaging pixel array detectors for x-rays, generally above 20 keV, where silicon sensors become unacceptably transparent. Unfortunately CdTe suffers from polarization, which can alter the response of the material over time and with accumulated dose. Most prior studies used long integration times or CdTe that was not of the hole-collecting Schottky type. We investigated the temporal response of hole-collecting Schottky type CdTe sensors on timescales ranging from tens of nanoseconds to several seconds. We found that the material shows signal persistence on the timescale of hundreds of milliseconds attributed to the detrapping of a shallow trap, and additional persistence on sub-microsecond timescales after polarization. The results show that this type of CdTe can be used for time resolved studies down to approximately 100 ns. However quantitative interpretation of the signal requires careful attention to bias voltages, polarization and exposure history.

  3. Highly sensitive hydrogen sensor based on graphite-InP or graphite-GaN Schottky barrier with electrophoretically deposited Pd nanoparticles

    Directory of Open Access Journals (Sweden)

    Zdansky Karel

    2011-01-01

    Full Text Available Abstract Depositions on surfaces of semiconductor wafers of InP and GaN were performed from isooctane colloid solutions of palladium (Pd nanoparticles (NPs in AOT reverse micelles. Pd NPs in evaporated colloid and in layers deposited electrophoretically were monitored by SEM. Diodes were prepared by making Schottky contacts with colloidal graphite on semiconductor surfaces previously deposited with Pd NPs and ohmic contacts on blank surfaces. Forward and reverse current-voltage characteristics of the diodes showed high rectification ratio and high Schottky barrier heights, giving evidence of very small Fermi level pinning. A large increase of current was observed after exposing diodes to flow of gas blend hydrogen in nitrogen. Current change ratio about 700,000 with 0.1% hydrogen blend was achieved, which is more than two orders-of-magnitude improvement over the best result reported previously. Hydrogen detection limit of the diodes was estimated at 1 ppm H2/N2. The diodes, besides this extremely high sensitivity, have been temporally stable and of inexpensive production. Relatively more expensive GaN diodes have potential for functionality at high temperatures.

  4. Impacts of growth orientation and N incorporation on the interface-states and the electrical characteristics of Cu/GaAsN Schottky barrier diodes

    Science.gov (United States)

    Dong, Chen; Han, Xiuxun; Li, Jian; Gao, Xin; Ohshita, Yoshio

    2017-12-01

    The frequency dependent capacitance-voltage (C-V) and conductance-voltage (G/ω-V) characteristics of Schottky barrier diodes (SBDs) with Cu contacts on Si doped GaAsN epilayers with (100) and (311)A/B orientations have been investigated in the frequency range from 20 kHz to 1 MHz at room temperature. C, G/ω and the deduced series resistance (Rs) show strong dependences on the applied frequency in the forward bias region, which is closely correlated to the frequency-dependent response of interface states (Nss). In GaAsN SBDs with all three growth orientations, the increasing N composition is found to increase the peak value of capacitance and enhance its dependence on frequency, which thus implies a general rule that increasing N incorporation causes an increase in Nss. The increasing extent of Nss due to N incorporation, however, differs a lot for different growth orientations as analyzed by using Hill-Coleman method. It is revealed that (311)B is the promising growth orientation to suppress the Nss generation over a wider N composition range in GaAsN Schottky devices. The reduced formation probability of non-substitutional N due to the efficient N incorporation on the (311)B plane is considered to be responsible for the observations.

  5. Simulation design of high reverse blocking high-K/low-K compound passivation AlGaN/GaN Schottky barrier diode with gated edge termination

    Science.gov (United States)

    Bai, Zhiyuan; Du, Jiangfeng; Xin, Qi; Li, Ruonan; Yu, Qi

    2017-11-01

    In this paper, a novel high-K/low-K compound passivation AlGaN/GaN Schottky Barrier Diode (CPG-SBD) is proposed to improve the off-state characteristics of AlGaN/GaN schottky barrier diode with gated edge termination (GET-SBD) by adding low-K blocks in to the high-K passivation layer. The reverse leakage current of CPG-SBD can be reduced to 1.6 nA/mm by reducing the thickness of high-K dielectric under GET region to 5 nm, while the forward voltage and on-state resistance keep 1 V and 3.8 Ω mm, respectively. Breakdown voltage of CPG-SBDs can be improved by inducing discontinuity of the electric field at the high-K/low-K interface. The breakdown voltage of the optimized CPG-SBD with 4 blocks of low-K can reach 1084 V with anode to cathode distance of 5 μm yielding a high FOM of 5.9 GW/cm2. From the C-V simulation results, CPG-SBDs induce no parasitic capacitance by comparison of the GET-SBDs.

  6. Schottky barrier height control at epitaxial NiAl/GaAs(001) interfaces by means of variable bandgap interlayers

    Energy Technology Data Exchange (ETDEWEB)

    Chambers, S.A.

    1992-11-01

    Recent developments in the use of interlayers to tailor the Schottky barrier height (SBH) at a metal/GaAs interface are discussed. The goal has been to gain control of band bending in the interfacial region by modifying both the interface Fermi energy and the charge density in the depletion region. The approach has been to grow both the interlayer and the metal overlayer under ultrahigh vacuum conditions by molecular beam epitaxy, and then to determine the chemistry of interface formation, structure, and band bending by x-ray photoelectron spectroscopy and diffraction and by low-energy electron diffraction. The interface Fermi energy can be changed from the usual midgap value of 0.7--0.8 eV relative to the band edge by the use of epitaxial transition metal aluminide (TMA) overlayers such as NiAl. The unique chemistry of interface formation between this intermetallic compound and GaAs pins the Fermi level {approximately}0.3--0.4 eV above the valence band maximum, and results in a SBH of {approximately}1 eV. The SBH can be increased to {approximately}1.2 eV by the use of a wide bandgap interlayer such as AlAs. The charge density in the depletion region can be changed by growing an n{sup +}-type group IV interlayer between the TMA overlayer and GaAs substrate. Charge transfer from the interlayer to an n-type substrate reduces the space charge density, and thereby lowers the band bending and, thus, the SBH to {approximately}0.5 eV. The use of these interlayers then produces a range of SBH values of {approximately}0.7 eV, which is a significant improvement over the rather narrow range of 0.1--0.2 eV that results from conventional metallizations. The fundamental interface science that underpins these results is discussed, and an application to complementary digital GaAs circuit design that may significantly reduce gate leakage is given.

  7. Schottky barrier height control at epitaxial NiAl/GaAs(001) interfaces by means of variable bandgap interlayers

    Energy Technology Data Exchange (ETDEWEB)

    Chambers, S.A.

    1992-11-01

    Recent developments in the use of interlayers to tailor the Schottky barrier height (SBH) at a metal/GaAs interface are discussed. The goal has been to gain control of band bending in the interfacial region by modifying both the interface Fermi energy and the charge density in the depletion region. The approach has been to grow both the interlayer and the metal overlayer under ultrahigh vacuum conditions by molecular beam epitaxy, and then to determine the chemistry of interface formation, structure, and band bending by x-ray photoelectron spectroscopy and diffraction and by low-energy electron diffraction. The interface Fermi energy can be changed from the usual midgap value of 0.7--0.8 eV relative to the band edge by the use of epitaxial transition metal aluminide (TMA) overlayers such as NiAl. The unique chemistry of interface formation between this intermetallic compound and GaAs pins the Fermi level [approximately]0.3--0.4 eV above the valence band maximum, and results in a SBH of [approximately]1 eV. The SBH can be increased to [approximately]1.2 eV by the use of a wide bandgap interlayer such as AlAs. The charge density in the depletion region can be changed by growing an n[sup +]-type group IV interlayer between the TMA overlayer and GaAs substrate. Charge transfer from the interlayer to an n-type substrate reduces the space charge density, and thereby lowers the band bending and, thus, the SBH to [approximately]0.5 eV. The use of these interlayers then produces a range of SBH values of [approximately]0.7 eV, which is a significant improvement over the rather narrow range of 0.1--0.2 eV that results from conventional metallizations. The fundamental interface science that underpins these results is discussed, and an application to complementary digital GaAs circuit design that may significantly reduce gate leakage is given.

  8. Observation and Measurement of Negative Differential Resistance on PtSi Schottky Junctions on Porous Silicon

    Directory of Open Access Journals (Sweden)

    Mansor Mohtashamifar

    2010-01-01

    Full Text Available Nanosize porous Si is made by two step controlled etching of Si. The first etching step is carried on the Si surface and the second is performed after deposition of 75 Å of platinum on the formed surface. A platinum silicide structure with a size of less than 25 nm is formed on the porous Si surface, as measured with an Atomic Forced Microscope (AFM. Differential resistance curve as a function of voltage in 77 K and 100 K shows a negative differential resistance and indicates the effect of quantum tunneling. In general form, the ratio of maximum to minimum tunneling current (PVR and the number of peaks in I-V curves reduces by increasing the temperature. However, due to accumulation of carriers behind the potential barrier and superposition of several peaks, it is observed that the PVR increases at 100 K and the maximum PVR at 100 K is 189.6.

  9. The ultraviolet radiation detectors based on wide-bandgap Schottky barrier structures

    CERN Document Server

    Blank, T V; Konstantinov, O V

    2002-01-01

    Recently, much attention has been given to measure and control ultraviolet radiation (UVR) from the Sun and artificial sources. We present photodetectors based on different wide-bandgap surface-barrier structures, which exhibit linear photocurrent-radiant flux characteristics in the range 10 sup - sup 2 -10 sup 3 W/m sup 2 and can register different types of UVR. The use of light filter UFS-6 with GaP photodetector results in a spectral photosensitivity range corresponding to the Sun UV radiation if observed on Earth. The spectral sensitivity range of the photodetectors based on 4H-SiC is near the spectrum of relative effectiveness of various wavelengths in bactericidal UVR. The photosensitivity of the surface-barrier photodetectors based on wide-bandgap semiconductors exhibits the essential decline in the short-wavelength UVR region (5-6 eV), which is the region of intrinsic absorption of the semiconductor. We propose a hot exciton model, according to which the hot excitons can form in the process of the pho...

  10. Tunnel barrier schottky

    Energy Technology Data Exchange (ETDEWEB)

    Chu, Rongming; Cao, Yu; Li, Zijian; Williams, Adam J.

    2018-02-20

    A diode includes: a semiconductor substrate; a cathode metal layer contacting a bottom of the substrate; a semiconductor drift layer on the substrate; a graded aluminum gallium nitride (AlGaN) semiconductor barrier layer on the drift layer and having a larger bandgap than the drift layer, the barrier layer having a top surface and a bottom surface between the drift layer and the top surface, the barrier layer having an increasing aluminum composition from the bottom surface to the top surface; and an anode metal layer directly contacting the top surface of the barrier layer.

  11. The Fabrication and Characterization of Ni/4H-SiC Schottky Diode Radiation Detectors with a Sensitive Area of up to 4 cm2

    Directory of Open Access Journals (Sweden)

    Lin-Yue Liu

    2017-10-01

    Full Text Available Silicon carbide (SiC detectors of an Ni/4H-SiC Schottky diode structure and with sensitive areas of 1–4 cm2 were fabricated using high-quality lightly doped epitaxial 4H-SiC material, and were tested in the detection of alpha particles and pulsed X-rays/UV-light. A linear energy response to alpha particles ranging from 5.157 to 5.805 MeV was obtained. The detectors were proved to have a low dark current, a good energy resolution, and a high neutron/gamma discrimination for pulsed radiation, showing the advantages in charged particle detection and neutron detection in high-temperature and high-radiation environments.

  12. An Integrated 520-600 GHz Sub-Harmonic Mixer and Tripler Combination Based on GaAs MMIC Membrane Planar Schottky Diodes

    Science.gov (United States)

    Thomas, B.; Gill, J.; Maestrini, A.; Lee, C.; Lin, R.; Sin, S.; Peralta, A.; Mehdi, I.

    2011-01-01

    We present here the design, development and test of an integrated sub-millimeter front-end featuring a 520-600 GHz sub-harmonic mixer and a 260-300 GHz frequency tripler in a single cavity. Both devices used GaAs MMIC membrane planar Schottky diode technology. The sub-harmonic mixer/tripler circuit has been tested using conventional machined as well as silicon micro-machined blocks. Measurement results on the metal block give best DSB mixer noise temperature of 2360 K and conversion losses of 7.7 dB at 520 GHz. Preliminary results on the silicon micro-machined blocks give a DSB mixer noise temperature of 4860 K and conversion losses of 12.16 dB at 540 GHz. The LO input power required to pump the integrated tripler/sub-harmonic mixer for both packages is between 30 and 50 mW

  13. Real-time continuous-wave terahertz line scanner based on a compact 1 × 240 InGaAs Schottky barrier diode array detector.

    Science.gov (United States)

    Han, Sang-Pil; Ko, Hyunsung; Kim, Namje; Lee, Won-Hui; Moon, Kiwon; Lee, Il-Min; Lee, Eui Su; Lee, Dong Hun; Lee, Wangjoo; Han, Seong-Tae; Choi, Sung-Wook; Park, Kyung Hyun

    2014-11-17

    We demonstrate real-time continuous-wave terahertz (THz) line-scanned imaging based on a 1 × 240 InGaAs Schottky barrier diode (SBD) array detector with a scan velocity of 25 cm/s, a scan line length of 12 cm, and a pixel size of 0.5 × 0.5 mm². Foreign substances, such as a paper clip with a spatial resolution of approximately 1 mm that is hidden under a cracker, are clearly detected by this THz line-scanning system. The system consists of the SBD array detector, a 200-GHz gyrotron source, a conveyor system, and several optical components such as a high-density polyethylene cylindrical lens, metal cylindrical mirror, and THz wire-grid polarizer. Using the THz polarizer, the signal-to-noise ratio of the SBD array detector improves because the quality of the source beam is enhanced.

  14. Influence of 12 MeV electron irradiation on the electrical and photovoltaic properties of Schottky type solar cell based on Carmine

    Energy Technology Data Exchange (ETDEWEB)

    Aydogan, S., E-mail: saydogan@atauni.edu.t [Atatuerk University, Science Faculty, Department of Physics, Erzurum (Turkey); Tueruet, A. [Atatuerk University, Science Faculty, Department of Physics, Erzurum (Turkey)

    2011-08-15

    A Schottky diode with configuration Au/Carmine/p-Si/Al has been fabricated and it has been seen that the thin film on the p-Si substrate has exhibited a good rectifying behavior. The current-voltage (I-V) characteristics of the device have been investigated in dark before electron irradiation and under white light illumination and after 12 MeV electron irradiation with fluency of 3x10{sup 12} e{sup -}/cm{sup 2}. It has been seen that the device is sensitive to illumination and to electron irradiation. The barrier height value has decreased under illumination. The ideality factor and series resistance values have increased by 12 MeV electron irradiation. Furthermore, it has also seen that the reverse bias current and capacitance of the device have decreased after electron irradiation. This has been attributed to decrease in net ionized dopant concentration with electron irradiation.

  15. Development of a high-voltage waveguide photodetector comprised of Schottky diodes and based on the Ge-Si structure with Ge quantum dots for portable thermophotovoltaic converters

    Science.gov (United States)

    Pakhanov, N. A.; Pchelyakov, O. P.; Yakimov, A. I.; Voitsekhovskii, A. V.

