WorldWideScience

Sample records for buried semiconductor heterostructures

  1. Fabrication of Tunable Sampled Grating DBR Laser Integrated Monolithically with Optical Semiconductor Amplifier Using Planar Buried Heterostructure

    Science.gov (United States)

    Oh, Su Hwan; Lee, Ji-Myon; Kim, Soo; Ko, Hyunsung; Lee, Chul-Wook; Park, Sahnggi; Park, Moon-Ho

    2004-10-01

    We have demonstrated a high-power widely tunable sampled grating (SG) DBR laser integrated monolithically with optical semiconductor amplifier (SOA), using planar buried heterostructure (PBH). The measured threshold current was 5 mA on average with 60 chips randomly selected which is lowest among the typical average values. Fiber-coupled output power was 12.4 dBm and the output power variation was ˜1 dB for the whole tuning range.

  2. Buried heterostructure vertical-cavity surface-emitting laser with semiconductor mirrors

    CERN Document Server

    Zhao, G; Deppe, D G; Konthasinghe, K; Muller, A

    2012-01-01

    We report a buried heterostructure vertical-cavity surface-emitting laser fabricated by epitaxial regrowth over an InGaAs quantum well gain medium. The regrowth technique enables microscale lateral confinement that preserves a high cavity quality factor (loaded $Q\\approx$ 4000) and eliminates parasitic charging effects found in existing approaches. Under optimal spectral overlap between gain medium and cavity mode (achieved here at $T$ = 40 K) lasing was obtained with an incident optical power as low as $P_{\\rm th}$ = 10 mW ($\\lambda_{\\rm p}$ = 808 nm). The laser linewidth was found to be $\\approx$3 GHz at $P_{\\rm p}\\approx$ 5 $P_{\\rm th}$.

  3. The Novel Semiconductor Nanowire Heterostructures

    Institute of Scientific and Technical Information of China (English)

    J.Q.Hu; Y.Bando; J.H.Zhan; D.Golberg

    2007-01-01

    1 Results If one-dimensional heterostructures with a well-defined compositional profile along the wire radial or axial direction can be realized within semiconductor nanowires, new nano-electronic devices,such as nano-waveguide and nano-capcipator, might be obtained. Here,we report the novel semiconducting nanowire heterostructures:(1) Si/ZnS side-to-side biaxial nanowires and ZnS/Si/ZnS sandwich-like triaxial nanowires[1],(2) Ga-Mg3N2 and Ga-ZnS metal-semiconductor nanowire heterojunctions[2-3]and (3) ...

  4. 10 Gbps Colorless Optical Source in Wavelength-Division Multiplexed Passive Optical Networks for Monolithic Integration of Deep-Ridge Waveguide Electroabsorption Modulator with Planar Buried-Heterostructure Semiconductor Optical Amplifier

    Science.gov (United States)

    Kim, Dong Churl; Kim, Ki Soo; Kim, Hyun-Soo; Choi, Byung-Seok; Kwon, O.-Kyun

    2012-05-01

    For the 10 Gbps colorless optical source in wavelength-division multiplexed passive optical networks (WDM-PONs), we have fabricated a semiconductor optical amplifier-reflective electorabsorption modulator (SOA-REAM) by monolithic integration of deep-ridge waveguide REAM (DRW-REAM) with planar buried-heterostructure (PBH) SOA using a PNP-current blocking layer. The SOA-REAM has a spot-size convertor for easy fiber coupling. Using a butterfly module with an SMA connector, we have packaged the SOA-REAM. At a -10 dBm input power of 1550 nm, the saturation output power is about 6 dBm. At 10.7 Gbps, we can obtain clear eye diagrams, and the power penalty at 10-9 bit-error rate (BER) after 20 km transmission is less than 1 dB over 35 nm.

  5. OPENING ADDRESS: Heterostructures in Semiconductors

    Science.gov (United States)

    Grimmeiss, Hermann G.

    1996-01-01

    Good morning, Gentlemen! On behalf of the Nobel Foundation, I should like to welcome you to the Nobel Symposium on "Heterostructures in Semiconductors". It gives me great pleasure to see so many colleagues and old friends from all over the world in the audience and, in particular, to bid welcome to our Nobel laureates, Prof. Esaki and Prof. von Klitzing. In front of a different audience I would now commend the scientific and technological importance of heterostructures in semiconductors and emphatically emphasise that heterostructures, as an important contribution to microelectronics and, hence, information technology, have changed societies all over the world. I would also mention that information technology is one of the most important global key industries which covers a wide field of important areas each of which bears its own character. Ever since the invention of the transistor, we have witnessed a fantastic growth in semiconductor technology, leading to more complex functions and higher densities of devices. This development would hardly be possible without an increasing understanding of semiconductor materials and new concepts in material growth techniques which allow the fabrication of previously unknown semiconductor structures. But here and today I will not do it because it would mean to carry coals to Newcastle. I will therefore not remind you that heterostructures were already suggested and discussed in detail a long time before proper technologies were available for the fabrication of such structures. Now, heterostructures are a foundation in science and part of our everyday life. Though this is certainly true, it is nevertheless fair to say that not all properties of heterostructures are yet understood and that further technologies have to be developed before a still better understanding is obtained. The organisers therefore hope that this symposium will contribute not only to improving our understanding of heterostructures but also to opening new

  6. Long wave polar modes in semiconductor heterostructures

    CERN Document Server

    Trallero-Giner, C; Garca̕-Moliner, F 0

    1998-01-01

    Long Wave Polar Modes in Semiconductor Heterostructures is concerned with the study of polar optical modes in semiconductor heterostructures from a phenomenological approach and aims to simplify the model of lattice dynamics calculations. The book provides useful tools for performing calculations relevant to anyone who might be interested in practical applications. The main focus of Long Wave Polar Modes in Semiconductor Heterostructures is planar heterostructures (quantum wells or barriers, superlattices, double barrier structures etc) but there is also discussion on the growing field of quan

  7. Electronic structure of semiconductor-metal-semiconductor heterostructures

    Science.gov (United States)

    Masri, Pierre

    For the first time, we present in this article a microscopic self-consistent theory of the electronic structure of semiconductor-metal-semiconductor (SMS) heterostructures. This is done within the framework of a tight-binding approximation. We use a one-band model and a simplified two-band model to describe metal and semiconductor bulk bands, respectively. Results are given for a material-symmetrical and interface-assymetrical SMS structure: this involves the same semiconductors, but different interface polarities (anion- and cation-like interfaces). These results include metal-like states (built-in metal band) and metal-induced semiconductor-like states. The relevance of the charge neutrality condition to this feature and to the determination of the position of the SMS Fermi level is discussed. We also emphasize the confining role of interfaces, with respect to semiconductor-like states, within the semiconductor gap.

  8. Analysis of quantum semiconductor heterostructures by ballistic electron emission spectroscopy

    Science.gov (United States)

    Guthrie, Daniel K.

    1998-09-01

    The microelectronics industry is diligently working to achieve the goal of gigascale integration (GSI) by early in the 21st century. For the past twenty-five years, progress toward this goal has been made by continually scaling down device technology. Unfortunately, this trend cannot continue to the point of producing arbitrarily small device sizes. One possible solution to this problem that is currently under intensive study is the relatively new area of quantum devices. Quantum devices represent a new class of microelectronic devices that operate by utilizing the wave-like nature (reflection, refraction, and confinement) of electrons together with the laws of quantum mechanics to construct useful devices. One difficulty associated with these structures is the absence of measurement techniques that can fully characterize carrier transport in such devices. This thesis addresses this need by focusing on the study of carrier transport in quantum semiconductor heterostructures using a relatively new and versatile measurement technique known as ballistic electron emission spectroscopy (BEES). To achieve this goal, a systematic approach that encompasses a set of progressively more complex structures is utilized. First, the simplest BEES structure possible, the metal/semiconductor interface, is thoroughly investigated in order to provide a foundation for measurements on more the complex structures. By modifying the semiclassical model commonly used to describe the experimental BEES spectrum, a very complete and accurate description of the basic structure has been achieved. Next, a very simple semiconductor heterostructure, a Ga1-xAlxAs single-barrier structure, was measured and analyzed. Low-temperature measurements on this structure were used to investigate the band structure and electron-wave interference effects in the Ga1-xAlxAs single barrier structure. These measurements are extended to a simple quantum device by designing, measuring, and analyzing a set of

  9. Synthesis and applications of heterostructured semiconductor nanocrystals

    Science.gov (United States)

    Khon, Elena

    Semiconductor nanocrystals (NCs) have been of great interest to researchers for several decades due to their unique optoelectronic properties. These nanoparticles are widely used for a variety of different applications. However, there are many unresolved issues that lower the efficiency and/or stability of devices which incorporate these NCs. Our research is dedicated to addressing these issues by identifying potential problems and resolving them, improving existing systems, generating new synthetic strategies, and/or building new devices. The general strategies for the synthesis of different nanocrystals were established in this work, one of which is the colloidal growth of gold domains onto CdS semiconductor nanocrystals. Control of shape and size was achieved simply by adjusting the temperature and the time of the reaction. Depending on the exact morphology of Au and CdS domains, fabricated nano-composites can undergo evaporation-induced self-assembly onto a substrate, which is very useful for building devices. CdS/Au heterostructures can assemble in two different ways: through end-to-end coupling of Au domains, resulting in the formation of one-dimensional chains; and via side-by-side packing of CdS nanorods, leading to the onset of two-dimensional superlattices. We investigated the nature of exciton-plasmon interactions in Au-tipped CdS nanorods using femtosecond transient absorption spectroscopy. The study demonstrated that the key optoelectronic properties of electrically coupled metal and semiconductor domains are significantly different from those observed in systems with weak inter-domain coupling. In particular, strongly-coupled nanocomposites promote mixing of electronic states at semiconductor-metal domain interfaces, which causes a significant suppression of both plasmon and exciton carrier excitations. Colloidal QDs are starting to replace organic molecules in many different applications, such as organic light emmiting diods (OLEDs), due to their

  10. Dynamics of multi-photon processes in semiconductor heterostructures

    OpenAIRE

    Marti, Daniel

    2003-01-01

    The present work is devoted to the study of the dynamics of multi-photon processes in semiconductor heterostructures. A time-dependent description is important for understanding in detail the transient response of semiconductors excited by ultrashort optical pulses. In the first part of this thesis, we set up a phenomenological model based on rate equations, in order to investigate the possibility of measuring degenerate two-photon gain in a semiconductor microcavity. The amplification predic...

  11. Engineering charge transport by heterostructuring solution-processed semiconductors

    Science.gov (United States)

    Voznyy, Oleksandr; Sutherland, Brandon R.; Ip, Alexander H.; Zhitomirsky, David; Sargent, Edward H.

    2017-06-01

    Solution-processed semiconductor devices are increasingly exploiting heterostructuring — an approach in which two or more materials with different energy landscapes are integrated into a composite system. Heterostructured materials offer an additional degree of freedom to control charge transport and recombination for more efficient optoelectronic devices. By exploiting energetic asymmetry, rationally engineered heterostructured materials can overcome weaknesses, augment strengths and introduce emergent physical phenomena that are otherwise inaccessible to single-material systems. These systems see benefit and application in two distinct branches of charge-carrier manipulation. First, they influence the balance between excitons and free charges to enhance electron extraction in solar cells and photodetectors. Second, they promote radiative recombination by spatially confining electrons and holes, which increases the quantum efficiency of light-emitting diodes. In this Review, we discuss advances in the design and composition of heterostructured materials, consider their implementation in semiconductor devices and examine unexplored paths for future advancement in the field.

  12. Room Temperature Operation of a Buried Heterostructure Photonic Crystal Quantum Cascade Laser

    CERN Document Server

    Peretti, R; Wolf, J M; Bonzon, C; Süess, M J; Lourdudoss, S; Metaferia, W; Beck, M; Faist, J

    2015-01-01

    We demonstrated room temperature operation of deep etched photonic crystal quantum cascade laser emitting around 8.5 micron. We fabricated buried heterostructure photonic crystals, resulting in single mode laser emission on a high order slow Bloch modes of the photonic crystal, between high symmetry points of the Brillouin.

  13. Metamaterial-inspired perfect tunnelling in semiconductor heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Jelinek, L [Department of Electromagnetic Field, Czech Technical University in Prague, Prague (Czech Republic); Baena, J D [Department of Physics, National University of Colombia, Bogota (Colombia); Voves, J [Department of Microelectronics, Czech Technical University in Prague, Prague (Czech Republic); Marques, R, E-mail: l_jelinek@us.es [Department of Electronics and Electromagnetism, University of Seville, Seville (Spain)

    2011-08-15

    In this paper, we use a formal analogy of the electromagnetic wave equation and the Schroedinger equation in order to study the phenomenon of perfect tunnelling (tunnelling with unitary transmittance) in a one-dimensional semiconductor heterostructure. Using the Kane model of a semiconductor, we show that this phenomenon can indeed exist, resembling all the interesting features of the corresponding phenomenon in classical electromagnetism in which metamaterials (substances with negative material parameters) are involved. We believe that these results can pave the way toward interesting applications in which metamaterial ideas are transferred into the semiconductor domain.

  14. Advanced Semiconductor Heterostructures Novel Devices, Potential Device Applications and Basic Properties

    CERN Document Server

    Stroscio, Michael A

    2003-01-01

    This volume provides valuable summaries on many aspects of advanced semiconductor heterostructures and highlights the great variety of semiconductor heterostructures that has emerged since their original conception. As exemplified by the chapters in this book, recent progress on advanced semiconductor heterostructures spans a truly remarkable range of scientific fields with an associated diversity of applications. Some of these applications will undoubtedly revolutionize critically important facets of modern technology. At the heart of these advances is the ability to design and control the pr

  15. Semiconductor-oxide heterostructured nanowires using postgrowth oxidation.

    Science.gov (United States)

    Wallentin, Jesper; Ek, Martin; Vainorious, Neimantas; Mergenthaler, Kilian; Samuelson, Lars; Pistol, Mats-Erik; Reine Wallenberg, L; Borgström, Magnus T

    2013-01-01

    Semiconductor-oxide heterointerfaces have several electron volts high-charge carrier potential barriers, which may enable devices utilizing quantum confinement at room temperature. While a single heterointerface is easily formed by oxide deposition on a crystalline semiconductor, as in MOS transistors, the amorphous structure of most oxides inhibits epitaxy of a second semiconductor layer. Here, we overcome this limitation by separating epitaxy from oxidation, using postgrowth oxidation of AlP segments to create axial and core-shell semiconductor-oxide heterostructured nanowires. Complete epitaxial AlP-InP nanowire structures were first grown in an oxygen-free environment. Subsequent exposure to air converted the AlP segments into amorphous aluminum oxide segments, leaving isolated InP segments in an oxide matrix. InP quantum dots formed on the nanowire sidewalls exhibit room temperature photoluminescence with small line widths (down to 15 meV) and high intensity. This optical performance, together with the control of heterostructure segment length, diameter, and position, opens up for optoelectrical applications at room temperature.

  16. Dual computational basis qubit in semiconductor heterostructures

    Science.gov (United States)

    Gilbert, M. J.; Akis, R.; Ferry, D. K.

    2003-08-01

    Advances in quantum computing have revealed computing capabilities that threaten to render many of the public encryption codes useless against the hacking potential for a quantum-mechanical-based computing system. This potential forces the study of viable methods to keep vital information secure from third-party eavesdropping. In this letter, we propose a coupled electronic waveguide device to create a qubit with two computational bases. The characteristics we have obtained by simulating such devices suggest a possible way of implementing quantum cryptography in semiconductor device architectures.

  17. Unselective regrowth buried heterostructure long-wavelength superluminescent diode realized with MOVPE

    Energy Technology Data Exchange (ETDEWEB)

    Ding Ying [Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China)]. E-mail: yingding@red.semi.ac.cn; Zhou Fan [Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China); Chen Weixi [School of Physics, Peking University, Beijing 100871 (China); Wang Wei [Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China)

    2007-01-15

    A novel unselective regrowth buried heterostructure (BH) long-wavelength superluminescent diode (SLD), which has a grade-strained bulk InGaAs active region, was developed by metalorganic vapor-phase epitaxy (MOVPE). The 3 dB emission spectrum bandwidth of the SLD is about 65 nm with the range from 1596 to 1661 nm at 90 mA and from 1585 to 1650 nm at 150 mA.An output power of 3.5 mW is obtained at 200 mA injection current under CW operation at room temperature.

  18. Nanoengineering the second order susceptibility in semiconductor quantum dot heterostructures.

    Science.gov (United States)

    Zielinski, Marcin; Winter, Shoshana; Kolkowski, Radoslaw; Nogues, Claude; Oron, Dan; Zyss, Joseph; Chauvat, Dominique

    2011-03-28

    We study second-harmonic generation from single CdTe/CdS core/shell rod-on-dot nanocrystals with different geometrical parameters, which allow to fine tune the nonlinear properties of the nanostructure. These hybrid semiconductor-semiconductor nanoparticles exhibit extremely strong and stable second-harmonic emission, although the size of CdTe core is still within the strong quantum confinement regime. The orientation sensitive polarization response is analyzed by means of a pointwise additive model of the third-order tensors associated to the nanoparticle components. These findings prove that engineering of semiconducting complex heterostructures at the single nanoparticle scale can lead to extremely bright nanometric nonlinear light sources.

  19. The use of synchrotron radiation techniques in the characterization of strained semiconductor heterostructures and thin films [review article

    Science.gov (United States)

    Lamberti, C.

    2004-05-01

    In the last couple of decades, high-performance electronic and optoelectronic devices based on semiconductor heterostructures have been required to obtain increasingly strict and well-defined performances, needing a detailed control, at the atomic level, of the structural composition of the buried interfaces. This goal has been achieved by an improvement of the epitaxial growth techniques and by the parallel use of increasingly sophisticated characterization techniques. Among them, a leading role has been certainly played by those exploiting synchrotron radiation (SR) sources. In fact synchrotron radiation has distinct advantages as a photon source, notably high brilliance and continuous energy spectrum; by using the latter characteristic atomic selectivity can be obtained and this is of fundamental help to investigate the structural environment of atoms present only in a few angstrom (Å) thick interface layers of heterostructures. The third generation synchrotron radiation sources have allowed to reach the limit of measuring a monolayer of material, corresponding to about 10 14 atoms/cm 2. Since, in the last decade, the use of intentionally strained heterostructures has greatly enhanced the performance of electrical and electro-optical semiconductor, a particular attention will be devoted to intentionally strained superlattices. First the effect of strain on the band lineups alignments in strained heterostructures will be discussed deeply. Then the attention will be focused on to review the most important results obtained by several groups in the characterization of semiconductor heterostructures using the following structural SR techniques: (i) X-ray absorption-based techniques such as EXAFS, polarization-dependent EXAFS, surface EXAFS and NEXAFS (or XANES); (ii) X-ray diffraction-based techniques such as high-resolution XRD, grazing incidence XRD, XRD reciprocal space maps, X-ray standing waves and diffraction anomalous fine structure (DAFS); (iii

  20. Novel applications of optical techniques to the study of buried semiconductor interfaces

    Science.gov (United States)

    Wilson, Barbara A.

    1989-01-01

    Detailed electronic and structural information about buried semiconductor interfaces obtained through application of optical techniques is discussed. The measurements described include the determination of band discontinuities, strain, and disorder associated with semiconductor heterointerfaces. The contactless and nondestructive nature of these optical techniques is particularly important for the study of heterointerfaces which are inherently inaccessible to direct electrical or physical contact.

  1. Evolution of electron spin polarization in semiconductor heterostructures

    Science.gov (United States)

    Pershin, Yuriy; Privman, Vladimir

    2004-03-01

    Last years theoretical and experimental investigations of electron spin-related effects in semiconductor heterostructures have received much consideration because of idea to create a semiconductor device based on the manipulation of electron spin. High degree of electron spin polarization is of crucial importance in operation of spintronic devices. We study possibilities to increase electron spin relaxation time by different means in systems where the D'yakonov-Perel' relaxation mechanism is dominant. Specifically, we show that the electron spin relaxation time in a two-dimensional electron gas with an antidote lattice increases exponentially with antidote radius for certain values of parameters. In another approach, we propose to use electron spin polarization having non-homogeneous direction of spin polarization vector in operation of a spintronic device. It is found that that the electron spin relaxation time essentially depends on the initial spin polarization distribution. This effect has its origin in the coherent spin precession of electrons diffusing in the same direction. We predict a long spin relaxation time of a novel structure: a spin coherence standing wave and discuss its experimental realization.

  2. DARPA-URI Consortium Meetings on Submicron Heterostructures of Diluted Magnetic Semiconductors.

    Science.gov (United States)

    1987-01-01

    B 35, 7464 (1987). 46. S. Rodriguez, A. Camacho and L. Quiroga, "Electrostatic and Magnetostatic Modes in Semiconductor Superlattices", (to appear in...AD-RI93 499 DARPA-URI CONSORTIUM MEETINGS ON SUSMICRON IETEROSTRUCTURES OF DILUTED MAGNETIC SEMICONDUCTORS (U) PURDUE UNIV LRFRYETTE IN 1987 N91114-86...o FILE COPY (SUBMICRON HETEROSTRUCTURES ,it OF DILUTED MAGNETIC SEMICONDUCTORS ANNUAL REPORT 1986-87 The Principal Investigators along with their co

  3. Photocatalytic Reduction of CO2 over Heterostructure Semiconductors into Value-Added Chemicals.

    Science.gov (United States)

    Guo, Ling-Ju; Wang, Yan-Jie; He, Tao

    2016-08-01

    Photoreduction of CO2 , which utilizes solar energy to convert CO2 into hydrocarbons, can be an effective means to overcome the increasing energy crisis and mitigate the rising emissions of greenhouse gas. This article covers recent advances in the CO2 photoreduction over heterostructure-based photocatalysts. The fundamentals of CO2 photoreduction and classification of the heterostructured photocatalysts are discussed first, followed by the latest work on the CO2 photoreduction over heterostructured photocatalysts in terms of the classification of the coupling semiconductors. Finally, a brief summary and a perspective on the challenges in this area are presented.

  4. Semiconductor quantum dots enhanced graphene/CdTe heterostructure solar cells by photo-induced doping

    CERN Document Server

    Li, Xiaoqiang; Wang, Peng; Xu, Zhijuan; Zhong, Huikai; Wu, Zhiqian; Lin, Shisheng

    2015-01-01

    Photo-induced doping is employed into graphene based solar cell through designing of a novel type of solar cell based on graphene/CdTe Schottky heterostructure. By coating a layer of ultrathin CdSe quantum dots onto graphene/CdTe heterostructure, the performance of the graphene/CdTe solar cell is improved by about 50%. Photo-induced doping is mainly accounted for this enhancement, as evidenced by resistance, photoluminescence and quantum efficiency measurements. This work demonstrates a general and feasible way of designing novel type of solar cells based on two dimensional materials/semiconductor heterostructures.

  5. P T -Symmetric Coupled-Resonator Waveguide Based on Buried Heterostructure Nanocavities

    Science.gov (United States)

    Takata, Kenta; Notomi, Masaya

    2017-05-01

    We propose and theoretically study a parity-time (P T )-symmetric photonic-crystal coupled-resonator optical waveguide (CROW) based on buried heterostructure nanocavities which has potential scalability and controllability. We analytically reveal its spectral transport properties with a tight-binding model and show the possibility of the wide-range control of its group velocity using the P T phase transition. While the group velocity at the P T phase-transition point diverges, the group-velocity dispersion converges. A numerical estimation of the system response to temporal pulse inputs shows that the pulse broadening is not severe in a device of hundreds of micrometers in size. Furthermore, a longer pulse duration results in a higher upper limit of the pulse peak velocity, which can be, in principle, superluminal. We next perform numerical simulations on the considered photonic-crystal slab structures with the finite-element method, and we successfully observe P T phase transitions. In the simulated parameter range, gain and loss coefficients of the order of 100 cm-1 meet the condition for the maximum group-velocity coefficient in the context of the tight-binding approach. A 9.3-fold increase in the group velocity at 1502 nm is obtained in a three-dimensional device by switching between the conventional and P T -symmetric CROWs. Meanwhile, we also encounter band smoothing around the phase transition, which hampers the group-velocity divergence. Our simulation result indicates that it arises from interfering evanescent waves decaying out of the device structure, and we discuss ways to suppress this effect.

  6. High power, high efficiency window buried heterostructure GaAlAs superluminescent diode with an integrated absorber

    Energy Technology Data Exchange (ETDEWEB)

    Kwong, N.S.K.; Lau, K.Y.; Bar-Chaim, N.; Ury, I.; Lee, K.J.

    1987-12-07

    A superluminescent diode (SLD) based on a proven high power, high efficiency ''window-'' type index-guided buried heterostructure laser is demonstrated. Lasing is suppressed for SLD operation by antireflection coating and by incorporating an unpumped absorber section. The resulting device emits high optical power (14 mW) in the SLD mode at very low injection current (50 mA). The spectral modulation depth is below 14% over the entire emission spectral bandwidth of 20 nm, with a symmetrical beam divergence (20/sup 0/ x 40/sup 0/) and a stable transverse mode.

  7. Tracking Ultrafast Carrier Dynamics in Single Semiconductor Nanowire Heterostructures

    Directory of Open Access Journals (Sweden)

    Taylor A.J.

    2013-03-01

    Full Text Available An understanding of non-equilibrium carrier dynamics in silicon (Si nanowires (NWs and NW heterostructures is very important due to their many nanophotonic and nanoelectronics applications. Here, we describe the first measurements of ultrafast carrier dynamics and diffusion in single heterostructured Si nanowires, obtained using ultrafast optical microscopy. By isolating individual nanowires, we avoid complications resulting from the broad size and alignment distribution in nanowire ensembles, allowing us to directly probe ultrafast carrier dynamics in these quasi-one-dimensional systems. Spatially-resolved pump-probe spectroscopy demonstrates the influence of surface-mediated mechanisms on carrier dynamics in a single NW, while polarization-resolved femtosecond pump-probe spectroscopy reveals a clear anisotropy in carrier lifetimes measured parallel and perpendicular to the NW axis, due to density-dependent Auger recombination. Furthermore, separating the pump and probe spots along the NW axis enabled us to track space and time dependent carrier diffusion in radial and axial NW heterostructures. These results enable us to reveal the influence of radial and axial interfaces on carrier dynamics and charge transport in these quasi-one-dimensional nanosystems, which can then be used to tailor carrier relaxation in a single nanowire heterostructure for a given application.

  8. The Ben Daniel-Duke Model Applied to Semiconductor Heterostructure - Part 2

    Directory of Open Access Journals (Sweden)

    Cornel Hatiegan

    2009-10-01

    Full Text Available We investigate the semiconductor heterostructure with the Ben DanielDuke model applied for the lowest conduction states Ga As-Ga (1 as and for the heavy levels at k⊥ = 0 in any heterostructures (1. In a quantic level we obtained the familiar staircase density of states (2. In (3 we calculated the incrgy position of the interface state in a single HgTe-CdTe heterojonction. We also obtained the existence of the interface state relies only on the relative position of the I’8 edges of HgTe and CdTe, their actual energy position, as well as their behavior at k⊥ ≠ 0 .

  9. InP-Based Heterostructure Design and Growth for Semiconductor Nanomembrane Optoelectronics on Si and on Flexible Substrates

    Science.gov (United States)

    2014-05-21

    AFRL-AFOSR-UK-TR-2014-0015 InP-based heterostructure design and growth for semiconductor nanomembrane optoelectronics on Si and...TITLE AND SUBTITLE InP-based heterostructure design and growth for semiconductor nanomembrane optoelectronics on Si and on flexible substrates...on the realization of ultracompact microcavity lasers directly integrated on silicon. Using a stamp-assisted transfer-printing technology, silicon

  10. A model of axial heterostructure formation in III-V semiconductor nanowires

    Science.gov (United States)

    Dubrovskii, V. G.

    2016-03-01

    A kinetic model of the formation of axial heterostructures in nanocrystalline wires (nanowires, NWs) of III-V semiconductor compounds growing according to the vapor-liquid-solid (VLS) mechanism is proposed. A general system of nonstationary equations for effective fluxes of two elements of the same group (e.g., group III) is formulated that allows the composition profile of a heterostructure to be calculated as a function of the coordinate and epitaxial growth conditions, including the flux of a group V element. Characteristic times of the composition relaxation, which determine the sharpness of the heteroboundary (heterointerface), are determined in the linear approximation. A temporal interruption (arrest) of fluxes during the switching of elements for a period exceeding these relaxation times must increase sharpness of the heteroboundary. Model calculations of the composition profile in a double GaAs/InAs/GaAs axial heterostructure have been performed for various NW radii.

  11. Ballistic-electron-emission Microscopy of Semiconductor Heterostructures

    Science.gov (United States)

    Bell, L. Douglas; Narayanamurti, Venkatesh

    1997-01-01

    Balistic-electron-emission microscopy has developed from its beginning as a probe of Schottky barriers into a powerful nanometer-scale method for characterizing semiconductor interfaces and hot-electron transport.

  12. Device Concepts Based on Spin-dependent Transmission in Semiconductor Heterostructures

    Science.gov (United States)

    Ting, David Z. - Y.; Cartoixa, X.

    2004-01-01

    We examine zero-magnetic-field spin-dependent transmission in nonmagnetic semiconductor heterostructures with structural inversion asymmetry (SIA) and bulk inversion asymmetry (BIA), and report spin devices concepts that exploit their properties. Our modeling results show that several design strategies could be used to achieve high spin filtering efficiencies. The current spin polarization of these devices is electrically controllable, and potentially amenable to highspeed spin modulation, and could be integrated in optoelectronic devices for added functionality.

  13. Coherent phonon spectroscopy characterization of electronic bands at buried semiconductor heterointerfaces

    Energy Technology Data Exchange (ETDEWEB)

    Ishioka, Kunie, E-mail: ishioka.kunie@nims.go.jp [Nano Characterization Unit, National Institute for Materials Science, Tsukuba 305-0047 (Japan); Brixius, Kristina; Beyer, Andreas; Stolz, Wolfgang; Volz, Kerstin; Höfer, Ulrich [Faculty of Physics and Materials Sciences Center, Philipps-Universität Marburg, 35032 Marburg (Germany); Rustagi, Avinash; Stanton, Christopher J. [Department of Physics, University of Florida, Gainesville, Florida 32611 (United States); Petek, Hrvoje [Department of Physics and Astronomy and Pittsburgh Quantum Institute, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States)

    2016-02-01

    We demonstrate an all-optical approach to probe electronic band structure at buried interfaces involving polar semiconductors. Femtosecond optical pulses excite coherent phonons in epitaxial GaP films grown on Si(001) substrate. We find that the coherent phonon amplitude critically depends on the film growth conditions, specifically in the presence of antiphase domains, which are independently characterized by transmission electron microscopy. We determine the Fermi levels at the buried interface of GaP/Si from the coherent phonon amplitudes and demonstrate that the internal electric fields are created in the nominally undoped GaP films as well as the Si substrates, possibly due to the carrier trapping at the antiphase boundaries and/or at the interface.

  14. Oscillatory quantum interference effects in narrow-gap semiconductor heterostructures

    Science.gov (United States)

    Lillianfeld, R. B.; Kallaher, R. L.; Heremans, J. J.; Chen, Hong; Goel, N.; Chung, S. J.; Santos, M. B.; Van Roy, W.; Borghs, G.

    2010-01-01

    We investigate quantum interference phenomena in narrow bandgap semiconductors under strong spin-orbit interaction, by measuring the magnetoresistance across mesoscopic closed-path structures fabricated in two-dimensional electron systems. We discuss our results in terms of four quantum interference effects brought about by geometric phases acquired by the electron wave functions: the Aharonov-Bohm phase, the Altshuler-Aronov-Spivak effect, the Berry's phase due to the evolution of the spin degree of freedom, and the Aharonov-Casher phase.

  15. Physics and application of persistent spin helix state in semiconductor heterostructures

    Science.gov (United States)

    Kohda, Makoto; Salis, Gian

    2017-07-01

    In order to utilize the spin degree of freedom in semiconductors, control of spin states and transfer of the spin information are fundamental requirements for future spintronic devices and quantum computing. Spin orbit (SO) interaction generates an effective magnetic field for moving electrons and enables spin generation, spin manipulation and spin detection without using external magnetic field and magnetic materials. However, spin relaxation also takes place due to a momentum dependent SO-induced effective magnetic field. As a result, SO interaction is considered to be a double-edged sword facilitating spin control but preventing spin transport over long distances. The persistent spin helix (PSH) state solves this problem since uniaxial alignment of the SO field with SU(2) symmetry enables the suppression of spin relaxation while spin precession can still be controlled. Consequently, understanding the PSH becomes an important step towards future spintronic technologies for classical and quantum applications. Here, we review recent progress of PSH in semiconductor heterostructures and its device application. Fundamental physics of SO interaction and the conditions of a PSH state in semiconductor heterostructures are discussed. We introduce experimental techniques to observe a PSH and explain both optical and electrical measurements for detecting a long spin relaxation time and the formation of a helical spin texture. After emphasizing the bulk Dresselhaus SO coefficient γ, the application of PSH states for spin transistors and logic circuits are discussed.

  16. Vertical 2D/3D Semiconductor Heterostructures Based on Epitaxial Molybdenum Disulfide and Gallium Nitride.

    Science.gov (United States)

    Ruzmetov, Dmitry; Zhang, Kehao; Stan, Gheorghe; Kalanyan, Berc; Bhimanapati, Ganesh R; Eichfeld, Sarah M; Burke, Robert A; Shah, Pankaj B; O'Regan, Terrance P; Crowne, Frank J; Birdwell, A Glen; Robinson, Joshua A; Davydov, Albert V; Ivanov, Tony G

    2016-03-22

    When designing semiconductor heterostructures, it is expected that epitaxial alignment will facilitate low-defect interfaces and efficient vertical transport. Here, we report lattice-matched epitaxial growth of molybdenum disulfide (MoS2) directly on gallium nitride (GaN), resulting in high-quality, unstrained, single-layer MoS2 with strict registry to the GaN lattice. These results present a promising path toward the implementation of high-performance electronic devices based on 2D/3D vertical heterostructures, where each of the 3D and 2D semiconductors is both a template for subsequent epitaxial growth and an active component of the device. The MoS2 monolayer triangles average 1 μm along each side, with monolayer blankets (merged triangles) exhibiting properties similar to that of single-crystal MoS2 sheets. Photoluminescence, Raman, atomic force microscopy, and X-ray photoelectron spectroscopy analyses identified monolayer MoS2 with a prominent 20-fold enhancement of photoluminescence in the center regions of larger triangles. The MoS2/GaN structures are shown to electrically conduct in the out-of-plane direction, confirming the potential of directly synthesized 2D/3D semiconductor heterostructures for vertical current flow. Finally, we estimate a MoS2/GaN contact resistivity to be less than 4 Ω·cm(2) and current spreading in the MoS2 monolayer of approximately 1 μm in diameter.

  17. Photoluminescence efficiency in wide-band-gap iii-nitride semiconductors and their heterostructures

    OpenAIRE

    Jurkevičius, Jonas

    2016-01-01

    This doctoral thesis presents a study of photoluminescence efficiency in wide-band-gap III-nitride semiconductors. The work is aimed at investigation of efficiency-limiting processes and causes of efficiency droop in AlGaN epilayers and multiple quantum wells. Also, light emission in BGaN epilayers, which are prospective in view of lattice matching in AlGaN-based heterostructures, is investigated. Three mechanisms are revealed to be important for the droop in AlGaN and the dependence of their...

  18. Quantized conductance doubling and hard gap in a two-dimensional semiconductor-superconductor heterostructure

    DEFF Research Database (Denmark)

    Kjærgaard, Morten; Nichele, F; Suominen, Henri Juhani;

    2016-01-01

    Coupling a two-dimensional (2D) semiconductor heterostructure to a superconductor opens new research and technology opportunities, including fundamental problems in mesoscopic superconductivity, scalable superconducting electronics, and new topological states of matter. One route towards...... topological matter is by coupling a 2D electron gas with strong spin-orbit interaction to an s-wave superconductor. Previous efforts along these lines have been adversely affected by interface disorder and unstable gating. Here we show measurements on a gateable InGaAs/InAs 2DEG with patterned epitaxial Al......, yielding devices with atomically pristine interfaces between semiconductor and superconductor. Using surface gates to form a quantum point contact (QPC), we find a hard superconducting gap in the tunnelling regime. When the QPC is in the open regime, we observe a first conductance plateau at 4e(2)/h...

  19. Tunable Interface Non-linear Electron Transport in Semiconductor Nanowire Heterostructure and Its Application in Optoelectronics

    Science.gov (United States)

    Chen, Guannan

    Understanding the effects of finite size and dimensionality on the interaction of light with nanoscale semiconductor heterostructure is central to identifying and exploiting novel modes in optoelectronic devices. In type-I heterostructured core-shell GaAs/AlxGa1-xAs nanowires, the real space transfer (RST) of photogenerated hot electrons across the interface from the GaAs core to the AlxGa1-xAs shell forms the basis of a new family of optoelectronic devices by a carefully designed and optimized nanofabrication process. Due to the large mobility difference, we observed negative differential resistance (NDR) on single nanowire devices. External modulation of the transfer rates, manifested as a large tunability of the voltage onset of NDR, is achieved using three different modes: electrostatic gating, incident photon flux, and photon energy. In this dissertation, the physics of coupling of external control to transfer rate was investigated. The combined influences of geometric confinement, heterojunction shape and carrier scattering on hot-electron transfer is discussed. Temperature-dependent transport study under monochromatic tunable laser illumination reveals an ultrafast carrier dynamics related to RST of excess carriers, which provides an insight into hot carrier cooling. Device element showing adjustable phase shift and frequency doubling of ac modulation is demonstrated. For a full understanding, Carrier transport properties are probed through electron beam induced current, which is capable of imaging sub-surface feature in excess carrier transport. Along with simulation of injected electron trajectories, selective probing of core and shell by tuning electron beam energies reveals axial and bias dependent transport along parallel channels. The drift and diffusion component of the excess carrier current is deconvoluted from a coupled decay length, from which lower than bulk shell electron mobility is extracted. A precise knowledge of band edge discontinuities at

  20. Investigation of III-V semiconductor heterostructures for post-Si-CMOS applications

    Science.gov (United States)

    Bhatnagar, Kunal

    Silicon complementary metal-oxide-semiconductor (CMOS) technology in the past few decades has been driven by aggressive device scaling to increase performance, reduce cost and lower power consumption. However, as devices are scaled below the 100 nm region, performance gain has become increasingly difficult to obtain by traditional scaling. As we move towards advanced technology nodes, materials innovation and physical architecture are becoming the primary enabler for performance enhancement in CMOS technology rather than scaling. One class of materials that can potentially result in improved electrical performance are III-V semiconductors, which are ideal candidates for replacing the channel in Si CMOS owing to their high electron mobilities and capabilities for band-engineering. This work is aimed towards the growth and characterization of III-V semiconductor heterostructures and their application in post-Si-CMOS devices. The two main components of this study include the integration of III-V compound semiconductors on silicon for tunnel-junction Esaki diodes, and the investigation of carrier transport properties in low-power III-V n-channel FETs under uniaxial strain for advanced III-V CMOS solutions. The integration of III-V compound semiconductors with Si can combine the cost advantage and maturity of the Si technology with the superior performance of III-V materials. We have demonstrated high quality epitaxial growth of GaAs and GaSb on Si (001) wafers through the use of various buffer layers including AlSb and crystalline SrTiO3. These GaSb/Si virtual substrates were used for the fabrication and characterization of InAs/GaSb broken-gap Esaki-tunnel diodes as a possible solution for heterojunction Tunnel-FETs. In addition, the carrier transport properties of InAs channels were evaluated under uniaxial strain for the potential use of strain solutions in III-V CMOS.

  1. Electronic and Shallow Impurity States in Semiconductor Heterostructures Under an Applied Electric Field

    Institute of Scientific and Technical Information of China (English)

    ZHOU Hai-Yang; GU Shi-Wei; SHI Yao-Ming

    2005-01-01

    With the use of variational method to solve the effective mass equation, we have studied the electronic and shallow impurity states in semiconductor heterostructures under an applied electric field. The electron energy levels are calculated exactly and the impurity binding energies are calculated with the variational approach. It is found that the behaviors of electronic and shallow impurity states in heterostructures under an applied electric field are analogous to that of quantum wells. Our results show that with the increasing strength of electric field, the electron confinement energies increase, and the impurity binding energy increases also when the impurity is on the surface, while the impurity binding energy increases at first, to a peak value, then decreases to a value which is related to the impurity position when the impurity is away from the surface. In the absence of electric field, the result tends to the Levine's ground state energy (-1/4 effective Rydberg) when the impurity is on the surface, and the ground impurity binding energy tends to that in the bulk when the impurity is far away from the surface. The dependence of the impurity binding energy on the impurity position for different electric field is also discussed.

  2. Correlated micro-photoluminescence and electron microscopy studies of the same individual heterostructured semiconductor nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Todorovic, J; Van Helvoort, A T J [Department of Physics, Norwegian University of Science and Technology, NO-7491, Trondheim (Norway); Moses, A F; Karlberg, T; Olk, P; Dheeraj, D L; Fimland, B O; Weman, H, E-mail: a.helvoort@ntnu.no [Department of Electronics and Telecommunications, Norwegian University of Science and Technology, NO-7491, Trondheim (Norway)

    2011-08-12

    To correlate optical properties to structural characteristics, we developed a robust strategy for characterizing the same individual heterostructured semiconductor nanowires (NWs) by alternating low temperature micro-photoluminescence ({mu}-PL), low voltage scanning (transmission) electron microscopy and conventional transmission electron microscopy. The NWs used in this work were wurtzite GaAs core with zinc blende GaAsSb axial insert and AlGaAs radial shell grown by molecular beam epitaxy. The series of experiments demonstrated that high energy (200 kV) electrons are detrimental for the optical properties, whereas medium energy (5-30 kV) electrons do not affect the PL response. Thus, such medium energy electrons can be used to select NWs for correlated optical-structural studies prior to {mu}-PL or in NW device processing. The correlation between the three main {mu}-PL bands and crystal phases of different compositions, present in this heterostructure, is demonstrated for selected NWs. The positions where a NW fractures during specimen preparation can considerably affect the PL spectra of the NW. The effects of crystal-phase variations and lattice defects on the optical properties are discussed. The established strategy can be applied to other nanosized electro-optical materials, and other characterization tools can be incorporated into this routine.

  3. Electronic properties of electron and hole in type-II semiconductor nano-heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Rahul, K. Suseel [Department of Physics, Central University of Kerala, Riverside Transit Campus, Kasaragod, Kerala. India (India); Department of Physics, Sri Vyasa NSS College, Wadakkancheri, Thrissur, Kerala, PIN:680623. India (India); Souparnika, C. [Department of Physics, Sri Vyasa NSS College, Wadakkancheri, Thrissur, Kerala, PIN:680623. India (India); Salini, K.; Mathew, Vincent, E-mail: vincent@cukerala.ac.in [Department of Physics, Central University of Kerala, Riverside Transit Campus, Kasaragod, Kerala. India (India)

    2016-05-06

    In this project, we record the orbitals of electron and hole in type-II (CdTe/CdSe/CdTe/CdSe) semiconductor nanocrystal using effective mass approximation. In type-II the band edges of both valance and conduction band are higher than that of shell. So the electron and hole get confined in different layers of the hetero-structure. The energy eigen values and eigen functions are calculated by solving Schrodinger equation using finite difference matrix method. Based on this we investigate the effect of shell thickness and well width on energy and probability distribution of ground state (1s) and few excited states (1p,1d,etc). Our results predict that, type-II quantum dots have significant importance in photovoltaic applications.

  4. Difference of Oxide Hetero-structure Junctions with Semiconductor Electronic Devices

    Institute of Scientific and Technical Information of China (English)

    XIONG Guang-Cheng; CHEN Yuan-Sha; CHEN Li-Ping; LIAN Gui-Jun

    2008-01-01

    Charge carrier injection is performed in Pro.TCao.aMnOa (PCMO) hetero-structure junctions, exhibiting the stability without electric fields and dramatic changes in both resistance and interface barriers, which are entirely different from behaviour of semiconductor devices. The disappearance and reversion of interface barriers suggest that the adjustable resistance switching of such hereto-structure oxide devices should associate with motion of charge carriers across interfaces. The results suggest that injected carriers should be still staying in devices and result in changes of properties, which lead to a carrier self-trapping and releasing picture in a strongly correlated electronic framework. Observations in PCMO and oxygen deficient CeO2-δ devices show that oxides as functional materials could be used in microelectronics with some novel properties, in which the interface is very important.

  5. Density Functional Theory Simulations of Semiconductors for Photovoltaic Applications: Hybrid Organic-Inorganic Perovskites and III/V Heterostructures

    Directory of Open Access Journals (Sweden)

    Jacky Even

    2014-01-01

    Full Text Available Potentialities of density functional theory (DFT based methodologies are explored for photovoltaic materials through the modeling of the structural and optoelectronic properties of semiconductor hybrid organic-inorganic perovskites and GaAs/GaP heterostructures. They show how the properties of these bulk materials, as well as atomistic relaxations, interfaces, and electronic band-lineups in small heterostructures, can be thoroughly investigated. Some limitations of available standard DFT codes are discussed. Recent improvements able to treat many-body effects or based on density-functional perturbation theory are also reviewed in the context of issues relevant to photovoltaic technologies.

  6. Ferromagnetic semiconductor-metal transition in heterostructures of electron doped europium monoxide

    Energy Technology Data Exchange (ETDEWEB)

    Stollenwerk, Tobias

    2013-09-15

    In the present work, we develop and solve a self-consistent theory for the description of the simultaneous ferromagnetic semiconductor-metal transition in electron doped Europium monoxide. We investigate two different types of electron doping, Gadolinium impurities and Oxygen vacancies. Besides the conduction band occupation, we can identify low lying spin fluctuations on magnetic impurities as the driving force behind the doping induced enhancement of the Curie temperature. Moreover, we predict the signatures of these magnetic impurities in the spectra of scanning tunneling microscope experiments. By extending the theory to allow for inhomogeneities in one spatial direction, we are able to investigate thin films and heterostructures of Gadolinium doped Europium monoxide. Here, we are able to reproduce the experimentally observed decrease of the Curie temperature with the film thickness. This behavior is attributed to missing coupling partners of the localized 4f moments as well as to an electron depletion at the surface which leads to a reduction of the number of itinerant electrons. By investigating the influence of a metallic substrate onto the phase transition in Gadolinium doped Europium monoxide, we find that the Curie temperature can be increased up to 20%. However, as we show, the underlying mechanism of metal-interface induced charge carrier accumulation is inextricably connected to a suppression of the semiconductor-metal transition.

  7. Combining experiment and optical simulation in coherent X-ray nanobeam characterization of Si/SiGe semiconductor heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Tilka, J. A.; Park, J.; Ahn, Y.; Pateras, A.; Sampson, K. C.; Savage, D. E.; Lagally, M. G.; Evans, P. G., E-mail: pgevans@wisc.edu [Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Prance, J. R.; Simmons, C. B.; Coppersmith, S. N.; Eriksson, M. A. [Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Holt, M. V. [Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

    2016-07-07

    The highly coherent and tightly focused x-ray beams produced by hard x-ray light sources enable the nanoscale characterization of the structure of electronic materials but are accompanied by significant challenges in the interpretation of diffraction and scattering patterns. X-ray nanobeams exhibit optical coherence combined with a large angular divergence introduced by the x-ray focusing optics. The scattering of nanofocused x-ray beams from intricate semiconductor heterostructures produces a complex distribution of scattered intensity. We report here an extension of coherent x-ray optical simulations of convergent x-ray beam diffraction patterns to arbitrary x-ray incident angles to allow the nanobeam diffraction patterns of complex heterostructures to be simulated faithfully. These methods are used to extract the misorientation of lattice planes and the strain of individual layers from synchrotron x-ray nanobeam diffraction patterns of Si/SiGe heterostructures relevant to applications in quantum electronic devices. The systematic interpretation of nanobeam diffraction patterns from semiconductor heterostructures presents a new opportunity in characterizing and ultimately designing electronic materials.

  8. Combining experiment and optical simulation in coherent X-ray nanobeam characterization of Si/SiGe semiconductor heterostructures

    Science.gov (United States)

    Tilka, J. A.; Park, J.; Ahn, Y.; Pateras, A.; Sampson, K. C.; Savage, D. E.; Prance, J. R.; Simmons, C. B.; Coppersmith, S. N.; Eriksson, M. A.; Lagally, M. G.; Holt, M. V.; Evans, P. G.

    2016-07-01

    The highly coherent and tightly focused x-ray beams produced by hard x-ray light sources enable the nanoscale characterization of the structure of electronic materials but are accompanied by significant challenges in the interpretation of diffraction and scattering patterns. X-ray nanobeams exhibit optical coherence combined with a large angular divergence introduced by the x-ray focusing optics. The scattering of nanofocused x-ray beams from intricate semiconductor heterostructures produces a complex distribution of scattered intensity. We report here an extension of coherent x-ray optical simulations of convergent x-ray beam diffraction patterns to arbitrary x-ray incident angles to allow the nanobeam diffraction patterns of complex heterostructures to be simulated faithfully. These methods are used to extract the misorientation of lattice planes and the strain of individual layers from synchrotron x-ray nanobeam diffraction patterns of Si/SiGe heterostructures relevant to applications in quantum electronic devices. The systematic interpretation of nanobeam diffraction patterns from semiconductor heterostructures presents a new opportunity in characterizing and ultimately designing electronic materials.

  9. On the coherence/incoherence of electron transport in semiconductor heterostructure optoelectronic devices

    Science.gov (United States)

    Harrison, P.; Indjin, D.; Savić, I.; Ikonić, Z.; Evans, C. A.; Vukmirović, N.; Kelsall, R. W.; McTavish, J.; Jovanović, V. D.; Milanović, V.

    2008-02-01

    This paper compares and contrasts different theoretical approaches based on incoherent electron scattering transport with experimental measurements of optoelectronic devices formed from semiconductor heterostructures. The Monte Carlo method which makes no a priori assumptions about the carrier distribution in momentum or phase space is compared with less computationally demanding energy-balance rate equation models which assume thermalised carrier distributions. It is shown that the two approaches produce qualitatively similar results for hole transport in p-type Si 1-xGe x/Si superlattices designed for terahertz emission. The good agreement of the predictions of rate equation calculations with experimental measurements of mid- and far-infrared quantum cascade lasers, quantum well infrared photodetectors and quantum dot infrared photodetectors substantiate the assumption of incoherent scattering dominating the transport in these quantum well based devices. However, the paper goes on to consider the possibility of coherent transport through the density matrix method and suggests an experiment that could allow coherent and incoherent transport to be distinguished from each other.

  10. Ultrafast Study of Dynamic interfacial Exchange Coupling in Ferromagnet/Oxide/Semiconductor Heterostructures

    Science.gov (United States)

    Ou, Yu-Sheng; Chiu, Yi-Hsin; Harmon, Nicholas; Odenthal, Patrick; Sheffield, Matthew; Chilcote, Michael; Kawakami, Roland; Flatté, Michael; Johnston-Halperin, Ezekiel

    Time-resolved Kerr/Faraday rotation (TRKR/TRFR) is employed to study GaAs spin dynamics in the regime of strong and dynamic exchange coupling to an adjacent MgO/Fe layer. This study reveals a dramatic, resonant suppression in the inhomogeneous spin lifetime (T2*) in the GaAs layer. Further investigation of the magnetization dynamics of the neighboring Fe layer, also using TRKR/TRFR, reveals not only the expected Kittel-dispersion but also additional lower frequency modes with very short lifetime (65 ps) that are not easily observed with conventional ferromagnetic resonance (FMR) techniques. These results suggest the intriguing possibility of resonant dynamic spin transfer between the GaAs and Fe spin systems. We discuss the potential for this work to establish GaAs spin dynamics as an efficient detector of spin dissipation and transport in the regime of dynamically-driven spin injection in ferromagnet/semiconductor heterostructures. Center for Emergent Materials; U.S. Department of Energy.

  11. Aharonov-Bohm-type quantum interference effects in narrow gap semiconductor heterostructures

    Science.gov (United States)

    Lillianfeld, R. B.; Kallaher, R. L.; Heremans, J. J.; Chen, Hong; Goel, N.; Chung, S. J.; Santos, M. B.; van Roy, W.; Borghs, G.

    2009-03-01

    We present experiments on quantum interference phenomena in semiconductors with strong spin-orbit interaction, using mesoscopic parallel ring arrays fabricated on InSb/InAlSb and InAs/AlGaSb heterostructures. Both external electric field effects and temperature dependence of the ring magnetoresistance are examined. Top-gate voltage-dependent oscillations in ring resistance in the absence of an external magnetic field are suggestive of Aharonov-Casher interference. At low magnetic fields the ring magnetoresistance is dominated by oscillations with h/2e periodicity characteristic of Altshuler-Aronov-Spivak (AAS) oscillations, whereas the h/e periodicity characteristic of Aharonov-Bohm (AB) oscillations persists to high magnetic fields. Fourier spectra (FS) reveal AB amplitudes on the same order as AAS amplitudes at low fields, and in some samples reveal a splitting of the AB peaks, which has been interpreted as a signature of Berry's phase. The FS are also used to quantify the temperature dependence of the oscillation amplitudes (NSF DMR-0618235, DOE DE-FG02-08ER46532, NSF DMR-0520550).

  12. Suitability of Semiconductor Heterostructure over SiO2-Air Composition for One-Dimensional Photonic Crystal based Bandpass Filter

    Directory of Open Access Journals (Sweden)

    Arka Karmakar

    2013-05-01

    Full Text Available Bandpass filter characteristics is numerically computed for semiconductor heterostructure based onedimensional photonic crystal at different optical wavelengths by varying the structural parameters taking GaAs/AlxGa1-xAs as a suitable composition subject to normal incidence of electromagnetic wave. Transfer matrix technique is used for numerical analysis. Results are compared with conventionally used SiO2-air material system and significance improvements are observed at few desired spectra. Heterostructure provides larger passbandwidth with almost negligible ripple than conventional material system at 1330 nm or 1550 nm, which is required for present day optical communication network. Efficient tuning can be achieved by varying different layer dimensions for the preferred material composition which effectively changes the filter bandwidth in either side of the central wavelength, but it cost generation of ripples for the conventional system.

  13. Comparison of semi-insulating InAlAs and InP:Fe for InP-based buried-heterostructure QCLs

    Science.gov (United States)

    Flores, Y. V.; Aleksandrova, A.; Elagin, M.; Kischkat, J.; Kurlov, S. S.; Monastyrskyi, G.; Hellemann, J.; Golovynskyi, S. L.; Dacenko, O. I.; Kondratenko, S. V.; Tarasov, G. G.; Semtsiv, M. P.; Masselink, W. T.

    2015-09-01

    In a previous work [Flores et al., J. Cryst. Growth 398 (2014) 40] [3] we demonstrated the advantages of using a thin InAlAs spacer layer in the fabrication of buried-heterostructure quantum-cascade lasers (QCLs), as it improves the morphology of the interface between the laser core and the InP:Fe lateral cladding. In this paper we investigate aspects of InAlAs, which are relevant for its role as insulating lateral cladding of the laser sidewalls: carrier traps, electrical resistivity, and functionality as a sole lateral cladding. We find that a thin InAlAs spacer layer not only improves the regrowth interface morphology, but also eliminates interface-related shallow electronic states, thus improving the electrical resistivity of the interface. We further find that bulk InAlAs grown by gas-source molecular-beam epitaxy as well as InP:Fe are semi-insulating at room temperature, with specific resistivities of 3 ×107 Ω cm and 2 ×108 Ω cm, respectively. Both materials have also a high thermal activation energy for electrical conductivity (0.79 eV and 0.68 eV, respectively). In order to compare the performance of InP:Fe and InAlAs as a lateral cladding, lasers were fabricated from the same QCL wafer with differing stripe insulation materials. The resulting lasers differ mainly by the lateral insulation material: SiO2, InP:Fe (with InAlAs spacer), and pure InAlAs. All devices show a similar performance and similar temperature dependence, indicating insulating properties of InAlAs adequate for application in lateral regrowth of buried-heterostructure QCLs.

  14. Cross-sectional imaging of individual layers and buried interfaces of graphene-based heterostructures and superlattices

    Science.gov (United States)

    Haigh, S. J.; Gholinia, A.; Jalil, R.; Romani, S.; Britnell, L.; Elias, D. C.; Novoselov, K. S.; Ponomarenko, L. A.; Geim, A. K.; Gorbachev, R.

    2012-09-01

    By stacking various two-dimensional (2D) atomic crystals on top of each other, it is possible to create multilayer heterostructures and devices with designed electronic properties. However, various adsorbates become trapped between layers during their assembly, and this not only affects the resulting quality but also prevents the formation of a true artificial layered crystal upheld by van der Waals interaction, creating instead a laminate glued together by contamination. Transmission electron microscopy (TEM) has shown that graphene and boron nitride monolayers, the two best characterized 2D crystals, are densely covered with hydrocarbons (even after thermal annealing in high vacuum) and exhibit only small clean patches suitable for atomic resolution imaging. This observation seems detrimental for any realistic prospect of creating van der Waals materials and heterostructures with atomically sharp interfaces. Here we employ cross sectional TEM to take a side view of several graphene-boron nitride heterostructures. We find that the trapped hydrocarbons segregate into isolated pockets, leaving the interfaces atomically clean. Moreover, we observe a clear correlation between interface roughness and the electronic quality of encapsulated graphene. This work proves the concept of heterostructures assembled with atomic layer precision and provides their first TEM images.

  15. Spin-dependent Breit-Wigner and Fano resonances in photon-assisted electron transport through a semiconductor heterostructure

    Institute of Scientific and Technical Information of China (English)

    Hu Li-Yun; Zhou Bin

    2011-01-01

    We theoretically investigate the electron transmission through a seven-layer semiconductor heterostructure with the Dresselhaus spin-orbit coupling under two applied oscillating fields. Numerical results show that both of the spindependent symmetric Breit-Wigner and the asymmetric Fano resonances appear and that the properties of these two types of resonance peaks are dependent on the amplitude and the relative phases of the two applied oscillating fields.The modulation of the spin-polarization efficiency of transmitted electrons by the relative phase is also discussed.

  16. Low-voltage organic electronics based on a gate-tunable injection barrier in vertical graphene-organic semiconductor heterostructures.

    Science.gov (United States)

    Hlaing, Htay; Kim, Chang-Hyun; Carta, Fabio; Nam, Chang-Yong; Barton, Rob A; Petrone, Nicholas; Hone, James; Kymissis, Ioannis

    2015-01-14

    The vertical integration of graphene with inorganic semiconductors, oxide semiconductors, and newly emerging layered materials has recently been demonstrated as a promising route toward novel electronic and optoelectronic devices. Here, we report organic thin film transistors based on vertical heterojunctions of graphene and organic semiconductors. In these thin heterostructure devices, current modulation is accomplished by tuning of the injection barriers at the semiconductor/graphene interface with the application of a gate voltage. N-channel devices fabricated with a thin layer of C60 show a room temperature on/off ratio >10(4) and current density of up to 44 mAcm(-2). Because of the ultrashort channel intrinsic to the vertical structure, the device is fully operational at a driving voltage of 200 mV. A complementary p-channel device is also investigated, and a logic inverter based on two complementary transistors is demonstrated. The vertical integration of graphene with organic semiconductors via simple, scalable, and low-temperature fabrication processes opens up new opportunities to realize flexible, transparent organic electronic, and optoelectronic devices.

  17. Ratiometric, filter-free optical sensor based on a complementary metal oxide semiconductor buried double junction photodiode.

    Science.gov (United States)

    Yung, Ka Yi; Zhan, Zhiyong; Titus, Albert H; Baker, Gary A; Bright, Frank V

    2015-07-16

    We report a complementary metal oxide semiconductor integrated circuit (CMOS IC) with a buried double junction (BDJ) photodiode that (i) provides a real-time output signal that is related to the intensity ratio at two emission wavelengths and (ii) simultaneously eliminates the need for an optical filter to block Rayleigh scatter. We demonstrate the BDJ platform performance for gaseous NH3 and aqueous pH detection. We also compare the BDJ performance to parallel results obtained by using a slew scanned fluorimeter (SSF). The BDJ results are functionally equivalent to the SSF results without the need for any wavelength filtering or monochromators and the BDJ platform is not prone to errors associated with source intensity fluctuations or sensor signal drift.

  18. Band alignment of two-dimensional semiconductors for designing heterostructures with momentum space matching

    Science.gov (United States)

    Özçelik, V. Ongun; Azadani, Javad G.; Yang, Ce; Koester, Steven J.; Low, Tony

    2016-07-01

    We present a comprehensive study of the band alignments of two-dimensional (2D) semiconducting materials and highlight the possibilities of forming momentum-matched type I, II, and III heterostructures, an enticing possibility being atomic heterostructures where the constituent monolayers have band edges at the zone center, i.e., Γ valley. Our study, which includes the group IV and III-V compound monolayer materials, group V elemental monolayer materials, transition-metal dichalcogenides, and transition-metal trichalcogenides, reveals that almost half of these materials have conduction and/or valence band edges residing at the zone center. Using first-principles density functional calculations, we present the type of the heterostructure for 903 different possible combinations of these 2D materials which establishes a periodic table of heterostructures.

  19. Optical dynamics in low-dimensional semiconductor heterostructures. Quantum dots and quantum cascade lasers

    Energy Technology Data Exchange (ETDEWEB)

    Weber, Carsten

    2008-07-01

    This work is focused on the optical dynamics of mesoscopic semiconductor heterostructures, using as prototypes zero-dimensional quantum dots and quantum cascade lasers which consist of quasitwo- dimensional quantum wells. Within a density matrix theory, a microscopic many-particle theory is applied to study scattering effects in these structures: the coupling to external as well as local fields, electron-phonon coupling, coupling to impurities, and Coulomb coupling. For both systems, the investigated effects are compared to experimentally observed results obtained during the past years. In quantum dots, the three-dimensional spatial confinement leads to the necessity to consider a quantum kinetic description of the dynamics, resulting in non-Markovian electron-phonon effects. This can be seen in the spectral phonon sidebands due to interaction with acoustic phonons as well as a damping of nonlinear Rabi oscillations which shows a nonmonotonous intensity and pulse duration dependence. An analysis of the inclusion of the self-interaction of the quantum dot shows that no dynamical local field terms appear for the simple two-level model. Considering local fields which have their origin in many quantum dots, consequences for a two-level quantum dot such as a zero-phonon line broadening and an increasing signal in photon echo experiments are found. For the use of quantum dots in an optical spin control scheme, it is found that the dephasing due to the electron-phonon interaction can be dominant in certain regimes. Furthermore, soliton and breather solutions are studied analytically in nonlinear quantum dot ensembles. Generalizing to quasi-two-dimensional structures, the intersubband dynamics of quantum cascade laser structures is investigated. A dynamical theory is considered in which the temporal evolution of the subband populations and the current density as well as the influence of scattering effects is studied. In the nonlinear regime, the scattering dependence and

  20. Spatially correlated two-dimensional arrays of semiconductor and metal quantum dots in GaAs-based heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Nevedomskiy, V. N., E-mail: nevedom@mail.ioffe.ru; Bert, N. A.; Chaldyshev, V. V. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation); Preobrazhernskiy, V. V.; Putyato, M. A.; Semyagin, B. R. [Russian Academy of Sciences, Institute of Semiconductor Physics, Siberian Branch (Russian Federation)

    2015-12-15

    A single molecular-beam epitaxy process is used to produce GaAs-based heterostructures containing two-dimensional arrays of InAs semiconductor quantum dots and AsSb metal quantum dots. The twodimensional array of AsSb metal quantum dots is formed by low-temperature epitaxy which provides a large excess of arsenic in the epitaxial GaAs layer. During the growth of subsequent layers at a higher temperature, excess arsenic forms nanoinclusions, i.e., metal quantum dots in the GaAs matrix. The two-dimensional array of such metal quantum dots is created by the δ doping of a low-temperature GaAs layer with antimony which serves as a precursor for the heterogeneous nucleation of metal quantum dots and accumulates in them with the formation of AsSb metal alloy. The two-dimensional array of InAs semiconductor quantum dots is formed via the Stranski–Krastanov mechanism at the GaAs surface. Between the arrays of metal and semiconductor quantum dots, a 3-nm-thick AlAs barrier layer is grown. The total spacing between the arrays of metal and semiconductor quantum dots is 10 nm. Electron microscopy of the structure shows that the arrangement of metal quantum dots and semiconductor quantum dots in the two-dimensional arrays is spatially correlated. The spatial correlation is apparently caused by elastic strain and stress fields produced by both AsSb metal and InAs semiconductor quantum dots in the GaAs matrix.

  1. 1.5-μm and 10-Gb s-1 etched mesa buried heterostructure DFB-LD for datacenter networks

    Science.gov (United States)

    Kwon, Oh Kee; Lee, Chul Wook; Leem, Young Ahn; Kim, Ki Soo; Oh, Su Hwan; Nam, Eun Soo

    2015-10-01

    We report a 1.5 μm and 10 Gb s-1 etched mesa buried heterostructure λ/4-shifted distributed feedback laser diode (DFB-LD) for the low-cost application of WDM-based datacenter networks. To reduce the threshold current and improve the modulation bandwidth in a conventional p-/n-/p-InP current blocking structure, a thin undoped-InP (u-InP) layer was inserted between the side walls of the active region and the p-InP layer (i.e., a u-/p-/n-/p-InP structure), and the region containing the active region and the current blocking structures was etched in a mesa form (i.e., an etched mesa). From this work, it was found that a 300 μm long anti-reflection (AR)-AR DFB-LD with a mesa width of 8 μm is reduced by about 25% while a side mode suppression ratio is >50 dB and a 3 dB bandwidth is >10 GHz at a current of 40 mA; in addition, it shows a clear eye-opening with a dynamic extinction ratio of >4.5 dB at 10 Gb s-1, and a power penalty of transmission.

  2. Growth and properties of low-dimensional III-V semiconductor nanowire heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Heiss, Martin

    2010-08-25

    In this work the properties of GaAs nanowire based heterostructures are investigated. The nanowires and their heterostructures are synthesized with Molecular Beam Epitaxy. The optical and structural properties are characterized by means of low temperature confocal micro-photoluminescence spectroscopy and Transmission Electron Microscopy. Molecular Beam Epitaxy is a versatile technique that allows to switch from radial to axial growth in order to cap the nanowires by an epitaxial prismatic AlGaAs/GaAs heterostructure. This can passivate surface states and improve the optical properties. The effect of such a passivation layer is studied by quantitative comparison of the diameter dependence of photoluminescence in passivated and unpassivated nanowires. The passivation is an important prerequisite for more complex axial heterostructures. Evidence for radial confinement effects is found in passivated nanowires with core diameters smaller than 70 nm. Furthermore, the polarization dependence of light absorption and emission is investigated. Two different types of axial heterostructures are studied that have the potential to further enhance the functionality of such nanowires. In a first step, the possibility of growth of axial InGaAs heterostructure in the Au-free Molecular Beam Epitaxy growth regime is investigated. Suitable growth conditions are identified and the growth temperature window for both GaAs and InGaAs nanowires is determined. At the optimum growth temperature for GaAs nanowires, the incorporation of indium in the structure is limited to a few percent. It is shown that by lowering the growth temperature the indium concentration in the structure can be increased up to 20%. The optical properties of the synthesized axial heterostructures are investigated by means of micro-photoluminescence spectroscopy and Transmission Electron Microscopy. The second type of axial nanowire heterostructure investigated in the present work is characterized by a change in crystal

  3. Microscopic Theory of Coherent and Incoherent Optical Properties of Semiconductor Heterostructures

    OpenAIRE

    Schäfer, Martin

    2008-01-01

    During the last decades, semiconductors have become increasingly important for many technological applications due to their intriguing electronic properties. As an example, the conductivity of a semiconductors rises with increasing temperature which is opposite to the observations in metals. It is possible to modify the conductivity by the selective introduction of impurities. This so called doping allows for designing de...

  4. XRD fitting analysis of semiconductor heterostructures [Puolijohderakenteiden r\\"ontgendiffraktion sovitusanalyysi] (in Finnish)

    OpenAIRE

    Tilli, Juha-Matti

    2014-01-01

    Analysis of measured X-ray diffraction (XRD) data from heterostructures with fitting analysis is discussed, for which computer program was written. Lattice constant and Poisson's ratio of a multi-compound layer is calculated from Vegard's law. Layers are strained in in-plane direction causing additional strain in out-of-plane direction and may be only partially strained. For crystals, wavelength-dependent electric susceptibility is represented as Fourier series, components of which are calcul...

  5. Photoluminescence and photocatalytic activities of Ag/ZnO metal-semiconductor heterostructure

    Science.gov (United States)

    Sarma, Bikash; Deb, Sujit Kumar; Sarma, Bimal K.

    2016-10-01

    Present article focuses on the photocatalytic activities of ZnO nanorods and Ag/ZnO heterostructure deposited on polyethylene terephthalate (PET) substrate. ZnO nanorods are synthesized by thermal decomposition technique and Ag nanoparticles deposition is done by photo-deposition technique using UV light. X-ray diffraction studies reveal that the ZnO nanorods are of hexagonal wurtzite structure. Further, as-prepared samples are characterized by Scanning Electron Microscopy (SEM), Photoluminescence (PL) spectroscopy and UV-Vis spectroscopy. The surface plasmon resonance response of Ag/ZnO is found at 420 nm. The photocatalytic activities of the samples are evaluated by photocatalytic decolorization of methyl orange (MO) dye with UV irradiation. The degradation rate of MO increases with increase in irradiation time. The degradation of MO follows the first order kinetics. The photocatalytic activity of Ag/ZnO heterostructure is found to be more than that of ZnO nanorods. The PL intensity of ZnO nanorods is stronger than that of the Ag/ZnO heterostructure. The strong PL intensity indicates high recombination rate of photoinduced charge carriers which lowers the photocatalytic activity of ZnO nanorods. The charge carrier recombination is effectively suppressed by introducing Ag nanoparticles on the surface of the ZnO nanorods. This study demonstrates a strong relationship between PL intensity and photocatalytic activity.

  6. Semiconductor@metal-organic framework core-shell heterostructures: a case of ZnO@ZIF-8 nanorods with selective photoelectrochemical response.

    Science.gov (United States)

    Zhan, Wen-wen; Kuang, Qin; Zhou, Jian-zhang; Kong, Xiang-jian; Xie, Zhao-xiong; Zheng, Lan-sun

    2013-02-06

    Metal-organic frameworks (MOFs) and related material classes are attracting considerable attention for their applications in gas storage/separation as well as catalysis. In contrast, research concerning potential uses in electronic devices (such as sensors) is in its infancy, which might be due to a great challenge in the fabrication of MOFs and semiconductor composites with well-designed structures. In this paper, we proposed a simple self-template strategy to fabricate metal oxide semiconductor@MOF core-shell heterostructures, and successfully obtained freestanding ZnO@ZIF-8 nanorods as well as vertically standing arrays (including nanorod arrays and nanotube arrays). In this synthetic process, ZnO nanorods not only act as the template but also provide Zn(2+) ions for the formation of ZIF-8. In addition, we have demonstrated that solvent composition and reaction temperature are two crucial factors for successfully fabricating well-defined ZnO@ZIF-8 heterostructures. As we expect, the as-prepared ZnO@ZIF-8 nanorod arrays display distinct photoelectrochemical response to hole scavengers with different molecule sizes (e.g., H(2)O(2) and ascorbic acid) owing to the limitation of the aperture of the ZIF-8 shell. Excitingly, such ZnO@ZIF-8 nanorod arrays were successfully applied to the detection of H(2)O(2) in the presence of serous buffer solution. Therefore, it is reasonable to believe that the semiconductor@MOFs heterostructure potentially has promising applications in many electronic devices including sensors.

  7. Nanometer-Scale Compositional Structure in III-V Semiconductor Heterostructures Characterized by Scanning Tunneling Microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Allerman, A.A.; Bi, W.G.; Biefeld, R.M.; Tu, C.W.; Yu, E.T.; Zuo, S.L.

    1998-11-10

    Nanometer-scale compositional structure in InAsxP1.InNYAsxPl.x-Y/InP, grown by gas-source molecular-beam epitaxy and in InAsl-xPJkAsl$b#InAs heterostructures heterostructures grown by metal-organic chemical vapor deposition has been characterized using cross-sectional scanning tunneling microscopy. InAsxP1-x alloy layers are found to contain As-rich and P-rich clusters with boundaries formed preferentially within (T 11) and (111) crystal planes. Similar compositional structure is observed within InNYAsxP1-x-Y alloy layers. Imaging of InAsl-xp@Asl#bY superlattices reveals nanometer-scale clustering within both the hAsI-.p and InAsl$bY alloy layers, with preferential alignment of compositional features in the direction. Instances are observed of compositional structure correlated across a heterojunction interface, with regions whose composition corresponds to a smaller unstrained lattice, constant relative to the surrounding alloy material appearing to propagate across the interface.