    2017-03-01

    This paper demontstrates the possibility of developing a high-voltage waveguide photodetector comprised of Schottky diodes and based on a Au/Ge — Si structure with Ge quantum dots pseudomorphic to a silicon matrix, which ensures an increase in the external quantum yield and open-circuit voltage. It is shown on this photodetector that there is a great increase and broadening in sensitivity up to λ = 2.1 μm, which coincides with the main radiation range of a black (gray) body at the emitter temperatures from 1200 to 1700 °C, practically used in thermophotovoltaic converters. This state of the ensemble of Ge quantum dots by means of molecular beam epitaxy can be obtained only under the condition of low growth temperature (250-300 °C). It is established that, below the Si absorption edge, photoresponse on the photodetectors under consideration is determined by two main mechanisms: absorption on the ensemble of Ge quantum dots and Fowler emission. It is shown by the analysis of the Raman scattering spectra on the optical photons of Ge-Si structures that the quantum efficiency of photodetectors based on them in the first case is due to the degree of nonuniform stress relaxation in the array of Ge quantum dots. The photoresponse directly associated with the Ge quantum dots is manifested on Schottky diodes with a superthin intermediate oxide layer SiO2, which eliminates the second mechanism. In further development, the proposed photodetector architecture with pseudomorphic Ge quantum dots can be used both for portable thermophotovoltaic converters and fiber-optic data transmission systems at wavelengths corresponding to basic telecommunication standards (λ = 0.85, 1.3 and 1.55, 1.3, and 1.55 μm) on the basis of silicon technologies.

  16. Contact Metallization and Packaging Technology Development for SiC Bipolar Junction Transistors, PiN Diodes, and Schottky Diodes Designed for Long-Term Operations at 350degreeC

    Science.gov (United States)

    2006-05-01

    for high temperature contacts. A Bipolar Junction Transistor ( BJT ) in 4H-SiC can operate at higher temperatures (300oC) because its operation does not...AFRL-PR-WP-TR-2006-2181 CONTACT METALLIZATION AND PACKAGING TECHNOLOGY DEVELOPMENT FOR SiC BIPOLAR JUNCTION TRANSISTORS , PiN DIODES, AND...SUBTITLE CONTACT METALLIZATION AND PACKAGING TECHNOLOGY DEVELOPMENT FOR SiC BIPOLAR JUNCTION TRANSISTORS , PiN DIODES, AND SCHOTTKY DIODES DESIGNED

  17. The role of native point defects and surface chemical reactions in the formation of Schottky barriers and high n-type doping in zinc oxide

    Science.gov (United States)

    Doutt, Daniel R.

    ZnO has received renewed interest in recent years due to its exciting semiconductor properties and remarkable ability to grow nanostructures. As a wide band gap semiconductor, ZnO has many potential future applications including blue/UV light emitters, transparent conductors, biosensors, and electronic nanoscale devices. While the versatility of ZnO is exciting, many hurdles keep it from reaching full device potential. Chief among them are the role of native point defects and impurities in the fabrication of high quality contacts and high, yet controllable, n- and p-type doping. The scope of this work explores the electronic properties of ZnO surfaces and interfaces and the impact of native point defects on Schottky barrier formation and doping. The results presented here use a complement of depth-resolved cathodoluminescence spectroscopy (DRCLS), atomic force microscopy (AFM), Kelvin probe force microscopy (KPFM), and surface photovoltage spectroscopy (SPS) to show that surface treatment and processing plays a significant role in the quality, stability, and efficiency of potential next generation devices. This is evident in our results showing that the Zn-polar surface is more stable and capable of forming higher quality Au Schottky barriers as compared to the O-polar surface. We go on to reveal a significant metal sensitivity and surface polarity dependence that correlates with defects and interface chemistry on ZnO. We've also shown the significant impact of surface preparation and post processing techniques on the optical efficiency and stability of ZnO surfaces. Our measurements reveal that remote oxygen plasma (ROP) processing is capable of decreasing oxygen vacancy related defects (VO-R) on the O-polar surfaces as well as creating new zinc vacancy related (VZn-R) defects on the Zn-polar surface. Furthermore, we have correlated the formation of native point defects with interface chemical reactions and surface morphology on ZnO. With this, we were able to

  18. The electronic and chemical structure of the a-B3CO0.5:Hy-to-metal interface from photoemission spectroscopy: implications for Schottky barrier heights.

    Science.gov (United States)

    Driver, M Sky; Paquette, Michelle M; Karki, S; Nordell, B J; Caruso, A N

    2012-11-07

    The electronic and chemical structure of the metal-to-semiconductor interface was studied by photoemission spectroscopy for evaporated Cr, Ti, Al and Cu overlayers on sputter-cleaned as-deposited and thermally treated thin films of amorphous hydrogenated boron carbide (a-B(x)C:H(y)) grown by plasma-enhanced chemical vapor deposition. The films were found to contain ~10% oxygen in the bulk and to have approximate bulk stoichiometries of a-B(3)CO(0.5):H(y). Measured work functions of 4.7/4.5 eV and valence band maxima to Fermi level energy gaps of 0.80/0.66 eV for the films (as-deposited/thermally treated) led to predicted Schottky barrier heights of 1.0/0.7 eV for Cr, 1.2/0.9 eV for Ti, 1.2/0.9 eV for Al, and 0.9/0.6 eV for Cu. The Cr interface was found to contain a thick partial metal oxide layer, dominated by the wide-bandgap semiconductor Cr(2)O(3), expected to lead to an increased Schottky barrier at the junction and the formation of a space-charge region in the a-B(3)CO(0.5):H (y) layer. Analysis of the Ti interface revealed a thick layer of metal oxide, comprising metallic TiO and Ti (2)O (3), expected to decrease the barrier height. A thinner, insulating Al(2)O(3) layer was observed at the Al-to-a-B(3)CO(0.5):H(y) interface, expected to lead to tunnel junction behavior. Finally, no metal oxides or other new chemical species were evident at the Cu-to-a-B(3)CO(0.5):H(y) interface in either the core level or valence band photoemission spectra, wherein characteristic metallic Cu features were observed at very thin overlayer coverages. These results highlight the importance of thin-film bulk oxygen content on the metal-to-semiconductor junction character as well as the use of Cu as a potential Ohmic contact material for amorphous hydrogenated boron carbide semiconductor devices such as high-efficiency direct-conversion solid-state neutron detectors.

  19. Effect of annealing temperature on the characteristics of ZnO thin films

    Science.gov (United States)

    Chen, Yi; Jyoti, Nayak; Hyun-U, Ko; Kim, Jaehwan

    2012-11-01

    Effect of annealing temperature on characteristics of sol-gel driven ZnO thin film spin-coated on Si substrate was studied. The UV-visible transmittance of the sol decreased with the increase of the aging time and drastically reduced after 20 days aging time. Granular shape of ZnO crystallites was observed on the surface of the films annealed at 550, 650, and 750 °C, and the crystallite size increased with the increase of the annealing temperature. Consequently nodular shape of crystallites was formed upon increasing the annealing temperature to 850 °C and above. The current-voltage characteristics of the Schottky diodes fabricated with ZnO thin films with various annealing temperatures were measured and analyzed. It is found that, ZnO films showed the Schottky characteristics up to 750 °C annealing temperature. The Schottky diode characteristics were diminished upon increasing the annealing temperature above 850 °C. XPS analysis suggested that the absence of oxygen atoms in its oxidized state in stoichiometric surrounding, might be responsible for the diminished forward current of the Schottky diode when annealed above 850 °C.

  20. Nano-scale NiSi and n-type silicon based Schottky barrier diode as a near infra-red detector for room temperature operation

    Energy Technology Data Exchange (ETDEWEB)

    Roy, S. [Centre for Nanotechnology and Science, Indian Institute of Technology Bombay, Mumbai 400076 (India); Centre of Excellence in Nanoelectronics, Indian Institute of Technology Bombay, Mumbai 400076 (India); Midya, K.; Duttagupta, S. P., E-mail: sdgupta@ee.iitb.ac.in [Department of Electrical Engineering, Indian Institute of Technology Bombay, Mumbai 400076 (India); Centre of Excellence in Nanoelectronics, Indian Institute of Technology Bombay, Mumbai 400076 (India); Ramakrishnan, D. [Department of Earth Science, Indian Institute of Technology Bombay, Mumbai 400076 (India)

    2014-09-28

    The fabrication of nano-scale NiSi/n-Si Schottky barrier diode by rapid thermal annealing process is reported. The characterization of the nano-scale NiSi film was performed using Micro-Raman Spectroscopy and X-ray Photoelectron Spectroscopy (XPS). The thickness of the film (27 nm) has been measured by cross-sectional Secondary Electron Microscopy and XPS based depth profile method. Current–voltage (I–V) characteristics show an excellent rectification ratio (I{sub ON}/I{sub OFF} = 10⁵) at a bias voltage of ±1 V. The diode ideality factor is 1.28. The barrier height was also determined independently based on I–V (0.62 eV) and high frequency capacitance–voltage technique (0.76 eV), and the correlation between them has explained. The diode photo-response was measured in the range of 1.35–2.5 μm under different reverse bias conditions (0.0–1.0 V). The response is observed to increase with increasing reverse bias. From the photo-responsivity study, the zero bias barrier height was determined to be 0.54 eV.

  1. Enhancement of programming speed on gate-all-around poly-silicon nanowire nonvolatile memory using self-aligned NiSi Schottky barrier source/drain

    Science.gov (United States)

    Ho, Ching-Yuan; Chang, Yaw-Jen; Chiou, Y. L.

    2013-08-01

    The programming characteristics of gate-all-around silicon-oxide-nitride-oxide silicon (SONOS) nonvolatile memories are presented using NiSi/poly-Si nanowires (SiNW) Schottky barrier (SB) heterojunctions. The non-uniform thermal stress distribution on SiNW channels due to joule heating affected the carrier transport behavior. Under a high drain voltage, impact ionization was found as a large lateral field enhances carrier velocity. As gate voltage (Vg) increased, the difference in the drain current within a range of various temperature conditions can be mitigated because a high gate field lowers the SB height of a NiSi source/SiNW/NiSi drain junction to ensure efficient hot-carrier generation. By applying the Fowler-Nordheim programming voltage to the SONOS nanowire memory, the SB height (Φn = 0.34 eV) could be reduced by image force; thus, hot electrons could be injected from SB source/drain electrodes into the SiN storage node. To compare both SiNW and Si nanocrystal SONOS devices, the SB SiNW SONOS device was characterized experimentally to propose a wider threshold-voltage window, exhibiting efficient programming characteristics.

  2. Schottky solar cell using few-layered transition metal dichalcogenides toward large-scale fabrication of semitransparent and flexible power generator.

    Science.gov (United States)

    Akama, Toshiki; Okita, Wakana; Nagai, Reito; Li, Chao; Kaneko, Toshiro; Kato, Toshiaki

    2017-09-20

    Few-layered transition metal dichalcogenides (TMDs) are known as true two-dimensional materials, with excellent semiconducting properties and strong light-matter interaction. Thus, TMDs are attractive materials for semitransparent and flexible solar cells for use in various applications. Hoewver, despite the recent progress, the development of a scalable method to fabricate semitransparent and flexible solar cells with mono- or few-layered TMDs remains a crucial challenge. Here, we show easy and scalable fabrication of a few-layered TMD solar cell using a Schottky-type configuration to obtain a power conversion efficiency (PCE) of approximately 0.7%, which is the highest value reported with few-layered TMDs. Clear power generation was also observed for a device fabricated on a large SiO 2 and flexible substrate, demonstrating that our method has high potential for scalable production. In addition, systematic investigation revealed that the PCE and external quantum efficiency (EQE) strongly depended on the type of photogenerated excitons (A, B, and C) because of different carrier dynamics. Because high solar cell performance along with excellent scalability can be achieved through the proposed process, our fabrication method will contribute to accelerating the industrial use of TMDs as semitransparent and flexible solar cells.

  3. The determination of the interface state density distribution of the Al/methyl red/p-Si Schottky barrier diode by using a capacitance method

    Energy Technology Data Exchange (ETDEWEB)

    Kilicoglu, T. [Department of Physics, Faculty of Science and Art, University of Dicle, Diyarbakir 21280 (Turkey)]. E-mail: tahsin@dicle.edu.tr; Aydin, M.E. [Department of Physics, Faculty of Science and Art, University of Dicle, Diyarbakir 21280 (Turkey); Ocak, Y.S. [Department of Physics, Faculty of Science and Art, University of Dicle, Diyarbakir 21280 (Turkey)

    2007-01-15

    Al/methyl red/p-Si Schottky barrier diodes (SBD) have been fabricated by adding a solution of the non-polymeric organic compound methyl red in chloroform on top of p-Si substrates, and then evaporating the solvent. The electronic and interface state density distribution properties were obtained from the current-voltage (I-V) and the capacitance-voltage (C-V) characteristics (high and low frequency) of Al/methyl red/p-Si SBD at room temperature. The energy distribution of the interface state density located in the inorganic semiconductor band gap at the organic compound/inorganic semiconductor interface in the energy range from (0.675-E{sub v})eV to (0.783-E{sub v})eV has been determined. In addition, the interface state density N{sub ss} range from 6.12x10{sup 13}cm{sup -2}eV{sup -1} in (0.675-E{sub v})eV to 4.31x10{sup 12}cm{sup -2}eV{sup -1} in (0.783-E{sub v})eV. The interface state density has an exponential rise with bias from the mid-gap towards the top of the valence band.

  4. Tuning the p-type Schottky barrier in 2D metal/semiconductor interface:boron-sheet on MoSe2, and WSe2

    Science.gov (United States)

    Couto, W. R. M.; Miwa, R. H.; Fazzio, A.

    2017-10-01

    Van der Waals (vdW) metal/semiconductor heterostructures have been investigated through first-principles calculations. We have considered the recently synthesized borophene (Mannix et al 2015 Science 350 1513), and the planar boron sheets (S1 and S2) (Feng et al 2016 Nat. Chem. 8 563) as the 2D metal layer, and the transition metal dichalcogenides (TMDCs) MoSe2, and WSe2 as the semiconductor monolayer. We find that the energetic stability of those 2D metal/semiconductor heterojunctions is mostly ruled by the vdW interactions; however, chemical interactions also take place in borophene/TMDC. The electronic charge transfer at the metal/semiconductor interface has been mapped, where we find a a net charge transfer from the TMDCs to the boron sheets. Further electronic structure calculations reveal that the metal/semiconductor interfaces, composed by planar boron sheets S1 and S2, present a p-type Schottky barrier which can be tuned to a p-type ohmic contact by an external electric field.

  5. Low-Temperature Growth of Well-Aligned ZnO Nanorod Arrays by Chemical Bath Deposition for Schottky Diode Application

    Science.gov (United States)

    Yuan, Zhaolin

    2015-04-01

    A well-aligned ZnO nanorod array (ZNRA) was successfully grown on an indium tin oxide (ITO) substrate by chemical bath deposition at low temperature. The morphology, crystalline structure, transmittance spectrum and photoluminescence spectrum of as-grown ZNRA were investigated by field emission scanning electron microscopy, x-ray diffraction, ultraviolet-visible spectroscopy and spectrophotometer, respectively. The results of these measurements showed that the ZNRA contained densely packed, aligned nanorods with diameters from 30 nm to 40 nm and a wurtzite structure. The ZNRA exhibited good optical transparency within the visible spectral range, with >80% transmission. Gold (Au) was deposited on top of the ZNRA, and the current-voltage characteristics of the resulting ITO/ZNRA/Au device in the dark were evaluated in detail. The ITO/ZNRA/Au device acted as a Schottky barrier diode with rectifying behaviour, low turn-on voltage (0.6 V), small reverse-bias saturation current (3.73 × 10-6 A), a high ideality factor (3.75), and a reasonable barrier height (0.65 V) between the ZNRA and Au.