  8. Fourier-transform-based model for carrier transport in semiconductor heterostructures: Longitudinal optical phonon scattering

    Energy Technology Data Exchange (ETDEWEB)

    Lü, X.; Schrottke, L.; Grahn, H. T. [Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e. V., Hausvogteiplatz 5–7, 10117 Berlin (Germany)

    2016-06-07

    We present scattering rates for electrons at longitudinal optical phonons within a model completely formulated in the Fourier domain. The total intersubband scattering rates are obtained by averaging over the intrasubband electron distributions. The rates consist of the Fourier components of the electron wave functions and a contribution depending only on the intersubband energies and the intrasubband carrier distributions. The energy-dependent part can be reproduced by a rational function, which allows for the separation of the scattering rates into a dipole-like contribution, an overlap-like contribution, and a contribution which can be neglected for low and intermediate carrier densities of the initial subband. For a balance between accuracy and computation time, the number of Fourier components can be adjusted. This approach facilitates an efficient design of complex heterostructures with realistic, temperature- and carrier density-dependent rates.

  9. Development of High Quantum Efficiency UV/Blue Photocathode Epitaxial Semiconductor Heterostructures for Scintillation and Cherenkov Radiation Detection

    Science.gov (United States)

    Leopold, Daniel J.

    2002-01-01

    The primary goal of this research project was to further extend the use of advanced heteroepitaxial-semiconductor crystal growth techniques such as molecular beam epitaxy (MBE) and to demonstrate significant gains in UV/blue photonic detection by designing and fabricating atomically-tailored heteroepitaxial GaAlN/GaInN photocathode device structures. This NASA Explorer technology research program has focused on the development of photocathodes for Cherenkov and scintillation radiation detection. Support from the program allowed us to enhance our MBE system to include a nitrogen plasma source and a magnetic bearing turbomolecular pump for delivery and removal of high purity atomic nitrogen during GaAlN/GaInN film growth. Under this program we have also designed, built and incorporated a cesium activation stage. In addition, a connected UHV chamber with photocathode transfer/positioner components as well as a hybrid phototube stage was designed and built to make in-situ quantum efficiency measurements without ever having to remove the photocathodes from UHV conditions. Thus we have constructed a system with the capability to couple atomically-tailored MBE-grown photocathode heterostructures with real high gain readout devices for single photon detection evaluation.

  10. Magneto-transport studies of GaSb/InAs/GaSb double heterostructures Semiconductors

    CERN Document Server

    Takashina, K

    2002-01-01

    The electrical transport properties of GaSb/lnAs/GaSb double-heterostructures are examined experimentally. The structures are studied at low temperatures and high magnetic field. InAs/GaSb is a crossed-gap system where the conduction band minimum of InAs lies lower in energy than the valence band maximum of GaSb. The samples examined exploit this property to contain two-dimensional layers of electrons and holes. A description of the general electrical magneto-transport properties is given. Effects due to anticrossing behaviour between the electron and hole dispersion relations are demonstrated and discussed. It is shown that the anticrossing can lead to a non-monotonic temperature dependence of the resistivity. Under quantum Hall conditions, the system displays two types of behaviour. An insulating behaviour where both Hall and diagonal conductivities become vanishingly small, and a more conventional metallic behaviour where the Hall resistance is quantized and the diagonal resistivity disappears. It is found...

  11. Quantized conductance doubling and hard gap in a two-dimensional semiconductor-superconductor heterostructure

    DEFF Research Database (Denmark)

    Kjærgaard, Morten; Nichele, F; Suominen, Henri Juhani

    2016-01-01

    topological matter is by coupling a 2D electron gas with strong spin-orbit interaction to an s-wave superconductor. Previous efforts along these lines have been adversely affected by interface disorder and unstable gating. Here we show measurements on a gateable InGaAs/InAs 2DEG with patterned epitaxial Al......, consistent with theory. The hard-gap semiconductor-superconductor system demonstrated here is amenable to top-down processing and provides a new avenue towards low-dissipation electronics and topological quantum systems....

  12. Transmission electron microscopy of GaN based, doped semiconductor heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Pretorius, A.

    2006-07-01

    This thesis addresses the analysis of GaN based heterostructures with transmission electron microscopy (TEM). Basic properties of the material of interest are introduced in chapter 2. These include the structural and optical properties as well as an introduction to the growth methods used for the samples analysed in this work. In chapter 3 a brief theoretical treatment of TEM is given. As one main topic of this work is the determination of the In concentration in InGaN islands using strain state analysis, a detailed description of the method is given. Chapter 4 describes the results obtained for pyramidal defects present in metalorganic vapour phase epitaxy grown GaN:Mg with high dopant concentration. Based on the experimental results and the well established knowledge that GaN of inverted polarity is present inside the pyramidal defects, a variety of basal plane inversion domain boundary models was set up. From these models, HRTEM images were simulated using the multislice approach, followed by a quantitative comparison to experimentally obtained HRTEM images. Another focus of this work is the analysis of In{sub x}Ga{sub 1-x}N islands grown on GaN presented in chapter 5. Following a literature survey which describes different methods used to obtain In{sub x}Ga{sub 1-x}N islands, the first topic is the distinction of In{sub x}Ga{sub 1-x}N islands and metal droplets, which can form during growth. This is followed by the experimental results of molecular beam epitaxy and metalorganic vapour phase epitaxy grown In{sub x}Ga{sub 1-x}N island and quantum dot samples. (orig.)

  13. Time-resolved optical studies of wide-gap II-VI semiconductor heterostructures

    Science.gov (United States)

    Wang, Hong

    ZnSe and ZnSe-based quantum well and superlattice structures are potential candidates for light emitting devices and other optical devices such as switches and modulators working in the blue-green wavelength range. Carrier dynamics studies of these structures are important in evaluating device performance as well as understanding the underlying physical processes. In this thesis, a carrier dynamics investigation is conducted for temperature from 77K to 295K on CdZnSSe/ZnSSe single quantum well structure (SQW) and ZnSe/ZnSTe superlattice fabricated by molecular beam epitaxy (MBE). Two experimental techniques with femtosecond time resolution are used in this work: up-conversion technique for time- resolved photoluminescence (PL) and pump-probe technique for time-resolved differential absorption studies. For both heterostructures, the radiative recombination is dominated by exciton transition due to the large exciton binding energy as a result of quantum confinement effect. The measured decay time of free exciton PL in CdZnSSe/ZnSSe SQW increases linearly with increasing temperature which agrees with the theoretical prediction by considering the conservation of momentum requirement for radiative recombination. However, the recombination of free carriers is also observed in CdZnSSe/ZnSSe SQW for the whole temperature range studied. On the other hand, in ZnSe/ZnSTe superlattice structures, the non- radiative recombination processes are non-negligible even at 77K and become more important in higher temperature range. The relaxation processes such as spectral hole burning, carrier thermalization and hot-carrier cooling are observed in ZnSe/ZnSTe superlattices at room temperature (295K) by the femtosecond pump-probe measurements. A rapid cooling of the thermalized hot- carrier from 763K to 450K within 4ps is deduced. A large optical nonlinearity (i.e., the induced absorption change) around the heavy-hole exciton energy is also obtained.

  14. Semiconductor to Metal Transition Characteristics of VO2/NiO Epitaxial Heterostructures Integrated with Si(100)

    Science.gov (United States)

    Molaei, Roya

    O/c-YSZ/Si(100) heterostructures were used as template to grow fully relaxed VO2 thin films. The detailed x-ray diffraction, transmission electron microscopy (TEM), electrical characterization results for the deposited films will be presented. In the framework on domain matching epitaxy, epitaxial growth of VO2 (tetragonal crystal structure at growth temperature) on NiO has been explained. Our detailed phi-scan X-ray diffraction measurements corroborate our understanding of the epitaxial growth and in-plane atomic arrangements at the interface. It was observed that the transition characteristics (sharpness, over which electrical property changes are completed, amplitude, transition temperature, and hysteresis) are a strong function of microstructure, strain, and stoichiometry. We have shown that by the choosing the right template layer, strain in the VO2 thin films can be fully relaxed and near-bulk VO2 transition temperatures can be achieved. Finally, I will present my research work on modification of semiconductor-to-metal transition characteristics and effect on room temperature magnetic properties of VO2 thin films upon laser annealing. While the microstructure (epitaxy, crystalline quality etc.) and phase were preserved, we envisage these changes to occur as a result of introduction of oxygen vacancies upon laser treatment.

  15. Heterostructures and quantum devices

    CERN Document Server

    Einspruch, Norman G

    1994-01-01

    Heterostructure and quantum-mechanical devices promise significant improvement in the performance of electronic and optoelectronic integrated circuits (ICs). Though these devices are the subject of a vigorous research effort, the current literature is often either highly technical or narrowly focused. This book presents heterostructure and quantum devices to the nonspecialist, especially electrical engineers working with high-performance semiconductor devices. It focuses on a broad base of technical applications using semiconductor physics theory to develop the next generation of electrical en

  16. Microscopic theory of coherent and incoherent optical properties of semiconductor heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Schaefer, Martin

    2008-09-02

    An important question is whether there is a regime in which lasing from indirect semiconductors is possible. Thus, we discuss this question in this thesis. It is shown that under incoherent emission conditions it is possible to create an exciton condensate in multiple-quantum-well (MQW) systems. The influence of a MQW structure on the exciton lifetime is investigated. For the description of the light-matter interaction of a QW in the coherent excitation regime, the semiconductor Bloch equation (SBE) are used. The incoherent regime is described by the semiconductor luminescence equations (SLE). In principle it is even possible to couple SBE and SLE. The resulting theory is able to describe interactions between coherent and incoherent processes we investigate both, the coherent and the incoherent light-emission regime. Thus we define the investigated system and introduce the many-body Hamiltonian that describes consistently the light-matter interaction in the classical and the quantum limit. We introduce the SBE that allow to compute the light-matter interaction in the coherent scenario. The extended scattering model is used to investigate the absorption of a Ge QW for different time delays after the excitations. In this context, we analyze whether there is a regime in which optical gain can be realized. Then we apply a transfer-matrix method to include into our calculations the influence of the dielectric environment on the optical response. Thereafter the SLE for a MQW system are introduced. We derive a scheme that allows for decoupling environmental effects from the pure PL-emission properties of the QW. The PL of the actual QW system is obtained by multiplying this filter function and the free-space PL that describes the quantum emission into a medium with spatially constant background-refractive index. It is studied how the MQW-Bragg structure influences the PL-emission properties compared to the emission of a single QW device. As a last feature, it is shown

  17. Infrared generation in low-dimensional semiconductor heterostructures via quantum coherence

    CERN Document Server

    Belyanin, A A; Kocharovsky, V V; Scully, M O; Capasso, F; Kocharovsky, Vl. V.

    2000-01-01

    A new scheme for infrared generation without population inversion between subbands in quantum-well and quantum-dot lasers is presented and documented by detailed calculations. The scheme is based on the simultaneous generation at three frequencies: optical lasing at the two interband transitions which take place simultaneously, in the same active region, and serve as the coherent drive for the IR field. This mechanism for frequency down-conversion does not rely upon any ad hoc assumptions of long-lived coherences in the semiconductor active medium. And it should work efficiently at room temperature with injection current pumping. For optimized waveguide and cavity parameters, the intrinsic efficiency of the down-conversion process can reach the limiting quantum value corresponding to one infrared photon per one optical photon. Due to the parametric nature of IR generation, the proposed inversionless scheme is especially promising for long-wavelength (far- infrared) operation.

  18. Assessment of Anisotropic Semiconductor Nanorod and Nanoplatelet Heterostructures with Polarized Emission for Liquid Crystal Display Technology

    Energy Technology Data Exchange (ETDEWEB)

    Cunningham, Patrick D.; Souza, João B.; Fedin, Igor; She, Chunxing; Lee, Byeongdu; Talapin, Dmitri V.

    2016-06-28

    Semiconductor nanorods can emit linear-polarized light at efficiencies over 80%. Polarization of light in these systems, confirmed through single-rod spectroscopy, can be explained on the basis of the anisotropy of the transition dipole moment and dielectric confinement effects. Here we report emission polarization in macroscopic semiconductor polymer composite films containing CdSe/CdS nanorods and colloidal CdSe nanoplatelets. Anisotropic nanocrystals dispersed in polymer films of poly butyl-co-isobutyl methacrylate (PBiBMA) can be stretched mechanically in order to obtain unidirectionally aligned arrays. A high degree of alignment, corresponding to an orientation factor of 0.87, was achieved and large areas demonstrated polarized emission, with the contrast ratio I-parallel to/I-perpendicular to= 5.6, making these films viable candidates for use in liquid crystal display (LCD) devices. To some surprise, we observed significant optical anisotropy and emission polarization for 2D CdSe nanoplatelets with the electronic structure of quantum wells. The aligned nanorod arrays serve as optical funnels, absorbing unpolarized light and re-emitting light from deep-green to red with quantum efficiencies over 90% and high degree of linear polarization. Our results conclusively demonstrate the benefits of anisotropic nanostructures for LCD backlighting. The polymer films with aligned CdSe/CdS dot-in-rod and rod-in-rod nanostructures show more than 2-fold enhancement of brightness compared to the emitter layers with randomly oriented nanostructures. This effect can be explained as the combination of linearly polarized luminescence and directional emission from individual nanostructures.

  19. Fabrication of Axial and Radial Heterostructures for Semiconductor Nanowires by Using Selective-Area Metal-Organic Vapor-Phase Epitaxy

    Directory of Open Access Journals (Sweden)

    K. Hiruma

    2012-01-01

    Full Text Available The fabrication of GaAs- and InP-based III-V semiconductor nanowires with axial/radial heterostructures by using selective-area metal-organic vapor-phase epitaxy is reviewed. Nanowires, with a diameter of 50–300 nm and with a length of up to 10 μm, have been grown along the 〈111〉B or 〈111〉A crystallographic orientation from lithography-defined SiO2 mask openings on a group III-V semiconductor substrate surface. An InGaAs quantum well (QW in GaAs/InGaAs nanowires and a GaAs QW in GaAs/AlGaAs or GaAs/GaAsP nanowires have been fabricated for the axial heterostructures to investigate photoluminescence spectra from QWs with various thicknesses. Transmission electron microscopy combined with energy dispersive X-ray spectroscopy measurements have been used to analyze the crystal structure and the atomic composition profile for the nanowires. GaAs/AlGaAs, InP/InAs/InP, and GaAs/GaAsP core-shell structures have been found to be effective for the radial heterostructures to increase photoluminescence intensity and have enabled laser emissions from a single GaAs/GaAsP nanowire waveguide. The results have indicated that the core-shell structure is indispensable for surface passivation and practical use of nanowire optoelectronics devices.

  20. MESOSCOPIC SUPERCONDUCTOR SEMICONDUCTOR HETEROSTRUCTURES

    NARCIS (Netherlands)

    KLAPWIJK, TM

    1994-01-01

    A summary is given of recent results on carrier transport in mesoscopic conductors with superconducting electrodes. Three-dimensional transport in the diffusive limit is studied with crystalline silicon membranes sandwiched between two niobium electrodes or between one electrode superconducting and

  1. Evaluation of a gate-first process for AlGaN/GaN metal-oxide-semiconductor heterostructure field-effect transistors with low ohmic annealing temperature

    Science.gov (United States)

    Liuan, Li; Jiaqi, Zhang; Yang, Liu; Jin-Ping, Ao

    2016-03-01

    In this paper, TiN/AlOx gated AlGaN/GaN metal-oxide-semiconductor heterostructure field-effect transistors (MOS-HFETs) were fabricated for gate-first process evaluation. By employing a low temperature ohmic process, ohmic contact can be obtained by annealing at 600 °C with the contact resistance approximately 1.6 Ω·mm. The ohmic annealing process also acts as a post-deposition annealing on the oxide film, resulting in good device performance. Those results demonstrated that the TiN/AlOx gated MOS-HFETs with low temperature ohmic process can be applied for self-aligned gate AlGaN/GaN MOS-HFETs. Project supported by the International Science and Technology Collaboration Program of China (Grant No. 2012DFG52260).

  2. Two-dimensional semiconductor HfSe{sub 2} and MoSe{sub 2}/HfSe{sub 2} van der Waals heterostructures by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Aretouli, K. E.; Tsipas, P.; Tsoutsou, D.; Marquez-Velasco, J.; Xenogiannopoulou, E.; Giamini, S. A.; Vassalou, E.; Kelaidis, N.; Dimoulas, A., E-mail: a.dimoulas@inn.demokritos.gr [Institute of Nanoscience and Nanotechnology, National Center for Scientific Research “Demokritos,” 15310, Aghia Paraskevi, Athens (Greece)

    2015-04-06

    Using molecular beam epitaxy, atomically thin 2D semiconductor HfSe{sub 2} and MoSe{sub 2}/HfSe{sub 2} van der Waals heterostructures are grown on AlN(0001)/Si(111) substrates. Details of the electronic band structure of HfSe{sub 2} are imaged by in-situ angle resolved photoelectron spectroscopy indicating a high quality epitaxial layer. High-resolution surface tunneling microscopy supported by first principles calculations provides evidence of an ordered Se adlayer, which may be responsible for a reduction of the measured workfunction of HfSe{sub 2} compared to theoretical predictions. The latter reduction minimizes the workfunction difference between the HfSe{sub 2} and MoSe{sub 2} layers resulting in a small valence band offset of only 0.13 eV at the MoSe{sub 2}/HfSe{sub 2} heterointerface and a weak type II band alignment.

  3. CdSe/beta-Pb0.33V2O5 heterostructures: Nanoscale semiconductor interfaces with tunable energetic configurations for solar energy conversion and storage

    Science.gov (United States)

    Milleville, Christopher C.

    This dissertation focuses on the formation and characterization of semiconductor heterostructures, consisting of light-harvesting cadmium selenide quantum dots (CdSe QDs) and single crystalline lead vanadium oxide nanowires (β-Pb0.33V2O5 NWs), for the purpose of excited-state charge transfer and photocatalytic production of solar fuels. We reported two distinct routes for assembling CdSe/β-Pb0.33V2O5 heterostructures: linker-assisted assembly (LAA) mediated by a bifunctional ligand and successive ionic layer adsorption and reaction (SILAR). In the former case, the thiol end of a molecular linker, cysteine (Cys) is found to bind to the QD surface, whereas a protonated amine moiety interacts electrostatically with the negatively charged NW surface. In the alternative SILAR route, the surface coverage of CdSe on the β-Pb0.33V2O5 NWs is tuned by varying the number of successive precipitation cycles. Hard X-ray photoelectron spectroscopy (HAXPES) measurements revealed that the mid-gap states of β-Pb0.33V2O5 NWs are closely overlapped in energy with the valence band edges of CdSe QDs, suggesting that hole transfer from the valence band of CdSe into the mid-gap states is possible. Preliminary evidence of hole transfer was obtained through photoluminescence quenching experiments. Steady-state and time-resolved photoluminescence measurements on Cys-CdSe dispersions, mixed dispersions of Cys-CdSe QDs and β-Pb0.33V¬2O5 NWs, and mixed dispersions of Cys-CdS QDs and V2O5 revealed a greater extent of quenching of the emission of Cys-CdSe QDs by β Pb0.33V¬2O5 relative to V2O5. V2O5, devoid of mid-gap states, is unable to accept holes from CdSe and therefore should not quench emission to the same extent as β-Pb0.33V¬2O5. The additional quenching was dynamic, consistent with a mechanism involving the transfer of photogenerated holes from CdSe QDs to the mid-gap states of β Pb0.33V2O5. Transient absorption spectroscopy (TA) was used to probe the dynamics of interfacial

  4. Ultrafast dynamics in InAs quantum dot and GaInNAs quantum well semiconductor heterostructures

    OpenAIRE

    Malins, David B

    2007-01-01

    The quantum confined Stark effect (QCSE) and ultrafast absorption dynamics near the bandedge have been investigated in p-i-n waveguides comprising quantum confined heterostructures grown on GaAs substrates, for emission at 1.3um. The materials are; isolated InAs/InGaAs dot-in-a-well (DWELL) quantum dots (QD), bilayer InAs quantum dots and GaInNAs multiple quantum wells (MQW). The focus was to investigate these dynamics in a planar waveguide geometry, for the purpose of large scale integ...

  5. Electronic structure, lattice dynamics, and optical properties of a novel van der Waals semiconductor heterostructure: InGaSe2

    Science.gov (United States)

    Ibarra-Hernández, Wilfredo; Elsayed, Hannan; Romero, Aldo H.; Bautista-Hernández, Alejandro; Olguín, Daniel; Cantarero, Andrés

    2017-07-01

    There is a growing interest in the property dependence of transition metal dichalcogenides as a function of the number of layers and formation of heterostructures. Depending on the stacking, doping, edge effects, and interlayer distance, the properties can be modified, which opens the door to novel applications that require a detailed understanding of the atomic mechanisms responsible for those changes. In this work, we analyze the electronic properties and lattice dynamics of a heterostructure constructed by simultaneously stacking InSe layers and GaSe layers bounded by van der Waals forces. We have assumed the same space group of GaSe, P 6 ¯m 2 as it becomes the lower energy configuration for other considered stackings. The structural, vibrational, and optical properties of this layered compound have been calculated using density functional theory. The structure is shown to be energetically, thermally, and elastically stable, which indicates its possible chemical synthesis. A correlation of the theoretical physical properties with respect to its parent compounds is extensively discussed. One of the most interesting properties is the low thermal conductivity, which indicates its potential use in thermolectric applications. Additionally, we discuss the possibility of using electronic gap engineering methods, which can help us to tune the optical emission in a variable range close to that used in the field of biological systems (NIR). Finally, the importance of considering properly van der Waals dispersion in layered materials has been emphasized as included in the exchange correlation functional. As for the presence of atoms with important spin-orbit coupling, relativistic corrections have been included.

  6. Controlling the interface charge density in GaN-based metal-oxide-semiconductor heterostructures by plasma oxidation of metal layers

    Energy Technology Data Exchange (ETDEWEB)

    Hahn, Herwig, E-mail: herwig.hahn@rwth-aachen.de; Kalisch, Holger; Vescan, Andrei [GaN Device Technology, RWTH Aachen University, 52074 Aachen (Germany); JARA-Fundamentals of Future Information Technologies, 52425 Jülich (Germany); Pécz, Béla [MTA EK MFA, Konkoly Thege Street 29-33, 1121 Budapest (Hungary); Kovács, András [JARA-Fundamentals of Future Information Technologies, 52425 Jülich (Germany); Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C) and Forschungszentrum Jülich, Peter Grünberg Institut (PGI-5), 52425 Jülich (Germany); Heuken, Michael [GaN Device Technology, RWTH Aachen University, 52074 Aachen (Germany); AIXTRON SE, 52134 Herzogenrath (Germany)

    2015-06-07

    In recent years, investigating and engineering the oxide-semiconductor interface in GaN-based devices has come into focus. This has been driven by a large effort to increase the gate robustness and to obtain enhancement mode transistors. Since it has been shown that deep interface states act as fixed interface charge in the typical transistor operating regime, it appears desirable to intentionally incorporate negative interface charge, and thus, to allow for a positive shift in threshold voltage of transistors to realise enhancement mode behaviour. A rather new approach to obtain such negative charge is the plasma-oxidation of thin metal layers. In this study, we present transmission electron microscopy and energy dispersive X-ray spectroscopy analysis as well as electrical data for Al-, Ti-, and Zr-based thin oxide films on a GaN-based heterostructure. It is shown that the plasma-oxidised layers have a polycrystalline morphology. An interfacial amorphous oxide layer is only detectable in the case of Zr. In addition, all films exhibit net negative charge with varying densities. The Zr layer is providing a negative interface charge density of more than 1 × 10{sup 13 }cm{sup –2} allowing to considerably shift the threshold voltage to more positive values.

  7. Molecular-beam epitaxy growth and structural characterization of semiconductor-ferromagnet heterostructures by grazing incidence X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Satapathy, D.K.

    2005-12-19

    The present work is devoted to the growth of the ferromagnetic metal MnAs on the semiconductor GaAs by molecular-beam epitaxy (MBE). The MnAs thin films are deposited on GaAs by molecular-beam epitaxy (MBE). Grazing incidence diffraction (GID) and reflection high-energy electron diffraction (RHEED) are used in situ to investigate the nucleation, evolution of strain, morphology and interfacial structure during the MBE growth. Four stages of the nucleation process during growth of MnAs on GaAs(001) are revealed by RHEED azimuthal scans. GID shows that further growth of MnAs films proceed via the formation of relaxed islands at a nominal thickness of 2.5 ML which increase in size and finally coalesce to form a continuous film. Early on, an ordered array of misfit dislocations forms at the interface releasing the misfit strain even before complete coalescence occurs. The fascinating complex nucleation process of MnAs on GaAs(0 0 1) contains elements of both Volmer-Weber and Stranski-Krastanov growth. A nonuniform strain amounting to 0.66%, along the [1 -1 0] direction and 0.54%, along the [1 1 0] direction is demonstrated from x-ray line profile analysis. A high correlation between the defects is found along the GaAs[1 1 0] direction. An extremely periodic array of misfit dislocations with a period of 4.95{+-}0.05 nm is formed at the interface along the [1 1 0] direction which releases the 7.5% of misfit. The inhomogeneous strain due to the periodic dislocations is confined at the interface within a layer of 1.6 nm thickness. The misfit along the [1 -1 0] direction is released by the formation of a coincidence site lattice. (orig.)

  8. 铁磁半导体/半导体/铁磁半导体异质结中光子辅助量子输运特性%Photon-assisted Quantum transport of the Electron Through Ferromagnetic Semiconductor/semiconductor/ferromagnetic Semiconductor Heterostructure

    Institute of Scientific and Technical Information of China (English)

    程永喜; 聂一行

    2011-01-01

    Based on effective quality approximation and Floquet theory, the quantum transport of the electron through ferromagnetic semiconductor/semiconductor/ferromagnetic semiconductor heterostructure with the spin-orbit coupling and an applied oscillatory field were studied. It is find that spin-orbit coupling not only leads to spin flip, but also induces splitting of the bound state level in well, as a result two peaks of Fano resonance occur in conductivity. The magnetizations on both sides of the well and the angle between them can modulate the spin-flip and the resonance location.%基于有效质量近似和Floquet理论,考虑自旋-轨道耦合和外场驱动作用下,研究铁磁半导体/半导体/铁磁半导体异质结中的量子输运特性.结果表明自旋-轨道相互作用不仅使自旋发生翻转,而且束缚态能级发生劈裂,从而使电导率中出现两个Fano共振峰.势阱两边的磁化强度以及两边磁化强度之间的夹角对自旋翻转和共振位置具有调制作用.

  9. Heterostructure single-crystal silicon photovoltaic cell. Type A, semiconductor heterojunction silicon devices. Annual report, September 28, 1976-November 30, 1977

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, A.K.; Feng, T.; Fishman, C.

    1977-01-01

    Important electrical properties for the SnO/sub 2//Si heterostructure solar cell are summarized. The maximum theoretical efficiency and practically achievable efficiency are calculated. The method of fabricating the solar cell is described, and cost estimates and recommendations are given. A paper entitled SnO/sub 2//Si Solar Cells - Heterostructure or Schottky Barrier or MIS Type Device is appended which was previously abstracted for EDB. (LEW)

  10. Influence of phonons on semiconductor quantum emission

    Energy Technology Data Exchange (ETDEWEB)

    Feldtmann, Thomas

    2009-07-06

    A microscopic theory of interacting charge carriers, lattice vibrations, and light modes in semiconductor systems is presented. The theory is applied to study quantum dots and phonon-assisted luminescence in bulk semiconductors and heterostructures. (orig.)

  11. Evidence of type-II band alignment in III-nitride semiconductors: experimental and theoretical investigation for In 0.17 Al 0.83 N/GaN heterostructures.

    Science.gov (United States)

    Wang, Jiaming; Xu, Fujun; Zhang, Xia; An, Wei; Li, Xin-Zheng; Song, Jie; Ge, Weikun; Tian, Guangshan; Lu, Jing; Wang, Xinqiang; Tang, Ning; Yang, Zhijian; Li, Wei; Wang, Weiying; Jin, Peng; Chen, Yonghai; Shen, Bo

    2014-10-06

    Type-II band alignment structure is coveted in the design of photovoltaic devices and detectors, since it is beneficial for the transport of photogenerated carriers. Regrettably, for group-III-nitride wide bandgap semiconductors, all existing devices are limited to type-I heterostructures, owing to the unavailable of type-II ones. This seriously restricts the designing flexibility for optoelectronic devices and consequently the relevant performance of this material system. Here we show a brandnew type-II band alignment of the lattice-matched In 0.17 Al 0.83 N/GaN heterostructure from the perspective of both experimental observations and first-principle theoretical calculations. The band discontinuity is dominated by the conduction band offset ΔEC, with a small contribution from the valence band offset ΔEV which equals 0.1 eV (with E(AlInN(VBM) being above E(GaN)(VBM)). Our work may open up new prospects to realize high-performance III-Nitrides optoelectronic devices based on type-II energy band engineering.

  12. Heterostructures of transition metal dichalcogenides

    KAUST Repository

    Amin, Bin

    2015-08-24

    The structural, electronic, optical, and photocatalytic properties of out-of-plane and in-plane heterostructures of transition metal dichalcogenides are investigated by (hybrid) first principles calculations. The out-of-plane heterostructures are found to be indirect band gap semiconductors with type-II band alignment. Direct band gaps can be achieved by moderate tensile strain in specific cases. The excitonic peaks show blueshifts as compared to the parent monolayer systems, whereas redshifts occur when the chalcogen atoms are exchanged along the series S-Se-Te. Strong absorption from infrared to visible light as well as excellent photocatalytic properties can be achieved.

  13. Photocorrosion metrology of photoluminescence emitting GaAs/AlGaAs heterostructures

    Science.gov (United States)

    Aithal, Srivatsa; Liu, Neng; Dubowski, Jan J.

    2017-01-01

    High sensitivity of the photoluminescence (PL) effect to surface states and chemical reactions on surfaces of PL emitting semiconductors has been attractive in monitoring photo-induced microstructuring of such materials. To address the etching at nano-scale removal rates, we have investigated mechanisms of photocorrosion of GaAs/Al0.35Ga0.65As heterostructures immersed either in deionized water or aqueous solution of NH4OH and excited with above-bandgap radiation. The difference in photocorrosion rates of GaAs and Al0.35Ga0.65As appeared weakly dependent on the bandgap energy of these materials, and the intensity of an integrated PL signal from GaAs quantum wells or a buried GaAs epitaxial layer was found dominated by the surface states and chemical reactivity of heterostructure surfaces revealed during the photocorrosion process. Under optimized photocorrosion conditions, the method allowed resolving a 1 nm thick GaAs sandwiched between Al0.35Ga0.65As layers. We demonstrate that this approach can be used as an inexpensive, and simple room temperature tool for post-growth diagnostics of interface locations in PL emitting quantum wells and other nano-heterostructures.

  14. Epitaxial Halide Perovskite Lateral Double Heterostructure.

    Science.gov (United States)

    Wang, Yiping; Chen, Zhizhong; Deschler, Felix; Sun, Xin; Lu, Toh-Ming; Wertz, Esther A; Hu, Jia-Mian; Shi, Jian

    2017-03-28

    Epitaxial III-V semiconductor heterostructures are key components in modern microelectronics, electro-optics, and optoelectronics. With superior semiconducting properties, halide perovskite materials are rising as promising candidates for coherent heterostructure devices. In this report, spinodal decomposition is proposed and experimentally implemented to produce epitaxial double heterostructures in halide perovskite system. Pristine epitaxial mixed halide perovskites rods and films were synthesized via van der Waals epitaxy by chemical vapor deposition method. At room temperature, photon was applied as a knob to regulate the kinetics of spinodal decomposition and classic coarsening. By this approach, halide perovskite double heterostructures were created carrying epitaxial interfaces and outstanding optical properties. Reduced Fröhlich electron-phonon coupling was discovered in coherent halide double heterostructure, which is hypothetically attributed to the classic phonon confinement effect widely existing in III-V double heterostructures. As a proof-of-concept, our results suggest that halide perovskite-based epitaxial heterostructures may be promising for high-performance and low-cost optoelectronics, electro-optics, and microelectronics. Thus, ultimately, for practical device applications, it may be worthy to pursue these heterostructures via conventional vapor phase epitaxy approaches widely practised in III-V field.

  15. X-ray diffraction study of epitaxial heterostructures of II-VI CdTe and ZnTe semiconductors; Etude par diffraction de rayons X d`heterostructures epitaxiees a base des semi-conducteurs II-VI CdTe et ZnTe

    Energy Technology Data Exchange (ETDEWEB)

    Bouchet-Boudet, N.

    1996-10-07

    This work deals with the structural study of II-VI semiconductor (CdTe and ZnTe) heterostructures by X-ray diffraction and reflectivity. These heterostructures have a high lattice parameter misfit and are grown by Molecular Beam Epitaxy. Two main subjects are developed: the characterization of ZnTe wires, grown by step propagation on a CdTe (001) vicinal surface, and the study of the vertical correlations in Cd{sub 0.8}Zn{sub 0.2}Te / CdTe superlattices and superlattices made of ZnTe fractional layers spaced by CdTe. The growth of organised system is up to date; its aim is to realize quantum boxes (or wires) superlattices which are laterally and vertically ordered. The deformation along the growth axis induced by a ZnTe fractional layer inserted in a CdTe matrix is modelled, in the kinematical approximation, to reproduce the reflectivity measured around the substrate (004) Bragg peak. The lateral periodicity of the wires, deposited on a vicinal surface is a new and difficult subject. Some results are obtained on a vertical superlattice grown on a 1 deg. mis-cut surface. The in-plane and out-of-plane correlation lengths of a Cd{sub 0.8}Zn{sub 0.2}Te / CdTe superlattice are deduced from the diffused scattered intensity measured at grazing incidence. The calculations are made within the `distorted Wave Born Approximation`. The vertical correlation in ZnTe boxes (or wines) superlattices can be measured around Bragg peaks. It is twice bigger in a superlattice grown on a 2 deg. mis-cut substrate than a nominal one. (author). 74 refs.

  16. Micron thick Gd{sub 2}O{sub 3} films for GaN/AlGaN metal–oxide–semiconductor heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Grave, Daniel A. [Materials Science and Engineering Department, Pennsylvania State University, State College, PA 16802 (United States); The Applied Research Laboratory, Pennsylvania State University, State College, PA 16802 (United States); Robinson, Joshua A. [Materials Science and Engineering Department, Pennsylvania State University, State College, PA 16802 (United States); Wolfe, Douglas E. [Materials Science and Engineering Department, Pennsylvania State University, State College, PA 16802 (United States); The Applied Research Laboratory, Pennsylvania State University, State College, PA 16802 (United States); Engineering Science and Mechanics Department, Pennsylvania State University, State College, PA 16802 (United States)

    2015-08-31

    One micron thick Gd{sub 2}O{sub 3} films were grown on GaN/AlGaN heterostructures by reactive electron beam physical vapor deposition. The films were of cubic bixbyite phase with strong (222) out-of-plane and in-plane textures. The films showed a columnar microstructure with feather-like growth. Transmission electron microscopy analysis and selected area diffraction showed highly oriented single crystal like growth near the film interface which degraded as the film thickness increased. Capacitance–voltage (C–V) characteristics show that the Gd{sub 2}O{sub 3} device results in a negative threshold shift of approximately 1.9 V. Hysteresis of 0.9 V was extracted from the C–V curve corresponding to a trapped charge density of 6.9 × 10{sup 10} cm{sup −2}. The conduction mechanisms were found to be dominated by Poole–Frenkel conduction between 50 and 100 °C and Schottky emission between 125 and 200 °C. The trap height for Poole–Frenkel conduction was 0.46 eV and the Schottky barrier height was 0.79 eV. - Highlights: • One micron thick Gd{sub 2}O{sub 3} films were deposited on GaN/AlGaN heterostructures. • Gd{sub 2}O{sub 3} films were cubic phase with strong (222) biaxial orientation. • Films were governed by Poole–Frenkel conduction and Schottky conduction.

  17. Effect of AlN growth temperature on trap densities of in-situ metal-organic chemical vapor deposition grown AlN/AlGaN/GaN metal-insulator-semiconductor heterostructure field-effect transistors

    Directory of Open Access Journals (Sweden)

    Joseph J. Freedsman

    2012-06-01

    Full Text Available The trapping properties of in-situ metal-organic chemical vapor deposition (MOCVD grown AlN/AlGaN/GaN metal-insulator-semiconductor heterostructure field-effect transistors (MIS-HFETs with AlN layers grown at 600 and 700 °C has been quantitatively analyzed by frequency dependent parallel conductance technique. Both the devices exhibited two kinds of traps densities, due to AlN (DT-AlN and AlGaN layers (DT-AlGaN respectively. The MIS-HFET grown at 600 °C showed a minimum DT-AlN and DT-AlGaN of 1.1 x 1011 and 1.2 x 1010 cm-2eV-1 at energy levels (ET -0.47 and -0.36 eV. Further, the gate-lag measurements on these devices revealed less degradation ∼ ≤ 5% in drain current density (Ids-max. Meanwhile, MIS-HFET grown at 700 °C had more degradation in Ids-max ∼26 %, due to high DT-AlN and DT-AlGaN of 3.4 x 1012 and 5 x 1011 cm-2eV-1 positioned around similar ET. The results shows MIS-HFET grown at 600 °C had better device characteristics with trap densities one order of magnitude lower than MIS-HFET grown at 700 °C.

  18. Heterostructure terahertz devices.

    Science.gov (United States)

    Ryzhii, Victor

    2008-08-19

    The terahertz (THz) range of frequencies is borderline between microwave electronics and photonics. It corresponds to the frequency bands of molecular and lattice vibrations in gases, fluids, and solids. The importance of the THz range is in part due to numerous potential and emerging applications which include imaging and characterization, detection of hazardous substances, environmental monitoring, radio astronomy, covert inter-satellite communications, as well as biological and medical applications. During the last decades marked progress has been achieved in the development, fabrication, and practical implementation of THz devices and systems. This is primarily owing to the utilization of gaseous and free electron lasers and frequency converters using nonlinear optical phenomena as sources of THz radiation. However, such devices and hence the systems based on them are fairly cumbersome. This continuously stimulates an extensive search for new compact and efficient THz sources based on semiconductor heterostructures. Despite tremendous efforts lasting several decades, the so-called THz gap unbridged by semiconductor heterostructure electron and optoelectron devices still exists providing appropriate levels of power of the generated THz radiation. The invention and realization of quantum cascade lasers made of multiple quantum-well heterostructures already resulted in the partial solution of the problem in question, namely, in the successful coverage of the high-frequency portion of the THz gap (2-3 THz and higher). Further advancement to lower frequencies meets, perhaps, fundamental difficulties. All this necessitates further extensive theoretical and experimental studies of more or less traditional and novel semiconductor heterostructures as a basis for sources of THz radiation. This special issue includes 11 excellent original papers submitted by several research teams representing 14 institutions in Europe, America, and Asia. Several device concepts which

  19. Preface: Heterostructure terahertz devices

    Science.gov (United States)

    Ryzhii, Victor

    2008-08-01

    The terahertz (THz) range of frequencies is borderline between microwave electronics and photonics. It corresponds to the frequency bands of molecular and lattice vibrations in gases, fluids, and solids. The importance of the THz range is in part due to numerous potential and emerging applications which include imaging and characterization, detection of hazardous substances, environmental monitoring, radio astronomy, covert inter-satellite communications, as well as biological and medical applications. During the last decades marked progress has been achieved in the development, fabrication, and practical implementation of THz devices and systems. This is primarily owing to the utilization of gaseous and free electron lasers and frequency converters using nonlinear optical phenomena as sources of THz radiation. However, such devices and hence the systems based on them are fairly cumbersome. This continuously stimulates an extensive search for new compact and efficient THz sources based on semiconductor heterostructures. Despite tremendous efforts lasting several decades, the so-called THz gap unbridged by semiconductor heterostructure electron and optoelectron devices still exists providing appropriate levels of power of the generated THz radiation. The invention and realization of quantum cascade lasers made of multiple quantum-well heterostructures already resulted in the partial solution of the problem in question, namely, in the successful coverage of the high-frequency portion of the THz gap (2-3 THz and higher). Further advancement to lower frequencies meets, perhaps, fundamental difficulties. All this necessitates further extensive theoretical and experimental studies of more or less traditional and novel semiconductor heterostructures as a basis for sources of THz radiation. This special issue includes 11 excellent original papers submitted by several research teams representing 14 institutions in Europe, America, and Asia. Several device concepts which

  20. Spinodal Decomposition-Enabled Halide Perovskite Double Heterostructure with Reduced Fr\\"ohlich Electron-Phonon Coupling

    OpenAIRE

    Wang, Yiping; Chen, Zhizhong; Deschler, Felix; Sun, Xin; Lu, Toh-Ming; Wertz, Esther; Hu, Jia-Mian; Shi, Jian

    2016-01-01

    Epitaxial III-V semiconductor heterostructures are key components in modern microelectronics, electro-optics and optoelectronics. With superior semiconducting properties, halide perovskite materials are rising as promising candidates for coherent heterostructure devices. In this report, spinodal decomposition is proposed and experimentally implemented to produce epitaxial double heterostructures in halide perovskite system. Pristine epitaxial mixed halide perovskites rods and films were synth...

  1. Investigation of temperature dependent threshold voltage variation of Gd2O3/AlGaN/GaN metal-oxide-semiconductor heterostructure

    Directory of Open Access Journals (Sweden)

    Atanu Das

    2012-09-01

    Full Text Available Temperature dependent threshold voltage (Vth variation of GaN/AlGaN/Gd2O3/Ni-Au structure is investigated by capacitance-voltage measurement with temperature varying from 25°C to 150°C. The Vth of the Schottky device without oxide layer is slightly changed with respect to temperature. However, variation of Vth is observed for both as-deposited and annealed device owing to electron capture by the interface traps or bulk traps. The Vth shifts of 0.4V and 3.2V are obtained for as-deposited and annealed device respectively. For annealed device, electron capture process is not only restricted in the interface region but also extended into the crystalline Gd2O3 layer through Frenkel-Poole emission and hooping conduction, resulting in a larger Vth shift. The calculated trap density for as-deposited and annealed device is 3.28×1011∼1.12×1011 eV−1cm−2 and 1.74×1012∼7.33×1011 eV−1cm−2 respectively in measured temperature range. These results indicate that elevated temperature measurement is necessary to characterize GaN/AlGaN heterostructure based devices with oxide as gate dielectric.

  2. Semiconductor Lasers and Their Application in Optical Fiber Communication.

    Science.gov (United States)

    Agrawal, Govind P.

    1985-01-01

    Working principles and operating characteristics of the extremely compact and highly efficient semiconductor lasers are explained. Topics include: the p-n junction; Fabry-Perot cavity; heterostructure semiconductor lasers; materials; emission characteristics; and single-frequency semiconductor lasers. Applications for semiconductor lasers include…

  3. Colloidal nanorod heterostructures for photovoltaics and optoelectronics

    Science.gov (United States)

    Shim, Moonsub

    2017-05-01

    Colloidal quantum dots (QDs) synthesized in versatile, easy-to-process solutions are opening up exciting prospects in multiple areas, especially in biomedical imaging, photovoltaics, solid-state lighting and displays. The success of most of these prospects relies on high-quality heterostructures that improve optical properties. In particular, the core/shell heterostructure with a type I straddling band offset has been indispensable but the applicability is often limited to those exploiting only photoluminescence. QDs and their heterostructures can also be made with anisotropic shapes that allow access to essentially an unlimited number of combinations of size, shape and composition. Structures that allow enhancement of optical properties and physical accessibility for carrier injection/extraction simultaneously can open up new and exciting prospects in photovoltaics and optoelectronics. This topical review focuses on nanorod-based colloidal semiconductor heterostructures. Two-component, type II staggered band offset nanorod heterostructures capable of efficiently separating photoinduced charges are first discussed. Double heterojunction nanorods that contain three different phases are then considered with respect to their novelty and potential as emissive materials in light-emitting diodes. We conclude with an outlook on the possibility of developing colloidal nanorods that contain epitaxial interfaces beyond the conventional semiconductor heterojunctions.

  4. Impact of GaN cap on charges in Al₂O₃/(GaN/)AlGaN/GaN metal-oxide-semiconductor heterostructures analyzed by means of capacitance measurements and simulations

    Energy Technology Data Exchange (ETDEWEB)

    Ťapajna, M., E-mail: milan.tapajna@savba.sk; Jurkovič, M.; Válik, L.; Haščík, Š.; Gregušová, D.; Kuzmík, J. [Institute of Electrical Engineering, Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava (Slovakia); Brunner, F.; Cho, E.-M. [Ferdinand-Braun-Institut, Leibniz Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Strasse 4, 12489 Berlin (Germany); Hashizume, T. [Research Center for Integrated Quantum Electronics (RCIQE), Hokkaido University, 060-0814 Sapporo, Japan and JST-CREST, 102-0075 Tokyo (Japan)

    2014-09-14

    Oxide/semiconductor interface trap density (D{sub it}) and net charge of Al₂O₃/(GaN)/AlGaN/GaN metal-oxide-semiconductor high-electron mobility transistor (MOS-HEMT) structures with and without GaN cap were comparatively analyzed using comprehensive capacitance measurements and simulations. D{sub it} distribution was determined in full band gap of the barrier using combination of three complementary capacitance techniques. A remarkably higher D{sub it} (∼5–8 × 10¹²eV⁻¹ cm⁻²) was found at trap energies ranging from EC-0.5 to 1 eV for structure with GaN cap compared to that (D{sub it} ∼ 2–3 × 10¹²eV⁻¹ cm⁻²) where the GaN cap was selectively etched away. D{sub it} distributions were then used for simulation of capacitance-voltage characteristics. A good agreement between experimental and simulated capacitance-voltage characteristics affected by interface traps suggests (i) that very high D{sub it} (>10¹³eV⁻¹ cm⁻²) close to the barrier conduction band edge hampers accumulation of free electron in the barrier layer and (ii) the higher D{sub it} centered about EC-0.6 eV can solely account for the increased C-V hysteresis observed for MOS-HEMT structure with GaN cap. Analysis of the threshold voltage dependence on Al₂O₃ thickness for both MOS-HEMT structures suggests that (i) positive charge, which compensates the surface polarization, is not necessarily formed during the growth of III-N heterostructure, and (ii) its density is similar to the total surface polarization charge of the GaN/AlGaN barrier, rather than surface polarization of the top GaN layer only. Some constraints for the positive surface compensating charge are discussed.

  5. Current transport in graphene/AlGaN/GaN vertical heterostructures probed at nanoscale

    Science.gov (United States)

    Fisichella, Gabriele; Greco, Giuseppe; Roccaforte, Fabrizio; Giannazzo, Filippo

    2014-07-01

    Vertical heterostructures combining two or more graphene (Gr) layers separated by ultra-thin insulating or semiconductor barriers represent very promising systems for next generation electronics devices, due to the combination of high speed operation with wide-range current modulation by a gate bias. They are based on the specific mechanisms of current transport between two-dimensional-electron-gases (2DEGs) in close proximity. In this context, vertical devices formed by Gr and semiconductor heterostructures hosting an ``ordinary'' 2DEG can be also very interesting. In this work, we investigated the vertical current transport in Gr/Al0.25Ga0.75N/GaN heterostructures, where Gr is separated from a high density 2DEG by a ~24 nm thick AlGaN barrier layer. The current transport from Gr to the buried 2DEG was characterized at nanoscale using conductive atomic force microscopy (CAFM) and scanning capacitance microscopy (SCM). From these analyses, performed both on Gr/AlGaN/GaN and on AlGaN/GaN reference samples using AFM tips with different metal coatings, the Gr/AlGaN Schottky barrier height ΦB and its lateral uniformity were evaluated, as well as the variation of the carrier densities of graphene (ngr) and AlGaN/GaN 2DEG (ns) as a function of the applied bias. A low Schottky barrier (~0.40 eV) with excellent spatial uniformity was found at the Gr/AlGaN interface, i.e., lower compared to the measured values for metal/AlGaN contacts, which range from ~0.6 to ~1.1 eV depending on the metal workfunction. The electrical behavior of the Gr/AlGaN contact has been explained by Gr interaction with AlGaN donor-like surface states located in close proximity, which are also responsible of high n-type Gr doping (~1.3 × 1013 cm-2). An effective modulation of ns by the Gr Schottky contact was demonstrated by capacitance analysis under reverse bias. From this basic understanding of transport properties in Gr/AlGaN/GaN heterostructures, novel vertical field effect transistor concepts

  6. In situ observation of surface reactions with synchrotron radiation induced semiconductor processes by infrared reflection absorption spectroscopy using buried metal layer substrates; Umekomi kinzokuso kiban wo mochiita sekigai hansha kyushu supekutoruho ni yoru hoshako reiki handotai process hanno no sonoba kansatsu

    Energy Technology Data Exchange (ETDEWEB)

    Yoshigoe, A.; Hirano, S. [The Graduate University for Advanced Studies, Yokohama (Japan); Mase, K.; Urisu, T. [Institute for Molecular Science, Aichi (Japan)

    1996-11-20

    It is known that infrared reflection absorption spectroscopy (IRAS) on semiconductor or insulator surfaces becomes practicable by using buried metal layer (BML) substrates, in which the metal thin film is buried order semiconductor or insulator films. In this work, IRAS has been measured for Langmuir-Blodgett films deposited on the BML substrate with SiO2/Al/Si(100) structure and the observed spectrum intensity has been quantitatively compared with the calculation assuming the ideal multilayer structure for the BML substrate. The BML-IRAS using CoSi2 has been adopted to the detection of SiHn on the Si (100) substrate during synchrotron radiation (SR) stimulated Si2H6 gas source molecular beam epitaxy. It has been found that SiH2 and SiH3 on the Si (100) surface are easily decomposed by SR, but SiH can`t be decomposed. From these experiments, it has been concluded that the BML-IRAS is an useful in situ observation technique for the photo-stimulated surface reactions. 26 refs., 9 figs.

  7. Integration, gap formation, and sharpening of III-V heterostructure nanowires by selective etching

    DEFF Research Database (Denmark)

    Kallesoe, C.; Mølhave, Kristian; Larsen, K. F.

    2010-01-01

    Epitaxial growth of heterostructure nanowires allows for the definition of narrow sections with specific semiconductor composition. The authors demonstrate how postgrowth engineering of III-V heterostructure nanowires using selective etching can form gaps, sharpening of tips, and thin sections si...

  8. Plasmonics in buried structures

    OpenAIRE

    Romero, I. T.; García de Abajo, Francisco Javier

    2009-01-01

    We describe plasmon propagation in silica-filled coupled nanovoids fully buried in gold. Propagation bands and band gaps are shown to be tunable through the degree of overlap and plasmon hybridization between contiguous voids. The effect of disorder and fabrication imperfections is thoroughly investigated. Our work explores a novel paradigm for plasmon photonics relying on plasmon modes in metal-buried structures, which can benefit from long propagation distances, cancelation of radiative los...

  9. Epitaxial silicon and germanium on buried insulator heterostructures and devices

    Science.gov (United States)

    Bojarczuk, N. A.; Copel, M.; Guha, S.; Narayanan, V.; Preisler, E. J.; Ross, F. M.; Shang, H.

    2003-12-01

    Future microelectronics will be based upon silicon or germanium-on-insulator technologies and will require an ultrathin (<10 nm), flat silicon or germanium device layer to reside upon an insulating oxide grown on a silicon wafer. The most convenient means of accomplishing this is by epitaxially growing the entire structure on a silicon substrate. This requires a high quality crystalline oxide and the ability to epitaxially grow two dimensional, single crystal films of silicon or germanium on top of this oxide. We describe a method based upon molecular beam epitaxy and solid-phase epitaxy to make such structures and demonstrate working field-effect transistors on germanium-on-insulator layers.

  10. Band alignment of two-dimensional lateral heterostructures

    Science.gov (United States)

    Zhang, Junfeng; Xie, Weiyu; Zhao, Jijun; Zhang, Shengbai

    2017-03-01

    Recent experimental synthesis of two-dimensional (2D) heterostructures opens a door to new opportunities in tailoring the electronic properties for novel 2D devices. Here, we show that a wide range of lateral 2D heterostructures could have a prominent advantage over the traditional three-dimensional (3D) heterostructures, because their band alignments are insensitive to the interfacial conditions. They should be at the Schottky-Mott limits for semiconductor-metal junctions and at the Anderson limits for semiconductor junctions, respectively. This fundamental difference from the 3D heterostructures is rooted in the fact that, in the asymptotic limit of large distance, the effect of the interfacial dipole vanishes for 2D systems. Due to the slow decay of the dipole field and the dependence on the vacuum thickness, however, studies based on first-principles calculations often failed to reach such a conclusion. Taking graphene/hexagonal-BN and MoS2/WS2 lateral heterostructures as the respective prototypes, we show that the converged junction width can be order of magnitude longer than that for 3D junctions. The present results provide vital guidance to high-quality transport devices wherever a lateral 2D heterostructure is involved.

  11. Nonlinear Laser Spectroscopy Studies of Semiconductor Heterostructures

    Science.gov (United States)

    1993-01-14

    2301/Al 11. SUWPUENOTARY NOTES II& W.TNUUUIO/AVALAWISJT STATEMINT 12 3~.g7"miy Coal UNLIMITED 3 1I& AUSTRAC ? (AMaiium 200 wv* JN1419930 SEE ATTACH PAGE...IIth> 35). Optical feedback may also play a role , though replacing the polarizer with an optical isolator (isolation >40 dB) did not increase the...angle between the polarization directions of d, play a role , although replacing the polarizer with an and b.. Assigning d. to the primary polarization

  12. Heterostructure of Au nanocluster tipping on a ZnS quantum rod: controlled synthesis and novel luminescence

    Science.gov (United States)

    Tian, Yang; Wang, Ligang; Yu, Shanshan; Zhou, Weiwei

    2015-08-01

    Heterostructures of metal nanoparticles and semiconductors are widely studied for their unique properties. However, few reports are available on the heterostructure of metal nanoclusters and semiconductors. In the present study, a heterostructure, in which gold nanoclusters selectively locate at ZnS quantum rod (QR) tips, was fabricated using a two-step solvothermal route. The composition, intrinsic crystallography, and junction of the prepared heterostructure were thoroughly investigated, and it was observed to exhibit novel luminescent behaviours. By comparison with the individual components of ZnS QRs and gold clusters, the resultant heterostructure shows an enhanced exciton emission and complete depression of defect emission for the ZnS component, and a pronounced red emission for the gold nanocluster component. The mechanism of these properties and the charge transfer between gold nanoclusters and ZnS QRs were also explored. The size and location of gold in the heterostructure were also controlled during synthesis to study their effects on the luminescence.

  13. Buried Craters of Utopia

    Science.gov (United States)

    2003-01-01

    MGS MOC Release No. MOC2-365, 19 May 2003Beneath the northern plains of Mars are numerous buried meteor impact craters. One of the most heavily-cratered areas, although buried, occurs in Utopia Planitia, as shown in this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image. The history of Mars is complex; impact craters provide a tool by which to understand some of that history. In this case, a very ancient, cratered surface was thinly-buried by younger material that is not cratered at all. This area is near 48.1oN, 228.2oW; less than 180 km (112 mi) west of the Viking 2 lander site. Sunlight illuminates the scene from the lower left.

  14. Electrical Properties of the ZnO/Si Heterostructure

    Institute of Scientific and Technical Information of China (English)

    刘磁辉; 林碧霞; 朱俊杰; 付竹西; 彭聪; 杨震; 陈宇林

    2001-01-01

    The electrical properties of a type of semiconductor heterostructure fabricated by depositing zinc oxide film on a silicon substrate are investigated. The I - V, I - T curves, and deep level transient spectra are measured. From these results, we acquire the information of the characteristics of the junction, and compute some energy levelsof the samples.

  15. Plasmonics in buried structures.

    Science.gov (United States)

    Romero, I; García de Abajo, F J

    2009-10-12

    We describe plasmon propagation in silica-filled coupled nanovoids fully buried in gold. Propagation bands and band gaps are shown to be tunable through the degree of overlap and plasmon hybridization between contiguous voids. The effect of disorder and fabrication imperfections is thoroughly investigated. Our work explores a novel paradigm for plasmon photonics relying on plasmon modes in metal-buried structures, which can benefit from long propagation distances, cancelation of radiative losses, minimum crosstalk between neighboring waveguides, and maximum optical integration in three-dimensional arrangements.

  16. Hydrogen in semiconductors II

    CERN Document Server

    Nickel, Norbert H; Weber, Eicke R; Nickel, Norbert H

    1999-01-01

    Since its inception in 1966, the series of numbered volumes known as Semiconductors and Semimetals has distinguished itself through the careful selection of well-known authors, editors, and contributors. The "Willardson and Beer" Series, as it is widely known, has succeeded in publishing numerous landmark volumes and chapters. Not only did many of these volumes make an impact at the time of their publication, but they continue to be well-cited years after their original release. Recently, Professor Eicke R. Weber of the University of California at Berkeley joined as a co-editor of the series. Professor Weber, a well-known expert in the field of semiconductor materials, will further contribute to continuing the series' tradition of publishing timely, highly relevant, and long-impacting volumes. Some of the recent volumes, such as Hydrogen in Semiconductors, Imperfections in III/V Materials, Epitaxial Microstructures, High-Speed Heterostructure Devices, Oxygen in Silicon, and others promise that this tradition ...

  17. Imaging and controlling plasmonic interference fields at buried interfaces

    Science.gov (United States)

    Lummen, Tom T. A.; Lamb, Raymond J.; Berruto, Gabriele; Lagrange, Thomas; Dal Negro, Luca; García de Abajo, F. Javier; McGrouther, Damien; Barwick, B.; Carbone, F.

    2016-10-01

    Capturing and controlling plasmons at buried interfaces with nanometre and femtosecond resolution has yet to be achieved and is critical for next generation plasmonic devices. Here we use light to excite plasmonic interference patterns at a buried metal-dielectric interface in a nanostructured thin film. Plasmons are launched from a photoexcited array of nanocavities and their propagation is followed via photon-induced near-field electron microscopy (PINEM). The resulting movie directly captures the plasmon dynamics, allowing quantification of their group velocity at ~0.3 times the speed of light, consistent with our theoretical predictions. Furthermore, we show that the light polarization and nanocavity design can be tailored to shape transient plasmonic gratings at the nanoscale. This work, demonstrating dynamical imaging with PINEM, paves the way for the femtosecond and nanometre visualization and control of plasmonic fields in advanced heterostructures based on novel two-dimensional materials such as graphene, MoS2, and ultrathin metal films.

  18. Photo doping effect in graphene/BN heterostructure

    Science.gov (United States)

    Ju, Long; Velasco, Jairo, Jr.; Hwang, Edwin; Kim, Jonghwan; Wang, Feng

    2013-03-01

    Boron nitride has been demonstrated as an ideal substrate to achieve high mobility in graphene. At the same time We observed strong change of graphene transport properties by shining light on graphene/BN heterostructure. This is attributed to photo doping effect induced by impurity excitation in BN. Optical spectroscopy based on this photo-doping effects enables us to probe impurities in crystalline BN. Such information will be important for potential applications based on graphene/BN heterostructures. The potential of applying similar technique to probe defects in other insulators and semiconductors will also be discussed.

  19. In-plane heterostructures of Sb/Bi with high carrier mobility

    Science.gov (United States)

    Zhao, Pei; Wei, Wei; Sun, Qilong; Yu, Lin; Huang, Baibiao; Dai, Ying

    2017-06-01

    In-plane two-dimensional (2D) heterostructures have been attracting public attention due to their distinctive properties. However, the pristine materials that can form in-plane heterostructures are reported only for graphene, hexagonal BN, transition-metal dichalcogenides. It will be of great significance to explore more suitable 2D materials for constructing such ingenious heterostructures. Here, we demonstrate two types of novel seamless in-plane heterostructures combined by pristine Sb and Bi monolayers by means of first-principle approach based on density functional theory. Our results indicate that external strain can serve as an effective strategy for bandgap engineering, and the transition from semiconductor to metal occurs when a compressive strain of -8% is applied. In addition, the designed heterostructures possess direct band gaps with high carrier mobility (˜4000 cm2 V-1 s-1). And the mobility of electrons and holes have huge disparity along the direction perpendicular to the interface of Sb/Bi in-plane heterostructures. It is favorable for carriers to separate spatially. Finally, we find that the band edge positions of Sb/Bi in-plane heterostructures can meet the reduction potential of hydrogen generation in photocatalysis. Our results not only offer alternative materials to construct versatile in-plane heterostructures, but also highlight the applications of 2D in-plane heterostructures in diverse nanodevices and photocatalysis.

  20. Synthesis, fabrication and characterization of Ge/Si axial nanowire heterostructure tunnel FETs

    Energy Technology Data Exchange (ETDEWEB)

    Picraux, Samuel T [Los Alamos National Laboratory; Dayeh, Shadi A [Los Alamos National Laboratory

    2010-01-01

    Axial Ge/Si heterostructure nanowires allow energy band-edge engineering along the axis of the nanowire, which is the charge transport direction, and the realization of asymmetric devices for novel device architectures. This work reports on two advances in the area of heterostructure nanowires and tunnel FETs: (i) the realization of 100% compositionally modulated Si/Ge axial heterostructure nanowires with lengths suitable for device fabrication and (ii) the design and implementation of Schottky barrier tunnel FETs on these nanowires for high-on currents and suppressed ambipolar behavior. Initial prototype devices resulted in a current drive in excess of 100 {micro}A/{micro}m (I/{pi}D) and 10{sup 5} I{sub on}/I{sub off} ratios. These results demonstrate the potential of such asymmetric heterostructures (both in the semiconductor channel and metal-semiconductor barrier heights) for low-power and high performance electronics.

  1. Understanding the role of buried interface charges in a metal-oxide-semiconductor stack of Ti/Al{sub 2}O{sub 3}/Si using hard x-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Church, J. R.; Opila, R. L. [University of Delaware, Newark, Delaware 19711 (United States); Weiland, C. [Synchrotron Research, Inc., Upton, New York 11973 (United States)

    2015-04-27

    Hard X-ray photoelectron spectroscopy (HAXPES) analyses were carried out on metal-oxide-semiconductor (MOS) samples consisting of Si, thick and thin Al{sub 2}O{sub 3}, and a Ti metal cap. Using Si 1s and C 1s core levels for an energy reference, the Al 1s and Si 1s spectra were analyzed to reveal information about the location and roles of charges throughout the MOS layers. With different oxide thicknesses (2 nm and 23 nm), the depth sensitivity of HAXPES is exploited to probe different regions in the MOS structure. Post Ti deposition results indicated unexpected band alignment values between the thin and thick films, which are explained by the behavior of mobile charge within the Al{sub 2}O{sub 3} layer.

  2. Semiconductors and semimetals epitaxial microstructures

    CERN Document Server

    Willardson, Robert K; Beer, Albert C; Gossard, Arthur C

    1994-01-01

    Newly developed semiconductor microstructures can now guide light and electrons resulting in important consequences for state-of-the-art electronic and photonic devices. This volume introduces a new generation of epitaxial microstructures. Special emphasis has been given to atomic control during growth and the interrelationship between the atomic arrangements and the properties of the structures.Key Features* Atomic-level control of semiconductor microstructures* Molecular beam epitaxy, metal-organic chemical vapor deposition* Quantum wells and quantum wires* Lasers, photon(IR)detectors, heterostructure transistors

  3. Semiconductor nanoparticles for quantum devices

    Science.gov (United States)

    Erokhin, Victor; Carrara, Sandro; Amenitch, H.; Bernstorff, S.; Nicolini, Claudio

    1998-09-01

    Semiconductor nanoparticles were synthesized by exposing fatty acid salt Langmuir-Blodgett films to the atmosphere of 0957-4484/9/3/004/img8. The particle sizes were characterized by small-angle x-ray scattering of their solutions using synchrotron radiation source at higher resolution, as it was impossible previously to study it with usual laboratory x-ray sources. The particle sizes were found to correspond with the demands of single-electron and quantum junctions. Semiconductor heterostructures were grown by self-aggregation of these particles of different types. Electrical properties of these nanostructures were studied by using STM. Voltage-current characteristics revealed the presence of differential negative resistance. Measurements confirmed the formation of semiconductor superlattices directed towards a development of new nanodevices, such as tunnelling diodes and semiconductor lasers.

  4. Graphene/h-BN/ZnO van der Waals tunneling heterostructure based ultraviolet photodetector.

    Science.gov (United States)

    Wu, Zhiqian; Li, Xiaoqiang; Zhong, Huikai; Zhang, Shengjiao; Wang, Peng; Kim, Tae-ho; Kwak, Sung Soo; Liu, Cheng; Chen, Hongsheng; Kim, Sang-Woo; Lin, Shisheng

    2015-07-27

    We report a novel ultraviolet photodetector based on graphene/h-BN/ZnO van der Waals heterostructure. Graphene/ZnO heterostructure shows poor rectification behavior and almost no photoresponse. In comparison, graphene/h-BN/ZnO structure shows improved electrical rectified behavior and surprising high UV photoresponse (1350AW(-1)), which is two or three orders magnitude larger than reported GaN UV photodetector (0.2~20AW(-1)). Such high photoresponse mainly originates from the introduction of ultrathin two-dimensional (2D) insulating h-BN layer, which behaves as the tunneling layer for holes produced in ZnO and the blocking layer for holes in graphene. The graphene/h-BN/ZnO heterostructure should be a novel and representative 2D heterostructure for improving the performance of 2D materials/Semiconductor heterostructure based optoelectronic devices.

  5. Spin-Orbit induced semiconductor spin guides

    OpenAIRE

    Valin-Rodriguez, Manuel; Puente, Antonio; Serra, Llorens

    2002-01-01

    The tunability of the Rashba spin-orbit coupling allows to build semiconductor heterostructures with space modulated coupling intensities. We show that a wire-shaped spin-orbit modulation in a quantum well can support propagating electronic states inside the wire only for a certain spin orientation and, therefore, it acts as an effective spin transmission guide for this particular spin orientation.

  6. Electron scattering times in ZnO based polar heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Falson, J., E-mail: j.falson@fkf.mpg.de [Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), The University of Tokyo, Tokyo 113-8656 (Japan); Department of Advanced Materials Science, The University of Tokyo, Kashiwa 277-8561 (Japan); Max Planck Institute for Solid State Research, D-70569 Stuttgart (Germany); Kozuka, Y. [Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), The University of Tokyo, Tokyo 113-8656 (Japan); Smet, J. H. [Max Planck Institute for Solid State Research, D-70569 Stuttgart (Germany); Arima, T. [Department of Advanced Materials Science, The University of Tokyo, Kashiwa 277-8561 (Japan); RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198 (Japan); Tsukazaki, A. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); PRESTO, Japan Science and Technology Agency (JST), Tokyo 102-0075 (Japan); Kawasaki, M. [Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), The University of Tokyo, Tokyo 113-8656 (Japan); RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198 (Japan)

    2015-08-24

    The remarkable historic advances experienced in condensed matter physics have been enabled through the continued exploration and proliferation of increasingly richer and cleaner material systems. In this work, we report on the scattering times of charge carriers confined in state-of-the-art MgZnO/ZnO heterostructures displaying electron mobilities in excess of 10{sup 6} cm{sup 2}/V s. Through an examination of low field quantum oscillations, we obtain the effective mass of charge carriers, along with the transport and quantum scattering times. These times compare favorably with high mobility AlGaAs/GaAs heterostructures, suggesting the quality of MgZnO/ZnO heterostructures now rivals that of traditional semiconductors.

  7. Graphene/CdTe heterostructure solar cell and its enhancement with photo-induced doping

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Shisheng, E-mail: shishenglin@zju.edu.cn; Chen, Hongsheng [Department of Information Science and Electronic Engineering, Zhejiang University, Hangzhou 310027 (China); State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027 (China); Li, Xiaoqiang; Zhang, Shengjiao; Wang, Peng; Xu, Zhijuan; Zhong, Huikai; Wu, Zhiqian [Department of Information Science and Electronic Engineering, Zhejiang University, Hangzhou 310027 (China)

    2015-11-09

    We report a type of solar cell based on graphene/CdTe Schottky heterostructure, which can be improved by surface engineering as graphene is atomic thin. By coating a layer of ultrathin CdSe quantum dots onto graphene/CdTe heterostructure, the power conversion efficiency is increased from 2.08% to 3.10%. Photo-induced doping is mainly accounted for this enhancement, as evidenced by field effect transport, Raman, photoluminescence, and quantum efficiency measurements. This work demonstrates a feasible way of improving the performance of graphene/semiconductor heterostructure solar cells by combining one dimensional with two dimensional materials.

  8. Admittance and subthreshold characteristics of atomic-layer-deposition Al2O3 on In0.53Ga0.47As in surface and buried channel flatband metal-oxide-semiconductor field effect transistors

    Science.gov (United States)

    Paterson, G. W.; Bentley, S. J.; Holland, M. C.; Thayne, I. G.; Ahn, J.; Long, R. D.; McIntyre, P. C.; Long, A. R.

    2012-05-01

    The admittances and subthreshold characteristics of capacitors and MOSFETs on buried and surface In0.53Ga0.47As channel flatband wafers, with a dielectric of Al2O3 deposited on In0.53Ga0.47As, are reported. The admittance characteristics of both wafers indicate the presence of defect states within the oxide, in common with a number of other oxides on In0.53Ga0.47As. The two wafers studied have not been hydrogen annealed, but do show some similar features to FGA treated oxides on n+ substrates. We discuss how the possible presence of residual hydroxyl ions in as-grown Al2O3 may explain these similarities and also account for many of the changes in the properties of FGA treated n+ samples. The issues around the comparison of subthreshold swing (SS) results and the impact of transistor design parameters on the energy portion of the defect state distribution affecting efficient device switching are discussed. The interface state model is applied to low source-drain voltage SS data to extract an effective interface state density (Dit) that includes interface and oxide traps. The logarithmic gate voltage sweep rate dependence of the SS Dit is used to extract an oxide trap density (Dot) and a simple method is used to estimate the Fermi level position within the band gap, Et. The Al2O3 Dit(Et) and Dot(Et) distributions are found to be similar to each other and to the results of our analysis of Gd0.25Ga0.15O0.6/Ga2O3 and HfO2/Al2O3 on In0.53Ga0.47As, adding weight to the suggestion of there being a common defect state distribution and perhaps a common cause of defects states for a number of oxides on In0.53Ga0.47As.

  9. Electrically-Generated Spin Polarization in Non-Magnetic Semiconductors

    Science.gov (United States)

    2016-03-31

    AFRL-AFOSR-VA-TR-2016-0143 Electrically -generated spin polarization in non-magnetic semiconductors Vanessa Sih UNIVERSITY OF MICHIGAN Final Report 03...SUBTITLE (YIP) - Electrically -generated spin polarization in non-magnetic semiconductors 5a. CONTRACT NUMBER 5b. GRANT NUMBER FA9550-12-1-0258 5c...that produced electrically -generated electron spin polarization in non-magnetic semiconductor heterostructures. Electrically -generated electron spin

  10. Ballistic electron emissions microscopy (BEEM) of ferromagnet-semiconductor interfaces; Ballistische Elektronen Emissions Mikroskopie (BEEM) an Ferromagnet-Halbleitergrenzflaechen

    Energy Technology Data Exchange (ETDEWEB)

    Obernhuber, S.

    2007-04-15

    For current research on spin-transistors it is important to know the characteristics of ferromagnet semiconductor interfaces. The ballistic electron emission microscopy (BEEM) is a method to investigate such a buried interface with nanometer resolution. In this work several ferromagnet/GaAs(110) interfaces have been analysed concerning their homogeneity and mean local Schottky-barrier heights (SBH) have been determined. In Addition, the resulting integral SBH was calculated from the distribution of the local SBHs and compared with the SBH determined from voltage/current characteristics. The areas with a low SBH dominate the current conduction across the interface. Additional BEEM measurements on (AlGaAs/GaAs) heterostructures have been performed. This heterostructures consist of 50 nm AlGaAs/GaAs layers. The results of the BEEM measurements indicate, that the GaAs QWs are defined by AlGaAs barriers. The transition from AlGaAs to GaAs is done within 10 nm. (orig.)

  11. Magnet-in-the-Semiconductor Nanomaterials: High Electron Mobility in All-Inorganic Arrays of FePt/CdSe and FePt/CdS Core-Shell Heterostructures.