  6. Schottky barrier contacts formed on polar and nonpolar Mg{sub x}Zn{sub 1-x}O films grown by remote plasma enhanced MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, A.; Hayashi, T.; Temmyo, J. [Research Institute of Electronics, Shizuoka University, 3-5-1 Johoku, Hamamatsu 432-8011 (Japan); Hierro, A.; Tabares, G.; Ulloa, J.M.; Munoz, E. [Dpto. Ingenieria Electronica and ISOM, Universidad Politechnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain)

    2010-06-15

    The growth of Mg{sub x}Zn{sub 1-x}O films of both polar and nonpolar orientation in was successfully carried out by remote-plasma-enhanced MOCVD (RPE-MOCVD) technique. The polar face of as-grown film had a vertically aligned columnar growth with respect to the sapphire (11-20) substrate. These columns had an average diameter of about 40 nm. In contrast, the nonpolar face of as-grown film had a sword-shape lying with an average width of 250 nm on the sapphire (10-12) substrate. Au/Schottky diodes (SDs) were fabricated on both polar face of c-plane (0001) Mg{sub x}Zn{sub 1-x}O and nonpolar face of a-plane (11-20) Mg{sub x}Zn{sub 1-x}O. A rectifying behavior had been achieved and a series resistance was increased with Mg contents in both polar and nonpolar diodes. A residual electron concentration was decreased with the Mg content from 3 x 10{sup 17} cm{sup -3} at x = 0 to 1.2 x 10{sup 16} cm{sup -3} at x = 0.18 in the case of nonpolar films. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  7. Capacitance behavior of InAlN Schottky diodes in presence of large concentrations of shallow and deep states related to oxygen

    Science.gov (United States)

    Py, M. A.; Lugani, L.; Taniyasu, Y.; Carlin, J.-F.; Grandjean, N.

    2015-05-01

    The capacitance-voltage-temperature characteristics of nonintentionally doped In0.16Al0.84N/n+-GaN Schottky diodes were measured at 1 MHz and in the 90-400 K range. They are discussed in the framework of existing theories, which properly treat the Poisson's equation, especially near the edge of the space-charge region, the so-called transition region. The concentration of a shallow donor and of a deep DX-like center, previously reported, is properly determined. The key parameter to discuss the temperature dependence of the capacitance is the ratio between the frequency of the small ac modulating signal and the temperature-dependent emission rate associated to each level. The capacitance-voltage C-Va curves were successfully fitted using a three parameters expression over the full range of temperatures. The concentration of both shallow and deep levels exceeds a few 1018 cm-3. Based on secondary ion mass spectrometry profiling, we assign both levels to the dominant oxygen impurity. This result supports our previous assignment of the shallow donor to a substitutional oxygen atom on a nitrogen site and the deep state to an O-related DX center, naturally explaining its high concentration. The sluggish kinetics at low temperatures, associated to the large concentration of deep levels located near the transition region, is illustrated by hysteresis loops in the C-Va curves below 270 K. Furthermore, the contribution of free carriers to the capacitance is revealed below 150 K, when both shallow and deep donors cannot respond anymore due to an emission rate lower than the 1 MHz modulating frequency. Finally, the presence of a highly doped thin surface barrier, as already reported in other III-nitrides, finds further support.

  8. Ultra-low turn-on voltage and on-resistance vertical GaN-on-GaN Schottky power diodes with high mobility double drift layers

    Science.gov (United States)

    Fu, Houqiang; Huang, Xuanqi; Chen, Hong; Lu, Zhijian; Baranowski, Izak; Zhao, Yuji

    2017-10-01

    This letter reports the implementation of double-drift-layer (DDL) design into GaN vertical Schottky barrier diodes (SBDs) grown on free-standing GaN substrates. This design balances the trade-off between desirable forward turn-on characteristics and high reverse breakdown capability, providing optimal overall device performances for power switching applications. With a well-controlled metalorganic chemical vapor deposition process, the doping concentration of the top drift layer was reduced, which served to suppress the peak electric field at the metal/GaN interface and increase the breakdown voltages of the SBDs. The bottom drift layer was moderately doped to achieve low on-resistance to reduce power losses. At forward bias, the devices exhibited a record low turn-on voltage of 0.59 V, an ultra-low on-resistance of 1.65 mΩ cm2, a near unity ideality factor of 1.04, a high on/off ratio of ˜1010, and a high electron mobility of 1045.2 cm2/(V s). Detailed comparisons with conventional single-drift-layer (SDL) GaN vertical SBDs indicated that DDL design did not degrade the forward characteristics of the SBDs. At reverse bias, breakdown voltages of the DDL GaN SBDs were considerably enhanced compared to those of the conventional SDL devices. These results showed that GaN vertical SBDs with DDL designs are promising candidates for high efficiency, high voltage, high frequency power switching applications.

  9. Cupric and cuprous oxide by reactive ion beam sputter deposition and the photosensing properties of cupric oxide metal–semiconductor–metal Schottky photodiodes

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Min-Jyun; Lin, Yong-Chen; Chao, Liang-Chiun, E-mail: lcchao@mail.ntust.edu.tw; Lin, Pao-Hung; Huang, Bohr-Ran

    2015-08-15

    Highlights: • CuO and Cu{sub 2}O were deposited by reactive ion beam sputter deposition. • Single phase CuO thin film is obtained with Ar:O{sub 2} = 2:1. • CuO MSM PD shows photoresponse from 400 nm to 1.30 μm. • CuO MSM PD is RC limited with a decay time less than 1 μs. - Abstract: Cupric (CuO) and cuprous (Cu{sub 2}O) oxide thin films have been deposited by reactive ion beam sputter deposition at 400 °C with an Ar:O{sub 2} ratio from 2:1 to 12:1. With an Ar:O{sub 2} ratio of 2:1, single phase polycrystalline CuO thin films were obtained. Decreasing oxygen flow rate results in CuO + Cu{sub 2}O and Cu{sub 2}O + Cu mixed thin films. As Ar:O{sub 2} ratio reaches 12:1, Cu{sub 2}O nanorods with diameter of 250 nm and length longer than 1 μm were found across the sample. Single phase CuO thin film exhibits an indirect band gap of 1.3 eV with a smooth surface morphology. CuO metal–semiconductor–metal (MSM) Schottky photodiodes (PD) were fabricated by depositing Cu interdigitated electrodes on CuO thin films. Photosensing properties of the CuO PD were characterized from 350 to 1300 nm and a maximum responsivity of 43 mA/W was found at λ = 700 nm. The MSM PD is RC limited with a decay time constant less than 1 μs.

  10. The Annealing Effects of ZnO Thin Films on Characteristic Parameters of Au/ZnO Schottky Contacts on n-Si

    OpenAIRE

    A. Toprak; T. Kilicoglu; Y.S. Ocak; K. Akkilic

    2012-01-01

    200 nm ZnO thin films have been grown on n type Silicon substrates by DC sputtering technique. One of the thin films has been annealed at 300 ºC for 45 minutes. The Au front contacts on ZnO thin films have been formed by evaporation of Au metal by means of shadow mask. It has been seen that the rectification ratio of Au/ZnO device obtained using annealed ZnO thin film is higher than the one obtained using unannealed ZnO thin film. The characteristic parameters of Au/ZnO junctions such as idea...

  11. Tunable photovoltaic effect and solar cell performance of self-doped perovskite SrTiO3

    Directory of Open Access Journals (Sweden)

    K. X. Jin

    2012-12-01

    Full Text Available We report on the tunable photovoltaic effect of self-doped single-crystal SrTiO3 (STO, a prototypical perovskite-structured complex oxide, and evaluate its performance in Schottky junction solar cells. The photovaltaic characteristics of vacuum-reduced STO single crystals are dictated by a thin surface layer with electrons donated by oxygen vacancies. Under UV illumination, a photovoltage of 1.1 V is observed in the as-received STO single crystal, while the sample reduced at 750 °C presents the highest incident photon to carrier conversion efficiency. Furthermore, in the STO/Pt Schottky junction, a power conversion efficiency of 0.88% was achieved under standard AM 1.5 illumination at room temperature. This work establishes STO as a high-mobility photovoltaic semiconductor with potential of integration in self-powered oxide electronics.

  12. Introduction to Space Charge Effects in Semiconductors

    CERN Document Server

    Böer, Karl W

    2010-01-01

    This book is the most comprehensive one to describe the basics of space-charge effects in semiconductors, starting from basic principles to advanced application in semiconducting devices. It uses detailed analyses of the transport, Poisson, and continuity equations to demonstrate the behavior of the solution curves of the complete set of field and current distributions, along with quantitative descriptions of the relevant band models of typical pn-junction and Schottky barrier devices. It emphasizes the relevance to actual devices and sets these results apart from more simple models of networks of diodes and resistors. The book is especially important for people interested in detail analysis of solar cells and their efficiencies.

  13. High temperature operation of n-AlGaN channel metal semiconductor field effect transistors on low-defect AlN templates

    Science.gov (United States)

    Muhtadi, S.; Hwang, S.; Coleman, A.; Asif, F.; Lunev, A.; Chandrashekhar, M. V. S.; Khan, A.

    2017-05-01

    We report room-temperature to 200 °C operation of n-Al0.65Ga0.35N channel metal semiconductor field effect transistors (MESFET) grown over high-quality AlN/sapphire templates. For this temperature range, the source-drain currents, threshold voltages, and dc-transconductance values remain nearly unchanged with an estimated field-effect mobility of ˜90 cm2/V-s at 200 °C and currents of >100 mA/mm. The analysis of the temperature dependent current-voltage characteristics of the gate-source Schottky barrier diode reveals that the leakage currents arise from Frenkel-Poole emission. The capacitance-voltage data show no hysteresis, indicating a high quality Schottky barrier interface. These MESFET's have excellent potential for use as a high temperature power electronic or a solar-blind ultraviolet sensing device.

  14. Effect of temperature on passive film formation of UNS N08031 Cr-Ni alloy in phosphoric acid contaminated with different aggressive anions

    OpenAIRE

    ESCRIVÁ CERDÁN, CLARA; Blasco Tamarit, María Encarnación; García García, Dionisio Miguel; García Antón, José; Akid, R.; Walton, J.

    2013-01-01

    tThe influence of temperature and the effect of aggressive anions on the electrochemical behaviour of UNSN08031 stainless steel in a contaminated phosphoric acid solution were evaluated. Stabilisation of thepassive film was studied by potentiodynamic polarisation curves, potentiostatic tests, electrochemicalimpedance spectroscopy (EIS) measurements, Mott Schottky analysis and X-ray photoelectron spec-troscopy (XPS). The stability of the passive film was found to decrease as temperature increa...

  15. Optical Orientation and Inverse Spin Hall Effect as Effective Tools to Investigate Spin-Dependent Diffusion

    Directory of Open Access Journals (Sweden)

    Marco Finazzi

    2016-11-01

    Full Text Available In this work we address optical orientation, a process consisting in the excitation of spin polarized electrons across the gap of a semiconductor. We show that the combination of optical orientation with spin-dependent scattering leading to the inverse spin-Hall effect, i.e., to the conversion of a spin current into an electrical signal, represents a powerful tool to generate and detect spin currents in solids. We consider a few examples where these two phenomena together allow addressing the spin-dependent transport properties across homogeneous samples or metal/semiconductor Schottky junctions.

  16. Design and optimization of high-performance slot-microring Si-photodetector based on internal photoemission effect

    Science.gov (United States)

    Hosseinifar, Mitra; Ahmadi, Vahid; Ebnali-Heidari, Majid

    2017-08-01

    This paper presents the design and optimization of a microring resonator enhanced-internal photoemission effect-photodetectors (MRRE-IPE-PDs) suitable for optical communication. Two PD configurations are considered: the first consists of an MRR that is partially surrounded by a nanolayer of silicide with a single Schottky barrier on p-Si MRR; and the second consists of a silicide film buried in the width midpoints of a Si-based MRR where photoemission occurs over the two Schottky barriers. Several silicides are considered for the stripe (PtSi, Pd2Si, TaSi2 and CoSi2). The important features of the device, such as quantum efficiency (QE), responsivity, CW sensitivity and dark current are discussed and the trade-off between 3 dB bandwidth and QE are analyzed for nanoscaled absorption layer. In this regard, some design curves are presented for the optimized MRRE-IPE-PDs. Additionally, this paper reveals substantial improvement via comparisons with QE and responsivity measurements reported in the literature. Bandwidth-efficiency product of 61-71 GHz, responsivities of 0.8-0.9 and QE of 64-71% and the minimum receiver sensitivity of -65 to -66 dBm are also predicted for single and double Schottky barriers, respectively.

  17. Au-gated SrTiO{sub 3} field-effect transistors with large electron concentration and current modulation

    Energy Technology Data Exchange (ETDEWEB)

    Verma, Amit, E-mail: averma@nd.edu; Jena, Debdeep [Department of Electrical Engineering, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Raghavan, Santosh; Stemmer, Susanne [Materials Department, University of California, Santa Barbara, California 93106 (United States)

    2014-09-15

    We report the fabrication of low-leakage rectifying Pt and Au Schottky diodes and Au-gated metal-semiconductor field effect transistors (MESFETs) on n-type SrTiO{sub 3} thin films grown by hybrid molecular beam epitaxy. In agreement with previous studies, we find that compared to Pt, Au provides a higher Schottky barrier height with SrTiO{sub 3}. As a result of the large dielectric constant of SrTiO{sub 3} and the large Schottky barrier height of Au, the Au-gated MESFETs are able to modulate ∼1.6 × 10{sup 14 }cm{sup −2} electron density, the highest modulation yet achieved using metal gates in any material system. These MESFETs modulate current densities up to ∼68 mA/mm, ∼20× times larger than the best demonstrated SrTiO{sub 3} MESFETs. We also discuss the roles of the interfacial layer, and the field-dependent dielectric constant of SrTiO{sub 3} in increasing the pinch off voltage of the MESFET.

  18. Piezotronic and Piezophototronic Effects

    KAUST Repository

    Wang, Zhong Lin

    2010-05-06

    Owing to the polarization of ions in a crystal that has noncentral symmetry, a piezoelectric potential (piezopotential) is created in the material by applying a stress. The creation of piezopotential together with the presence of Schottky contacts are the fundamental physics responsible for a few important nanotechnologies. The nanogenerator is based on the piezopotential-driven transient flow of electrons in the external load. On the basis of nanomaterials in the wurtzite semiconductors, such as ZnO and GaN, electronics fabricated by using a piezopotential as a gate voltage are called piezotronics, with applications in strain/force/pressure-triggered/controlled electronic devices, sensors, and logic gates. The piezophototronic effect is a result of three-way coupling among piezoelectricity, photonic excitation, and semiconductor transport, which allows tuning and controlling of electro-optical processes by a strain-induced piezopotential. © 2010 American Chemical Society.

  19. van der Waals Schottky barriers as interface probes of the correlation between chemical potential shifts and charge density wave formation in 1 T -TiSe2 and 2 H -NbSe2

    Science.gov (United States)

    Li, Ang J.; Zhu, Xiaochen; Rhodes, Daniel; Samouce, Christopher C.; Balicas, Luis; Hebard, Arthur F.

    2017-09-01

    Layered transition-metal dichalcogenide (TMD) materials, i.e., 1 T -TiSe2 and 2 H -NbSe2 , harbor a second-order charge density wave (CDW) transition where phonons play a key role for the periodic modulations of conduction electron densities and associated lattice distortions. We systematically study the transport and capacitance characteristics over a wide temperature range of Schottky barriers formed by intimately contacting freshly exfoliated flakes of 1 T -TiSe2 and 2 H -NbSe2 to n -type GaAs semiconductor substrates. The extracted temperature-dependent parameters (zero-bias barrier height, ideality, and built-in potential) reflect changes at the TMD/GaAs interface induced by CDW formation for both TMD materials. The measured built-in potential reveals chemical-potential shifts relating to CDW formation. With decreasing temperature a peak in the chemical-potential shifts during CDW evolution indicates a competition between electron energy redistributions and a combination of lattice strain energies and Coulomb interactions. These modulations of chemical potential in CDW systems, such as 1 T -TiSe2 and 2 H -NbSe2 harboring second-order phase transitions, reflect a corresponding conversion from short-range to long-range order.

  20. Contact effects in graphene nanoribbon transistors.

    Science.gov (United States)

    Liang, Gengchiau; Neophytou, Neophytos; Lundstrom, Mark S; Nikonov, Dmitri E

    2008-07-01

    The effects of the various contact types and shapes on the performance of Schottky barrier graphene nanoribbon field-effect-transistors (GNRFETs) have been investigated using a real-space quantum transport simulator based on the NEGF approach self-consistently coupled to a three-dimensional Poisson solver for treating the electrostatics. The device channel considered is a double gate semiconducting armchair nanoribbon. The types of contacts considered are (a) a semi-infinite normal metal, (b) a semi-infinite graphene sheet, (c) finite size rectangular shape armchair graphene contacts, (d) finite size wedge shape graphene contacts, and (e) zigzag graphene nanoribbon contacts. Among these different contact types, the semi-infinite graphene sheet contacts show the worst performance because of their very low density of states around the Dirac point resulting in low transmission possibility through the Schottky barrier, both at ON and OFF states. Although all other types of contacts can have significant enhancement in I ON to I OFF ratio, the zigzag GNR contacts show promising and size invariant performance due to the metallic properties.

  1. Reconfigurable Complementary Monolayer MoTe2 Field-Effect Transistors for Integrated Circuits.

    Science.gov (United States)

    Larentis, Stefano; Fallahazad, Babak; Movva, Hema C P; Kim, Kyounghwan; Rai, Amritesh; Taniguchi, Takashi; Watanabe, Kenji; Banerjee, Sanjay K; Tutuc, Emanuel

    2017-05-23

    Transition metal dichalcogenides are of interest for next generation switches, but the lack of low resistance electron and hole contacts in the same material has hindered the development of complementary field-effect transistors and circuits. We demonstrate an air-stable, reconfigurable, complementary monolayer MoTe2 field-effect transistor encapsulated in hexagonal boron nitride, using electrostatically doped contacts. The introduction of a multigate design with prepatterned bottom contacts allows us to independently achieve low contact resistance and threshold voltage tuning, while also decoupling the Schottky contacts and channel gating. We illustrate a complementary inverter and a p-i-n diode as potential applications.

  2. Effect of growth temperature on photoluminescence and piezoelectric characteristics of ZnO nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Water, Walter [Institute of Electro-Optical and Materials Science, National Formosa University, Yunlin 632, Taiwan (China); Fang, T.-H. [Institute of Electro-Optical and Materials Science, National Formosa University, Yunlin 632, Taiwan (China); Institute of Mechanical and Electromechanical Engineering, National Formosa University, Yunlin 632, Taiwan (China)], E-mail: fang.tehua@msa.hinet.net; Ji, L.-W.; Lee, C.-C. [Institute of Electro-Optical and Materials Science, National Formosa University, Yunlin 632, Taiwan (China)

    2009-02-25

    ZnO nanowire arrays were synthesized on Au-coated silicon (1 0 0) substrates by using vapour-liquid-solid process in this work. The effect of growth temperatures on the crystal structure and the surface morphology of ZnO nanowires were investigated by X-ray diffraction and scanning electron microscope. The absorption and optical characteristics of the nanowires were examined by Ultraviolet/Visible spectroscopy, and photoluminescence, respectively. The photoluminescence results exhibited ZnO nanowires had an ultraviolet and blue emission at 383 and 492 nm. Then a nanogenerator with ZnO nanowire arrays was fabricated and demonstrated Schottky-like current-voltage characteristics.

  3. EIS, Mott Schottky and EFM analysis of the electrochemical stability and dielectric properties of Ca-P-Ag and Ca-P-Si-Ag coatings obtained by plasma electrolytic oxidation in Ti6Al4V

    Directory of Open Access Journals (Sweden)

    Sara María Leal-Marin

    2017-01-01

    Full Text Available El Ti6Al4V ELI (ASTM F136 es una de las aleaciones más empleadas en dispositivos de osteosíntesis y reemplazo articular. Sin embargo, las propiedades de esta aleación pueden ser mejoradas respecto a su biocompatibilidad y osteointegración con el tejido óseo a través de recubrimientos. El objetivo de este trabajo fue evaluar el comportamiento electroquímico de un recubrimiento obtenido por oxidación por plasma electrolítico sobre Ti6Al4V ELI empleando soluciones electrolíticas enriquecidas con iones de PO4 2-, Ca+2, Si+4 y varias concentraciones de Ag+1. Los recubrimientos se caracterizaron mediante espectroscopia de impedancia electroquímica (EIS y Mott-Schottky (M-S en una celda de tres electrodos con una solución fisiológica simulada. El comportamiento electroquímico se contrastó con microscopía de fuerza electrostática (EFM, donde se analizó el potencial eléctrico del recubrimiento. Los resultados de EIS mostraron mejores propiedades de estabilidad frente a la corrosión en los sustratos recubiertos con Ca- P-Ag, comparados con los recubiertos con Ca-P-Si-Ag. Los espectros de Nyquist y Bode mostraron relajaciones relacionadas con la transferencia de carga hacia la doble capa electroquímica como reflejo de los cambios microestructurales y de conductividad de los recubrimientos, dada por la presencia particular en cada caso, de los elementos contenidos en estos. De acuerdo con los resultados de M-S, todas las muestras ensayadas presentaron un comportamiento con dopado tipo n, cuya conductividad incrementó con la inclusión de plata. Mediante EFM se observaron mayores contrastes en el potencial, fase y la amplitud de los recubrimientos con mayor cantidad de plata respecto al Ti6Al4V sin recubrir.

  4. Electric field and space-charge distribution in SI GaAs: effect of high-energy proton irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Castaldini, A.; Cavallini, A. E-mail: anna.cavallini@bo.infn.it; Polenta, L.; Canali, C.; Nava, F

    1999-04-21

    The effect of irradiation on semi-insulating gallium arsenide Schottky diodes has been investigated by means of surface potential measurements and spectroscopic techniques. Before and after irradiation the electric field exhibits a Mott barrier-like distribution, and the box-shaped space charge modifies its distribution with irradiation. The increase in density or the generation of some traps changes the compensation ratio producing a deeper active region and a more homogeneous distribution of the electric field. The latter phenomenon is also observed by EBIC images of edge-mounted diodes.

  5. Electric field and space-charge distribution in SI GaAs: effect of high-energy proton irradiation

    CERN Document Server

    Castaldini, A; Polenta, L; Canali, C; Nava, F

    1999-01-01

    The effect of irradiation on semi-insulating gallium arsenide Schottky diodes has been investigated by means of surface potential measurements and spectroscopic techniques. Before and after irradiation the electric field exhibits a Mott barrier-like distribution, and the box-shaped space charge modifies its distribution with irradiation. The increase in density or the generation of some traps changes the compensation ratio producing a deeper active region and a more homogeneous distribution of the electric field. The latter phenomenon is also observed by EBIC images of edge-mounted diodes.

  6. Silicon Schottky Diode Safe Operating Area

    Science.gov (United States)

    Casey, Megan C.; Campola, Michael J.; Lauenstein, Jean-Marie; Wilcox, Edward P.; Phan, Anthony M.; LaBel, Kenneth A.

    2016-01-01

    Vulnerability of a variety of candidate spacecraft electronics to total ionizing dose and displacement damage is studied. Devices tested include optoelectronics, digital, analog, linear bipolar devices, and hybrid devices.

  7. Feasibility Study of Schottky Emitter Arrays

    NARCIS (Netherlands)

    Dokania, A.K.

    2010-01-01

    In this thesis an attempt is made to make a step forward in the development of next a generation scanning electron lithography machine for sub 25nm chip making. One of the challenges for such a system is to have sufficient beam-lets with enough current for parallel writing which requires a

  8. Performance assessment of nanoscale Schottky MOSFET as ...

    Indian Academy of Sciences (India)

    Author Affiliations. Zahra Ahangari1 Morteza Fathipour2. Department of Electrical Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran; School of Electrical and Computer Engineering, University of Tehran, Tehran, Iran ...

  9. Photon energy dependence of photo-induced inverse spin-Hall effect in Pt/GaAs and Pt/Ge

    Energy Technology Data Exchange (ETDEWEB)

    Isella, Giovanni, E-mail: giovanni.isella@polimi.it; Bottegoni, Federico; Ferrari, Alberto; Finazzi, Marco; Ciccacci, Franco [LNESS-Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy)

    2015-06-08

    We report the photon energy dependence of photo-induced inverse spin Hall effect (ISHE) in Pt/GaAs and Pt/Ge Schottky junctions. The experimental results are compared with a spin drift-diffusion model, which highlights the role played by the different spin lifetime in the two semiconductors, in determining the energy dependence of the ISHE signal detected in the Pt layer. The good qualitative agreement between experiments and modelling indicates that photo-induced ISHE can be used as a tool to characterize spin lifetime in semiconductors.

  10. Asymmetric nonlinear response of the quantized Hall effect

    Science.gov (United States)

    Siddiki, A.; Horas, J.; Kupidura, D.; Wegscheider, W.; Ludwig, S.

    2010-11-01

    An asymmetric breakdown of the integer quantized Hall effect (IQHE) is investigated. This rectification effect is observed as a function of the current value and its direction in conjunction with an asymmetric lateral confinement potential defining the Hall bar. Our electrostatic definition of the Hall bar via Schottky gates allows a systematic control of the steepness of the confinement potential at the edges of the Hall bar. A softer edge (flatter confinement potential) results in more stable Hall plateaus, i.e. a breakdown at a larger current density. For one soft and one hard edge, the breakdown current depends on its direction, resembling rectification. This nonlinear magneto-transport effect confirms the predictions of an emerging screening theory of the IQHE.

  11. Low dislocation density InAlN/AlN/GaN heterostructures grown on GaN substrates and the effects on gate leakage characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Kotani, Junji, E-mail: kotani.junji-01@jp.fujitsu.com; Yamada, Atsushi; Ishiguro, Tetsuro; Tomabechi, Shuichi; Nakamura, Norikazu [Fujitsu Laboratories Ltd., 10-1 Morinosato-Wakamiya, Atsugi, Kanagawa 243-0197 (Japan)

    2016-04-11

    This paper reports on the electrical characterization of Ni/Au Schottky diodes fabricated on InAlN high-electron-mobility transistor (HEMT) structures grown on low dislocation density free-standing GaN substrates. InAlN HEMT structures were grown on sapphire and GaN substrates by metal-organic vapor phase epitaxy, and the effects of threading dislocation density on the leakage characteristics of Ni/Au Schottky diodes were investigated. Threading dislocation densities were determined to be 1.8 × 10{sup 4 }cm{sup −2} and 1.2 × 10{sup 9 }cm{sup −2} by the cathodoluminescence measurement for the HEMT structures grown on GaN and sapphire substrates, respectively. Leakage characteristics of Ni/Au Schottky diodes were compared between the two samples, and a reduction of the leakage current of about three to four orders of magnitude was observed in the forward bias region. For the high reverse bias region, however, no significant improvement was confirmed. We believe that the leakage current in the low bias region is governed by a dislocation-related Frenkel–Poole emission, and the leakage current in the high reverse bias region originates from field emission due to the large internal electric field in the InAlN barrier layer. Our results demonstrated that the reduction of dislocation density is effective in reducing leakage current in the low bias region. At the same time, it was also revealed that another approach will be needed, for instance, band modulation by impurity doping and insertion of insulating layers beneath the gate electrodes for a substantial reduction of the gate leakage current.

  12. The Effect of the Electron Tunneling on the Photoelectric Hot Electrons Generation in Metallic-Semiconductor Nanostructures

    Science.gov (United States)

    Elsharif, Asma M.

    2018-01-01

    Semiconductor photonic crystals (MSPhC) were used to convert solar energy into hot electrons. An experimental model was designed by using metallic semiconductor photonic crystals (MSPhC). The designed MSPhC is based on TiO2/Au schottky contact. The model has similar nanocavity structure for broad gold absorption, but the materials on top of the cavity were changed to a metal and a semiconductor in order to collect the hot electrons. Detailed design steps and characterization have shown a broadband sub-bandgap photoresponse at a wavelength of 590 nm. This is due to the surface plasmon absorption by the wafer-scale Au/TiO2 metallic-semiconductor photonic crystal. Analytical calculation of the hot electron transport from the Au thin layer to the TiO2 conduction band is discussed. This theoretical study is based on the quantum tunneling effect. The photo generation of the hot electrons was undertaken at different wavelengths in Au absorber followed by tunneling through a schottky barrier into a TiO2 collector. The presence of a tunnel current from the absorber to the collector under illumination, offers a method to extract carriers from a hot-electron distribution at few bias voltages is presented in this study. The effects of doping different concentrations of the semiconductor on the evolution of the current characteristics were also investigated and discussed. The electrical characteristics were found to be sensitive to any change in the thickness of the barrier.