    Science.gov (United States)

    Son, Jae Sung; Lee, Jong-Soo; Shevchenko, Elena V; Talapin, Dmitri V

    2013-06-06

    We report a colloidal synthesis and electrical and magnetotransport properties of multifunctional "magnet-in-the-semiconductor" nanostructures composed of FePt core and CdSe or CdS shell. Thin films of all-inorganic FePt/CdSe and FePt/CdS core-shell nanostructures capped with In2Se4(2-) molecular chalcogenide (MCC) ligands exhibited n-type charge transport with high field-effect electron mobility of 3.4 and 0.02 cm(2)/V·s, respectively. These nanostructures also showed a negative magnetoresistance characteristic for spin-dependent tunneling. We discuss the mechanism of charge transport and gating in the arrays of metal/semiconductor core-shell nanostructures.

  12. Probing Molecular Organization and Electronic Dynamics at Buried Organic Interfaces

    Science.gov (United States)

    Roberts, Sean

    2015-03-01

    Organic semiconductors are a promising class of materials due to their ability to meld the charge transport capabilities of semiconductors with many of the processing advantages of plastics. In thin film organic devices, interfacial charge transfer often comprises a crucial step in device operation. As molecular materials, the density of states within organic semiconductors often reflect their intermolecular organization. Truncation of the bulk structure of an organic semiconductor at an interface with another material can lead to substantial changes in the density of states near the interface that can significantly impact rates for interfacial charge and energy transfer. Here, we will present the results of experiments that utilize electronic sum frequency generation (ESFG) to probe buried interfaces in these materials. Within the electric dipole approximation, ESFG is only sensitive to regions of a sample that experience a breakage of symmetry, which occurs naturally at material interfaces. Through modeling of signals measured for thin organic films using a transfer matrix-based formalism, signals from buried interfaces between two materials can be isolated and used to uncover the interfacial density of states.

  13. High pressure semiconductor physics I

    CERN Document Server

    Willardson, R K; Paul, William; Suski, Tadeusz

    1998-01-01

    Since its inception in 1966, the series of numbered volumes known as Semiconductors and Semimetals has distinguished itself through the careful selection of well-known authors, editors, and contributors. The "Willardson and Beer" Series, as it is widely known, has succeeded in publishing numerous landmark volumes and chapters. Not only did many of these volumes make an impact at the time of their publication, but they continue to be well-cited years after their original release. Recently, Professor Eicke R. Weber of the University of California at Berkeley joined as a co-editor of the series. Professor Weber, a well-known expert in the field of semiconductor materials, will further contribute to continuing the series' tradition of publishing timely, highly relevant, and long-impacting volumes. Some of the recent volumes, such as Hydrogen in Semiconductors, Imperfections in III/V Materials, Epitaxial Microstructures, High-Speed Heterostructure Devices, Oxygen in Silicon, and others promise indeed that this tra...

  14. Semiconductor High-Energy Radiation Scintillation Detector

    CERN Document Server

    Kastalsky, A; Spivak, B

    2006-01-01

    We propose a new scintillation-type detector in which high-energy radiation produces electron-hole pairs in a direct-gap semiconductor material that subsequently recombine producing infrared light to be registered by a photo-detector. The key issue is how to make the semiconductor essentially transparent to its own infrared light, so that photons generated deep inside the semiconductor could reach its surface without tangible attenuation. We discuss two ways to accomplish this, one based on doping the semiconductor with shallow impurities of one polarity type, preferably donors, the other by heterostructure bandgap engineering. The proposed semiconductor scintillator combines the best properties of currently existing radiation detectors and can be used for both simple radiation monitoring, like a Geiger counter, and for high-resolution spectrography of the high-energy radiation. The most important advantage of the proposed detector is its fast response time, about 1 ns, essentially limited only by the recombi...

  15. Modulation of electronic structures of MoSe2/WSe2 van der Waals heterostructure by external electric field

    Science.gov (United States)

    Zhang, Fang; Li, Wei; Dai, Xianqi

    2017-10-01

    By using first-principles calculations, we investigate the electronic structures of MoSe2/WSe2 van der Waals(vdW) heterostructure by applying external electric field(Eext) perpendicular to the layers. It is demonstrated that MoSe2/WSe2 heterostructure is a type-II vdW heterostructure. The band gap of MoSe2/WSe2 is significantly modulated by Eext, eventually a semiconductor-to-metal transition can be realized. The positive and negative Eext have different effects on the band gap due to the intrinsic spontaneous electric polarization in MoSe2/WSe2 heterostructure. Moreover, MoSe2/WSe2 heterobilayer experiences transitions from type-II to type-I and then to type-II under various Eext. The present study provides great application potential of ultrathin MoSe2/WSe2 heterostructure in future nano- and optoelectronics.

  16. Two-dimensional Ni(OH)2-XS2 (X = Mo and W) heterostructures

    Science.gov (United States)

    Tang, Zhen-Kun; Tong, Chuan-Jia; Geng, Wei; Zhang, Deng-Yu; Liu, Li-Min

    2015-09-01

    Two-dimensional (2D) van der Waals (vdW) heterostructures have received a lot of attention because of their wide applications in electronics and optoelectronics. In this work, the electronic structures and optical properties of nickel hydroxides (Ni(OH)2) and transition metal dichalcogenides (XS2, X = Mo, W) heterostructures are studied by hybrid density functional theory. The results reveal that all the considered Ni(OH)2-XS2 heterostructures are indirect semiconductors with a band gap of 0.040-0.825 eV. Additionally, the AB stacked Ni(OH)2-XS2 heterostructures are more stable than the AA stacked one. Interestingly, the complete electron-hole separation is found in the Ni(OH)2-XS2 heterostructure, and its conduction band minimum and valence band maximum are located on the XS2 and Ni(OH)2 layers, respectively. Besides, the optical absorption peaks of Ni(OH)2-XS2 heterostructures are mainly located within the visible light region. These fascinating electronic structures and optical absorption of the Ni(OH)2-XS2 heterostructures make them promising candidates for applications in 2D optoelectronics.

  17. Trilayer TMDC Heterostructures for MOSFETs and Nanobiosensors

    Science.gov (United States)

    Datta, Kanak; Shadman, Abir; Rahman, Ehsanur; Khosru, Quazi D. M.

    2017-02-01

    Two dimensional materials such as transition metal dichalcogenides (TMDC) and their bi-layer/tri-layer heterostructures have become the focus of intense research and investigation in recent years due to their promising applications in electronics and optoelectronics. In this work, we have explored device level performance of trilayer TMDC heterostructure (MoS2/MX2/MoS2; M = Mo or, W and X = S or, Se) metal oxide semiconductor field effect transistors (MOSFETs) in the quantum ballistic regime. Our simulation shows that device `on' current can be improved by inserting a WS2 monolayer between two MoS2 monolayers. Application of biaxial tensile strain reveals a reduction in drain current which can be attributed to the lowering of carrier effective mass with increased tensile strain. In addition, it is found that gate underlap geometry improves electrostatic device performance by improving sub-threshold swing. However, increase in channel resistance reduces drain current. Besides exploring the prospect of these materials in device performance, novel trilayer TMDC heterostructure double gate field effect transistors (FETs) are proposed for sensing Nano biomolecules as well as for pH sensing. Bottom gate operation ensures these FETs operating beyond Nernst limit of 59 mV/pH. Simulation results found in this work reveal that scaling of bottom gate oxide results in better sensitivity while top oxide scaling exhibits an opposite trend. It is also found that, for identical operating conditions, proposed TMDC FET pH sensors show super-Nernst sensitivity indicating these materials as potential candidates in implementing such sensor. Besides pH sensing, all these materials show high sensitivity in the sub-threshold region as a channel material in nanobiosensor while MoS2/WS2/MoS2 FET shows the least sensitivity among them.

  18. A Ge/Si heterostructure nanowire-based double quantum dot with integrated charge sensor

    DEFF Research Database (Denmark)

    Hu, Yongjie; Churchill, Hugh; Reilly, David;

    2007-01-01

    Coupled electron spins in semiconductor double quantum dots hold promise as the basis for solid-state qubits. To date, most experiments have used III-V materials, in which coherence is limited by hyperfine interactions. Ge/Si heterostructure nanowires seem ideally suited to overcome this limitati...

  19. Semiconductor statistics

    CERN Document Server

    Blakemore, J S

    1987-01-01

    In-depth exploration of the implications of carrier populations and Fermi energies examines distribution of electrons in energy bands and impurity levels of semiconductors. Also: kinetics of semiconductors containing excess carriers, particularly in terms of trapping, excitation, and recombination.

  20. The Physics of Semiconductors An Introduction Including Nanophysics and Applications

    CERN Document Server

    Grundmann, Marius

    2010-01-01

    The Physics of Semiconductors contains ample material for a comprehensive upper-level undergraduate or beginning graduate course, guiding readers to the point where they can choose a special topic and begin supervised research. The textbook provides a balance between essential aspects of solid-state and semiconductor physics, on the one hand, and the principles of various semiconductor devices and their applications in electronic and photonic devices, on the other. It highlights many practical aspects of semiconductors such as alloys, strain, heterostructures, nanostructures, that are necessary in modern semiconductor research but typically omitted in textbooks. Coverage also includes additional advanced topics, such as Bragg mirrors, resonators, polarized and magnetic semiconductors. The text derives explicit formulas for many results to support better understanding of the topics. The Physics of Semiconductors requires little or no prior knowledge of solid-state physics and evolved from a highly regarded two...

  1. The Physics of Semiconductors An Introduction Including Devices and Nanophysics

    CERN Document Server

    Grundmann, Marius

    2006-01-01

    The Physics of Semiconductors provides material for a comprehensive upper-level-undergrauate and graduate course on the subject, guiding readers to the point where they can choose a special topic and begin supervised research. The textbook provides a balance between essential aspects of solid-state and semiconductor physics, on the one hand, and the principles of various semiconductor devices and their applications in electronic and photonic devices, on the other. It highlights many practical aspects of semiconductors such as alloys, strain, heterostructures, nanostructures, that are necessary in modern semiconductor research but typically omitted in textbooks. For the interested reader some additional advanced topics are included, such as Bragg mirrors, resonators, polarized and magnetic semiconductors are included. Also supplied are explicit formulas for many results, to support better understanding. The Physics of Semiconductors requires little or no prior knowledge of solid-state physics and evolved from ...

  2. Catalysts, Protection Layers, and Semiconductors

    DEFF Research Database (Denmark)

    Chorkendorff, Ib

    2015-01-01

    Hydrogen is the simplest solar fuel to produce and in this presentation we shall give a short overview of the pros and cons of various tandem devices [1]. The large band gap semiconductor needs to be in front, but apart from that we can chose to have either the anode in front or back using either...... acid or alkaline conditions. Since most relevant semiconductors are very prone to corrosion the advantage of using buried junctions and using protection layers offering shall be discussed [2-4]. Next we shall discuss the availability of various catalysts for being coupled to these protections layers...... and how their stability may be evaluated [5, 6]. Examples of half-cell reaction using protection layers for both cathode and anode will be discussed though some of recent examples under both alkaline and acidic conditions. Si is a very good low band gap semiconductor and by using TiO2 as a protection...

  3. Near-Unity Absorption in van der Waals Semiconductors for Ultrathin Optoelectronics.

    Science.gov (United States)

    Jariwala, Deep; Davoyan, Artur R; Tagliabue, Giulia; Sherrott, Michelle C; Wong, Joeson; Atwater, Harry A

    2016-09-14

    We demonstrate near-unity, broadband absorbing optoelectronic devices using sub-15 nm thick transition metal dichalcogenides (TMDCs) of molybdenum and tungsten as van der Waals semiconductor active layers. Specifically, we report that near-unity light absorption is possible in extremely thin (<15 nm) van der Waals semiconductor structures by coupling to strongly damped optical modes of semiconductor/metal heterostructures. We further fabricate Schottky junction devices using these highly absorbing heterostructures and characterize their optoelectronic performance. Our work addresses one of the key criteria to enable TMDCs as potential candidates to achieve high optoelectronic efficiency.

  4. General shape control of colloidal CdS, CdSe, CdTe quantum rods and quantum rod heterostructures.

    Science.gov (United States)

    Shieh, Felice; Saunders, Aaron E; Korgel, Brian A

    2005-05-12

    We report a general synthetic method for the formation of shape-controlled CdS, CdSe and CdTe nanocrystals and mixed-semiconductor heterostructures. The crystal growth kinetics can be manipulated by changing the injection rate of the chalcogen precursor, allowing the particle shape-spherical or rodlike-to be tuned without changing the underlying chemistry. A single injection of precursor leads to isotropic spherical growth, whereas multiple injections promote epitaxial growth along the length of the c-axis. This method was extended to produce linear type I and type II semiconductor nanocrystal heterostructures.

  5. Subnanometer scale characterization of III-V-heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Lakner, H. [Gerhard-Mercator-Univ. Duisburg (Germany). Werkstoffe der Elektrotechnik

    1996-12-31

    Heterostructures based on III-V semiconductors play a dominant role for the production of optoelectronic /1/ and electronic high-speed or high-frequency /2/ devices. The necessary band-gap engineering is achieved by optimized growth procedures which allow to change the chemical composition and the crystal structure (e.g., strain or ordering) on the subnanometer scale. The evaluation of individual heterointerfaces with respect to chemical composition and crystal structure requires characterization techniques which offer the necessary high spatial resolution. Scanning transmission electron microscopy (STEM) offers several of such quantitative techniques. It is the intention of this paper to demonstrate the capabilities of STEM in the subnanometer characterization of III-V-heterostructures based on InP-substrates. Additionally, the data obtained from nanocharacterization can be correlated to device performance.

  6. Electron spin and charge in semiconductor quantum dots

    NARCIS (Netherlands)

    Elzerman, J.M.

    2004-01-01

    In this thesis, the spin and charge degree of freedom of electrons in semiconductor lateral and vertical quantum dots are experimentally investigated. The lateral quantum dot devices are defined in a two-dimensional electron gas (2DEG) below the surface of a GaAs/AlGaAs heterostructure, by metallic

  7. Potential of semiconductor nanowires for single photon sources

    NARCIS (Netherlands)

    Harmand, J.-C.; Liu, L.; Patriarche, G.; Tchernycheva, M.; Akopian, N.; Perinetti, U.; Zwiller, V.

    2009-01-01

    The catalyst-assisted growth of semiconductor nanowires heterostructures offers a very flexible way to design and fabricate single photon emitters. The nanowires can be positioned by organizing the catalyst prior to growth. Single quantum dots can be formed in the core of single nanowires which can

  8. Monitoring of stress relaxation and defect formation in metamorphic III-V semiconductor heterostructures for high-efficiency solar cells; Kontrolle von Spannungsrelaxation und Defektbildung in metamorphen III-V Halbleiterheterostrukturen fuer hocheffiziente Solarzellen

    Energy Technology Data Exchange (ETDEWEB)

    Schoene, Jan

    2009-07-21

    The paper discusses the further development of monolithic III-V multiple solar cells with three pn transitions for applications in concentrating PV systems. These triple solar cells consist of a GaInP upper cell, a GaInAs middle cell and a germanium lower cell, which are connected via electrically conducting and optically transparent tunnel diodes. Efficiencies are higher than 40 % with concentrated light. Demands on materials for III-V high-efficiency solar cells are extremely high. Especially in the metamorphic triple solar cell, for which compound semiconductors with different interatomic distances are deposited epitactically on each other, crystal defects may occur that impair the performance of the solar cell. The use of appropriate layer growing concepts may manipulate the formation of crystal defects and minimize their influence on solar cell performance. Both conventional and high-resolution transmission electron microscopy (TEM and HRTEM) as well as high-resolution X-ray diffraction (HRXRD) were applied successfully for investigating defect formation and layer stresses. In the investigations described, these methods were applied to develop a high-efficiency triple solar cell with a world first efficiency of 41.1 percent in concentrated light. [German] Diese Arbeit beschaeftigt sich mit der Weiterentwicklung von monolithischen III-V-Mehrfach-Solarzellen mit drei pn-Uebergaengen fuer die Anwendung in konzentrierenden Photovoltaiksystemen. Diese Tripelsolarzellen bestehen aus einer GaInP-Oberzelle, einer GaInAs-Mittelzelle und einer Germanium-Unterzelle, die mittels elektrisch leitender und optisch transparenter Tunneldioden verbunden sind. Derartige Solarzellen erzielen mittlerweile Rekordwirkungsgrade von mehr als 40 % unter konzentriertem Licht. Bei den III-V Hocheffizienzsolarzellen sind die Anforderungen an die Materialqualitaet ausserordentlich hoch. Insbesondere bei der metamorphen Tripelsolarzelle, bei der Verbindungshalbleiter mit unterschiedlichen

  9. Picosecond optical pulse generation at gigahertz rates by direct modulation of a semiconductor laser

    Science.gov (United States)

    Auyeung, J.

    1981-01-01

    We report the generation of picosecond pulses by the direct modulation of a buried heterostructure GaAlAs diode laser. Pulse width of 28 ps is achieved at a repetition frequency of 2.5 GHz. Pulse width dependence on the experimental parameters is described.

  10. 47 CFR 32.2423 - Buried cable.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 2 2010-10-01 2010-10-01 false Buried cable. 32.2423 Section 32.2423... FOR TELECOMMUNICATIONS COMPANIES Instructions for Balance Sheet Accounts § 32.2423 Buried cable. (a) This account shall include the original cost of buried cable as well as the cost of other material...

  11. Transport properties of Fibonacci heterostructures: a nonparabolic approach

    Science.gov (United States)

    Palomino-Ovando, M.; Cocoletzi, G. H.

    1998-07-01

    A fourth order hamiltonian is used to explore transport properties of semiconductor Fibonacci heterostructures. The tunneling current and time delay are obtained for different Fibonacci sequences constructed withGaAsandAlxGa1 - xAs. Energy minibands are calculated to study the fractal dimension and critical electronic states in quasi-periodic arrays. Results show that nonparabolic corrections produce changes in the tunneling current, time delay and fractal dimension, and a low voltage shift of the current peaks compared with the parabolic theory. The electronic states preserve their critical nature in the presence of nonparabolic effects.

  12. Theory buried under heavy description

    Directory of Open Access Journals (Sweden)

    Vivian B. Martin Ph.D.

    2010-12-01

    Full Text Available In journalism when a reporter puts the main news or point of the story deep down in the text, we say she’s buried the lead, the lead being the main point of the story and usually the first paragraph. In Children in Genocide: extreme traumatization and affect regulation, psychoanalyst Suzanne Kaplan buries her theory. Her study of the after effects of trauma among Holocaust survivors who were children during their persecution and survivors of atrocities during the Rwandan atrocities of the 1990s, is filled with highly descriptive material from the many interviews that serve as data. An interesting grounded theory is peeking out from under all the disciplinary discourse and historical background one must read through to get to what grounded theory readers will consider the juicy parts: concepts on affect regulation in trauma survivors.

  13. Enhanced Photoelectrochemical Performance from Rationally Designed Anatase/Rutile TiO2 Heterostructures.

    Science.gov (United States)

    Cao, Fengren; Xiong, Jie; Wu, Fangli; Liu, Qiong; Shi, Zhiwei; Yu, Yanhao; Wang, Xudong; Li, Liang

    2016-05-18

    In a photoelectrochemical (PEC) cell for water splitting, the critical issue is charge separation and transport, which is usually completed by designing semiconductor heterojunctions. TiO2 anatase-rutile mixed junctions could largely improve photocatalytic properties, but impairs PEC water splitting performance. We designed and prepared two types of TiO2 heterostructures with the anatase thin film and rutile nanowire phases organized in different sequences. The two types of heterostructures were used as PEC photoanodes for water splitting and demonstrated completely opposite results. Rutile nanowires on anatase film demonstrated enhanced photocurrent density and onset potential, whereas strong negative performance was obtained from anatase film on rutile nanowire structures. The mechanism was investigated by photoresponse, light absorption and reflectance, and electrochemical impedance spectra. This work revealed the significant role of phase sequence in performance gain of anatase-rutile TiO2 heterostructured PEC photoanodes.

  14. Semiconductor spintronics

    CERN Document Server

    Xia, Jianbai; Chang, Kai

    2012-01-01

    Semiconductor Spintronics, as an emerging research discipline and an important advanced field in physics, has developed quickly and obtained fruitful results in recent decades. This volume is the first monograph summarizing the physical foundation and the experimental results obtained in this field. With the culmination of the authors' extensive working experiences, this book presents the developing history of semiconductor spintronics, its basic concepts and theories, experimental results, and the prospected future development. This unique book intends to provide a systematic and modern foundation for semiconductor spintronics aimed at researchers, professors, post-doctorates, and graduate students, and to help them master the overall knowledge of spintronics.

  15. BATATA: a buried muon hodoscope

    Science.gov (United States)

    Sánchez, F.; Supanitsky, A. D.; Medina-Tanco, G.; Paic, G.; Salazar, M. E. Patiño; D'Olivo, J. C.; Molina, R. Alfaro

    2009-04-01

    Muon hodoscopes have several applications, ranging from astrophysics to fundamental particle physics. In this work, we present a detector dedicated to the study, at ground level, of the main signals of cosmic-ray induced showers above 6 PeV. The whole detector is composed by a set of three parallel dual-layer scintillator planes buried at fix depths ranging from 120 g/cm2 to 600 g/cm2 and by a triangular array of water cerenkov detectors located nearby on ground.

  16. Binary group III-nitride based heterostructures: band offsets and transport properties

    Science.gov (United States)

    Roul, Basanta; Kumar, Mahesh; Rajpalke, Mohana K.; Bhat, Thirumaleshwara N.; Krupanidhi, S. B.

    2015-10-01

    In the last few years, there has been remarkable progress in the development of group III-nitride based materials because of their potential application in fabricating various optoelectronic devices such as light emitting diodes, laser diodes, tandem solar cells and field effect transistors. In order to realize these devices, growth of device quality heterostructures are required. One of the most interesting properties of a semiconductor heterostructure interface is its Schottky barrier height, which is a measure of the mismatch of the energy levels for the majority carriers across the heterojunction interface. Recently, the growth of non-polar III-nitrides has been an important subject due to its potential improvement on the efficiency of III-nitride-based opto-electronic devices. It is well known that the c-axis oriented optoelectronic devices are strongly affected by the intrinsic spontaneous and piezoelectric polarization fields, which results in the low electron-hole recombination efficiency. One of the useful approaches for eliminating the piezoelectric polarization effects is to fabricate nitride-based devices along non-polar and semi-polar directions. Heterostructures grown on these orientations are receiving a lot of focus due to enhanced behaviour. In the present review article discussion has been carried out on the growth of III-nitride binary alloys and properties of GaN/Si, InN/Si, polar InN/GaN, and nonpolar InN/GaN heterostructures followed by studies on band offsets of III-nitride semiconductor heterostructures using the x-ray photoelectron spectroscopy technique. Current transport mechanisms of these heterostructures are also discussed.

  17. High pressure in semiconductor physics II

    CERN Document Server

    Willardson, R K; Suski, Tadeusz; Paul, William

    1998-01-01

    Since its inception in 1966, the series of numbered volumes known as Semiconductors and Semimetals has distinguished itself through the careful selection of well-known authors, editors, and contributors. The "Willardson and Beer" Series, as it is widely known, has succeeded in publishing numerous landmark volumes and chapters. Not only did many of these volumes make an impact at the time of their publication, but they continue to be well-cited years after their original release. Recently, Professor Eicke R. Weber of the University of California at Berkeley joined as a co-editor of the series. Professor Weber, a well-known expert in the field of semiconductor materials, will further contribute to continuing the series' tradition of publishing timely, highly relevant, and long-impacting volumes. Some of the recent volumes, such as Hydrogen in Semiconductors, Imperfections in III/V Materials, Epitaxial Microstructures, High-Speed Heterostructure Devices, Oxygen in Silicon, and others promise indeed that this tra...

  18. Silicon/silicon germanium heterostructures: Materials, physics, quantum functional devices and their integration with heterostructure bipolar transistors

    Science.gov (United States)

    Chung, Sung-Yong

    With the advent of the first transistor in 1947, the integrated circuit (IC) industry has rapidly expanded with the tremendous advances in the development of IC technology. The driving force in the evolution of IC technology is the reduction of transistor sizes. Without a doubt, transistor miniaturization will face fundamental physical limitations imposed by further dimensional scaling of silicon transistors in the near future. According to the 2004 International Technology Roadmap for Semiconductors (ITRS), the width of a gate electrode for complementary metal-oxide-semiconductor (CMOS) is projected to be a mere 7 nm by the end of 2018. No further solutions have been found. Since the 2001 ITRS, tunneling devices have been evaluated as an emerging technology to augment silicon CMOS. Transistor circuitry incorporating tunneling devices realized using III-V semiconductors has exhibited superior performance over its transistor-only counterparts. However, due to fundamental differences in material properties, such technology is not readily compatible with the mainstream platforms (>95% market share of semiconductors) of CMOS and HBT technologies. Recently, we demonstrated the successful monolithic integration of Si-based resonant interband tunnel diodes (RITDs) with CMOS and SiGe HBT, which makes them more attractive than III-V based tunnel diodes for system level integration. This dissertation is concerned with the development of quantum functional tunneling devices, RITDs, and high-speed transistors, HBTs, using Si/SiGe heterostructures as well as material growth and electrical properties of Si/SiGe heterostructures. Emphasis is placed on the development of Si/SiGe-based RITDs, HBTs, and their monolithic integration for 3-terminal negative differential resistance (NDR) devices. The operating principles of Si-based RITDs and the integration of RITD with HBT are also discussed.

  19. A.E.S. characterisation of small dimensional heterostructures

    CERN Document Server

    Gelsthorpe, A J

    2001-01-01

    the surface. The CMA also incorporates an electrostatic lens that deflects electrons onto the detectors along the same path independent of their energy. The operation and characterisation of the modified CMA and its electrostatic lens is described. Application to topographical features that show artefacts is also described. The CMA system can also be used to perform depth profiling by ion beam bevelling. This technique is applied to multi-layered heterostructures and a comparison is made between this, ion beam milling and chemical bevelling. Surface analysis is used to examine the outer layers of solid material to determine their properties and composition, and has many applications in industry. Atomic composition of the surface can be determined by Auger analysis. Depth profiles can also be obtained by exposing layers buried within a structure and then analysing them. This thesis presents improved techniques for analysing complex structures that have multiple thin layers or have significant topographical fea...

  20. Semiconductor heterojunctions

    CERN Document Server

    Sharma, B L

    1974-01-01

    Semiconductor Heterojunctions investigates various aspects of semiconductor heterojunctions. Topics covered include the theory of heterojunctions and their energy band profiles, electrical and optoelectronic properties, and methods of preparation. A number of heterojunction devices are also considered, from photovoltaic converters to photodiodes, transistors, and injection lasers.Comprised of eight chapters, this volume begins with an overview of the theory of heterojunctions and a discussion on abrupt isotype and anisotype heterojunctions, along with graded heterojunctions. The reader is then

  1. Buried Waste Integrated Demonstration Plan

    Energy Technology Data Exchange (ETDEWEB)

    Kostelnik, K.M.

    1991-12-01

    This document presents the plan of activities for the Buried Waste Integrated Demonstration (BWID) program which supports the environmental restoration (ER) objectives of the Department of Energy (DOE) Complex. Discussed in this plan are the objectives, organization, roles and responsibilities, and the process for implementing and managing BWID. BWID is hosted at the Idaho National Engineering Laboratory (INEL), but involves participants from throughout the DOE Complex, private industry, universities, and the international community. These participants will support, demonstrate, and evaluate a suite of advanced technologies representing a comprehensive remediation system for the effective and efficient remediation of buried waste. The processes for identifying technological needs, screening candidate technologies for applicability and maturity, selecting appropriate technologies for demonstration, field demonstrating, evaluation of results and transferring technologies to environmental restoration programs are also presented. This document further describes the elements of project planning and control that apply to BWID. It addresses the management processes, operating procedures, programmatic and technical objectives, and schedules. Key functions in support of each demonstration such as regulatory coordination, safety analyses, risk evaluations, facility requirements, and data management are presented.

  2. The physics of semiconductors an introduction including nanophysics and applications

    CERN Document Server

    Grundmann, Marius

    2016-01-01

    The 3rd edition of this successful textbook contains ample material for a comprehensive upper-level undergraduate or beginning graduate course, guiding readers to the point where they can choose a special topic and begin supervised research. The textbook provides a balance between essential aspects of solid-state and semiconductor physics, on the one hand, and the principles of various semiconductor devices and their applications in electronic and photonic devices, on the other. It highlights many practical aspects of semiconductors such as alloys, strain, heterostructures, nanostructures, that are necessary in modern semiconductor research but typically omitted in textbooks. Coverage also includes additional advanced topics, such as Bragg mirrors, resonators, polarized and magnetic semiconductors, nanowires, quantum dots, multi-junction solar cells, thin film transistors, carbon-based nanostructures and transparent conductive oxides. The text derives explicit formulas for many results to support better under...

  3. Local droplet etching – Nanoholes, quantum dots, and air-gap heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Heyn, Ch.; Sonnenberg, D.; Graf, A.; Kerbst, J.; Stemmann, A.; Hansen, W. [Institute of Applied Physics, University of Hamburg, Jungiusstr. 11, 20355 Hamburg (Germany)

    2014-05-15

    Local droplet etching (LDE) allows the self-organized generation of nanoholes in semiconductor surfaces and is fully compatible with molecular beam epitaxy (MBE). The influence of the process parameters as well as of droplet and substrate materials on the LDE nanohole morphology is discussed. Furthermore, recent applications of LDE, the fabrication of quantum dots by hole filling and the creation of air-gap heterostructures are addressed.

  4. Magneto-electroluminescence of organic heterostructures: Analytical theory and spectrally resolved measurements

    OpenAIRE

    Liu,Feilong; Kelley, Megan R.; Crooker, Scott A.; Nie, Wanyi; Mohite, Aditya D.; Ruden, P. Paul; Smith, Darryl L.

    2014-01-01

    The effect of a magnetic field on the electroluminescence of organic light emitting devices originates from the hyperfine interaction between the electron/hole polarons and the hydrogen nuclei of the host molecules. In this paper, we present an analytical theory of magneto-electroluminescence for organic semiconductors. To be specific, we focus on bilayer heterostructure devices. In the case we are considering, light generation at the interface of the donor and acceptor layers results from th...

  5. Identification of defects in semiconductors

    CERN Document Server

    Stavola, Michael; Weber, Eicke R; Stavola, Michael

    1998-01-01

    Since its inception in 1966, the series of numbered volumes known as Semiconductors and Semimetals has distinguished itself through the careful selection of well-known authors, editors, and contributors.The"Willardson and Beer"Series, as it is widely known, has succeeded in publishing numerous landmark volumes and chapters. Not only did many of these volumes make an impact at the time of their publication, but they continue to be well-cited years after their original release. Recently, Professor Eicke R. Weber of the University of California at Berkeley joined as a co-editor of the series. Professor Weber, a well-known expert in the field of semiconductor materials, will further contribute to continuing the series' tradition of publishing timely, highly relevant, and long-impacting volumes. Some of the recent volumes, such as Hydrogen in Semiconductors, Imperfections in III/V Materials, Epitaxial Microstructures, High-Speed Heterostructure Devices,Oxygen in Silicon, and others promise indeed that this traditi...

  6. Directional interlayer spin-valley transfer in two-dimensional heterostructures

    Science.gov (United States)

    Schaibley, John R.; Rivera, Pasqual; Yu, Hongyi; Seyler, Kyle L.; Yan, Jiaqiang; Mandrus, David G.; Taniguchi, Takashi; Watanabe, Kenji; Yao, Wang; Xu, Xiaodong

    2016-12-01

    Van der Waals heterostructures formed by two different monolayer semiconductors have emerged as a promising platform for new optoelectronic and spin/valleytronic applications. In addition to its atomically thin nature, a two-dimensional semiconductor heterostructure is distinct from its three-dimensional counterparts due to the unique coupled spin-valley physics of its constituent monolayers. Here, we report the direct observation that an optically generated spin-valley polarization in one monolayer can be transferred between layers of a two-dimensional MoSe2-WSe2 heterostructure. Using non-degenerate optical circular dichroism spectroscopy, we show that charge transfer between two monolayers conserves spin-valley polarization and is only weakly dependent on the twist angle between layers. Our work points to a new spin-valley pumping scheme in nanoscale devices, provides a fundamental understanding of spin-valley transfer across the two-dimensional interface, and shows the potential use of two-dimensional semiconductors as a spin-valley generator in two-dimensional spin/valleytronic devices for storing and processing information.

  7. Operation of a semiconductor microcavity under electric excitation

    CERN Document Server

    Karpov, Denis V

    2016-01-01

    We present a microscopic theory for the description of the bias-controlled operation of an exciton-polariton-based heterostructure, in particular, the polariton laser. Combining together the Poisson equations for the scalar electric potential and Fermi quasi-energies of electrons and holes in a semiconductor heterostructure, the Boltzmann equation for the incoherent excitonic reservoir and the Gross-Pitaevskii equation for the exciton-polariton mean field, we simulate the dynamics of the system minimising the number of free parameters and for the first time build a theoretical threshold characteristics: number of particles vs applied bias. This approach, which also accounts for the nonlinear (exciton-exciton) interaction, particle lifetime, and which can, in principle, account for any relaxation mechanisms for the carriers of charge inside the heterostructure or polariton loss, allows to completely describe modern experiments on polariton transport and model new devices.

  8. Escher-like quasiperiodic heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Barriuso, A G; Monzon, J J; Sanchez-Soto, L L [Departamento de Optica, Facultad de Fisica, Universidad Complutense, 28040 Madrid (Spain); Costa, A F [Departamento de Matematicas Fundamentales, Facultad de Ciencias, Universidad Nacional de Educacion a Distancia, Senda del Rey 9, 28040 Madrid (Spain)

    2009-05-15

    Quasiperiodic heterostructures present unique structural, electronic and vibrational properties, connected to the existence of incommensurate periods. We go beyond previous schemes, such as Fibonacci or Thue-Morse, based on substitutional sequences, by introducing construction rules generated by tessellations of the unit disc by regular polygons. We explore some of the properties exhibited by these systems. (fast track communication)

  9. GaN heterostructures for biosensing and radiation detection

    Energy Technology Data Exchange (ETDEWEB)

    Howgate, John D.

    2012-12-11

    In this thesis I show the results from our investigation of the interface between gallium nitride wide bandgap semiconductor heterostructures and (bio)molecular systems on their surfaces for biosensing, bioelectronics, and photoelectric applications, with a large emphasis on the processes arising from high energy ionizing irradiation, including heterostructure photoelectric gain mechanisms. Wide bandgap semiconductors, such as gallium nitride, have received increasing attention as potential components in advanced organic/inorganic hybrid systems. Working to further this topic, we determine a new semiconductor alignment required for low energy photo-induced charge transfer ionization of alkyl chains well below the energy normally required for molecular cleavage, show original results of the influence of binding methods on enzyme functionality in conjunction with a novel electrochemical and environmental control system and demonstrate new possibilities to significantly improve upon pH measurements through the use of high sensitivity devices. Furthermore, based on the extension of this work to support future studies of radiation effects on cell systems, we present a detailed characterization of new simultaneous chemical sensing and ionizing radiation dosimetry using single devices. We found that their pH sensitivity was retained during X-ray irradiation and that the fundamental characteristics can be used to separate the irradiation signal from the pH response without compromising operational stability. These data provide clear indications of the separate response mechanism tied to the presence of a two-dimensional electron gas channel. Here, we found new results exhibiting exceptionally high gains and independence of the well-known persistent photoconductivity for soft X-rays and high energy particles in the ultralow dose-rate regime. This material system provides the capability for high sensitivity and resolution real time monitoring, which is competitive with and

  10. Oxide semiconductors

    CERN Document Server

    Svensson, Bengt G; Jagadish, Chennupati

    2013-01-01

    Semiconductors and Semimetals has distinguished itself through the careful selection of well-known authors, editors, and contributors. Originally widely known as the ""Willardson and Beer"" Series, it has succeeded in publishing numerous landmark volumes and chapters. The series publishes timely, highly relevant volumes intended for long-term impact and reflecting the truly interdisciplinary nature of the field. The volumes in Semiconductors and Semimetals have been and will continue to be of great interest to physicists, chemists, materials scientists, and device engineers in academia, scient

  11. Semiconductor electrochemistry

    CERN Document Server

    Memming, Rüdiger

    2015-01-01

    Providing both an introduction and an up-to-date survey of the entire field, this text captivates the reader with its clear style and inspiring, yet solid presentation. The significantly expanded second edition of this milestone work is supplemented by a completely new chapter on the hot topic of nanoparticles and includes the latest insights into the deposition of dye layers on semiconductor electrodes. In his monograph, the acknowledged expert Professor Memming primarily addresses physical and electrochemists, but materials scientists, physicists, and engineers dealing with semiconductor technology and its applications will also benefit greatly from the contents.