  13. Au/P3HT:PCBM/n-Si Schottky Bariyer Diyotlarda PCBM Konsantrasyonunun Kapasitans-Voltaj (C-V ve İletkenlik-Voltaj (G/w-V Karakteristiklerine Etkisi ve Dielektrik Özelliklerin İncelemesi

    Directory of Open Access Journals (Sweden)

    Hüseyin Muzaffer ŞAĞBAN

    2016-01-01

    Full Text Available Bu çalışmada, farklı P3HT:PCBM katkı oranları (4:1 ve 10:1 kullanılarak hazırlanan altın/poly(3-hexylthiophene:[6,6]-phenyl C61 butyric acid methyl ester/n-tipi silisyum (Au/P3HT:PCBM/n-Si metal–polimer–yarıiletken (MPY Schottky bariyer diyotların (SBD kapasitans-voltaj (C-V ve iletkenlik-voltaj (G/w-V karakteristikleri, oda sıcaklığında ve 1 MHz frekans değerinde karşılaştırılmıştır. 4:1 ve 10:1 P3HT:PCBM katkı oranlarına sahip numuneler için, C-V ve G/w-V ölçümlerinden arayüzey durum yoğunlukları (Nss ve seri dirençleri (RS hesaplanmıştır. Analiz sonuçlarına göre aktif katman (P3HT:PCBM içerisindeki PCBM katkısının arttırılmasıyla yani 4:1 oranında P3HT:PCBM arayüzey kullanılarak üretilen MPY SBD daha ideal performans göstermiştir. Bu sonuç göz önüne alınarak, daha iyi bir performans sergileyen 4:1 P3HT:PCBM katkı oranına sahip Au/P3HT:PCBM/n-Si MPY SBD’nin frekansa bağlı dielektrik karakteristikleri, oda sıcaklığında 10 kHz-2 MHz frekans aralığında yapılan ölçümler ile incelenmiştir. 4:1 P3HT:PCBM oranı ile üretilen MPY SBD için C-V ve G/w-V ölçümleri kullanılarak, dielektrik sabit (ε', dielektrik kayıp (ε'', kayıp tanjantı (tanδ, ac iletkenlik (sac ve elektrik modülünün reel ve imajiner kısımları (M' ve M'' hesaplanmıştır. Buna göre, ε' ve ε'' değerleri frekansın artmasıyla azalmaktayken kayıp tanjantı değerlerinde ise frekansla neredeyse hiçbir değişim olmadığı gözlemlenmiştir. ε' ve ε'' değerlerinde frekansa bağlı olarak ortaya çıkan bu değişimin arayüzey polarizasyonundan kaynaklandığı düşünülmektedir. Diğer yandan, sac, M' ve M'' parametrelerinin ise artan frekans ile arttığı gözlemlenmiştir. Elde edilen sonuçlar doğrultusunda, Au/P3HT:PCBM/n-Si MPY SBD için bu parametrelerin güçlü bir şekilde frekansa bağlı olduğu bulunmuştur. Bununla birlikte, bu çalışmada, P3HT:PCBM organik polimer

  14. Two-dimensional plasmons in lateral carbon nanotube network structures and their effect on the terahertz radiation detection

    Energy Technology Data Exchange (ETDEWEB)

    Ryzhii, V. [Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577 (Japan); Institute of Ultra High Frequency Semiconductor Electronics of RAS, Moscow 117105 (Russian Federation); Center for Photonics and Infrared Engineering, Bauman Moscow State Technical University, Moscow 111005 (Russian Federation); Otsuji, T. [Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577 (Japan); Ryzhii, M. [Department of Computer Science and Engineering, University of Aizu, Aizu-Wakamatsu 965-8580 (Japan); Leiman, V. G. [Department of General Physics, Moscow Institute of Physics and Technology, Dolgoprudny, 147100 (Russian Federation); Fedorov, G. [Department of General Physics, Moscow Institute of Physics and Technology, Dolgoprudny, 147100 (Russian Federation); Physics Department, Moscow State Pedagogical University, Moscow 119991 (Russian Federation); Goltzman, G. N.; Titova, N. [Physics Department, Moscow State Pedagogical University, Moscow 119991 (Russian Federation); Gayduchenko, I. A. [Physics Department, Moscow State Pedagogical University, Moscow 119991 (Russian Federation); National Research Center “Kurchatov Institute,” Moscow 123182 (Russian Federation); Coquillat, D.; But, D.; Knap, W. [Laboratoire Charles Coulomb UMR 5221, Universite Montpellier 2 and CNRS, F-34095, Montpellier (France); Mitin, V. [Department of Electrical Engineering, University at Buffalo, Buffalo, New York 1460-1920 (United States); Shur, M. S. [Departments of Electrical, Computer, and Systems Engineering and Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

    2016-07-28

    We consider the carrier transport and plasmonic phenomena in the lateral carbon nanotube (CNT) networks forming the device channel with asymmetric electrodes. One electrode is the Ohmic contact to the CNT network and the other contact is the Schottky contact. These structures can serve as detectors of the terahertz (THz) radiation. We develop the device model for collective response of the lateral CNT networks which comprise a mixture of randomly oriented semiconductor CNTs (s-CNTs) and quasi-metal CNTs (m-CNTs). The proposed model includes the concept of the collective two-dimensional (2D) plasmons in relatively dense networks of randomly oriented CNTs (CNT “felt”) and predicts the detector responsivity spectral characteristics exhibiting sharp resonant peaks at the signal frequencies corresponding to the 2D plasmonic resonances. The detection mechanism is the rectification of the ac current due the nonlinearity of the Schottky contact current-voltage characteristics under the conditions of a strong enhancement of the potential drop at this contact associated with the plasmon excitation. The detector responsivity depends on the fractions of the s- and m-CNTs. The burning of the near-contact regions of the m-CNTs or destruction of these CNTs leads to a marked increase in the responsivity in agreement with our experimental data. The resonant THz detectors with sufficiently dense lateral CNT networks can compete and surpass other THz detectors using plasmonic effects at room temperatures.

  15. Reduction of interface traps between poly-Si and SiO2 layers through the dielectric recovery effect during delayed pulse bias stress

    Science.gov (United States)

    Lee, Dong Uk; Pak, Sangwoo; Lee, Daemyoung; Kim, Yihun; Yang, Haechang; Hong, Sanghoo; Lee, Seungjun; Kim, Eun Kyu

    2017-06-01

    We investigate the interface trap behavior between tunneling oxide and poly-Si channel layer post erase/write cycling with a delayed pulse by using deep level transient spectroscopy. For comparison of the defect states depending on the stress pulses, a Schottky and a metal-oxide semiconductor device were fabricated. A defect state at about E c -0.51 eV in the Schottky device was measured before the annealing process. Three-hole trap states with activation energies of E v +0.28 eV, E v +0.53 eV, and E v +0.76 eV appeared after the post-annealing process. The electron trap was about E c -0.15 eV after erase/write 3000 cycling was applied at ±10 V for 100 ms at 25 °C and 85 °C. These defect states may have an effect on the charge loss behavior of the electrons localized in the charge trap layer at the retention mode of three-dimensional non-volatile memory devices. Dramatically, after the endurance stress was applied with a delayed pulse of 300 cycling at 85 °C for 50.4 h, no interface traps of the deep level transient spectroscopy spectra appeared. Dielectric recovery can decrease the density of the interface trap and improve the retention properties. This may have been caused by the passivation effect on the dangling bond of the interface traps.

  16. Impurity doping effects on the orbital thermodynamic properties of hydrogenated graphene, graphane, in Harrison model

    Science.gov (United States)

    Yarmohammadi, Mohsen

    2016-12-01

    Using the Harrison model and Green's function technique, impurity doping effects on the orbital density of states (DOS), electronic heat capacity (EHC) and magnetic susceptibility (MS) of a monolayer hydrogenated graphene, chair-like graphane, are investigated. The effect of scattering between electrons and dilute charged impurities is discussed in terms of the self-consistent Born approximation. Our results show that the graphane is a semiconductor and its band gap decreases with impurity. As a remarkable point, comparatively EHC reaches almost linearly to Schottky anomaly and does not change at low temperatures in the presence of impurity. Generally, EHC and MS increases with impurity doping. Surprisingly, impurity doping only affects the salient behavior of py orbital contribution of carbon atoms due to the symmetry breaking.

  17. Effects of electrode material and configuration on the characteristics of planar resistive switching devices

    KAUST Repository

    Peng, H.Y.

    2013-11-13

    We report that electrode engineering, particularly tailoring the metal work function, measurement configuration and geometric shape, has significant effects on the bipolar resistive switching (RS) in lateral memory devices based on self-doped SrTiO3 (STO) single crystals. Metals with different work functions (Ti and Pt) and their combinations are used to control the junction transport (either ohmic or Schottky-like). We find that the electric bias is effective in manipulating the concentration of oxygen vacancies at the metal/STO interface, influencing the RS characteristics. Furthermore, we show that the geometric shapes of electrodes (e.g., rectangular, circular, or triangular) affect the electric field distribution at the metal/oxide interface, thus plays an important role in RS. These systematic results suggest that electrode engineering should be deemed as a powerful approach toward controlling and improving the characteristics of RS memories. 2013 Author(s).

  18. A Single Polyaniline Nanofiber Field Effect Transistor and Its Gas Sensing Mechanisms

    Directory of Open Access Journals (Sweden)

    Yuquan Chen

    2011-06-01

    Full Text Available A single polyaniline nanofiber field effect transistor (FET gas sensor fabricated by means of electrospinning was investigated to understand its sensing mechanisms and optimize its performance. We studied the morphology, field effect characteristics and gas sensitivity of conductive nanofibers. The fibers showed Schottky and Ohmic contacts based on different electrode materials. Higher applied gate voltage contributes to an increase in gas sensitivity. The nanofiber transistor showed a 7% reversible resistance change to 1 ppm NH3 with 10 V gate voltage. The FET characteristics of the sensor when exposed to different gas concentrations indicate that adsorption of NH3 molecules reduces the carrier mobility in the polyaniline nanofiber. As such, nanofiber-based sensors could be promising for environmental and industrial applications.

  19. Electron Photoemission in Plasmonic Nanoparticle Arrays: Analysis of Collective Resonances and Embedding Effects

    CERN Document Server

    Zhukovsky, Sergei V; Uskov, Alexander V; Protsenko, Igor E; Lavrinenko, Andrei V

    2013-01-01

    We theoretically study the characteristics of photoelectron emission in plasmonic nanoparticle arrays. Nanoparticles are partially embedded in a semiconductor, forming Schottky barriers at metal/semiconductor interfaces through which photoelectrons can tunnel from the nanoparticle into the semiconductor; photodetection in the infrared range, where photon energies are below the semiconductor band gap (insufficient for band-to-band absorption in semiconductor), is therefore possible. The nanoparticles are arranged in a sparse rectangular lattice so that the wavelength of the lattice-induced Rayleigh anomalies can overlap the wavelength of the localized surface plasmon resonance of the individual particles, bringing about collective effects from the nanoparticle array. Using full-wave numerical simulations, we analyze the effects of lattice constant, embedding depth, and refractive index step between the semiconductor layer and an adjacent transparent conductive oxide layer. We show that the presence of refracti...

  20. Current transmission and nonlinear effects in un-gated thermionic cathode RF guns

    Energy Technology Data Exchange (ETDEWEB)

    Edelen, J. P. [Fermilab; Harris, J. R. [Air Force Weapons Lab

    2017-05-03

    Un-gated thermionic cathode RF guns are well known as a robust source of electrons for many accelerator applications. These sources are in principle scalable to high currents without degradation of the transverse emittance due to control grids but they are also known for being limited by back-bombardment. While back-bombardment presents a significant limitation, there is still a lack of general understanding on how emission over the whole RF period will affect the nature of the beams produced from these guns. In order to improve our understanding of how these guns can be used in general we develop analytical models that predict the transmission efficiency as a function of the design parameters, study how bunch compression and emission enhancement caused by Schottky barrier lowering affect the output current profile in the gun, and study the onset of space-charge limited effects and the resultant virtual cathode formation leading to a modulation in the output current distribution.

  1. Beneficial effect of shot peening on steamside oxidation of 300-series austenitic steels: An electrochemical study

    Science.gov (United States)

    Bystrianský, Václav; Krausová, Aneta; Macák, Jan; Děd, Jiří; Eltai, Elsadig; Hamouda, Abdel Magid

    2018-01-01

    The formation of a protective oxide ensures the good corrosion resistance of austenitic steels in high temperature steam. However after long-term interaction even the protective oxide may tend to exfoliate and cause operational problems. With shot peening believed to be an effective method for mitigating steamside oxidation and exfoliation, we compared oxide layers formed on two materials: AISI 316H with a rugged untreated surface and Super304H with a shot-peened surface. In addition to conventional methods (SEM/EDS, Raman spectroscopy), Mott-Schottky analysis was used to characterize the oxide layers in order to determine the quality of the protective oxide. The oxides formed on Super 304H showed unexpected semiconducting behaviour with a significantly lower charge carrier density, thereby supporting the benefits of shot peening. Our findings extend the knowledge applicable to the design of more efficient coal-fired power plants.

  2. Thickness effect on the structure, grain size, and local piezoresponse of self-polarized lead lanthanum zirconate titanate thin films

    Energy Technology Data Exchange (ETDEWEB)

    Melo, M.; Araújo, E. B., E-mail: eudes@dfq.feis.unesp.br [Departamento de Física e Química, Faculdade de Engenharia de Ilha Solteira, UNESP—Univ. Estadual Paulista, 15385-000 Ilha Solteira, SP (Brazil); Shvartsman, V. V. [Institute for Materials Science, University Duisburg-Essen, 45141 Essen (Germany); Shur, V. Ya. [Institute of Natural Sciences, Ural Federal University, 620000 Ekaterinburg (Russian Federation); Kholkin, A. L. [Institute of Natural Sciences, Ural Federal University, 620000 Ekaterinburg (Russian Federation); Department of Physics and CICECO—Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro (Portugal)

    2016-08-07

    Polycrystalline lanthanum lead zirconate titanate (PLZT) thin films were deposited on Pt/TiO{sub 2}/SiO{sub 2}/Si substrates to study the effects of the thickness and grain size on their structural and piezoresponse properties at nanoscale. Thinner PLZT films show a slight (100)-orientation tendency that tends to random orientation for the thicker film, while microstrain and crystallite size increases almost linearly with increasing thickness. Piezoresponse force microscopy and autocorrelation function technique were used to demonstrate the existence of local self-polarization effect and to study the thickness dependence of correlation length. The obtained results ruled out the bulk mechanisms and suggest that Schottky barriers near the film-substrate are likely responsible for a build-in electric field in the films. Larger correlation length evidence that this build-in field increases the number of coexisting polarization directions in larger grains leading to an alignment of macrodomains in thinner films.

  3. Electric-pulse-induced resistance switching effect in the bulk of La0.5Ca0.5MnO3 ceramics

    Directory of Open Access Journals (Sweden)

    M. L. Wu

    2014-04-01

    Full Text Available In the majority of contributions, the electrical–pulse-induced resistance (EPIR switching effect of perovskite manganites is thought to originate from the extrinsic interfacial Schottky barrier between the metal electrode and the surface of sample. In this work, La0.5Ca0.5MnO3 (LCMO ceramic samples were synthesized by solid state reaction and the transport properties, especially, the EPIR effect and memristor behavior were investigated under 4-wire method using silver-glue as electrodes. Although the I-V characteristic of LCMO shows an ohmic linearity under the 4-wire mode at room temperature, a stable and remarkable EPIR can still be observed when the pulse voltage is more than a critical value. This bulk EPIR effect is novel for rare - earth doped manganites.

  4. Perspective analysis of tri gate germanium tunneling field-effect transistor with dopant segregation region at source/drain

    Science.gov (United States)

    Liu, Liang-kui; Shi, Cheng; Zhang, Yi-bo; Sun, Lei

    2017-04-01

    A tri gate Ge-based tunneling field-effect transistor (TFET) has been numerically studied with technology computer aided design (TCAD) tools. Dopant segregated Schottky source/drain is applied to the device structure design (DS-TFET). The characteristics of the DS-TFET are compared and analyzed comprehensively. It is found that the performance of n-channel tri gate DS-TFET with a positive bias is insensitive to the dopant concentration and barrier height at n-type drain, and that the dopant concentration and barrier height at a p-type source considerably affect the device performance. The domination of electron current in the entire BTBT current of this device accounts for this phenomenon and the tri-gate DS-TFET is proved to have a higher performance than its dual-gate counterpart.

  5. Induction heating effect on the performance of flexible MoS2 field-effect transistors

    Science.gov (United States)

    Shin, Jong Mok; Choi, Jun hee; Kim, Do-Hyun; Jang, Ho-Kyun; Yun, Jinyoung; Na, Junhong; Kim, Gyu-Tae

    2017-10-01

    We investigated the induction heating effect on device characteristics of flexible molybdenum disulfide (MoS2) field-effect transistors (FETs). A polyimide film was employed as a flexible substrate, and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate was coated on the flexible substrate as a bottom gate. After the annealing process on the flexible MoS2 FETs by induction heating, the field effect mobility was enhanced from 2.13 to 5.58 cm2/V.s with the slight increase of the on-off ratio from 5.17 × 102 to 1.98 × 103. Moreover, the low field mobility was almost unchanged from 7.75 to 7.33 cm2/V.s, indicating that the induction heating mainly contributed to the enhancement of the device performances by contact improvement between electrodes and MoS2. With the simple model of the diode and resistor connected in series, it was confirmed that the Schottky diode disappeared with contact enhancement. Our findings can contribute to the contact improvement with minimum damage when low dimensional nanomaterials are used as channel materials on flexible substrates.

  6. A review on plasmonic metal⿿TiO2 composite for generation, trapping, storing and dynamic vectorial transfer of photogenerated electrons across the Schottky junction in a photocatalytic system

    Science.gov (United States)

    Gomathi Devi, L.; Kavitha, R.

    2016-01-01

    The titania based nanomaterials are an attractive candidates for energy and environmental applications. TiO2 is one of the most important photocatalyst for its special multiple characteristics like high reactivity, low toxicity, low cost, high flexibility, long term stability especially in aqueous medium, shows relatively high energy conversion efficiency, easy to prepare several modifications with various morphologies, with good recycle ability, favorable band edge positions and superior physicochemical and optoelectronic properties. However, large band gap of titania and massive charge carrier recombination impairs its wide photocatalytic applications. As an alternative to various strategies reported extensively in literature, noble metal deposition on the titania surface seems to be effective and reliable method for increasing the life time of excitonic pairs and to extend the band gap absorption to visible range of the solar spectrum. In this focused review, we discuss the fundamental and critical issues in the photocatalytic activity of metal deposited titania taking into consideration the influence of various parameters like preparation methods, metal dispersion on titania, formation of heterojunctions and optimum metal loadings on the interfacial charge carrier dynamics. The metal deposition onto the varied hierarchical morphology, crystal structure, defective surface of titania along with extended modification like simultaneous doping and heterostructure coupling with other semiconductors is also highlighted. It was revealed that deposited metal is involved in multiple crucial roles like; (i) it serves as passive electron sink with high capacity to store electrons to suppress photogenerated charge carrier recombination; (ii) it facilitates rapid dioxygen reduction to generate reactive free radicals; (iii) visible light response for titania can be achieved through surface plasmon resonance effect; (iv) direct excitation of metal nanoparticles especially

  7. Li-doping effects on the electrical properties of ZnO films prepared by the chemical-bath deposition method

    Energy Technology Data Exchange (ETDEWEB)

    Mohamed, Galal A. [Faculty of Science, Physics Department, Assuit University, Assuit (Egypt); Abd El-Moiz, A.B. [Faculty of Science, Physics Department, Assuit University, Assuit (Egypt)]. E-mail: abdelmoiz@myway.com; Rashad, M. [Faculty of Science, Physics Department, Assuit University, Assuit (Egypt)

    2005-12-15

    Zn{sub 1-} {sub x} Li {sub x} O thin films, with x varying from 0.0 to 0.5, successfully have been deposited on glass substrates using the chemical bath deposition (CBD) technique. J-E characteristics, DC conductivity and dielectric measurements have been carried out. These measurements were done as a function of temperature, Li concentration and applied electric field intensity. The J-E characteristics are explained in terms of the Pool-Frenkel and Schottky effects. The J-E relation and DC conductivity are strongly dependent on both the Li concentration and applied electric field intensity. Dielectric hysteresis was observed between heating and cooling runs which revealed that the dielectric constant often increases slowly in the low-temperature region, then increases faster above the phase transition.

  8. High-frequency fluctuation measurements by far-infrared laser Faraday-effect polarimetry-interferometry and forward scattering system on MST.

    Science.gov (United States)

    Ding, W X; Lin, L; Duff, J R; Brower, D L

    2014-11-01

    Magnetic fluctuation-induced transport driven by global tearing modes has been measured by Faraday-effect polarimetry and interferometry (phase measurements) in the MST reversed field pinch. However, the role of small-scale broadband magnetic and density turbulence in transport remains unknown. In order to investigate broadband magnetic turbulence, we plan to upgrade the existing detector system by using planar-diode fundamental waveguide mixers optimized for high sensitivity. Initial tests indicate these mixers have ×10 sensitivity improvement compared to currently employed corner-cube Schottky-diode mixers and ×5 lower noise. Compact mixer design will allow us to resolve the wavenumbers up to k ∼ 1-2 cm(-1) for beam width w = 1.5 cm and 15 cm(-1) for beam width w = 2 mm. The system can also be used to measure the scattered signal (amplitude measurement) induced by both plasma density and magnetic fluctuations.

  9. Effect of annealing temperature on the electrical properties of Au/Ta{sub 2}O{sub 5}/n-GaN metal-insulator-semiconductor (MIS) structure

    Energy Technology Data Exchange (ETDEWEB)

    Prasanna Lakshmi, B.; Rajagopal Reddy, V.; Janardhanam, V. [Sri Venkateswara University, Department of Physics, Tirupati (India); Siva Pratap Reddy, M.; Lee, Jung-Hee [Kyungpook National University, School of Electrical Engineering and Computer Science, Daegu (Korea, Republic of)

    2013-11-15

    We report on the effect of an annealing temperature on the electrical properties of Au/Ta{sub 2}O{sub 5}/n-GaN metal-insulator-semiconductor (MIS) structure by current-voltage (I-V) and capacitance-voltage (C-V) measurements. The measured Schottky barrier height ({Phi} {sub bo}) and ideality factor n values of the as-deposited Au/Ta{sub 2}O{sub 5}/n-GaN MIS structure are 0.93 eV (I-V) and 1.19. The barrier height (BH) increases to 1.03 eV and ideality factor decreases to 1.13 upon annealing at 500 {sup circle} C for 1 min under nitrogen ambient. When the contact is annealed at 600 {sup circle} C, the barrier height decreases and the ideality factor increases to 0.99 eV and 1.15. The barrier heights obtained from the C-V measurements are higher than those obtained from I-V measurements, and this indicates the existence of spatial inhomogeneity at the interface. Cheung's functions are also used to calculate the barrier height ({Phi} {sub bo}), ideality factor (n), and series resistance (R{sub s}) of the Au/Ta{sub 2}O{sub 5}/n-GaN MIS structure. Investigations reveal that the Schottky emission is the dominant mechanism and the Poole-Frenkel emission occurs only in the high voltage region. The energy distribution of interface states is determined from the forward bias I-V characteristics by taking into account the bias dependence of the effective barrier height. It is observed that the density value of interface states for the annealed samples with interfacial layer is lower than that of the density value of interface states of the as-deposited sample. (orig.)

  10. Schottky Heterodyne Receivers with Full Waveguide Bandwidth Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposal is responsive to NASA SBIR Subtopic S1.03: Passive Microwave Technology, specifically the fourth bullet item; "Low noise (<2000 K DSB), compactly...

  11. Abrupt Schottky Junctions in Al/Ge Nanowire Heterostructures

    OpenAIRE

    Kral, S.; Zeiner, C.; St?ger-Pollach, M.; Bertagnolli, E.; Den Hertog, M.I.; Lopez-Haro, M.; Robin, E.; El Hajraoui, K.; Lugstein, A.

    2015-01-01

    In this Letter we report on the exploration of axial metal/semiconductor (Al/Ge) nanowire heterostructures with abrupt interfaces. The formation process is enabled by a thermal induced exchange reaction between the vapor?liquid?solid grown Ge nanowire and Al contact pads due to the substantially different diffusion behavior of Ge in Al and vice versa. Temperature-dependent I?V measurements revealed the metallic properties of the crystalline Al nanowire segments with a maximum current carrying...

  12. Real-Time Schottky Measurements in the LHC

    CERN Document Server

    AUTHOR|(CDS)2241943; Aune, D.

    The accelerator complex at the European Organization for Nuclear Research (CERN) is a diverse collection of machines, tailored for different energy ranges, and concatenated in order to accelerate/decelerate particle beams. Leading up to CERN’s flagship accelerator, the Large Hadron Collider (LHC), every accelerator in the chain boosts the particles to higher energies before they are injected into the next machine in the sequence. The LHC is a circular synchrotron accelerator consisting of two 27-kilometer vacuum tubes equipped with superconducting magnets and accelerating RF cavities in order to increase the energy of the particles along the way. Inside the vacuum tubes, two counter-rotating high-energy particle beams travel at velocities close to the speed of light before they are made to collide inside particle detectors at a centre-of-mass energy of 13 TeV. As the particles are accelerated, they experience various external and internal forces. RF cavities are used to boost the speed of the particles an...

  13. Nanogenerator comprising piezoelectric semiconducting nanostructures and Schottky conductive contacts

    Science.gov (United States)

    Wang, Zhong L. (Inventor); Wang, Xudong (Inventor); Song, Jinhui (Inventor); Zhou, Jun (Inventor); He, Jr-Hau (Inventor)

    2011-01-01

    A semiconducting device includes a substrate, a piezoelectric wire, a structure, a first electrode and a second electrode. The piezoelectric wire has a first end and an opposite second end and is disposed on the substrate. The structure causes the piezoelectric wire to bend in a predetermined manner between the first end and the second end so that the piezoelectric wire enters a first semiconducting state. The first electrode is coupled to the first end and the second electrode is coupled to the second end so that when the piezoelectric wire is in the first semiconducting state, an electrical characteristic will be exhibited between the first electrode and the second electrode.

  14. Adapting Schottky Diode Detector Technology to a Space Platform

    Science.gov (United States)

    1988-02-10

    information from this data. The magnetic fielh’can be measured using induction in a wound coil or solenoid. Several coil schemes are currently enployed...surface of the blocks should be machined with a ’honeycomb’ structure to reduce surface reflections and provide recessed cavities in order to simulate a...Cryogenics. This unit is a dc- brushless , I watt split-Stirling engine that cools to 77 degrees K. A picture of the unit is reproduced in Figure 4.2

  15. High temperature annealing effects on deep-level defects in a high purity semi-insulating 4H-SiC substrate

    Science.gov (United States)

    Iwamoto, Naoya; Azarov, Alexander; Ohshima, Takeshi; Moe, Anne Marie M.; Svensson, Bengt G.

    2015-07-01

    Effects of high-temperature annealing on deep-level defects in a high-purity semi-insulating 4H silicon carbide substrate have been studied by employing current-voltage, capacitance-voltage, junction spectroscopy, and chemical impurity analysis measurements. Secondary ion mass spectrometry data reveal that the substrate contains boron with concentration in the mid 1015 cm-3 range, while other impurities including nitrogen, aluminum, titanium, vanadium and chromium are below their detection limits (typically ˜1014 cm-3). Schottky barrier diodes fabricated on substrates annealed at 1400-1700 °C exhibit metal/p-type semiconductor behavior with a current rectification of up to 8 orders of magnitude at bias voltages of ±3 V. With increasing annealing temperature, the series resistance of the Schottky barrier diodes decreases, and the net acceptor concentration in the substrates increases approaching the chemical boron content. Admittance spectroscopy results unveil the presence of shallow boron acceptors and deep-level defects with levels in lower half of the bandgap. After the 1400 °C annealing, the boron acceptor still remains strongly compensated at room temperature by deep donor-like levels located close to mid-gap. However, the latter decrease in concentration with increasing annealing temperature and after 1700 °C, the boron acceptor is essentially uncompensated. Hence, the deep donors are decisive for the semi-insulating properties of the substrates, and their thermal evolution limits the thermal budget for device processing. The origin of the deep donors is not well-established, but substantial evidence supporting an assignment to carbon vacancies is presented.

  16. Depletion of parallel conducting layers in high mobility In0.53Ga0.47As/In0.52Al0.48As modulation doped field effect transistors

    Science.gov (United States)

    Skuras, E.; Gavalas, A.; Spathara, D.; Makris, Th.; Anagnostopoulos, D.; Stanley, C. R.; Long, A. R.

    2013-12-01

    Self-consistent calculations for solving the Poisson and Schrödinger equations were performed in order to study parallel conduction in the In0.52Al0.48As barrier layer in In0.53Ga0.47As/In0.52Al0.48As Modulation Doped Field Effect Transistors. It is shown that the parallel conducting layer occupied sub-bands can be entirely depleted by wet chemical etching of the upper part of the un-doped In0.52Al0.48As Schottky layer without affecting the total carrier concentration at the In0.53Ga0.47As quantum well.

  17. Depletion of parallel conducting layers in high mobility In{sub 0.53}Ga{sub 0.47}As/In{sub 0.52}Al{sub 0.48}As modulation doped field effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Skuras, E., E-mail: eskuras@cc.uoi.gr; Gavalas, A., E-mail: eskuras@cc.uoi.gr; Spathara, D., E-mail: eskuras@cc.uoi.gr; Makris, Th., E-mail: eskuras@cc.uoi.gr; Anagnostopoulos, D., E-mail: eskuras@cc.uoi.gr [Department of Material, Engineering, University of Ioannina, Ioannina 45110 (Greece); Stanley, C. R. [School of Engineering, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Long, A. R. [School of Physics and Astronomy, Kelvin Building, University of Glasgow, Glasgow G12 8QQ (United Kingdom)

    2013-12-04

    Self-consistent calculations for solving the Poisson and Schrödinger equations were performed in order to study parallel conduction in the In{sub 0.52}Al{sub 0.48}As barrier layer in In{sub 0.53}Ga{sub 0.47}As/In{sub 0.52}Al{sub 0.48}As Modulation Doped Field Effect Transistors. It is shown that the parallel conducting layer occupied sub-bands can be entirely depleted by wet chemical etching of the upper part of the un-doped In{sub 0.52}Al{sub 0.48}As Schottky layer without affecting the total carrier concentration at the In{sub 0.53}Ga{sub 0.47}As quantum well.