  12. Semiconductor statistics

    CERN Document Server

    Blakemore, J S

    1962-01-01

    Semiconductor Statistics presents statistics aimed at complementing existing books on the relationships between carrier densities and transport effects. The book is divided into two parts. Part I provides introductory material on the electron theory of solids, and then discusses carrier statistics for semiconductors in thermal equilibrium. Of course a solid cannot be in true thermodynamic equilibrium if any electrical current is passed; but when currents are reasonably small the distribution function is but little perturbed, and the carrier distribution for such a """"quasi-equilibrium"""" co

  13. One-Dimensional (1-D) Nanoscale Heterostructures

    Institute of Scientific and Technical Information of China (English)

    Guozhen SHEN; Di CHEN; Yoshio BANDO; Dmitri GOLBERG

    2008-01-01

    One-dimensional (1-D) nanostructures have been attracted much attention as a result of their exceptional properties, which are different from bulk materials. Among 1-D nanostructures, 1-D heterostructures with modulated compositions and interfaces have recently become of particular interest with respect to potential applications in nanoscale building blocks of future optoelectronic devices and systems. Many kinds of methods have been developed for the synthesis of 1-D nanoscale heterostructures. This article reviews the most recent development, with an emphasize on our own recent efforts, on 1-D nanoscale heterostructures, especially those synthesized from the vapor deposition methods, in which all the reactive precursors are mixed together in the reaction chamber. Three types of 1-D nanoscale heterostructures, defined from their morphologies characteristics, are discussed in detail, which include 1-D co-axial core-shell heterostructures, 1-D segmented heterostructures and hierarchical heterostructures. This article begins with a brief survey of various methods that have been developed for synthesizing 1-D nanoscale heterostructures and then mainly focuses on the synthesis, structures and properties of the above three types of nanoscale heterostructures. Finally, this review concludes with personal views towards the topic of 1-D nanoscale heterostructures.

  14. Electric field modulation of the band structure in MoS2/WS2 van der waals heterostructure

    Science.gov (United States)

    Li, Wei; Wang, Tianxing; Dai, Xianqi; Wang, Xiaolong; Zhai, Caiyun; Ma, Yaqiang; Chang, Shanshan; Tang, Yanan

    2017-01-01

    Using density functional theory calculations, we investigate the bandstructure of MoS2/WS2 van der waals heterostructure by applying external electric field perpendicular to the layers. It is demonstrated that the MoS2/WS2 is a type-II heterostructure, and therefore the electrons and holes are spatially separated. The band gap of MoS2/WS2 heterostructure continuously decreases with increasing external electric field, eventually a transition from semiconductor to metal is observed. Applying external electric field along +z direction and -z directions has different effects on the band gap due to the intrinsic spontaneous polarization in MoS2/WS2 heterostructure. The calculated result indicates that the band inversion in MoS2/WS2 heterostructure can be induced by changing the strength of the external electric field. The external electric field can significantly tune the band offsets almost linearly and modify the band alignment between MoS2 and WS2. The present study would open a new avenue for application of such transition-metal dichalcogenides heterostructures in future nano- and optoelectronics.

  15. High-power 850-870-nm pulsed lasers based on heterostructures with narrow and wide waveguides

    Energy Technology Data Exchange (ETDEWEB)

    Ladugin, M A; Koval' , Yu P; Marmalyuk, Aleksandr A; Petrovskii, V A; Bagaev, T A; Andreev, A Yu; Padalitsa, A A; Simakov, V A [Open Joint-Stock Company ' M.F. Stel' makh Polyus Research and Development Institute' , Moscow (Russian Federation)

    2013-05-31

    The power and spectral characteristics of pulsed laser diode arrays operating in the spectral range of 850-870 nm and based on heterostructures of two different types (with narrow and wide waveguides) are studied. It is found that the power-current characteristics of the laser arrays of both types are linear within the pump current range of 10-50 A and that the steepness of these characteristics decreases at currents exceeding 80 A. The decrease in the slope efficiency is more noticeable for laser arrays based on heterostructures with wide waveguides. (semiconductor lasers. physics and technology)

  16. Analysis of Recombination in CdTe Heterostructures With Time-Resolved Two-Photon Excitation Microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kuciauskas, Darius; Wernsing, Keith; Jensen, Soren Alkaersig; Barnes, Teresa M.; Myers, Thomas H.; Bartels, Randy A.

    2016-11-01

    We used time-resolved photoluminescence micro-scopy to analyze charge carrier transport and recombination in CdTe double heterostructures fabricated by molecular beam epitaxy (MBE). This allowed us to determine the charge carrier mobility in this system, which was found to be 500-625 cm2/(V s). Charge carrier lifetimes in the 15-100 ns range are limited by the interface recombination, and the data indicate higher interface recombination velocity near extended defects. This study describes a new method to analyze the spatial distribution of the interface recombination velocity and the interface defects in semiconductor heterostructures.

  17. Semiconductor Nanowire Light Emitting Diodes Grown on Metal: A Direction towards Large Scale Fabrication of Nanowire Devices

    OpenAIRE

    Sarwar, A. T. M. Golam; Carnevale, Santino D.; Yang, Fan; Kent, Thomas F.; Jamison, John J.; McComb, David W.; Myers, Roberto C.

    2015-01-01

    Bottom up nanowires are attractive for realizing semiconductor devices with extreme heterostructures because strain relaxation through the nanowire sidewalls allows the combination of highly lattice mismatched materials without creating dislocations. The resulting nanowires are used to fabricate light emitting diodes (LEDs), lasers, solar cells and sensors. However, expensive single crystalline substrates are commonly used as substrates for nanowire heterostructures as well as for epitaxial d...

  18. Intraband Absorption In Gaas-(ga,al)as Variably Spaced Semiconductor Superlattices Under Crossed Electric And Magnetic Fields

    OpenAIRE

    Reyes-Gomez, E; Raigoza, N; Oliveira, LE

    2013-01-01

    A theoretical study of the intraband absorption properties of GaAs-Ga1-xAlxAs variably spaced semiconductor superlattices under crossed magnetic and electric fields is presented. Calculations are performed for the applied electric field along the growth-axis direction, whereas the magnetic field is considered parallel to the heterostructure layers. By defining a critical electric field so that the heterostructure energy levels are aligned in the absence of the applied magnetic fields, one fin...

  19. Compound Semiconductor Materials, Devices and Circuits

    Science.gov (United States)

    1988-06-01

    Semiconductors", L.A. Coldren, J.G. Mendoza - Alvarez and R.H. Yan, Aopl. Phys. Lett., 51, 792-794 (1987). JSEP PUBLICATIONS AND PRESENTATIONS 1. "Room...self-consistent Monte Carlo transport formulation and its applicat... to small graded heterostructure devices; (e) optical modulation based on the...L.F. Eastman 1 0 TASK 3 FUNDAMENTAL PHENOMENON IN ULTRASHORT DEVICES E.D. Wolf, L.F. Eastman and P.J. Tasker 1 9 TASK 4 ENSEMBLE MONTE CARLO

  20. Locating a buried earth penetrator

    Energy Technology Data Exchange (ETDEWEB)

    Caffey, T.W.H.

    1977-11-01

    The purpose of this work was to assist the recovery of a buried earth penetrator by locating the vertical projection of the penetator upon the surface within a horizontal radius error of one meter. The penetrator will carry a small coil which is driven by an alternating current to form a magnetic dipole. Five measurements of the magnetic field vector upon the surface of the earth are shown to be sufficient for determining not only the xyz-coordinates of the dipole, but also the orientation of the dipole axis. The theory, computation process, and field tests are comprehensively described. Results of 26 field tests with the dipole at 9 different combinations of location and orientation are given. Average radial and vertical location errors are 0.27 m and -0.05 m, respectively, while the mean errors in the tilt and orientation angles of the dipole axis are 3 degrees and 8 degrees, respectively. The results are applied to the design of a locating system for a Pershing II penetrator which contains a recessed, rear-mounted coil.

  1. Building Structural Complexity in Semiconductor Nanocrystals through Chemical Transformations

    OpenAIRE

    Sadtler, Bryce F

    2010-01-01

    Methods are presented for synthesizing nanocrystal heterostructures comprised of two semiconductor materials epitaxially attached within individual nanostructures. The chemical transformation of cation exchange, where the cations within the lattice of an ionic nanocrystal are replaced with a different metal ion species, is used to alter the chemical composition at specific regions of a nanocrystal. Partial cation exchange was performed in cadmium sulfide (CdS) nanorods of well-defined size an...

  2. Semiconductor Detectors; Detectores de Semiconductores

    Energy Technology Data Exchange (ETDEWEB)

    Cortina, E.

    2007-07-01

    Particle detectors based on semiconductor materials are among the few devices used for particle detection that are available to the public at large. In fact we are surrounded by them in our daily lives: they are used in photoelectric cells for opening doors, in digital photographic and video camera, and in bar code readers at supermarket cash registers. (Author)

  3. Effects of Coupling Lens on Optical Refrigeration of Semiconductors

    Institute of Scientific and Technical Information of China (English)

    DING Kai; ZENG Yi-Ping

    2008-01-01

    Optical refrigeration of semiconductors is encountering efficiency difficulties caused by nonradiative recombination and luminescence trapping.A commonly used approach for enhancing luminescence efficiency of a semiconductor device is coupling a lens with the device. We quantitatively study the effects of a coupling lens on optical refrigeration based on rate equations and photon recycling,and calculated cooling efficiencies of different coupling mechanisms and of different lens materials.A GaAs/GaInP heterostructure coupled with a homo-epitaxial GaInP hemispherical lens is recommended.

  4. Anodic bonded 2D semiconductors: from synthesis to device fabrication.

    Science.gov (United States)

    Chen, Zhesheng; Gacem, Karim; Boukhicha, Mohamed; Biscaras, Johan; Shukla, Abhay

    2013-10-18

    Two-dimensional semiconductors are increasingly relevant for emergent applications and devices, notably for hybrid heterostructures with graphene. We fabricate few-layer, large-area (a few tens of microns across) samples of the III-VI semiconductors GaS, GaSe and InSe using the anodic bonding method and characterize them by simultaneous use of optical microscopy, atomic force microscopy and Raman spectroscopy. Two-terminal devices with a gate are constructed to show the feasibility of applications based on these.

  5. Anodic bonded 2D semiconductors: from synthesis to device fabrication

    Science.gov (United States)

    Chen, Zhesheng; Gacem, Karim; Boukhicha, Mohamed; Biscaras, Johan; Shukla, Abhay

    2013-10-01

    Two-dimensional semiconductors are increasingly relevant for emergent applications and devices, notably for hybrid heterostructures with graphene. We fabricate few-layer, large-area (a few tens of microns across) samples of the III-VI semiconductors GaS, GaSe and InSe using the anodic bonding method and characterize them by simultaneous use of optical microscopy, atomic force microscopy and Raman spectroscopy. Two-terminal devices with a gate are constructed to show the feasibility of applications based on these.

  6. CO2-Induced Defect Engineering: A New Protocol by Doping Vacancies in 2D Heterostructures for Enhanced Visible-Light Photocatalysis

    Science.gov (United States)

    Ren, Yumei; Wang, Chongze; Qi, Yuhang; Chen, Zhimin; Jia, Yu; Xu, Qun

    2017-10-01

    Defect engineering has emerged as an efficient and promising strategy in the field of semiconductor materials, while assembling controllable vacancy defects and two-dimensional (2D) heterostructures into together is a great challenge. In this work, 2D heterostructures of WS2/WO3·H2O doped with oxide vacancies have been synthesized successfully with assistance of supercritical CO2. And the fascinating heterostructures have been evidenced by their significant photocatalysis performance for water splitting. Theoretical calculations demonstrate that the vacancies in the obtained 2D heterostructures can narrow the effective band gap and improve the carrier separation efficiency as well. This wok will provide a positive strategy for fabrication of advanced photocatalyst and a new perspective in understanding the synergistic effect of structural and electronic regulations.

  7. Heterostructure Intervalley Transferred Electron Effects

    Institute of Scientific and Technical Information of China (English)

    XUE Fang-Shi

    2001-01-01

    A Gunn active layer is used as an X electron probe to detect the X tunnelling current in the GaAs-AlAs heterostructure, from which a new heterostructure intervalley transferred electron (HITE) device is obtained. In the 8 mm band, the highest pulse output power of these diodes is 2.65 W and the highest conversion efficiency is 18%. The dc and rf performance of the HITE devices was simulated by the band mixing resonant tunnelling theory and Monte Carlo transport simulation. The HITE effect has transformed the transit-time dipole-layer mode in the Gunn diode into a relaxation oscillation mode in the HITE device. From the comparison of simulated results to the measured data, the HITE effect is demonstrated straightforwardly

  8. Monolithic 1310nm buried heterostructure VCSEL using InGaAsP/InP DBR reflectors

    Science.gov (United States)

    Francis, Daniel A.; Young, David B.; Walker, Jeff; Verma, Ashish; Gold, Dave; Decker, Chris

    2005-10-01

    We report on the first monolithic 1310 nm Vertical Cavity Surface Emitting Lasers (VCSELs) with top and bottom InGaAsP/InP distributed Bragg reflectors (DBRs). The lasers show single mode powers over 1.0 mW at room temperature and single mode powers up to 0.5 mW at 85 °C. The lasers, designed to be single mode, have side mode suppression ratios exceeding 45 dB over all temperatures and all powers.

  9. Synchrotron radiation studies of inorganic-organic semiconductor interfaces

    CERN Document Server

    Evans, D A; Vearey-Roberts, A R; Bushell, A; Cabailh, G; O'Brien, S; Wells, J W; McGovern, I T; Dhanak, V R; Kampen, T U; Zahn, D R T; Batchelor, D

    2003-01-01

    Organic semiconductors (polymers and small molecules) are widely used in electronic and optoelectronic technologies. Many devices are based on multilayer structures where interfaces play a central role in device performance and where inorganic semiconductor models are inadequate. Synchrotron radiation techniques such as photoelectron spectroscopy (PES), near-edge X-ray absorption fine structure (NEXAFS) and X-ray standing wave spectroscopy (XSW) provide a powerful means of probing the structural, electronic and chemical properties of these interfaces. The surface-specificity of these techniques allows key properties to be monitored as the heterostructure is fabricated. This methodology has been directed at the growth of hybrid organic-inorganic semiconductor interfaces involving copper phthalocyanine as the model organic material and InSb and GaAs as the model inorganic semiconductor substrates. Core level PES has revealed that these interfaces are abrupt and chemically inert due to the weak bonding between t...

  10. Progress in Group Ⅲ nitride semiconductor electronic devices

    Institute of Scientific and Technical Information of China (English)

    Hao Yue; Zhang Jinfeng; Shen Bo; Liu Xinyu

    2012-01-01

    Recently there has been a rapid domestic development in group Ⅲ nitride semiconductor electronic materials and devices.This paper reviews the important progress in GaN-based wide bandgap microelectronic materials and devices in the Key Program of the National Natural Science Foundation of China,which focuses on the research of the fundamental physical mechanisms of group Ⅲ nitride semiconductor electronic materials and devices with the aim to enhance the crystal quality and electric performance of GaN-based electronic materials,develop new GaN heterostructures,and eventually achieve high performance GaN microwave power devices.Some remarkable progresses achieved in the program will be introduced,including those in GaN high electron mobility transistors (HEMTs) and metal-oxide-semiconductor high electron mobility transistors (MOSHEMTs) with novel high-k gate insulators,and material growth,defect analysis and material properties of InAlN/GaN heterostructures and HEMT fabrication,and quantum transport and spintronic properties ofGaN-based heterostructures,and highelectric-field electron transport properties of GaN material and GaN Gunn devices used in terahertz sources.

  11. Graphene-based lateral heterostructure transistors exhibit better intrinsic performance than graphene-based vertical transistors as post-CMOS devices

    Science.gov (United States)

    Logoteta, Demetrio; Fiori, Gianluca; Iannaccone, Giuseppe

    2014-10-01

    We investigate the intrinsic performance of vertical and lateral graphene-based heterostructure field-effect transistors, currently considered the most promising options to exploit graphene properties in post-CMOS electronics. We focus on three recently proposed graphene-based transistors, that in experiments have exhibited large current modulation. Our analysis is based on device simulations including the self-consistent solution of the electrostatic and transport equations within the Non-Equilibrium Green's Function formalism. We show that the lateral heterostructure transistor has the potential to outperform CMOS technology and to meet the requirements of the International Technology Roadmap for Semiconductors for the next generation of semiconductor integrated circuits. On the other hand, we find that vertical heterostructure transistors miss these performance targets by several orders of magnitude, both in terms of switching frequency and delay time, due to large intrinsic capacitances, and unavoidable current/capacitance tradeoffs.

  12. American burying beetle site records : Valentine NWR

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This document is specific site records of American burying beetle on Valentine Nationl Wildlife Refuge to date. It includes a map of site location. A discussion...

  13. Epitaxy of Semiconductors Introduction to Physical Principles

    CERN Document Server

    Pohl, Udo W

    2013-01-01

    Introduction to Epitaxy provides the essential information for a comprehensive upper-level graduate course treating the crystalline growth of semiconductor heterostructures. Heteroepitaxy represents the basis of advanced electronic and optoelectronic devices today and is considered one of the top fields in materials research. The book covers the structural and electronic properties of strained epitaxial layers, the thermodynamics and kinetics of layer growth, and the description of the major growth techniques metalorganic vapor phase epitaxy, molecular beam epitaxy and liquid phase epitaxy. Cubic semiconductors, strain relaxation by misfit dislocations, strain and confinement effects on electronic states, surface structures and processes during nucleation and growth are treated in detail. The Introduction to Epitaxy requires only little knowledge on solid-state physics. Students of natural sciences, materials science and electrical engineering as well as their lecturers benefit from elementary introductions t...

  14. Semiconductor Optics

    CERN Document Server

    Klingshirn, Claus F

    2012-01-01

    This updated and enlarged new edition of Semiconductor Optics provides an introduction to and an overview of semiconductor optics from the IR through the visible to the UV, including linear and nonlinear optical properties, dynamics, magneto and electrooptics, high-excitation effects and laser processes, some applications, experimental techniques and group theory. The mathematics is kept as elementary as possible, sufficient for an intuitive understanding of the experimental results and techniques treated. The subjects covered extend from physics to materials science and optoelectronics. Significantly updated chapters add coverage of current topics such as electron hole plasma, Bose condensation of excitons and meta materials. Over 120 problems, chapter introductions and a detailed index make it the key textbook for graduate students in physics. The mathematics is kept as elementary as possible, sufficient for an intuitive understanding of the experimental results and techniques treated. The subjects covered ...

  15. Semiconductor sensors

    Energy Technology Data Exchange (ETDEWEB)

    Hartmann, Frank, E-mail: frank.hartmann@cern.c [Institut fuer Experimentelle Kernphysik, KIT, Wolfgang-Gaede-Str. 1, Karlsruhe 76131 (Germany)

    2011-02-01

    Semiconductor sensors have been around since the 1950s and today, every high energy physics experiment has one in its repertoire. In Lepton as well as Hadron colliders, silicon vertex and tracking detectors led to the most amazing physics and will continue doing so in the future. This contribution tries to depict the history of these devices exemplarily without being able to honor all important developments and installations. The current understanding of radiation damage mechanisms and recent R and D topics demonstrating the future challenges and possible technical solutions for the SLHC detectors are presented. Consequently semiconductor sensor candidates for an LHC upgrade and a future linear collider are also briefly introduced. The work presented here is a collage of the work of many individual silicon experts spread over several collaborations across the world.

  16. Two-dimensional hexagonal semiconductors beyond graphene

    Science.gov (United States)

    Nguyen, Bich Ha; Hieu Nguyen, Van

    2016-12-01

    The rapid and successful development of the research on graphene and graphene-based nanostructures has been substantially enlarged to include many other two-dimensional hexagonal semiconductors (THS): phosphorene, silicene, germanene, hexagonal boron nitride (h-BN) and transition metal dichalcogenides (TMDCs) such as MoS2, MoSe2, WS2, WSe2 as well as the van der Waals heterostructures of various THSs (including graphene). The present article is a review of recent works on THSs beyond graphene and van der Waals heterostructures composed of different pairs of all THSs. One among the priorities of new THSs compared to graphene is the presence of a non-vanishing energy bandgap which opened up the ability to fabricate a large number of electronic, optoelectronic and photonic devices on the basis of these new materials and their van der Waals heterostructures. Moreover, a significant progress in the research on TMDCs was the discovery of valley degree of freedom. The results of research on valley degree of freedom and the development of a new technology based on valley degree of freedom-valleytronics are also presented. Thus the scientific contents of the basic research and practical applications os THSs are very rich and extremely promising.

  17. Ultrafast dynamics of confined and localised excitons and biexcitons in low-dimensional semiconductors

    DEFF Research Database (Denmark)

    Hvam, Jørn Märcher; Langbein, Wolfgang; Borri, Paola

    1999-01-01

    Coherent optical spectroscopy in the form of nonlinear transient four-wave mixing (TFWM) and linear resonant Rayleigh scattering (RRS) has been applied to investigate the exciton dynamics of low-dimensional semiconductor heterostructures. The dephasing times of excitons are determined from...

  18. Computer-automated tuning of semiconductor double quantum dots into the single-electron regime

    NARCIS (Netherlands)

    Baart, T.A.; Eendebak, P.T.; Reichl, C.; Wegscheider, W.; Vandersypen, L.M.K.

    2016-01-01

    We report the computer-automated tuning of gate-defined semiconductor double quantum dots in GaAs heterostructures. We benchmark the algorithm by creating three double quantum dots inside a linear array of four quantum dots. The algorithm sets the correct gate voltages for all the gates to tune the

  19. Development of a Novel Optical Spectroscopy Tool for Studies of Coulomb Correlations in Semiconductors

    Science.gov (United States)

    2012-06-18

    statistics in semiconductor heterostructures such as QWs and quantum wires as well as other systems such as molecular aggregates and photosynthesis ...contributions to different resonances in the linear absorption spectrum. These states mostly confined to regions where QW thickness supports the respective...fact that the linear absorption spectrum demonstrates split resonances when the correlation radius of the spatial inhomogeneities exceeds the special

  20. Foreign-catalyst-free growth of InAs/InSb axial heterostructure nanowires on Si (111) by molecular-beam epitaxy.

    Science.gov (United States)

    So, Hyok; Pan, Dong; Li, Lixia; Zhao, Jianhua

    2017-03-01

    Epitaxial high-quality InAs/InSb axial heterostructure nanowires are of great interest due to their distinct advantages in fundamental research as well as applications in semiconductor electronic and quantum devices. Currently, nearly all the growth of InAs/InSb axial heterostructure nanowires is assisted with foreign catalysts such as Au, and work on foreign-catalyst-free growth of InAs/InSb axial heterostructure nanowires is lacking. Here we report on the growth of InAs/InSb axial heterostructure nanowires on Si (111) substrates by molecular-beam epitaxy without using any foreign catalysts. The Sb/In beam equivalent pressure (BEP) ratio is found to have important influence on the heterostructure nanowire morphology, and InSb nanowires can be epitaxially grown on InAs nanowire stems with a hexagonal prism and nanosheet-like shapes when the Sb/In BEP ratio varies from 10 to 20. Transmission electron microscopy studies reveal that the InAs nanowire stems have a mixture of zincblende (ZB) and wurtzite (WZ) crystal structures, while InSb nanowire parts have a pure ZB crystal structure free of stacking faults. Composition analysis of axial heterostructure nanowires provides clear evidence that the InSb nanowires are epitaxially grown on InAs nanowires in an In self-assisted vapor-liquid-solid manner. This study paves a new route for growing narrow-gap semiconductor heterostructures with strong spin-orbit interaction for the study of topological states, and the growth manner presented here is expected to be used to grow other In-based axial heterostructure nanowires.

  1. Anomalous Hall and spin Hall conductivities in three-dimensional ferromagnetic topological insulator/normal insulator heterostructures

    Science.gov (United States)

    Men'shov, Vladimir N.; Tugushev, Victor V.; Chulkov, Evgueni V.

    2016-05-01

    In this letter we theoretically demonstrate how an interface perturbation and size effect can be used to manipulate the transport properties of semiconductor heterostructures composed of a thin film of a three-dimensional topological insulator (TI) doped with magnetic impurities and sandwiched between topologically normal insulators. In the framework of a continual scheme, we argue that electron states of the TI film are strongly dominated by its thickness and magnetization as well as by an interface potential whose variation can lead to the modification of topological properties of the heterostructure. This opens diverse possibilities to efficiently tune intrinsic Hall conductivity in the system. We calculate a phase diagram of the heterostructure, which demonstrates a series of quantum transitions between distinct regimes of conductivity. We derive the anomalous Hall conductivity and the spin Hall conductivity dependences on the chemical potential. Applicability conditions of the used approach are also discussed.

  2. Critical thickness for the formation of misfit dislocations originating from prismatic slip in semipolar and nonpolar III-nitride heterostructures

    Science.gov (United States)

    Smirnov, A. M.; Young, E. C.; Bougrov, V. E.; Speck, J. S.; Romanov, A. E.

    2016-01-01

    We calculate the critical thickness for misfit dislocation (MD) formation in lattice mismatched semipolar and nonpolar III-nitride wurtzite semiconductor layers for the case of MDs originated from prismatic slip (PSMDs). It has been shown that there is a switch of stress relaxation modes from generation of basal slip originated MDs to PSMDs after the angle between c-axis in wurtzite crystal structure and the direction of semipolar growth reaches a particular value, e.g., ˜70° for Al0.13Ga0.87N/GaN ( h 0 h ¯ 1 ) semipolar heterostructures. This means that for some semipolar growth orientations of III-nitride heterostructures biaxial relaxation of misfit stress can be realized. The results of modeling are compared to experimental data on the onset of plastic relaxation in AlxGa1-xN/GaN heterostructures.

  3. Critical thickness for the formation of misfit dislocations originating from prismatic slip in semipolar and nonpolar III-nitride heterostructures

    KAUST Repository

    Smirnov, A. M.

    2016-01-20

    We calculate the critical thickness for misfit dislocation (MD) formation in lattice mismatched semipolar and nonpolar III-nitride wurtzite semiconductor layers for the case of MDs originated from prismatic slip (PSMDs). It has been shown that there is a switch of stress relaxation modes from generation of basal slip originated MDs to PSMDs after the angle between c-axis in wurtzite crystal structure and the direction of semipolar growth reaches a particular value, e.g., ∼70° for Al0.13Ga0.87N/GaN (h0h̄ 1) semipolar heterostructures. This means that for some semipolar growth orientations of III-nitride heterostructures biaxial relaxation of misfit stress can be realized. The results of modeling are compared to experimental data on the onset of plastic relaxation in AlxGa1−xN/GaN heterostructures.

  4. Partial hybridisation of electron-hole states in an InAs/GaSb double quantum well heterostructure

    Science.gov (United States)

    Knox, C. S.; Morrison, C.; Herling, F.; Ritchie, D. A.; Newell, O.; Myronov, M.; Linfield, E. H.; Marrows, C. H.

    2017-10-01

    InAs/GaSb coupled quantum well heterostructures are important semiconductor systems with applications ranging from spintronics to photonics. Most recently, InAs/GaSb heterostructures have been identified as candidate two-dimensional topological insulators, predicted to exhibit helical edge conduction via fully spin-polarised carriers. We study an InAs/GaSb double quantum well heterostructure with an AlSb barrier to decouple partially the 2D electrons and holes, and find conduction consistent with a 2D hole gas, with an effective mass of 0.235 ± 0.005 m 0, existing simultaneously with hybridised carriers with an effective mass of 0.070 ± 0.005 m 0, where m 0 is the bare electron mass.

  5. Critical thickness for the formation of misfit dislocations originating from prismatic slip in semipolar and nonpolar III-nitride heterostructures

    Directory of Open Access Journals (Sweden)

    A. M. Smirnov

    2016-01-01

    Full Text Available We calculate the critical thickness for misfit dislocation (MD formation in lattice mismatched semipolar and nonpolar III-nitride wurtzite semiconductor layers for the case of MDs originated from prismatic slip (PSMDs. It has been shown that there is a switch of stress relaxation modes from generation of basal slip originated MDs to PSMDs after the angle between c-axis in wurtzite crystal structure and the direction of semipolar growth reaches a particular value, e.g., ∼70° for Al0.13Ga0.87N/GaN ( h 0 h ̄ 1 semipolar heterostructures. This means that for some semipolar growth orientations of III-nitride heterostructures biaxial relaxation of misfit stress can be realized. The results of modeling are compared to experimental data on the onset of plastic relaxation in AlxGa1−xN/GaN heterostructures.

  6. Semiconductor nanostructures for artificial photosynthesis

    Science.gov (United States)

    Yang, Peidong

    2012-02-01

    Nanowires, with their unique capability to bridge the nanoscopic and macroscopic worlds, have already been demonstrated as important materials for different energy conversion. One emerging and exciting direction is their application for solar to fuel conversion. The generation of fuels by the direct conversion of solar energy in a fully integrated system is an attractive goal, but no such system has been demonstrated that shows the required efficiency, is sufficiently durable, or can be manufactured at reasonable cost. One of the most critical issues in solar water splitting is the development of a suitable photoanode with high efficiency and long-term durability in an aqueous environment. Semiconductor nanowires represent an important class of nanostructure building block for direct solar-to-fuel application because of their high surface area, tunable bandgap and efficient charge transport and collection. Nanowires can be readily designed and synthesized to deterministically incorporate heterojunctions with improved light absorption, charge separation and vectorial transport. Meanwhile, it is also possible to selectively decorate different oxidation or reduction catalysts onto specific segments of the nanowires to mimic the compartmentalized reactions in natural photosynthesis. In this talk, I will highlight several recent examples in this lab using semiconductor nanowires and their heterostructures for the purpose of direct solar water splitting.

  7. Large area molybdenum disulphide- epitaxial graphene vertical Van der Waals heterostructures

    Science.gov (United States)

    Pierucci, Debora; Henck, Hugo; Naylor, Carl H.; Sediri, Haikel; Lhuillier, Emmanuel; Balan, Adrian; Rault, Julien E.; Dappe, Yannick J.; Bertran, François; Fèvre, Patrick Le; Johnson, A. T. Charlie; Ouerghi, Abdelkarim

    2016-06-01

    Two-dimensional layered transition metal dichalcogenides (TMDCs) show great potential for optoelectronic devices due to their electronic and optical properties. A metal-semiconductor interface, as epitaxial graphene - molybdenum disulfide (MoS2), is of great interest from the standpoint of fundamental science, as it constitutes an outstanding platform to investigate the interlayer interaction in van der Waals heterostructures. Here, we study large area MoS2-graphene-heterostructures formed by direct transfer of chemical-vapor deposited MoS2 layer onto epitaxial graphene/SiC. We show that via a direct transfer, which minimizes interface contamination, we can obtain high quality and homogeneous van der Waals heterostructures. Angle-resolved photoemission spectroscopy (ARPES) measurements combined with Density Functional Theory (DFT) calculations show that the transition from indirect to direct bandgap in monolayer MoS2 is maintained in these heterostructures due to the weak van der Waals interaction with epitaxial graphene. A downshift of the Raman 2D band of the graphene, an up shift of the A1g peak of MoS2 and a significant photoluminescence quenching are observed for both monolayer and bilayer MoS2 as a result of charge transfer from MoS2 to epitaxial graphene under illumination. Our work provides a possible route to modify the thin film TDMCs photoluminescence properties via substrate engineering for future device design.

  8. Quantum mechanical solver for confined heterostructure tunnel field-effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Verreck, Devin, E-mail: devin.verreck@imec.be; Groeseneken, Guido [imec, Kapeldreef 75, 3001 Leuven (Belgium); Department of Electrical Engineering, KU Leuven, 3001 Leuven (Belgium); Van de Put, Maarten; Sorée, Bart; Magnus, Wim [imec, Kapeldreef 75, 3001 Leuven (Belgium); Departement of Physics, Universiteit Antwerpen, 2020 Antwerpen (Belgium); Verhulst, Anne S.; Collaert, Nadine; Thean, Aaron [imec, Kapeldreef 75, 3001 Leuven (Belgium); Vandenberghe, William G. [Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080 (United States)

    2014-02-07

    Heterostructure tunnel field-effect transistors (HTFET) are promising candidates for low-power applications in future technology nodes, as they are predicted to offer high on-currents, combined with a sub-60 mV/dec subthreshold swing. However, the effects of important quantum mechanical phenomena like size confinement at the heterojunction are not well understood, due to the theoretical and computational difficulties in modeling realistic heterostructures. We therefore present a ballistic quantum transport formalism, combining a novel envelope function approach for semiconductor heterostructures with the multiband quantum transmitting boundary method, which we extend to 2D potentials. We demonstrate an implementation of a 2-band version of the formalism and apply it to study confinement in realistic heterostructure diodes and p-n-i-n HTFETs. For the diodes, both transmission probabilities and current densities are found to decrease with stronger confinement. For the p-n-i-n HTFETs, the improved gate control is found to counteract the deterioration due to confinement.

  9. Two-Dimensional Electron Gas at SrTiO3-Based Oxide Heterostructures via Atomic Layer Deposition

    Directory of Open Access Journals (Sweden)

    Sang Woon Lee

    2016-01-01

    Full Text Available Two-dimensional electron gas (2DEG at an oxide interface has been attracting considerable attention for physics research and nanoelectronic applications. Early studies reported the formation of 2DEG at semiconductor interfaces (e.g., AlGaAs/GaAs heterostructures with interesting electrical properties such as high electron mobility. Besides 2DEG formation at semiconductor junctions, 2DEG was realized at the interface of an oxide heterostructure such as the LaAlO3/SrTiO3 (LAO/STO heterojunction. The origin of 2DEG was attributed to the well-known “polar catastrophe” mechanism in oxide heterostructures, which consist of an epitaxial LAO layer on a single crystalline STO substrate among proposed mechanisms. Recently, it was reported that the creation of 2DEG was achieved using the atomic layer deposition (ALD technique, which opens new functionality of ALD in emerging nanoelectronics. This review is focused on the origin of 2DEG at oxide heterostructures using the ALD process. In particular, it addresses the origin of 2DEG at oxide interfaces based on an alternative mechanism (i.e., oxygen vacancies.

  10. Metal-cluster-decorated TiO2 nanotube arrays: a composite heterostructure toward versatile photocatalytic and photoelectrochemical applications.

    Science.gov (United States)

    Xiao, Fang-Xing; Hung, Sung-Fu; Miao, Jianwei; Wang, Hsin-Yi; Yang, Hongbin; Liu, Bin

    2015-02-04

    Recent years have witnessed increasing interest in the solution-phase synthesis of atomically precise thiolate-protected gold clusters (Aux ); nonetheless, research on the photocatalytic properties of Aux -semiconductor nanocomposites is still in its infancy. In this work, recently developed glutathione-capped gold clusters and highly ordered nanoporous layer-covered TiO2 nanotube arrays (NP-TNTAs) are employed as nanobuilding blocks for the construction of a well-defined Aux /NP-TNTA heterostructure via a facile electrostatic self-assembly strategy. Versatile photocatalytic performances of the Aux /NP-TNTA heterostructure which acts as a model catalyst, including photocatalytic oxidation of organic pollutant, photocatalytic reduction of aromatic nitro compounds and photoelectrochemical (PEC) water splitting under simulated solar light irradiation, are systematically exploited. It is found that synergistic interaction stemming from monodisperse coverage of Aux clusters on NP-TNTAs in combination with hierarchical nanostructure of NP-TNTAs reinforce light absorption of Aux /NP-TNTA heterostructure especially within visible region, hence contributing to the significantly enhanced photocatalytic and PEC water splitting performances. Moreover, photocatalytic and PEC mechanisms over Aux /NP-TNTA heterostructure are elucidated and corresponding reaction models were presented. It is anticipated that this work could boost new insight for photocatalytic properties of metal-cluster-sensitized semiconductor nanocomposites. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Tuning Coupling Behavior of Stacked Heterostructures Based on MoS2, WS2, and WSe2

    Science.gov (United States)

    Wang, Fang; Wang, Junyong; Guo, Shuang; Zhang, Jinzhong; Hu, Zhigao; Chu, Junhao

    2017-03-01

    The interlayer interaction of vertically stacked heterojunctions is very sensitive to the interlayer spacing, which will affect the coupling between the monolayers and allow band structure modulation. Here, with the aid of density functional theory (DFT) calculations, an interesting phenomenon is found that MoS2-WS2, MoS2-WSe2, and WS2-WSe2 heterostructures turn into direct-gap semiconductors from indirect-gap semiconductors with increasing the interlayer space. Moreover, the electronic structure changing process with interlayer spacing of MoS2-WS2, MoS2-WSe2, and WS2-WSe2 is different from each other. With the help of variable-temperature spectral experiment, different electronic transition properties of MoS2-WS2, MoS2-WSe2, and WS2-WSe2 have been demonstrated. The transition transformation from indirect to direct can be only observed in the MoS2-WS2 heterostructure, as the valence band maximum (VBM) at the Γ point in the MoS2-WSe2 and WS2-WSe2 heterostructure is less sensitive to the interlayer spacing than those from the MoS2-WS2 heterostructure. The present work highlights the significance of the temperature tuning in interlayer coupling and advance the research of MoS2-WS2, MoS2-WSe2, and WS2-WSe2 based device applications.