  18. Effects

    Directory of Open Access Journals (Sweden)

    S.B. Hassan

    2015-01-01

    Full Text Available The effects of eggshell particles (ES on the microstructures and properties of Al–Cu–Mg/ES particulate composites have been studied. A total of 2–12 wt.% ES particles were added. The microstructures of the Al–Cu–Mg/eggshell particulate composites produced were examined by a scanning electron microscope with energy dispersive spectrometer (SEM/EDS. The physical and mechanical properties measured included: density, tensile strength, hardness values and impact energy. The results revealed that the tensile strength increased by 8.16% at 12 wt.% uncarbonized ES and 14.28% at 12 wt.% carbonized ES, the hardness values increased by 10.01% at 12 wt.% uncarbonized ES and 25.4% at 12 wt.% carbonized ES with decrease in the density by 6.50% at 12 wt.% uncarbonized ES and 7.4% at 12 wt.% carbonized ES. The impact energy decreased by 23.5% at 12 wt.% uncarbonized ES and 24.67% at 12 wt.% carbonized ES particles, respectively. These increases in strength and hardness values are attributed to the distribution of hard phases of the ES particles in the ductile Al–Cu–Mg alloy matrix. These results showed that using the carbonized eggshell as reinforcement in the Al–Cu–Mg alloy gives better physical and mechanical properties as compared to uncarbonized ES particles. Hence addition of ES particles upto 12 wt.% can be used as a low cost reinforcement for the production of metal matrix composites for engineering applications.

  19. Effects of Humidity and Temperature on Orange Dye-Based Organic Field Effect Transistors Fabricated at Different Gravity

    Science.gov (United States)

    Fatima, N.; Ahmed, M. M.; Karimov, Kh. S.

    2017-11-01

    This study reports the fabrication of organic field effect transistors (OFETs) using 3-[ethyl[4-[(4-nitrophenyl)azo]phenyl]amino]propanenitrile, usually known as Orange-Dye 25 (OD) and its composite with sugar. The study investigated the heat- and humidity-dependent electrical characteristics of the fabricated devices. Fabrication was carried out from the aqueous solution of the materials using different gravity conditions, i.e., at positive (normal) gravity (+1 g) and at negative gravity (-1 g). A thin layer (10-15 μm) of OD or OD:sugar was deposited by drop-casting on pre-fabricated drain and source silver (Ag) electrodes having 30 μm separation and 2 mm length followed by aluminum (Al) thermal evaporation to achieve a Schottky barrier. Devices fabricated using OD at -1 g were more sensitive in capacitance-temperature and impedance-humidity relationships than those fabricated at +1 g. Moreover, OFETs fabricated at -1 g using OD:sugar offered capacitance-temperature sensitivity much higher than the devices fabricated at +1 g. It has been observed that, in the drop-casting method, the properties of OFETs are dependent upon gravity as well as the solution composition employed for channel definition.

  20. Piezotronic effect in 1D van der Waals solid of elemental tellurium nanobelt for smart adaptive electronics

    Science.gov (United States)

    Gao, Shengjie; Wang, Yixiu; Wang, Ruoxing; Wu, Wenzhuo

    2017-10-01

    Emerging technologies in wearable systems demand that functional devices can adaptively interact with the human body, where mechanical stimuli are ubiquitous and abundant. However, the electrical manipulation of charge carriers underpins the operations of state-of-the-art devices, and the effective control of interfacial energetics for charge carriers by the dynamic mechanical stimuli is still a relatively unexplored degree of freedom for semiconductor nanodevices. Piezotronic effect in nanostructured piezoelectric semiconductors offers exciting opportunities in addressing the above challenges. Here we report the first experimental exploration of piezotronic effect in 1D van der Waals solid of p-type tellurium nanobelt and systematically investigate the strain-gated charge carriers transport properties. The strain-induced polarization charges at the [10\\bar{1}0] surfaces of Te nanobelt can modulate the electronic transport through the interfacial effect on the Schottky contacts and the volumetric effect on the conducting channel. The competing phenomenon between interfacial and volumetric effects has been studied for the first time in piezotronics. Our research allows the access to a broad range of characterization and application of Te nanomaterials for piezotronics and could guide the future study of piezotronic effect in other materials. This progress in piezotronics, together with emerging methods for deterministic production and assembly of nanomaterials, leads to compelling opportunities for research from basic studies of piezoelectricity and semiconductor properties in functional nanomaterials to the development of ‘smarter’ electronics and optoelectronics.

  1. A scanning probe mounted on a field-effect transistor: Characterization of ion damage in Si.

    Science.gov (United States)

    Shin, Kumjae; Lee, Hoontaek; Sung, Min; Lee, Sang Hoon; Shin, Hyunjung; Moon, Wonkyu

    2017-10-01

    We have examined the capabilities of a Tip-On-Gate of Field-Effect Transistor (ToGoFET) probe for characterization of FIB-induced damage in Si surface. A ToGoFET probe is the SPM probe which the Field Effect Transistor(FET) is embedded at the end of a cantilever and a Pt tip was mounted at the gate of FET. The ToGoFET probe can detect the surface electrical properties by measuring source-drain current directly modulated by the charge on the tip. In this study, a Si specimen whose surface was processed with Ga+ ion beam was prepared. Irradiation and implantation with Ga+ ions induce highly localized modifications to the contact potential. The FET embedded on ToGoFET probe detected the surface electric field profile generated by schottky contact between the Pt tip and the sample surface. Experimentally, it was shown that significant differences of electric field due to the contact potential barrier in differently processed specimens were observed using ToGOFET probe. This result shows the potential that the local contact potential difference can be measured by simple working principle with high sensitivity. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Contact research strategy for emerging molybdenum disulfide and other two-dimensional field-effect transistors

    Directory of Open Access Journals (Sweden)

    Yuchen Du

    2014-09-01

    Full Text Available Layered two-dimensional (2D semiconducting transition metal dichalcogenides (TMDs have been widely isolated, synthesized, and characterized recently. Numerous 2D materials are identified as the potential candidates as channel materials for future thin film technology due to their high mobility and the exhibiting bandgaps. While many TMD filed-effect transistors (FETs have been widely demonstrated along with a significant progress to clearly understand the device physics, large contact resistance at metal/semiconductor interface still remain a challenge. From 2D device research point of view, how to minimize the Schottky barrier effects on contacts thus reduce the contact resistance of metals on 2D materials is very critical for the further development of the field. Here, we present a review of contact research on molybdenum disulfide and other TMD FETs from the fundamental understanding of metal-semiconductor interfaces on 2D materials. A clear contact research strategy on 2D semiconducting materials is developed for future high-performance 2D FETs with aggressively scaled dimensions.

  3. Effects of Zn doping concentration on resistive switching ...

    Indian Academy of Sciences (India)

    However, the endurance characteristics show considerable differences; x = 0.3 shows the best endurance characteristics in more than 1000 switching cycles. The conduction mechanism of the Ag/La 1 − x Zn x MnO 3 /p + -Si is the Schottky emission mode at high resistance state. However, the conduction mechanism at low ...

  4. Damage effect and mechanism of the GaAs pseudomorphic high electron mobility transistor induced by the electromagnetic pulse

    Science.gov (United States)

    Xiao-Wen, Xi; Chang-Chun, Chai; Gang, Zhao; Yin-Tang, Yang; Xin-Hai, Yu; Yang, Liu

    2016-04-01

    The damage effect and mechanism of the electromagnetic pulse (EMP) on the GaAs pseudomorphic high electron mobility transistor (PHEMT) are investigated in this paper. By using the device simulation software, the distributions and variations of the electric field, the current density and the temperature are analyzed. The simulation results show that there are three physical effects, i.e., the forward-biased effect of the gate Schottky junction, the avalanche breakdown, and the thermal breakdown of the barrier layer, which influence the device current in the damage process. It is found that the damage position of the device changes with the amplitude of the step voltage pulse. The damage appears under the gate near the drain when the amplitude of the pulse is low, and it also occurs under the gate near the source when the amplitude is sufficiently high, which is consistent with the experimental results. Project supported by the National Basic Research Program of China (Grant No. 2014CB339900), and the Open Fund of Key Laboratory of Complex Electromagnetic Environment Science and Technology, China Academy of Engineering Physics (CAEP) (Grant No. 2015-0214.XY.K).

  5. Junctionless Diode Enabled by Self-Bias Effect of Ion Gel in Single-Layer MoS2 Device.

    Science.gov (United States)

    Khan, Muhammad Atif; Rathi, Servin; Park, Jinwoo; Lim, Dongsuk; Lee, Yoontae; Yun, Sun Jin; Youn, Doo-Hyeb; Kim, Gil-Ho

    2017-08-16

    The self-biasing effects of ion gel from source and drain electrodes on electrical characteristics of single layer and few layer molybdenum disulfide (MoS2) field-effect transistor (FET) have been studied. The self-biasing effect of ion gel is tested for two different configurations, covered and open, where ion gel is in contact with either one or both, source and drain electrodes, respectively. In open configuration, the linear output characteristics of the pristine device becomes nonlinear and on-off ratio drops by 3 orders of magnitude due to the increase in "off" current for both single and few layer MoS2 FETs. However, the covered configuration results in a highly asymmetric output characteristics with a rectification of around 103 and an ideality factor of 1.9. This diode like behavior has been attributed to the reduction of Schottky barrier width by the electric field of self-biased ion gel, which enables an efficient injection of electrons by tunneling at metal-MoS2 interface. Finally, finite element method based simulations are carried out and the simulated results matches well in principle with the experimental analysis. These self-biased diodes can perform a crucial role in the development of high-frequency optoelectronic and valleytronic devices.

  6. Highly Stable and Tunable Chemical Doping of Multilayer WS2 Field Effect Transistor: Reduction in Contact Resistance.

    Science.gov (United States)

    Khalil, Hafiz M W; Khan, Muhammad Farooq; Eom, Jonghwa; Noh, Hwayong

    2015-10-28

    The development of low resistance contacts to 2D transition-metal dichalcogenides (TMDs) is still a big challenge for the future generation field effect transistors (FETs) and optoelectronic devices. Here, we report a chemical doping technique to achieve low contact resistance by keeping the intrinsic properties of few layers WS2. The transfer length method has been used to investigate the effect of chemical doping on contact resistance. After doping, the contact resistance (Rc) of multilayer (ML) WS2 has been reduced to 0.9 kΩ·μm. The significant reduction of the Rc is mainly due to the high electron doping density, thus a reduction in Schottky barrier height, which limits the device performance. The threshold voltage of ML-WS2 FETs confirms a negative shift upon the chemical doping, as further confirmed from the positions of E(1)2g and A1g peaks in Raman spectra. The n-doped samples possess a high drain current of 65 μA/μm, with an on/off ratio of 1.05 × 10(6) and a field effect mobility of 34.7 cm(2)/(V·s) at room temperature. Furthermore, the photoelectric properties of doped WS2 flakes were also measured under deep ultraviolet light. The potential of using LiF doping in contact engineering of TMDs opens new ways to improve the device performance.

  7. Effect of Post-HALT Annealing on Leakage Currents in Solid Tantalum Capacitors

    Science.gov (United States)

    Teverovsky, Alexander

    2010-01-01

    Degradation of leakage currents is often observed during life testing of tantalum capacitors and is sometimes attributed to the field-induced crystallization in amorphous anodic tantalum pentoxide dielectrics. However, degradation of leakage currents and the possibility of annealing of degraded capacitors have not been investigated yet. In this work the effect of annealing after highly accelerated life testing (HALT) on leakage currents in various types of solid tantalum capacitors was analyzed. Variations of leakage currents with time during annealing at temperatures from 125 oC to 180 oC, thermally stimulated depolarization (TSD) currents, and I-V characteristics were measured to understand the conduction mechanism and the reason for current degradation. Annealing resulted in a gradual decrease of leakage currents and restored their initial values. Repeat HALT after annealing resulted in reproducible degradation of leakage currents. The observed results are explained based on ionic charge instability (drift/diffusion of oxygen vacancies) in the tantalum pentoxide dielectrics using a modified Schottky conduction mechanism.

  8. Negative Resistance Effect and Charge Transfer Mechanisms in the lon Beam Deposited Diamond Like Carbon Superlattices

    Directory of Open Access Journals (Sweden)

    Andrius VASILIAUSKAS

    2011-03-01

    Full Text Available In the present study DLC:SiOx/DLC/DLC:SiOx/nSi and DLC:SiOx/DLC/DLC:SiOx/pSi structures were fabricated by ion beam deposition using a closed drift ion source. Current-voltage (I-V characteristics of the multilayer samples were measured at room temperature. The main charge transfer mechanisms were considered. Unstable negative resistance effect was observed for some DLC:SiOx/DLC/DLC:SiOx/nSi and DLC:SiOx/DLC/DLC:SiOx/pSi structures. In the case of the diamond like carbon superlattices fabricated on nSi it was observed only during the first measurement. In the case of the some DLC:SiOx/DLC/DLC:SiOx/pSi negative resistance "withstood" several measurements. Changes of the charge carrier mechanisms were observed along with the dissapear of the negative resistance peaks. It seems, that in such a case influence of the bulk related charge transfer mechanisms such as Poole-Frenkel emission increased, while the influence of the contact limited charge transfer mechanisms such as Schottky emission decreased. Observed results were be explained by current flow through the local microconducting channels and subsequent destruction of the localized current pathways as a result of the heating by flowing electric current.http://dx.doi.org/10.5755/j01.ms.17.1.240

  9. Valence band states in Si-based p-type delta-doped field effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Orozco, J C; Vlaev, Stoyan J, E-mail: jcmover@correo.unam.m [Unidad Academica de Fisica, Universidad Autonoma de Zacatecas, Calzada Solidaridad esquina con Paseo la Bufa S/N, C.P. 98060, Zacatecas, Zac. (Mexico)

    2009-05-01

    We present tight-binding calculations of the hole level structure of delta-doped Field Effect Transistor in a Si matrix within the first neighbors sp{sup 3}s* semi-empirical tight-binding model including spin. We employ analytical expressions for Schottky barrier potential and the p-type delta-doped well based on a Thomas-Fermi approximation, we consider these potentials as external ones, so in the computations they are added to the diagonal terms of the tight-binding Hamiltonian, by this way we have the possibility to study the energy levels behavior as we vary the backbone parameters in the system: the two-dimensional impurity density (p{sub 2d}) of the p-type delta-doped well and the contact voltage (V{sub c}). The aim of this calculation is to demonstrate that the tight-binding approximation is suitable for device characterization that permits us to propose optimal values for the input parameters involved in the device design.

  10. Effect of nitrogen-accommodation ability of electrodes in SiNx-based resistive switching devices

    Science.gov (United States)

    Yang, Mei; Wang, Hong; Ma, Xiaohua; Gao, Haixia; Wang, Bin

    2017-12-01

    Nitrides could create opportunities of tuning resistive-switching (RS) characteristics due to their different electrical properties and ionic chemistry with oxides. Here, we reported on the effect of nitrogen-accommodation ability of electrodes in SiNx-based RS devices. The Ti/SiNx/Pt devices show a self-compliance bipolar RS with excellent reliability. The W/SiNx/Pt devices provide an unstable RS and fall to an intermediate resistance state (IRS) after a set process. The low resistance states of the Ti/SiNx/Pt devices obey Ohmic conduction and Frenkel-Poole emission from a conductive channel. The IRS of the W/SiNx/Pt devices conforms to Schottky emission and Fowler-Nordheim tunneling from a conductive channel/insulator/electrode structure. A nitrogen-ion-based model is proposed to explain the experimental results. According to the model, the nitrogen-accommodation ability of the electrodes dominates the nitrogen-reservoir size and the nitrogen-ion migration at the metal/SiNx interface, modulating the RS characteristics of the SiNx memory devices.