  12. Revealing the semiconductor–catalyst interface in buried platinum black silicon photocathodes

    Energy Technology Data Exchange (ETDEWEB)

    Aguiar, Jeffery A.; Anderson, Nicholas C.; Neale, Nathan R.

    2016-01-01

    Nanoporous 'black' silicon semiconductors interfaced with buried platinum nanoparticle catalysts have exhibited stable activity for photoelectrochemical hydrogen evolution even after months of exposure to ambient conditions. The mechanism behind this stability has not been explained in detail, but is thought to involve a Pt/Si interface free from SiOx layer that would adversely affect interfacial charge transfer kinetics. In this paper, we resolve the chemical composition and structure of buried Pt/Si interfaces in black silicon photocathodes from a micron to sub-nanometer level using aberration corrected analytical scanning transmission electron microscopy. Through a controlled electrodeposition of copper on samples aged for one month in ambient conditions, we demonstrate that the main active catalytic sites are the buried Pt nanoparticles located below the 400-800 nm thick nanoporous SiOx layer. Though hydrogen production performance degrades over 100 h under photoelectrochemical operating conditions, this burying strategy preserves an atomically clean catalyst/Si interface free of oxide or other phases under air exposure and provides an example of a potential method for stabilizing silicon photoelectrodes from oxidative degradation in photoelectrochemical applications.

  13. Semiconductor laser

    Energy Technology Data Exchange (ETDEWEB)

    Ito, K.; Shyuue, M.

    1982-09-25

    A distributed feedback semiconductor laser is proposed which generates several beams with equal wavelengths in different directions. For this purpose, 1 millimeter grooves are cut into the surface of an n-type conductance GaAs plate in three different directions; these grooves form a diffraction grating. The center of this plate has no grooves and is bombarded by an He/Ne laser beam. The diffraction gratings provide resonance properties and generate laser beams with wavelengths of 8850, 9000 and 9200 angstroms.

  14. Silicon Germanium Strained Layers and Heterostructures

    Science.gov (United States)

    Willander, M.; Nur, O.; Jain, S. C.

    2004-01-01

    The integration of strained-Si1 xGex into Si technology has enhanced the performance and extended the functionality of Si based circuits. The improvement of device performance is observed in both AC as well as DC characteristics of these devices. The category of such devices includes field effect as well as bipolar families. Speed performance in some based circuits has reached limits previously dominated by III-V heterostructures based devices. In addition, for some optoelectronics applications including photodetectors it is now possible to easily integrate strained-Si1 xGex based optical devices into standard Silicon technology. The impact of integrating strained and relaxed Si1 xGex alloys into Si technology is important. It has lead to stimulate Si research as well as offers easy options for performances that requires very complicated and costly process if pure Si has to be used. In this paper we start by discussing the strain and stability of Si1 xGex alloys. The origin and the process responsible for transient enhanced diffusion (TED) in highly doped Si containing layers will be mentioned. Due to the importance of TED for thin highly doped Boron strained-Si1 xGex layers and its degrading consequences, possible suppression design methods will be presented. Quantum well pchannel MOSFETs (QW-PMOSFETs) based on thin buried QW are solution to the low speed and weak current derivability. Different aspects of designing these devices for a better performance are briefly reviewed. Other FETs based on tensile strained Si on relaxed Si1 xGex for n-channel and modulation doped field effect transistors (MODFETs) showed excellent performance. Record AC performance well above 200GHz for fmax is already observed and this record is expected to increase in the coming years. Heterojunction bipolar transistors (HPTs) with thin strained-Si1 xGex highly doped base have lead to optimize the performance of the bipolar technology for many applications easily. The strategies of design

  15. Spin Dynamics of Electrons Confined in Silicon Heterostructures

    Science.gov (United States)

    Jock, Ryan Michael

    The spin states of electrons confined in silicon heterostructures have shown promise as qubits for quantum information processing. Recently, a host of single and few electron silicon quantum dot device architectures have arisen as implementations for quantum computation. These devices often combine regions of low density two-dimensional (2D) electrons, localized electrons, and interfaces depleted of electrons. Electron spin resonance (ESR) is a unique tool for probing the spin dynamics of both mobile and localized electrons at silicon heterointerfaces and investigating the effects limiting the ability to control electrons and their spin states in these structures. We use a continuous wave ESR method to examine localized 2D electron band-tail states at Si/SiO 2 interfaces in large area metal-oxide-semiconductor transistors. We compare two devices, fabricated in different laboratories, which display similar low temperature (4.2 K) peak mobilities. We find that one of the devices displays a smaller band-tail density of confined states and a shallower characteristic confinement. Thus, ESR reveals a difference in device quality, which is not apparent from mobility measurements, and is a valuable tool for evaluating the interface quality in Si/SiO2 heterostructures. Additionally, we use pulsed ESR techniques to study the spin dynamics of electrons confined in Si/SiGe heterostructures. For mobile 2D electrons, the density-dependent Dyakonov-Perel mechanism dominates spin relaxation. At low 2D densities, stronger electron-electron interactions cause an increase in the electron effective mass, leading to an increase in spin susceptibility. For very low densities, natural disorder localizes electrons at the silicon heterointerface. Naturally localized electrons in these structures display short spin relaxation times (ensembles of around 108 quantum dots in Si/SiGe heterostructures. By tailoring the device structure, a long electron spin relaxation time (T1 = 1.4 ms) is

  16. Synthesis of freestanding single-crystal perovskite films and heterostructures by etching of sacrificial water-soluble layers.

    Science.gov (United States)

    Lu, Di; Baek, David J; Hong, Seung Sae; Kourkoutis, Lena F; Hikita, Yasuyuki; Hwang, Harold Y

    2016-12-01

    The ability to create and manipulate materials in two-dimensional (2D) form has repeatedly had transformative impact on science and technology. In parallel with the exfoliation and stacking of intrinsically layered crystals, atomic-scale thin film growth of complex materials has enabled the creation of artificial 2D heterostructures with novel functionality and emergent phenomena, as seen in perovskite heterostructures. However, separation of these layers from the growth substrate has proved challenging, limiting the manipulation capabilities of these heterostructures with respect to exfoliated materials. Here we present a general method to create freestanding perovskite membranes. The key is the epitaxial growth of water-soluble Sr 3Al 2O 6 on perovskite substrates, followed by in situ growth of films and heterostructures. Millimetre-size single-crystalline membranes are produced by etching the Sr 3Al 2O 6 layer in water, providing the opportunity to transfer them to arbitrary substrates and integrate them with heterostructures of semiconductors and layered compounds.

  17. Synthesis of freestanding single-crystal perovskite films and heterostructures by etching of sacrificial water-soluble layers

    Science.gov (United States)

    Lu, Di; Baek, David J.; Hong, Seung Sae; Kourkoutis, Lena F.; Hikita, Yasuyuki; Hwang, Harold Y.

    2016-12-01

    The ability to create and manipulate materials in two-dimensional (2D) form has repeatedly had transformative impact on science and technology. In parallel with the exfoliation and stacking of intrinsically layered crystals, atomic-scale thin film growth of complex materials has enabled the creation of artificial 2D heterostructures with novel functionality and emergent phenomena, as seen in perovskite heterostructures. However, separation of these layers from the growth substrate has proved challenging, limiting the manipulation capabilities of these heterostructures with respect to exfoliated materials. Here we present a general method to create freestanding perovskite membranes. The key is the epitaxial growth of water-soluble Sr 3Al 2O 6 on perovskite substrates, followed by in situ growth of films and heterostructures. Millimetre-size single-crystalline membranes are produced by etching the Sr 3Al 2O 6 layer in water, providing the opportunity to transfer them to arbitrary substrates and integrate them with heterostructures of semiconductors and layered compounds.

  18. In plane conducting channel at the interface of CdO–ZnO isotype thin film heterostructure

    Energy Technology Data Exchange (ETDEWEB)

    Bera, A. [Department of Physics, National Institute of Technology Agartala, West Tripura 799 046 (India); Thapa, R. [SRM Research Institute, SRM University, Kattankulathur 603203, Tamil Nadu (India); Chattopadhyay, K.K. [Thin film and Nanoscience Laboratory, Department of Physics, Jadavpur University, Kolkata 700 032 (India); Saha, B., E-mail: biswajit.physics@gmail.com [Department of Physics, National Institute of Technology Agartala, West Tripura 799 046 (India)

    2015-05-25

    Highlights: • Radio frequency magnetron sputtering synthesis of CdO–ZnO isotype heterostructure. • Highly conducting channel at the interface of isotype heterostructure. • Charge accumulation and depletion at the interface due to band bending. - Abstract: Electrical transport properties of CdO–ZnO thin film heterostructure have been studied in this work. Highly conducting CdO thin film is deposited on glass substrate by radio frequency magnetron sputtering technique. ZnO thin film was deposited by employing the same technique on CdO coated glass substrate to prepare an isotype heterostructure of these two n-type metal oxide semiconductors. The CdO thin film was of very high electrical conductivity induced by oxygen deficient point defects. The films were characterized by X-ray diffraction measurements, X-ray photoelectron spectroscopic measurements, field emission scanning electron microscopic measurements and electrical conductivity measurements. Carrier diffusion and carrier tunneling through the interface potential lead to an outstanding conducting channel at the ZnO layer of the isotype thin film heterostructure modifying the band structure at the interface.

  19. Synthesis of Freestanding Single-crystal Perovskite Films and Heterostructures by Etching of Sacrificial Water-soluble Layers

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Di; Baek, David J.; Hong, Seung Sae; Kourkoutis, Lena F.; Hikita, Yasuyuki; Hwang, Harold Y.

    2016-08-22

    The ability to create and manipulate materials in two-dimensional (2D) form has repeatedly had transformative impact on science and technology. In parallel with the exfoliation and stacking of intrinsically layered crystals, atomic-scale thin film growth of complex materials has enabled the creation of artificial 2D heterostructures with novel functionality and emergent phenomena, as seen in perovskite heterostructures. However, separation of these layers from the growth substrate has proven challenging, limiting the manipulation capabilities of these heterostructures with respect to exfoliated materials. Here we present a general method to create freestanding perovskite membranes. The key is the epitaxial growth of water-soluble Sr3Al2O6 on perovskite substrates, followed by in situ growth of films and heterostructures. Millimetre-size single-crystalline membranes are produced by etching the Sr3Al2O6 layer in water, providing the opportunity to transfer them to arbitrary substrates and integrate them with heterostructures of semiconductors and layered compounds.

  20. General Considerations of the Electrostatic Boundary Conditions in Oxide Heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Higuchi, Takuya

    2011-08-19

    When the size of materials is comparable to the characteristic length scale of their physical properties, novel functionalities can emerge. For semiconductors, this is exemplified by the 'superlattice' concept of Esaki and Tsu, where the width of the repeated stacking of different semiconductors is comparable to the 'size' of the electrons, resulting in novel confined states now routinely used in opto-electronics. For metals, a good example is magnetic/non-magnetic multilayer films that are thinner than the spin-scattering length, from which giant magnetoresistance (GMR) emerged, used in the read heads of hard disk drives. For transition metal oxides, a similar research program is currently underway, broadly motivated by the vast array of physical properties that they host. This long-standing notion has been recently invigorated by the development of atomic-scale growth and probe techniques, which enables the study of complex oxide heterostructures approaching the precision idealized in Fig. 1(a). Taking the subset of oxides derived from the perovskite crystal structure, the close lattice match across many transition metal oxides presents the opportunity, in principle, to develop a 'universal' heteroepitaxial materials system. Hand-in-hand with the continual improvements in materials control, an increasingly relevant challenge is to understand the consequences of the electrostatic boundary conditions which arise in these structures. The essence of this issue can be seen in Fig. 1(b), where the charge sequence of the sublayer 'stacks' for various representative perovskites is shown in the ionic limit, in the (001) direction. To truly 'universally' incorporate different properties using different materials components, be it magnetism, ferroelectricity, superconductivity, etc., it is necessary to access and join different charge sequences, labelled here in analogy to the designations 'group IV, III-V, II

  1. Power semiconductors

    CERN Document Server

    Kubát, M

    1984-01-01

    The book contains a summary of our knowledge of power semiconductor structures. It presents first a short historic introduction (Chap. I) as well as a brief selection of facts from solid state physics, in particular those related to power semiconductors (Chap. 2). The book deals with diode structures in Chap. 3. In addition to fundamental facts in pn-junction theory, the book covers mainly the important processes of power structures. It describes the emitter efficiency and function of microleaks (shunts). the p +p and n + n junctions, and in particular the recent theory of the pin, pvn and p1tn junctions, whose role appears to be decisive for the forward mode not only of diode structures but also of more complex ones. For power diode structures the reverse mode is the decisive factor in pn-junction breakdown theory. The presentation given here uses engineering features (the multiplication factor M and the experimentally detected laws for the volume and surface of crystals), which condenses the presentation an...

  2. Magnetic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Bihler, Christoph

    2009-04-15

    In this thesis we investigated in detail the properties of Ga{sub 1-x}Mn{sub x}As, Ga{sub 1-x}Mn{sub x}P, and Ga{sub 1-x}Mn{sub x}N dilute magnetic semiconductor thin films with a focus on the magnetic anisotropy and the changes of their properties upon hydrogenation. We applied two complementary spectroscopic techniques to address the position of H in magnetic semiconductors: (i) Electron paramagnetic resonance, which provides direct information on the symmetry of the crystal field of the Mn{sup 2+} atoms and (ii) x-ray absorption fine structure analysis which allows to probe the local crystallographic neighborhood of the absorbing Mn atom via analysing the fine structure at the Mn K absorption edge. Finally, we discussed the obstacles that have to be overcome to achieve Curie temperatures above the current maximum in Ga{sub 1-x}Mn{sub x}As of 185 K. Here, we outlined in detail the generic problem of the formation of precipitates at the example of Ge:MN. (orig.)

  3. Strain induced piezoelectric effect in black phosphorus and MoS2 van der Waals heterostructure.

    Science.gov (United States)

    Huang, Le; Li, Yan; Wei, Zhongming; Li, Jingbo

    2015-11-10

    The structural, electronic, transport and optical properties of black phosphorus/MoS2 (BP/MoS2) van der Waals (vdw) heterostructure are investigated by using first principles calculations. The band gap of BP/MoS2 bilayer decreases with the applied normal compressive strain and a semiconductor-to-metal transition is observed when the applied strain is more than 0.85 Å. BP/MoS2 bilayer also exhibits modulation of its carrier effective mass and carrier concentration by the applied compressive strain, suggesting that mobility engineering and good piezoelectric effect can be realized in BP/MoS2 heterostructure. Because the type-II band alignment can facilitate the separation of photo-excited electrons and holes, and it can benefit from the great absorption coefficient in ultra-violet region, the BP/MoS2 shows great potential to be a very efficient ultra-violet photodetector.

  4. A Ge/Si heterostructure nanowire-based double quantum dot with integrated charge sensor

    DEFF Research Database (Denmark)

    Hu, Yongjie; Churchill, Hugh; Reilly, David

    2007-01-01

    : the predominance of spin-zero nuclei suppresses the hyperfine interaction and chemical synthesis creates a clean and defect-free system with highly controllable properties. Here we present a top gate-defined double quantum dot based on Ge/Si heterostructure nanowires with fully tunable coupling between the dots......Coupled electron spins in semiconductor double quantum dots hold promise as the basis for solid-state qubits. To date, most experiments have used III-V materials, in which coherence is limited by hyperfine interactions. Ge/Si heterostructure nanowires seem ideally suited to overcome this limitation...... and to the leads. We also demonstrate a novel approach to charge sensing in a one-dimensional nanostructure by capacitively coupling the double dot to a single dot on an adjacent nanowire. The double quantum dot and integrated charge sensor serve as an essential building block required to form a solid-state spin...

  5. Efficient photoelectrochemical hydrogen generation using heterostructures of Si and chemically exfoliated metallic MoS2.

    Science.gov (United States)

    Ding, Qi; Meng, Fei; English, Caroline R; Cabán-Acevedo, Miguel; Shearer, Melinda J; Liang, Dong; Daniel, Andrew S; Hamers, Robert J; Jin, Song

    2014-06-18

    We report the preparation and characterization of highly efficient and robust photocathodes based on heterostructures of chemically exfoliated metallic 1T-MoS2 and planar p-type Si for solar-driven hydrogen production. Photocurrents up to 17.6 mA/cm(2) at 0 V vs reversible hydrogen electrode were achieved under simulated 1 sun irradiation, and excellent stability was demonstrated over long-term operation. Electrochemical impedance spectroscopy revealed low charge-transfer resistances at the semiconductor/catalyst and catalyst/electrolyte interfaces, and surface photoresponse measurements also demonstrated slow carrier recombination dynamics and consequently efficient charge carrier separation, providing further evidence for the superior performance. Our results suggest that chemically exfoliated 1T-MoS2/Si heterostructures are promising earth-abundant alternatives to photocathodes based on noble metal catalysts for solar-driven hydrogen production.

  6. Influence of Au Nanoparticle Shape on Au@Cu2O Heterostructures

    Directory of Open Access Journals (Sweden)

    Jie Zhu

    2015-01-01

    Full Text Available Synthesis of metal-semiconductor heterostructures may allow the combination of function of the corresponding components and/or the enhanced performance resulting from the interactions between all the components. In this paper, Au@Cu2O core-shell heterostructures are prepared by a seed-growth method, using different-shaped Au nanocrystals as the seeds such as nanorods, octahedra, decahedra, dots, and nanocubes. The results revealed that the final structure of Au@Cu2O was greatly influenced by the shape of the seeds used. Exposure of Cu2O{111} and Cu2O{001} favored when the overgrowth happened on Au{111} and Au{001} surface, respectively. The size of the product can also be tuned by the amount of the seeds. The results reported here provide a thinking clue to modulate the shape and size of core-shell nanocrystals, which is useful in developing new materials with desired performance.

  7. Substitution of phthalocyanines affecting the properties of their films and heterostructures

    Science.gov (United States)

    Vertsimakha, Ya.; Mamykin, S.; Lutsyk, P.

    2012-08-01

    Optical and photovoltaic properties were studied for phthalocyanine derivatives: sulfonamide zinc phthalocyanine (ZPS), amine zinc phthalocyanine (ZPN) and amine metal-free phthalocyanine (HPN) thin films and thin-film heterostructures made of the phthalocyanine derivatives with organic semiconductors - N,N‧-dimethylperylene-tetracarboxylicacid diimide, pentacene, lead phthalocyanine. It was shown that sulphonamide substitution of phthalocyanine molecule practically does not affect the absorption spectra. NH2 substitution results in appearance of additional absorbance in long-wave range in comparison to the spectra of ZPS. The behavior can be explained by an increase of molecular aggregation due to more efficient interaction of NH2 substituted phthalocyanines. The photovoltaic sensitivity of the phthalocyanine films decreases in following sequence ZPS → ZPN → HPN. Thermal deposition of N,N‧-dimethylperylene-tetracarboxylicacid diimide and pentacene on thin films of the phthalocyanine derivatives results in formation of sufficiently high potential barrier at the interface. The highest photosensitivity was observed in the heterostructures with pentacene films.

  8. Scanning near-field infrared micro-spectroscopy on buried InAs quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Fehrenbacher, Markus; Jacob, Rainer; Winnerl, Stephan; Schneider, Harald; Helm, Manfred [Institut fuer Ionenstrahlphysik und Materialforschung, Helmholtz-Zentrum Dresden-Rossendorf (Germany); Wenzel, Marc Tobias; Krysztofinski, Anja; Ribbeck, Hans-Georg von; Eng, Lukas M. [Institut fuer Angewandte Photophysik, TU Dresden (Germany)

    2012-07-01

    Providing an optical resolution on the nanometer length scale, scanning near-field optical microscopy (SNOM) turned out to be a capable technique to investigate the optical properties of perovskites, buried semiconductors and single quantum dots. Thereby, the line-width of the observed resonances (5 - 8 meV) is significantly smaller than the inhomogeneously broadened line-width of other spectroscopic measurements. Using a scattering-type-SNOM (s-SNOM) combined with a tunable free-electron laser (FEL) light source we investigated the electronic structure of single InAs quantum dots, capped under a 70 nm thick GaAs layer. Spectroscopic near-field scans clearly identified two inter-sublevel transitions within the quantum dots at 85 meV and 120 meV, contrasting from the surrounding medium. Moreover, spatially scanning the s-SNOM tip at fixed excitation energies allowed mapping the 3D distribution of such buried quantum dots.

  9. Non-destructive imaging of buried electronic interfaces using a decelerated scanning electron beam.

    Science.gov (United States)

    Hirohata, Atsufumi; Yamamoto, Yasuaki; Murphy, Benedict A; Vick, Andrew J

    2016-09-02

    Recent progress in nanotechnology enables the production of atomically abrupt interfaces in multilayered junctions, allowing for an increase in the number of transistors in a processor. However, uniform electron transport has not yet been achieved across the entire interfacial area in junctions due to the existence of local defects, causing local heating and reduction in transport efficiency. To date, junction uniformity has been predominantly assessed by cross-sectional transmission electron microscopy, which requires slicing and milling processes that can potentially introduce additional damage and deformation. It is therefore essential to develop an alternative non-destructive method. Here we show a non-destructive technique using scanning electron microscopy to map buried junction properties. By controlling the electron-beam energy, we demonstrate the contrast imaging of local junction resistances at a controlled depth. This technique can be applied to any buried junctions, from conventional semiconductor and metal devices to organic devices.

  10. Semiconductor Laser Measurements Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — The Semiconductor Laser Measurements Laboratory is equipped to investigate and characterize the lasing properties of semiconductor diode lasers. Lasing features such...

  11. SEM based overlay measurement between resist and buried patterns

    Science.gov (United States)

    Inoue, Osamu; Okagawa, Yutaka; Hasumi, Kazuhisa; Shao, Chuanyu; Leray, Philippe; Lorusso, Gian; Baudemprez, Bart

    2016-03-01

    With the continuous shrink in pattern size and increased density, overlay control has become one of the most critical issues in semiconductor manufacturing. Recently, SEM based overlay of AEI (After Etch Inspection) wafer has been used for reference and optimization of optical overlay (both Image Based Overlay (IBO) and Diffraction Based Overlay (DBO)). Overlay measurement at AEI stage contributes monitor and forecast the yield after formation by etch and calibrate optical measurement tools. however those overlay value seems difficult directly for feedback to a scanner. Therefore, there is a clear need to have SEM based overlay measurements of ADI (After Develop Inspection) wafers in order to serve as reference for optical overlay and make necessary corrections before wafers go to etch. Furthermore, to make the corrections as accurate as possible, actual device like feature dimensions need to be measured post ADI. This device size measurement is very unique feature of CDSEM , which can be measured with smaller area. This is currently possible only with the CD-SEM. This device size measurement is very unique feature of CD-SEM , which can be measured with smaller area. In this study, we assess SEM based overlay measurement of ADI and AEI wafer by using a sample from an N10 process flow. First, we demonstrate SEM based overlay performance at AEI by using dual damascene process for Via 0 (V0) and metal 1 (M1) layer. We also discuss the overlay measurements between litho-etch-litho stages of a triple patterned M1 layer and double pattern V0. Second, to illustrate the complexities in image acquisition and measurement we will measure overlay between M1B resist and buried M1A-Hard mask trench. Finally, we will show how high accelerating voltage can detect buried pattern information by BSE (Back Scattering Electron). In this paper we discuss the merits of this method versus standard optical metrology based corrections.

  12. Inelastic light scattering by low-lying excitations of electrons in low-dimensional semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Pellegrini, V. [NEST CNR-INFM and Scuola Normale Superiore, Pisa (Italy); Pinczuk, A. [Department of Physics, Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States); Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey (United States)

    2006-11-15

    The low-dimensional electron systems that reside in artificial semiconductor heterostructures of great perfection are a contemporary materials base for explorations of collective phenomena. Studies of low-lying elementary excitations by inelastic light scattering offer insights on properties such energetics, interactions and spin magnetization. We review here recent light scattering results obtained from two-dimensional (2D) quantum fluids in semiconductor heterostructures under extreme conditions of low temperature and large magnetic field, where the quantum Hall phases are archetypes of novel behaviors. We also consider recent light scattering experiments that have probed the excitation spectra of few-electron states in semiconductor quantum dots. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. Scanning capacitance microscopy and spectroscopy applied to local charge modifications and characterization of nitride-oxide-silicon heterostructures

    Science.gov (United States)

    Dreyer, M.; Wiesendanger, R.

    1995-10-01

    We have combined a home-built capacitance sensor with a commercial scanning force microscope to obtain a Scanning Capacitance Microscope (SCM). The SCM has been used to study Nitride-Oxide-Silicon (NOS) heterostructures which offer potential applications in charge storage technology. Charge writing and reading on a submicrometer scale is demonstrated with our SCM setup. In addition, SCM appears to be very useful for the characterization of subsurface defects in semiconductor devices which are inaccessible by most of the other scanning probe microscopies. Finally, we introduce a novel spectroscopic mode of SCM operation which offers combined voltage-dependent and spatially resolved information about inhomogeneous charge distributions in semiconductor devices.

  14. Silicon on insulator with active buried regions

    Science.gov (United States)

    McCarthy, A.M.

    1996-01-30

    A method is disclosed for forming patterned buried components, such as collectors, sources and drains, in silicon-on-insulator (SOI) devices. The method is carried out by epitaxially growing a suitable sequence of single or multiple etch stop layers ending with a thin silicon layer on a silicon substrate, masking the silicon such that the desired pattern is exposed, introducing dopant and activating in the thin silicon layer to form doped regions. Then, bonding the silicon layer to an insulator substrate, and removing the silicon substrate. The method additionally involves forming electrical contact regions in the thin silicon layer for the buried collectors. 10 figs.

  15. Fully Coupled FE Analyses of Buried Structures

    Directory of Open Access Journals (Sweden)

    James T. Baylot

    1994-01-01

    Full Text Available Current procedures for determining the response of buried structures to the effects of the detonation of buried high explosives recommend decoupling the free-field stress analysis from the structure response analysis. A fully coupled (explosive–soil structure finite element analysis procedure was developed so that the accuracies of current decoupling procedures could be evaluated. Comparisons of the results of analyses performed using this procedure with scale-model experiments indicate that this finite element procedure can be used to effectively evaluate the accuracies of the methods currently being used to decouple the free-field stress analysis from the structure response analysis.

  16. Buried Waste Integrated Demonstration stakeholder involvement model

    Energy Technology Data Exchange (ETDEWEB)

    Kaupanger, R.M.; Kostelnik, K.M.; Milam, L.M.

    1994-04-01

    The Buried Waste Integrated Demonstration (BWID) is a program funded by the US Department of Energy (DOE) Office of Technology Development. BWID supports the applied research, development, demonstration, and evaluation of a suite of advanced technologies that together form a comprehensive remediation system for the effective and efficient remediation of buried waste. Stakeholder participation in the DOE Environmental Management decision-making process is critical to remediation efforts. Appropriate mechanisms for communication with the public, private sector, regulators, elected officials, and others are being aggressively pursued by BWID to permit informed participation. This document summarizes public outreach efforts during FY-93 and presents a strategy for expanded stakeholder involvement during FY-94.

  17. Tube-like ternary α-Fe2O3@SnO2@Cu2O sandwich heterostructures: synthesis and enhanced photocatalytic properties.

    Science.gov (United States)

    Tian, Qingyong; Wu, Wei; Sun, Lingling; Yang, Shuanglei; Lei, Mei; Zhou, Juan; Liu, Ying; Xiao, Xiangheng; Ren, Feng; Jiang, Changzhong; Roy, Vellaisamy A L

    2014-08-13

    Heterogeneous photocatalysis is of great interest for environmental remediation applications. However, fast recombination of photogenerated electron-hole pair and a low utilization rate of sunlight hinder the commercialization of currently available semiconductor photocatalysts. In this regard, we developed a unique ternary single core-double shell heterostructure that consists of α-Fe2O3@SnO2@Cu2O. This heterostructure exhibits a tube-like morphology possessing broad spectral response for the sunlight due to the combination of narrow bandgap and wide bandgap semiconductors forming a p-n heterojunction. To fabricate such a short nanotube (SNT), we used an anion-assisted hydrothermal route for deposition of α-Fe2O3, a seed-mediated deposition strategy for SnO2, and finally an aging process to deposit a Cu2O layer to complete the tube-like ternary α-Fe2O3@SnO2@Cu2O single core-double shell heterostructures. The morphology, composition, and photocatalytic properties of those ternary core-shell-shell heterostructures were characterized by various analytical techniques. These ternary heterostructures exhibited enhanced photocatalytic properties on the photodegradation of the organic dye of Rhodamine B (RhB) under simulated sunlight irradiation. The origin of enhanced photocatalytic activity is due to the synergistic effect of broad spectral response by combining narrow bandgap and wide bandgap semiconductors and, hence, an efficient charge separation of photogenerated electron-hole pairs facilitated through the p-n heterojunction. Furthermore, our unique structure provides an insight on the fabrication and controlled preparation of multilayer heterostructural photocatalysts that have intriguing properties.

  18. Rashba semiconductor as spin Hall material: Experimental demonstration of spin pumping in wurtzite $n$-GaN:Si

    OpenAIRE

    2016-01-01

    Pure spin currents in semiconductors are essential for implementation in the next generation of spintronic elements. Heterostructures of III- nitride semiconductors are currently employed as central building-blocks for lighting and high-power devices. Moreover, the long relaxation times and the spin-orbit coupling (SOC) in these materials indicate them as privileged hosts for spin currents and related phenomena. Spin pumping is an efficient mechanism for the inception of spin current and its ...

  19. EDITORIAL: Frontiers in semiconductor-based devices Frontiers in semiconductor-based devices

    Science.gov (United States)

    Krishna, Sanjay; Phillips, Jamie; Ghosh, Siddhartha; Ma, Jack; Sabarinanthan, Jayshri; Stiff-Roberts, Adrienne; Xu, Jian; Zhou, Weidong

    2009-12-01

    This special cluster of Journal of Physics D: Applied Physics reports proceedings from the Frontiers in Semiconductor-Based Devices Symposium, held in honor of the 60th birthday of Professor Pallab Bhattacharya by his former doctoral students. The symposium took place at the University of Michigan, Ann Arbor on 6-7 December 2009. Pallab Bhattacharya has served on the faculty of the Electrical Engineering and Computer Science Department at the University of Michigan, Ann Arbor for 25 years. During this time, he has made pioneering contributions to semiconductor epitaxy, characterization of strained heterostructures, self-organized quantum dots, quantum-dot optoelectronic devices, and integrated optoelectronics. Professor Bhattacharya has been recognized for his accomplishments by membership of the National Academy of Engineering, by chaired professorships (Charles M Vest Distinguished University Professor and James R Mellor Professor of Engineering), and by selection as a Fellow of the IEEE, among numerous other honors and awards. Professor Bhattacharya has also made remarkable contributions in education, including authorship of the textbook Semiconductor Optoelectronic Devices (Prentice Hall, 2nd edition) and the production of 60 PhD students (and counting). In fact, this development of critical human resources is one of the biggest impacts of Professor Bhattacharya's career. His guidance and dedication have shaped the varied professional paths of his students, many of whom currently enjoy successful careers in academia, industry, and government around the world. This special cluster acknowledges the importance of Professor Bhattacharya's influence as all of the contributions are from his former doctoral students. The symposium reflects the significant impact of Professor Bhattacharya's research in that the topics span diverse, critical research areas, including: semiconductor lasers and modulators, nanoscale quantum structure-based devices, flexible CMOS

  20. A single-electron probe for buried optically active quantum dot

    Directory of Open Access Journals (Sweden)

    T. Nakaoka

    2012-09-01

    Full Text Available We present a simple method that enables both single electron transport through a self-assembled quantum dot and photon emission from the dot. The quantum dot buried in a semiconductor matrix is electrically connected with nanogap electrodes through tunneling junctions formed by a localized diffusion of the nanogap electrode metals. Coulomb blockade stability diagrams for the optically-active dot are clearly resolved at 4.2 K. The position of the quantum dot energy levels with respect to the contact Fermi level is controlled by the kind of metal atoms diffused from the nanogap electrodes.

  1. Molecular and polymeric organic semiconductors for applications in photovoltaic devices

    CERN Document Server

    Meinhardt, G

    2000-01-01

    Photovoltaic devices based on molecular as well as polymeric semiconductors were investigated and characterized. The organic materials presented here exhibit the advantages of low price, low processing costs and the possibility of tuning their optical properties. The photovoltaic properties were investigated by photocurrent action spectroscopy and I/V-characterization and the electric field distribution in each layer by electroabsorption spectroscopy. Single layer devices of molecular semiconductors and semiconducting polymers like methyl-substituted polyparaphenylene, CN-Ether-PPV, copper-phthalocyanine, the terryleneimide DOTer, the perylene derivatives BBP-perylene and polyBBP-perylene show low photocurrents as well as a small photovoltaic effect in their pristine form. One way to enhance the performance is to blend the active layer with molecular dopands like a soluble form of titaniumoxophthalocyanine or the aromatic macromolecule RS19 or to combine two organic semiconductors in heterostructure devices. ...

  2. Wafer Fusion for Integration of Semiconductor Materials and Devices

    Energy Technology Data Exchange (ETDEWEB)

    Choquette, K.D.; Geib, K.M.; Hou, H.Q.; Allerman, A.A.; Kravitz, S.; Follstaedt, D.M.; Hindi, J.J.

    1999-05-01

    We have developed a wafer fusion technology to achieve integration of semiconductor materials and heterostructures with widely disparate lattice parameters, electronic properties, and/or optical properties for novel devices not now possible on any one substrate. Using our simple fusion process which uses low temperature (400-600 C) anneals in inert N{sub 2} gas, we have extended the scope of this technology to examine hybrid integration of dissimilar device technologies. As a specific example, we demonstrate wafer bonding vertical cavity surface emitting lasers (VCSELs) to transparent AlGaAs and GaP substrates to fabricate bottom-emitting short wavelength VCSELs. As a baseline fabrication technology applicable to many semiconductor systems, wafer fusion will revolutionize the way we think about possible semiconductor devices, and enable novel device configurations not possible by epitaxial growth.

  3. Detection of Buried Objects : The MUD Project

    NARCIS (Netherlands)

    Quesson, B.A.J.; Vossen, R. van; Zampolli, M.; Beckers, A.L.D.

    2011-01-01

    The aim of the Mine Underwater Detection (MUD) project at TNO is to experimentally investigate the acoustic and magnetic detection of explosives underwater, buried in a soft sediment layer. This problem is relevant for the protection of harbors and littoral assets against terrorist attacks and for

  4. Detection of Buried Objects : The MUD Project

    NARCIS (Netherlands)

    Quesson, B.A.J.; Vossen, R. van; Zampolli, M.; Beckers, A.L.D.