  11. Mobility Engineering in Vertical Field Effect Transistors Based on Van der Waals Heterostructures.

    Science.gov (United States)

    Shin, Yong Seon; Lee, Kiyoung; Kim, Young Rae; Lee, Hyangsook; Lee, I Min; Kang, Won Tae; Lee, Boo Heung; Kim, Kunnyun; Heo, Jinseong; Park, Seongjun; Lee, Young Hee; Yu, Woo Jong

    2018-01-15

    Vertical integration of 2D layered materials to form van der Waals heterostructures (vdWHs) offers new functional electronic and optoelectronic devices. However, the mobility in vertical carrier transport in vdWHs of vertical field-effect transistor (VFET) is not yet investigated in spite of the importance of mobility for the successful application of VFETs in integrated circuits. Here, the mobility in VFET of vdWHs under different drain biases, gate biases, and metal work functions is first investigated and engineered. The traps in WSe 2 are the main source of scattering, which influences the vertical mobility and three distinct transport mechanisms: Ohmic transport, trap-limited transport, and space-charge-limited transport. The vertical mobility in VFET can be improved by suppressing the trap states by raising the Fermi level of WSe 2 . This is achieved by increasing the injected carrier density by applying a high drain voltage, or decreasing the Schottky barrier at the graphene/WSe 2 and metal/WSe 2 junctions by applying a gate bias and reducing the metal work function, respectively. Consequently, the mobility in Mn vdWH at +50 V gate voltage is about 76 times higher than the initial mobility of Au vdWH. This work enables further improvements in the VFET for successful application in integrated circuits. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Piezoelectric effect in chemical vapour deposition-grown atomic-monolayer triangular molybdenum disulfide piezotronics

    KAUST Repository

    Qi, Junjie

    2015-06-25

    High-performance piezoelectricity in monolayer semiconducting transition metal dichalcogenides is highly desirable for the development of nanosensors, piezotronics and photo-piezotransistors. Here we report the experimental study of the theoretically predicted piezoelectric effect in triangle monolayer MoS2 devices under isotropic mechanical deformation. The experimental observation indicates that the conductivity of MoS2 devices can be actively modulated by the piezoelectric charge polarization-induced built-in electric field under strain variation. These polarization charges alter the Schottky barrier height on both contacts, resulting in a barrier height increase with increasing compressive strain and decrease with increasing tensile strain. The underlying mechanism of strain-induced in-plane charge polarization is proposed and discussed using energy band diagrams. In addition, a new type of MoS2 strain/force sensor built using a monolayer MoS2 triangle is also demonstrated. Our results provide evidence for strain-gating monolayer MoS2 piezotronics, a promising avenue for achieving augmented functionalities in next-generation electronic and mechanical–electronic nanodevices.

  13. High performance field-effect transistor based on multilayer tungsten disulfide.

    Science.gov (United States)

    Liu, Xue; Hu, Jin; Yue, Chunlei; Della Fera, Nicholas; Ling, Yun; Mao, Zhiqiang; Wei, Jiang

    2014-10-28

    Semiconducting two-dimensional transition metal chalcogenide crystals have been regarded as the promising candidate for the future generation of transistor in modern electronics. However, how to fabricate those crystals into practical devices with acceptable performance still remains as a challenge. Employing tungsten disulfide multilayer thin crystals, we demonstrate that using gold as the only contact metal and choosing appropriate thickness of the crystal, high performance transistor with on/off ratio of 10(8) and mobility up to 234 cm(2) V(-1) s(-1) at room temperature can be realized in a simple device structure. Furthermore, low temperature study revealed that the high performance of our device is caused by the minimized Schottky barrier at the contact and the existence of a shallow impurity level around 80 meV right below the conduction band edge. From the analysis on temperature dependence of field-effect mobility, we conclude that strongly suppressed phonon scattering and relatively low charge impurity density are the key factors leading to the high mobility of our tungsten disulfide devices.

  14. Simulation of diode characteristics of carbon nanotube field-effect transistors with symmetric source and drain contacts

    KAUST Repository

    Li, Jingqi

    2011-09-01

    The diode characteristics of carbon nanotube field-effect transistors (CNTFETs) with symmetric source and drain contacts have been experimentally found at zero gate voltage (Li J. et al., Appl. Phys. Lett., 92 (2008) 133111). We calculate this characteristic using a semiclassical method based on Schottky barrier transistor mechanism. The influences of metal work function, the diameter of the carbon nanotubes and the dielectric thickness on the rectification behavior have been studied. The calculation results show that the metal with a higher work function results in a better diode characteristics for a p-type CNTFET. For single-walled carbon nanotubes (SWNTs) with different band gaps, both forward current and reverse current increase with decreasing band gap, but the ratio of forward current to reverse current decreases with decreasing band gap. This result is well consistent with the experimental observations reported previously. The simulation of the dielectric thickness effect indicates that the thinner the dielectric layer, the better the rectification behavior. The CNTFETs without a bottom gate could not show the diode characteristics, which is consistent with the reported experimental observation. © 2011 Europhysics Letters Association.

  15. Effects of the buffer layer inserted between the transparent conductive oxide anode and the organic electron donor

    Energy Technology Data Exchange (ETDEWEB)

    Godoy, A.; Kouskoussa, B.; Benchouk, K.; Khelil, A. [Facultad Ciencias de la Salud, Universidad Diego Portales, Ejercito 141, Santiago de Chile (Chile); Cattin, L.; Soto, G.M. [Universite de Nantes, Nantes Atlantique Universites, Institut des Materiaux Jean Rouxel (IMN)-CNRS, Faculte des Sciences et Techniques, 2 rue de la Houssiniere, BP 92208, Nantes F-44000 (France); Toumi, L. [LPCM2E, Universite d' Oran Es-Senia, LPCM2E (Algeria); Diaz, F.R.; del Valle, M.A. [Laboratorio de Polimeros, Facultad de Quimica, Pontificia Universidad Catolica de Chile, Casilla 306, Correo 22, Santiago (Chile); Morsli, M.; Bernede, J.C. [Universite de Nantes, Nantes Atlantique Universites, LAMP, Faculte des Sciences et Techniques, 2 rue de la Houssiniere, BP 92208, Nantes F-44000 (France)

    2010-04-15

    In optoelectronic devices, the work function of the transparent conductive oxide, which is used as anode, does not match well the highest occupied molecular orbital of the organic material, which induces the formation of a barrier opposed to hole exchange at this interface. Therefore a thin buffer layer is often used to achieve good matching of the band structure at the interface. From experimental results it can be deduced that the main effects of the buffer layer consist in a better matching of the band structure at the interface anode/organic material and in a more homogeneous organic layer growth. We show that, whatever the nature of the buffer layer-metal, oxide, organic material - the classical Schottky-Mott model allows to anticipate, at least roughly, the behaviour of the contact, even if some dipole effect are often present. A good correlation between the ''metal/buffer layer'' work function and the barrier {phi}{sub b} for hole exchange at anode/organic electron donor interfaces is obtained, as expected by the model. (author)

  16. Enhanced photovoltaic effect in BiVO4 semiconductor by incorporation with an ultrathin BiFeO3 ferroelectric layer.

    Science.gov (United States)

    Dong, Wen; Guo, Yiping; Guo, Bing; Li, Hua; Liu, Hezhou; Joel, Thia Weikang

    2013-08-14

    The photovoltaic effect of BiVO4 semiconductor was investigated by incorporating an ultrathin BiFeO3 ferroelectric layer. It is found that the ultrathin ferroelectric layer with strong self-polarization and high carrier density is desirable to enhance the photovoltaic effect and to manipulate the photovoltaic polarity of the semiconductors. The photovoltage increases by 5-fold to 1 V, and the photocurrent density increases by 2-fold to 140 μA/cm(2), in which the photovoltage is the highest compared with the reported values in polycrystalline and epitaxial ferroelectric thin film solar cells. The mechanism for the observed effect is discussed on the basis of a polarization-induced Schottky-like barrier at the BiFeO3/fluorine doped tin oxide interface. Our work provides good guidance for fabrication of cost-effective semiconductor photovoltaic devices with high performance, and this kind of ultrathin ferroelectric film may also have promising applications in copper indium gallium selenide solar cell, dye-sensitized TiO2 solar cell, lighting emitting diode, and other photoelectron related devices.

  17. Unipolar resistive switching with forming-free and self-rectifying effects in Cu/HfO2/n-Si devices

    Directory of Open Access Journals (Sweden)

    M. J. Wang

    2016-02-01

    Full Text Available One of the most effective methods integrating self-rectifying RRAM is alleviating sneak current in crossbar architecture. In this work, to investigate RRAMs with excellent properties of self-rectifying effect, simple Cu/HfO2/n-Si tri-layer devices are fabricated and investigated through I − V characteristic measurement. The experimental results demonstrate that the device exhibits forming-free behavior and a remarkable rectifying effect in low resistance state (LRS with rectification ratio of 104 at ±1 V, as well as considerable OFF/ON ratio (resistive switching window of 104 at 1 V. The formation and annihilation of localized Cu conductive filament plays a key role in the resistive switching between low resistance state (LRS and high resistance state (HRS. In addition, intrinsic rectifying effect in LRS attributes to the Schottky contact between Cu filament and n-Si electrode. Furthermore, satisfactory switching uniformity of cycles and devices is observed. As indicated by the results, Cu/HfO2/n-Si devices have a high potential for high-density storage practical application due to its excellent properties.

  18. Importance of elastic finite-size effects: Neutral defects in ionic compounds

    Science.gov (United States)

    Burr, P. A.; Cooper, M. W. D.

    2017-09-01

    Small system sizes are a well-known source of error in density functional theory (DFT) calculations, yet computational constraints frequently dictate the use of small supercells, often as small as 96 atoms in oxides and compound semiconductors. In ionic compounds, electrostatic finite-size effects have been well characterized, but self-interaction of charge-neutral defects is often discounted or assumed to follow an asymptotic behavior and thus easily corrected with linear elastic theory. Here we show that elastic effects are also important in the description of defects in ionic compounds and can lead to qualitatively incorrect conclusions if inadequately small supercells are used; moreover, the spurious self-interaction does not follow the behavior predicted by linear elastic theory. Considering the exemplar cases of metal oxides with fluorite structure, we show that numerous previous studies, employing 96-atom supercells, misidentify the ground-state structure of (charge-neutral) Schottky defects. We show that the error is eliminated by employing larger cells (324, 768, and 1500 atoms), and careful analysis determines that elastic, not electrostatic, effects are responsible. The spurious self-interaction was also observed in nonoxide ionic compounds irrespective of the computational method used, thereby resolving long-standing discrepancies between DFT and force-field methods, previously attributed to the level of theory. The surprising magnitude of the elastic effects is a cautionary tale for defect calculations in ionic materials, particularly when employing computationally expensive methods (e.g., hybrid functionals) or when modeling large defect clusters. We propose two computationally practicable methods to test the magnitude of the elastic self-interaction in any ionic system. In commonly studied oxides, where electrostatic effects would be expected to be dominant, it is the elastic effects that dictate the need for larger supercells: greater than 96 atoms.

  19. Short-channel field-effect transistors with 9-atom and 13-atom wide graphene nanoribbons.

    Science.gov (United States)

    Llinas, Juan Pablo; Fairbrother, Andrew; Borin Barin, Gabriela; Shi, Wu; Lee, Kyunghoon; Wu, Shuang; Yong Choi, Byung; Braganza, Rohit; Lear, Jordan; Kau, Nicholas; Choi, Wonwoo; Chen, Chen; Pedramrazi, Zahra; Dumslaff, Tim; Narita, Akimitsu; Feng, Xinliang; Müllen, Klaus; Fischer, Felix; Zettl, Alex; Ruffieux, Pascal; Yablonovitch, Eli; Crommie, Michael; Fasel, Roman; Bokor, Jeffrey

    2017-09-21

    Bottom-up synthesized graphene nanoribbons and graphene nanoribbon heterostructures have promising electronic properties for high-performance field-effect transistors and ultra-low power devices such as tunneling field-effect transistors. However, the short length and wide band gap of these graphene nanoribbons have prevented the fabrication of devices with the desired performance and switching behavior. Here, by fabricating short channel (L ch ~ 20 nm) devices with a thin, high-κ gate dielectric and a 9-atom wide (0.95 nm) armchair graphene nanoribbon as the channel material, we demonstrate field-effect transistors with high on-current (I on > 1 μA at V d = -1 V) and high I on /I off ~ 10(5) at room temperature. We find that the performance of these devices is limited by tunneling through the Schottky barrier at the contacts and we observe an increase in the transparency of the barrier by increasing the gate field near the contacts. Our results thus demonstrate successful fabrication of high-performance short-channel field-effect transistors with bottom-up synthesized armchair graphene nanoribbons.Graphene nanoribbons show promise for high-performance field-effect transistors, however they often suffer from short lengths and wide band gaps. Here, the authors use a bottom-up synthesis approach to fabricate 9- and 13-atom wide ribbons, enabling short-channel transistors with 10(5) on-off current ratio.

  20. Effect of SrO on the electrical barrier formation and microstructure of TiO{sub 2} varistors

    Energy Technology Data Exchange (ETDEWEB)

    Delbrücke, Tiago, E-mail: tiagodt@gmail.com [Laboratory of Biomaterials & Advanced Ceramics, Engineering Materials Department, Federal University of Rio Grande do Sul, 91501-970, Porto Alegre, RS (Brazil); Pianaro, Sidnei A. [Interdisciplinary Laboratory of Ceramic Materials/LIMAC, Department of Materials Engineering, State University of Ponta Grossa, 84031-510, Ponta Grossa, PR (Brazil); Schmidt, Igor [Laboratory of Biomaterials & Advanced Ceramics, Engineering Materials Department, Federal University of Rio Grande do Sul, 91501-970, Porto Alegre, RS (Brazil); Cava, Sergio [Advanced Crystal Growth and Photonics, Technology Development Center, Federal University of Pelotas, 96010-900, Pelotas, RS (Brazil); Jurado, Jose R.; Sousa, Vânia C. [Laboratory of Biomaterials & Advanced Ceramics, Engineering Materials Department, Federal University of Rio Grande do Sul, 91501-970, Porto Alegre, RS (Brazil)

    2016-12-01

    TiO{sub 2}-based varistor materials with SrO dopants were prepared by the mechanical mixed oxides synthesis technique using conventional sintering at 1400 °C. I−V and microstructural characterization were performed. The composition range of 0.50–2.00 mol % SrO was studied and compared to pure TiO{sub 2}. Experimental evidence shows that small amounts of SrO improve the nonlinear properties of the samples significantly. Optimal varistor characteristics α = 5.50 and E{sub b} = 345 V/cm, were obtained with 1.00 mol % SrO-doped TiO{sub 2}. SrO in larger amounts causes the formation of precipitates of the SrTiO{sub 3} layer on the microstructure, being deleterious to the electrical properties. Therefore, dopants such as SrO or TiO{sub 2} play a special role in the morphology of the grain boundary and nonlinear response of these materials. An atomic defect model based on the double barrier Schottky type can be adopted to explain the formation of electrical barriers in TiO{sub 2} grain boundaries. - Highlights: • Training an effective potential barrier in the grain boundary, measured by electrical measurements on AC and DC. • Microstructure versus electrical properties. • Good properties getting varistor using a single dopant, forming a varistor binary system based on TiO{sub 2}.