    2011-01-01

    The aim of the Mine Underwater Detection (MUD) project at TNO is to experimentally investigate the acoustic and magnetic detection of explosives underwater, buried in a soft sediment layer. This problem is relevant for the protection of harbors and littoral assets against terrorist attacks and for t

  5. Detection of buried mines with seismic sonar

    Science.gov (United States)

    Muir, Thomas G.; Baker, Steven R.; Gaghan, Frederick E.; Fitzpatrick, Sean M.; Hall, Patrick W.; Sheetz, Kraig E.; Guy, Jeremie

    2003-10-01

    Prior research on seismo-acoustic sonar for detection of buried targets [J. Acoust. Soc. Am. 103, 2333-2343 (1998)] has continued with examination of the target strengths of buried test targets as well as targets of interest, and has also examined detection and confirmatory classification of these, all using arrays of seismic sources and receivers as well as signal processing techniques to enhance target recognition. The target strengths of two test targets (one a steel gas bottle, the other an aluminum powder keg), buried in a sand beach, were examined as a function of internal mass load, to evaluate theory developed for seismic sonar target strength [J. Acoust. Soc. Am. 103, 2344-2353 (1998)]. The detection of buried naval and military targets of interest was achieved with an array of 7 shaker sources and 5, three-axis seismometers, at a range of 5 m. Vector polarization filtering was the main signal processing technique for detection. It capitalizes on the fact that the vertical and horizontal components in Rayleigh wave echoes are 90 deg out of phase, enabling complex variable processing to obtain the imaginary component of the signal power versus time, which is unique to Rayleigh waves. Gabor matrix processing of this signal component was the main technique used to determine whether the target was man-made or just a natural target in the environment. [Work sponsored by ONR.

  6. 7 CFR 1755.505 - Buried services.

    Science.gov (United States)

    2010-01-01

    ..., RUS standard for splicing copper and fiber optic cables. (d) Buried service wire or cable shall be... shall be installed against a foundation wall or pillar to provide adequate support and mechanical... lightning rod grounding conductor or grounding electrode with at least a Number (No.) 6 AWG copper...

  7. EDITORIAL: Oxide semiconductors

    Science.gov (United States)

    Kawasaki, M.; Makino, T.

    2005-04-01

    growth of p-type layers, ferromagnetic behaviour in transition-metal doped oxide is also fuelling renewed interest from the spintronic point of view. Since some of the related reports remain controversial, a critical discussion of the magnetic properties of these doped oxides is made by Fukumura et al. Before the observation of electro-luminescence from the ZnO p-n homojunction reported by Tsukazaki et al (2005 Nature Mater. 4 42), the afore-mentioned advantages have been explored and exploited by alternative methods, such as heteroepitaxy in which p-n heterostructures can be obtained by depositing n-type ZnO films on other p-type oxides while still utilizing ZnO as their active layer. Researchers in Hosono's group observed the high-intensity band-edge emission from such heterostructures for the first time (Ohta H et al 2000 Appl. Phys. Lett. 77 475). They have also successfully extended their research fields to the development of a transparent oxide transistor based on homologous compounds, which is reviewed by Kamiya and Hosono in this special issue. As can be seen from these demonstrations, the advantage of oxides is, of course, based on the fact that many elements in the periodic table can form compounds with oxygen. Since the discovery of high-temperature superconductors, these multi-component oxides have exploited the new field known as the science of strongly correlated-electron materials, whose recent progress is reviewed by Inoue. Although the collection of papers included in this special issue covers a good cross-section of the development of oxide semiconductors and correlated-electron oxides to date, this is not meant to be exhaustive. There are a number of unavoidable omissions, such as theoretical studies except for some theoretical predictions on the room-temperature Bose-Einstein condensation of exciton-polaritons found in the article by Chichibu et al. We hope this issue promotes further development of this exciting field. The guest editors would like to

  8. Quantum confinement in perovskite oxide heterostructures: Tight binding instead of a nearly free electron picture

    OpenAIRE

    Zhong, Zhicheng; Zhang, Qinfang; Held, Karsten

    2013-01-01

    Most recently, orbital-selective quantum well states of $d$ electrons have been experimentally observed in SrVO$_3$ ultrathin films [K. Yoshimatsu et. al., Science 333, 319 (2011)] and SrTiO$_3$ surfaces [A. F. Santander-Syro et. al., Nature 469, 189 (2011)]. Hitherto, one tries to explain these experiments by a nearly free electron (NFE) model, an approach widely used for delocalized electrons in semiconductor heterostructures and simple metal films. We show that a tight binding (TB) model i...

  9. Photoreflectance Spectroscopy for Study of Si/SiGe/Si Heterostructure

    Institute of Scientific and Technical Information of China (English)

    Liu Zhihong; Chen Changchun; Lin Huiwang; Xiong Xiaoyi; Dou Weizhi; Tsien Pei-Hsin

    2004-01-01

    UHVCVD-grown Si/Si1- xGex/Si heterostructure was investigated by Photoreflectance spectroscopy (PR). The principle of PR used in semiconductor film was thoroughly described. According to the E1 transition energy in the Si1- xGex alloy, the Ge content in SiGe film with constant composition can be accurately characterized. In this study, determine the composition uniformity of larger diameter SiGe epiwafer by PR mapping technique was determined. These results show PR is very promising for Si1- xGex epilayer characterization with constant Ge content and can provide film measurements for production-worthy line monitor.

  10. Semiconductor laser. Halbleiterlaser

    Energy Technology Data Exchange (ETDEWEB)

    Wuenstel, K.; Gohla, B.; Tegude, F.; Luz, G.; Hildebrand, O.

    1987-08-27

    A highly modulable semiconductor laser and a process for its manufacture are described. The semiconductor laser has a substrate, a stack of semiconductor layers and electrical contacts. To reduce the capacity, the width of the stack of semiconductor layers is reduced at the sides by anisotropic etching. The electrical contacts are situated on the same side of the substrate and are applied in the same stage of the process. The semiconductor laser is suitable for monolithic integration in other components.

  11. Magnetoelectric Coupling in Composite Multiferroic Heterostructures

    Science.gov (United States)

    Hoffman, Jason

    In this work, we demonstrate a large charge-mediated magnetoelectric coupling in a PbZr0.2Ti0.8O3 / La0.8 Sr0.2MnO3 (PZT/LSMO) composite structure resulting from direct control of magnetism via charge carrier density. This approach has the advantage that its physical mechanism is transparent and the size of the effect can be quantified and understood qualitatively within the double-exchange model. Direct quantification of the charge-driven magnetic changes based on electronic, magnetic, and spectroscopic measurements show that both the spin state and spin configuration of LSMO are modulated. Using a combination of advanced physical vapor deposition techniques, we have grown epitaxial PZT/LSMO bilayer heterostructures on (001) SrTiO 3 substrates with excellent crystallinity, atomically smooth surfaces, low leakage current density, and abrupt interfaces. Magneto-optic Kerr effect (MOKE) magnetometry was used to directly interrogate the local magnetic state of the LSMO as a function of the PZT polarization state. We show direct control of magnetism via applied electric fields, including modulation of the magnetotransport behavior and magnetic-ordering temperature, on/off switching of magnetism, and hysteretic magnetization versus electric field (M-E) characteristics. The magnetoelectric coupling strength, which relates the change in magnetization to the applied electric field, is found to vary strongly with temperature, reaching a low temperature saturation value of +6 Oe cm / kV, much larger than observed in single-phase magnetoelectrics and too large to be explained by a simple band-filling model. To clarify the origin of the magnetoelectric coupling, we carried out near edge x-ray absorption measurements that revealed a well defined change in the position of the Mn absorption edge with the ferroelectric polarization, giving a direct measure of the change in Mn valency in LSMO. We explain these results in terms of an interfacial magnetic reconstruction, whereby the

  12. Photodetectors based on heterostructures for optoelectronic applications

    Science.gov (United States)

    Nabet, Bahram; Cola, Adriano; Cataldo, Andrea; Chen, Xiying; Quaranta, Fabio

    2002-09-01

    In this work we describe a family of optical devices based on heterojunction and heterodimensional structures and we investigate their static and dynamic properties. Such devices are good candidates, due to their high performance, for utilization as the sensing element for the realization of sensors in the fields of telecommunications, remote sensing, LIDAR and medical imaging. First, we present a Heterostructure Metal-Semiconductor-Metal (HMSM) photodetectors that employ a uniformly doped GaAs/AlGaAs heterojunction for the dual purpose of barrier height enhancement and creating an internal electric field that aids in the transport and collection of the photogenerated electrons. In this first family of devices, two doping levels are compared showing the direct effect of the aiding field due to modulation doping. Subsequently, we analyze a novel Resonant-Cavity-Enhanced (RCE) HMSM photodetector in which a Distributed Bragg Reflector (DBR) is employed in order to reduce the thickness of the absorption layer thus achieving good responsivity and high speed as well as wavelength selectivity. Current-voltage, current-temperature, photocurrent spectra, high-speed time response, and on-wafer frequency domain measurements point out the better performance of this last family of detectors, as they can operate in tens of Giga-Hertz range with low dark current and high responsivity. Particularly, the I-V curves show a very low dark current (around 10 picoamps at operative biases); C-V measurements highlight the low geometrical capacitance values; the photocurrent spectrum shows a clear peak at 850 nm wavelength, while time response measurements give a 3 dB bandwidth of about 30 GHz. Small signal model based on frequency domain data is also extracted in order to facilitate future photoreceiver design. Furthermore, two-dimensional numerical simulations have been carried out in order to predict the electrical properties of these detectors. Combination of very low dark current and

  13. Through-focal HAADF-STEM of buried nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Guerrero-Lebrero, M P; Pizarro, J; Guerrero, E; Galindo, P L; Yanez, A [Department Lenguajes y Sist. Informaticos, Universidad de Cadiz (Spain); Molina, S I, E-mail: maria.guerrero@uca.e [Department Ciencia de los Materiales e I.M. y Q.I. Universidad de Cadiz (Spain)

    2010-02-01

    High-Angle Annular Dark-Field Scanning Transmission Electron Microscopy (HAADF-STEM) in combination with strain mapping techniques provides a powerful tool for quantitative analysis of crystalline semiconductor materials. Due to the complex interaction of a focused probe and a sample in HAADF, the calculation of each pixel in a simulation process requires a complete multislice iteration, making the overall computing process a rather demanding task in time and memory. SICSTEM is a parallel software code recently developed for running on the University of Cadiz Supercomputer (3.75 Tflops) that allows the simulation of images from large nanostructures containing more than one million atoms. The software has been designed to be able to generate not only one dimensional line scans or two dimensional images, but also to perform optical sectioning in the STEM simulation process, providing an easy way to simulate 3D HAADF-STEM images. In this work we consider GaAs capped GaSb nanostructures epitaxially oriented on a GaAs substrate. A methodology has been developed by combining the through-focal series STEM imaging and image analysis to estimate shape and position of buried GaSb nanostructures.

  14. 47 CFR 32.6423 - Buried cable expense.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 2 2010-10-01 2010-10-01 false Buried cable expense. 32.6423 Section 32.6423... FOR TELECOMMUNICATIONS COMPANIES Instructions for Expense Accounts § 32.6423 Buried cable expense. (a) This account shall include expenses associated with buried cable. (b) Subsidiary record...

  15. Imaging the motion of electrons across semiconductor heterojunctions

    Science.gov (United States)

    Man, Michael K. L.; Margiolakis, Athanasios; Deckoff-Jones, Skylar; Harada, Takaaki; Wong, E. Laine; Krishna, M. Bala Murali; Madéo, Julien; Winchester, Andrew; Lei, Sidong; Vajtai, Robert; Ajayan, Pulickel M.; Dani, Keshav M.

    2017-01-01

    Technological progress since the late twentieth century has centred on semiconductor devices, such as transistors, diodes and solar cells. At the heart of these devices is the internal motion of electrons through semiconductor materials due to applied electric fields or by the excitation of photocarriers. Imaging the motion of these electrons would provide unprecedented insight into this important phenomenon, but requires high spatial and temporal resolution. Current studies of electron dynamics in semiconductors are generally limited by the spatial resolution of optical probes, or by the temporal resolution of electronic probes. Here, by combining femtosecond pump-probe techniques with spectroscopic photoemission electron microscopy, we imaged the motion of photoexcited electrons from high-energy to low-energy states in a type-II 2D InSe/GaAs heterostructure. At the instant of photoexcitation, energy-resolved photoelectron images revealed a highly non-equilibrium distribution of photocarriers in space and energy. Thereafter, in response to the out-of-equilibrium photocarriers, we observed the spatial redistribution of charges, thus forming internal electric fields, bending the semiconductor bands, and finally impeding further charge transfer. By assembling images taken at different time-delays, we produced a movie lasting a few trillionths of a second of the electron-transfer process in the photoexcited type-II heterostructure—a fundamental phenomenon in semiconductor devices such as solar cells. Quantitative analysis and theoretical modelling of spatial variations in the movie provide insight into future solar cells, 2D materials and other semiconductor devices.

  16. Manipulating Spin-Orbit Interaction in Semiconductors

    Science.gov (United States)

    Kohda, Makoto; Bergsten, Tobias; Nitta, Junsaku

    2008-03-01

    Spin-orbit interaction (SOI), where the orbital motion of electrons is coupled with the orientation of electron spins, originates from a relativistic effect. Generally, in nonrelativistic momentum, p = \\hbar k≪ m0c, the SOI is negligible. However, in a semiconductor heterostructure, the small energy-band gap (Eg ≪ m0c2) and the electron wave modulated by the atomic core potential markedly enhance the SOI. Since the SOI acts as an effective magnetic field, it may offer novel functionalities for controlling the spin degree of freedom such as the electrical spin generation and the electrical control of the spin precession in a semiconductor heterojunction. Here, we review recent experimental studies on the manipulation of the SOI in a semiconductor two-dimensional electron gas. We first present a theoretical overview of the Rashba SOI, which lifts the spin degeneracy due to structural inversion asymmetry. We then present experimental results on the quantum well (QW) thickness dependences of the Rashba SOI in InP/InGaAs/InAlAs asymmetric QWs by analyzing the weak antilocalization. Finally, we show quantum interference effects due to the spin precession in a small array of mesoscopic InGaAs rings, which is an experimental demonstration of the time-reversal Aharonov-Casher effect and the electromagnetic dual to the Al’tshuler-Aronov-Spivak effect.

  17. Formation of heteroepitaxy in different shapes of Au-CdSe metal-semiconductor hybrid nanostructures.

    Science.gov (United States)

    Haldar, Krishna Kanta; Pradhan, Narayan; Patra, Amitava

    2013-10-25

    Formation of heteroepitaxy and designing different-shaped heterostructured nanomaterials of metal and semiconductor in solution remains a frontier area of research. However, it is evident that the synthesis of such materials is not straightforward and needs a selective approach to retain both metal and semiconductor identities in the reaction system during heterostructure formation. Herein, the epitaxial growth of semiconductor CdSe on selected facets of metal Au seeds is reported and different shapes (flower, tetrapod, and core/shell) hetero-nanostructures are designed. These results are achieved by controlling the reaction parameters, and by changing the sequence and timing for introduction of different reactant precursors. Direct evidence of the formation of heteroepitaxy between {111} facets of Au and (0001) of wurtzite CdSe is observed during the formation of these three heterostructures. The mechanism of the evolution of these hetero-nanostructures and formation of their heteroepitaxy with the planes having minimum lattice mismatch are also discussed. This shape-control growth mechanism in hetero-nanostructures should be helpful to provide more information for establishing the fundamental study of heteroepitaxial growth for designing new nanomaterials. Such metal-semiconductor nanostructures may have great potential for nonlinear optical properties, in photovoltaic devices, and as chemical sensors.

  18. Nanoelectronics in oxides and semiconductors

    Science.gov (United States)

    Cheng, Guanglei

    The success of silicon industry lies on three major properties of silicon, an easily formed oxide layer to allow field effect operation, tunability of carrier density and high device scalability. All these features exist in oxides, together with some novel properties such as ferroelectricity, magnetic effects and metal-insulator transition. With the recent development in material growth method including molecular beam epitaxy (MBE), pulsed laser deposition (PLD) and reflection high energy electron diffraction (REED), atomically engineered oxide interfaces become available, thus opening the door to the novel oxide nanoelectronics. In this dissertation we create and study nanoelectronics in oxides, semiconductors and hybrid of these two. We used a conductive atomic force microscope tip to write single electron transistors in the 3-unit-cell-LaAlO 3/SrTiO3 heterostructure and observed ferroelectric tunneling behaviors. We also fabricated ferroelectric field transistors directly on silicon using strained SrTiO3 ferroelectric film and further confirmed the ferroelectric properties of this device. Meanwhile, we developed an ultrasensitive microwave capacitance sensor to study the electronic properties of self-assembled quantum dots and the switching mechanism of memristive devices. The integration of this sensor to a home made atomic force microscope provides an important tool to study the dielectric properties at nanoscale.

  19. Interface designed MoS2/GaAs heterostructure solar cell with sandwich stacked hexagonal boron nitride.

    Science.gov (United States)

    Lin, Shisheng; Li, Xiaoqiang; Wang, Peng; Xu, Zhijuan; Zhang, Shengjiao; Zhong, Huikai; Wu, Zhiqian; Xu, Wenli; Chen, Hongsheng

    2015-10-13

    MoS2 is a layered two-dimensional semiconductor with a direct band gap of 1.8 eV. The MoS2/bulk semiconductor system offers a new platform for solar cell device design. Different from the conventional bulk p-n junctions, in the MoS2/bulk semiconductor heterostructure, static charge transfer shifts the Fermi level of MoS2 toward that of bulk semiconductor, lowering the barrier height of the formed junction. Herein, we introduce hexagonal boron nitride (h-BN) into MoS2/GaAs heterostructure to suppress the static charge transfer, and the obtained MoS2/h-BN/GaAs solar cell exhibits an improved power conversion efficiency of 5.42%. More importantly, the sandwiched h-BN makes the Fermi level tuning of MoS2 more effective. By employing chemical doping and electrical gating into the solar cell device, PCE of 9.03% is achieved, which is the highest among all the reported monolayer transition metal dichalcogenide based solar cells.

  20. Fundamentals of semiconductor devices

    CERN Document Server

    Lindmayer, Joseph

    1965-01-01

    Semiconductor properties ; semiconductor junctions or diodes ; transistor fundamentals ; inhomogeneous impurity distributions, drift or graded-base transistors ; high-frequency properties of transistors ; band structure of semiconductors ; high current densities and mechanisms of carrier transport ; transistor transient response and recombination processes ; surfaces, field-effect transistors, and composite junctions ; additional semiconductor characteristics ; additional semiconductor devices and microcircuits ; more metal, insulator, and semiconductor combinations for devices ; four-pole parameters and configuration rotation ; four-poles of combined networks and devices ; equivalent circuits ; the error function and its properties ; Fermi-Dirac statistics ; useful physical constants.

  1. Spectroscopy and dynamics of charge transfer excitons in type-II band aligned quantum confined heterostructures

    Science.gov (United States)

    Kushavah, Dushyant; Mohapatra, P. K.; Rustagi, K. C.; Bahadur, D.; Vasa, P.; Singh, B. P.

    2015-05-01

    We illustrate effect of charge transfer (CT) in type-II quantum confined heterostructure by comparing CdSe quantum dots (QDs), CdSe/CdTe heterostructure quantum dots (HQDs) and CdSe/CdTe/CdSe quantum well-quantum dots (QWQDs) heterostructures. CdSe core QDs were synthesized using a kinetic growth method where QD size depends on reaction time. For shell coating we used modified version of successive ionic layer adsorption and reaction (SILAR). Size of different QDs ˜5 to 7 nm were measured by transmission electron microscopy (TEM). Strong red shift from ˜597 to ˜746 nm in photoluminescence (PL) spectra from QDs to QWQDs shows high tunability which is not possible with single constituent semiconductor QDs. PL spectra have been recorded at different temperatures (10K-300K). Room temperature time correlated single photon counting (TCSPC) measurements for QDs to QWQDs show three exponential radiative decay. The slowest component decay constant in QWQDs comes around eight fold to ˜51 ns as compared to ˜6.5 ns in HQD suggesting new opportunities to tailor the radiative carrier recombination rate of CT excitons.

  2. Spectroscopy and dynamics of charge transfer excitons in type-II band aligned quantum confined heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Kushavah, Dushyant [Centre for Research in Nanotechnology and Science, IIT Bombay-400076, Mumbai (India); Mohapatra, P. K.; Vasa, P.; Singh, B. P., E-mail: bhanups@iitb.ac.in [Department of physics, IIT Bombay, Mumbai-400076 (India); Rustagi, K. C. [Indian Institute of Science Education and Research Bhopal-462066, Bhopal (India); Bahadur, D. [Department of Metallurgical Engineering and Materials Science, IIT Bombay, Mumbai-400076 (India)

    2015-05-15

    We illustrate effect of charge transfer (CT) in type-II quantum confined heterostructure by comparing CdSe quantum dots (QDs), CdSe/CdTe heterostructure quantum dots (HQDs) and CdSe/CdTe/CdSe quantum well-quantum dots (QWQDs) heterostructures. CdSe core QDs were synthesized using a kinetic growth method where QD size depends on reaction time. For shell coating we used modified version of successive ionic layer adsorption and reaction (SILAR). Size of different QDs ∼5 to 7 nm were measured by transmission electron microscopy (TEM). Strong red shift from ∼597 to ∼746 nm in photoluminescence (PL) spectra from QDs to QWQDs shows high tunability which is not possible with single constituent semiconductor QDs. PL spectra have been recorded at different temperatures (10K-300K). Room temperature time correlated single photon counting (TCSPC) measurements for QDs to QWQDs show three exponential radiative decay. The slowest component decay constant in QWQDs comes around eight fold to ∼51 ns as compared to ∼6.5 ns in HQD suggesting new opportunities to tailor the radiative carrier recombination rate of CT excitons.

  3. Micro-Hall magnetic sensors with high magnetic sensitivity based on III-V heterostructures

    Science.gov (United States)

    Del Medico, S.; Benyattou, Taha; Guillot, Gerard; Venet, T.; Gendry, Michel; Tardy, Jacques; Chovet, Alain

    1996-04-01

    In this work, we propose solutions based on engineering of III-V heterostructures to develop new types of semiconductor magnetic sensors. These micro-Hall sensors use the properties of a 2D electron gas and the benefit of pseudomorphic material, in which both the alloy composition and the built-in strain offer additional degrees of freedom for band structure tailoring, to exhibit high magnetic sensitivity, good linearity, low temperature coefficient and high resolution. With the growth optimization which is described, two pseudomorphic In0.75Ga0.25As/In0.52Al0.48As heterostructures were grown on a semi- insulating InP substrate by molecular beam epitaxy. To understand better the influence of the heterostructure design on its electronic properties, a model involving the self-consistent solution of the Poisson and Schrodinger equations using the Fermi-Dirac statistics has been developed. These results have been used to optimize the structure design. A magnetic sensitivity of 346 V/AT with a temperature coefficient of -230 ppm/ degree(s)C between -80 degree(s)C and 85 degree(s)C has been obtained. The device show good linearity against magnetic field and also against the supply current. High signal-to-noise ratios corresponding to minimal magnetic field of 350 nT/Hz1/2 at 100 Hz and 120 nT/Hz1/2 at 1 kHz have been measured.

  4. Functionalization of AlGaN/GaN heterostructures with TFAAD

    Energy Technology Data Exchange (ETDEWEB)

    Schwarz, Stefan Udo [Institute of Microsystem Technology (IMTEK), University of Freiburg, Georges-Koehler-Allee 106, 79110 Freiburg (Germany); Cimalla, Volker; Nebel, Christoph; Ambacher, Oliver [Fraunhofer Institute for Applied Solid State Physics, Tullastrasse 72, 79108 Freiburg (Germany)

    2010-07-01

    AlGaN/GaN high electron mobility transistors (HEMTs) show great promise for the realization of sensors for biomolecular, pharmaceutical and medical purposes. The high sensitivity and the stability in biological solutions are great advantages of this principle. The transduction is based on the AlGaN/GaN heterostructure. Charges on its surface influence the electron density in the 2-dimensional electron gas (2DEG) near the interface of the heterostructure. For a specific sensor, biological recognition methods shall be used. Therefore biomolecules need to be covalently linked to the semiconductor. The surface must be functionalized with a single layer of molecules that form covalent bonds to the surface and present functional groups for the connection with the biomolecule. In this work we investigate the functionalization of AlGaN/GaN heterostructures with 10-Trifluoroacetamiddec-1-ene (TFAAD), a molecule that can bond to GaN in a photochemical reaction and has a protected Amino group for the further procedure. The focus is on the influence of the illumination spectrum and surface pretreatments on the reaction kinetics and the resulting layer morphology with respect to the designated application.

  5. Energy levels for lens-shaped self-assembled quantum dots heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Laureto, E.; Aquino, V.M. de; Iwamoto, H.; Silva, M.A.T. da; Fernandes, R.V.; Franchello, F.; Dias, I.F.L.; Duarte, J.L. [Universidade Estadual de Londrina, PR (Brazil). Dept. de Fisica; Maia, A.D.B.; Silva, E.C.F. da; Quivy, A.A. [Universidade de Sao Paulo (IF/USP), SP (Brazil). Inst. de Fisica

    2012-07-01

    Full text: The growth of self-organized quantum dots (SAQD's) by the Stranski-Krastanow (SK) mode is currently one of the most widely used methods for obtaining semiconductor heterostructures with quasi-three-dimensional confinement. Such heterostructures are interesting for technological applications such as sensors, photovoltaic, and lasers. The modeling of the structure of the QD and the theoretical prediction of eigenstates and eigenvalues considering the appropriate confinement potential, are crucial to the understanding and control of optical and transport properties for these heterostructures. In this work we presented the results of a theoretical model for QDs structures based on calculation outlined by Marzin and Bastard [1], with the dot forming a lens-shaped structure. Energy levels of the fundamental and excited states were obtained for electrons, heavy holes and light holes, confined in three dimensions. The eigenfunctions of the system are written as an expansion on eigenfunctions of a cylindrical system involving the dot, which go to zero on the surface of the cylinder. The calculations are performed using 3600 basis functions which give a high level of accuracy and greater stability to the results. Effects of stress are also taken into account in the calculations. Finally, the model predictions are confronted with experimental results of samples SAQD's grown in SK mode by Molecular Beam Epitaxy and characterized by photoluminescence measurements (PL) as a function of excitation intensity and temperature. [1] J.-Y. Marzin and G. Bastard, Solid State Communications 92, 437 (1994). (author)

  6. Microwave tunneling in heterostructures with electromagnetically induced transparency-like metamaterials based on solid state plasma

    Science.gov (United States)

    Kong, Xiang-kun; Li, Hai-ming; Bian, Bo-rui; Xue, Feng; Ding, Guo-wen; Yu, Shao-jie; Liu, Si-yuan

    2016-06-01

    Interference induced electromagnetic induced transparency (EIT)-like effect has demonstrated the ability to realize narrow transmission resonances within the single-resonator stop band. Due to the limited plasma density in actual devices, only few reports discuss the plasma metamaterials and truncated photonic crystals which support electromagnetically induced transparency. However, solid state plasma realized by some semiconductors have the advantages of higher order plasma density and the characteristics of the reconfiguration and tunability. Here, we conduct a numerical study of the perfect microwave tunneling in heterostructures composed of solid state plasma metamaterials and truncated photonic crystal. There is particular emphasis on the tunability of tunneling frequency by changing plasma frequency in solid state plasma, as well as the electric energy density distributions in heterostructures. It was found that, compared to conventional metal photonic crystal, the reflectance of tunneling mode can be reduced from -25.8 dB to -41.7 dB with an optimized Q-factor. Further study on electric energy density distribution confirms that EM wave in-plane localization originated from the EIT-like solid state plasma, which gives rise to the three-dimensional enhancement of sub-wavelength EM wave localization, is stronger than EM wave confinement along the propagation direction. Owing to the tunability of plasma, the tunneling frequency channel can be adjusted or reconfigured in a certain range without adjusting the geometry of the heterostructure. It suggests the fabrication for highly sensitive dielectric sensing, optical switches, and so on.

  7. Buried caldera of mauna kea volcano, hawaii.

    Science.gov (United States)

    Porter, S C

    1972-03-31

    An elliptical caldera (2.1 by 2.8 kilometers) at the summit of Mauna Kea volcano is inferred to lie buried beneath hawaiite lava flows and pyroclastic cones at an altitude of approximately 3850 meters. Stratigraphic relationships indicate that hawaiite eruptions began before a pre-Wisconsin period of ice-cap glaciation and that the crest of the mountain attained its present altitude and gross form during a glaciation of probable Early Wisconsin age.

  8. Unbound states in quantum heterostructures

    Directory of Open Access Journals (Sweden)

    Ferreira R

    2006-01-01

    Full Text Available AbstractWe report in this review on the electronic continuum states of semiconductor Quantum Wells and Quantum Dots and highlight the decisive part played by the virtual bound states in the optical properties of these structures. The two particles continuum states of Quantum Dots control the decoherence of the excited electron – hole states. The part played by Auger scattering in Quantum Dots is also discussed.

  9. EUO-Based Multifunctional Heterostructures

    Science.gov (United States)

    2015-06-06

    magnetic exchange interaction.20 In collaboration with Jochen Mannhart’s group we found a way to extend the large metal- to- insulator transition (MIT...conduction band,24,25 allowing for the temperature and magnetic field induced switching between non-linear and linear current-voltage characteristics...magnetoresistance and the metal- insulator transition resistance ratios of doped EuO by interfacing this semiconductor with niobium; the observed effect is

  10. Multiple instance learning for buried hazard detection

    Science.gov (United States)

    Rice, Joseph; Pinar, Anthony; Havens, Timothy C.; Webb, Adam; Schulz, Timothy J.

    2016-05-01

    Buried explosives hazards are one of the many deadly threats facing our Soldiers, thus the U.S. Army is interested in the detection and neutralization of these hazards. One method of buried target detection uses forward-looking ground-penetrating radar (FLGPR), and it has grown in popularity due to its ability to detect buried targets at a standoff distance. FLGPR approaches often use machine learning techniques to improve the accuracy of detection. We investigate an approach to explosive hazard detection that exploits multi-instance features to discriminate between hazardous and non-hazardous returns in FLGPR data. One challenge this problem presents is a high number of clutter and non-target objects relative to the number of targets present. Our approach learns a bag of words model of the multi-instance signatures of potential targets and confuser objects in order to classify alarms as either targets or false alarms. We demonstrate our method on test data collected at a U.S. Army test site.

  11. Blepharoptosis correction with buried suture method.

    Science.gov (United States)

    Park, Jang Woo; Kang, Moon Seok; Nam, Seung Min; Kim, Yong Bae

    2015-02-01

    Many surgical techniques have been developed to correct blepharoptosis, including the anterior levator resection or advancement, tarsoaponeurectomy, and Fasanella-Servat Müllerectomy. However, to minimize surgical scarring and reduce the postoperative recovery time, the procedure has been developed from a complete incision to a partial incision, which is appealing to patients. To aid the procedural development, this study describes a surgical technique in which the correction of blepharoptosis and a double eyelid fold operation are performed using a buried suture technique during the same operation. A retrospective review was conducted using the medical records and preoperative and postoperative photography of 121 patients who underwent simultaneous correction of blepharoptosis and had a double eyelid fold created between October 2010 and July 2011. All of the patients had mild (1-2 mm) or moderate (3-4 mm) bilateral blepharoptosis and excellent or good levator function (>8 mm). The average preoperative marginal reflex distance (MRD1) measured 1.174 (0.3) mm. No intraoperative complications occurred. The average postoperative MRD1 measured 3.968 (0.2) mm. There was statistical significance improvement between preoperative MRD1 and postoperative MRD1 (Pexposure keratopathy were noted. Blepharoptosis correction using the buried suture technique is an effective technique for young patients experiencing mild to moderate blepharoptosis who want to have the double eyelid fold operation using the buried suture technique.

  12. Vertical-Cavity In-plane Heterostructures: Physics and Applications

    DEFF Research Database (Denmark)

    Taghizadeh, Alireza; Mørk, Jesper; Chung, Il-Sug

    2015-01-01

    We show that the in-plane heterostructures realized in vertical cavities with high contrast grating(HCG) reflector enables exotic configurations of heterostructure and photonic wells. In photonic crystal heterostructures forming a photonic well, the property of a confined mode is determined by th...... to discuss the rich potential of this heterostructure as a platform for various physics studies and propose a system of two laterally coupled cavities which shows the breaking of parity-time symmetry as an example....

  13. Quantum processes in semiconductors

    CERN Document Server

    Ridley, B K

    2013-01-01

    Aimed at graduate students, this is a guide to quantum processes of importance in the physics and technology of semiconductors. The fifth edition includes new chapters that expand the coverage of semiconductor physics relevant to its accompanying technology.

  14. One-dimensional Si/Ge nanowires and their heterostructures for multifunctional applications-a review.

    Science.gov (United States)

    Ray, Samit K; Katiyar, Ajit K; Raychaudhuri, Arup K

    2017-03-03

    Remarkable progress has been made in the field of one-dimensional semiconductor nanostructures for electronic and photonic devices. Group-IV semiconductors and their heterostructures have dominated the years of success in microelectronic industry. However their use in photonic devices is limited since they exhibit poor optical activity due to indirect band gap nature of Si and Ge. Reducing their dimensions below a characteristic length scale of various fundamental parameters like exciton Bohr radius, phonon mean free path, critical size of magnetic domains, exciton diffusion length etc result in the significant modification of bulk properties. In particular, light emission from Si/Ge nanowires due to quantum confinement, strain induced band structure modification and impurity doping may lead to the integration of photonic components with mature silicon CMOS technology in near future. Several promising applications based on Si and Ge nanowires have already been well established and studied, while others are now at the early demonstration stage. The control over various forms of energy and carrier transport through the unconstrained dimension makes Si and Ge nanowires a promising platform to manufacture advanced solid-state devices. This review presents the progress of the research with emphasis on their potential application of Si/Ge nanowires and their heterostructures for electronic, photonic, sensing and energy devices.

  15. One-dimensional Si/Ge nanowires and their heterostructures for multifunctional applications—a review

    Science.gov (United States)

    Ray, Samit K.; Katiyar, Ajit K.; Raychaudhuri, Arup K.

    2017-03-01

    Remarkable progress has been made in the field of one-dimensional semiconductor nanostructures for electronic and photonic devices. Group-IV semiconductors and their heterostructures have dominated the years of success in microelectronic industry. However their use in photonic devices is limited since they exhibit poor optical activity due to indirect band gap nature of Si and Ge. Reducing their dimensions below a characteristic length scale of various fundamental parameters like exciton Bohr radius, phonon mean free path, critical size of magnetic domains, exciton diffusion length etc result in the significant modification of bulk properties. In particular, light emission from Si/Ge nanowires due to quantum confinement, strain induced band structure modification and impurity doping may lead to the integration of photonic components with mature silicon CMOS technology in near future. Several promising applications based on Si and Ge nanowires have already been well established and studied, while others are now at the early demonstration stage. The control over various forms of energy and carrier transport through the unconstrained dimension makes Si and Ge nanowires a promising platform to manufacture advanced solid-state devices. This review presents the progress of the research with emphasis on their potential application of Si/Ge nanowires and their heterostructures for electronic, photonic, sensing and energy devices.

  16. Handbook of spintronic semiconductors

    CERN Document Server

    Chen, Weimin

    2010-01-01

    Offers a review of the field of spintronic semiconductors. This book covers a range of topics, including growth and basic physical properties of diluted magnetic semiconductors based on II-VI, III-V and IV semiconductors, developments in theory and experimental techniques and potential device applications.

  17. An electrically injected rolled-up semiconductor tube laser

    Energy Technology Data Exchange (ETDEWEB)

    Dastjerdi, M. H. T.; Djavid, M.; Mi, Z., E-mail: zetian.mi@mcgill.ca [Department of Electrical and Computer Engineering, McGill University, 3480 University Street, Montreal, Quebec H3A 0E9 (Canada)

    2015-01-12

    We have demonstrated electrically injected rolled-up semiconductor tube lasers, which are formed when a coherently strained InGaAs/InGaAsP quantum well heterostructure is selectively released from the underlying InP substrate. The device exhibits strong coherent emission in the wavelength range of ∼1.5 μm. A lasing threshold of ∼1.05 mA is measured for a rolled-up tube with a diameter of ∼5 μm and wall thickness of ∼140 nm at 80 K. The Purcell factor is estimated to be ∼4.3.

  18. Multilayer heterostructures and their manufacture

    Energy Technology Data Exchange (ETDEWEB)

    Hammond, Scott R; Reese, Matthew; Rupert, Benjamin; Miedaner, Alexander; Curtis, Clavin; Olson, Dana; Ginley, David S

    2015-11-04

    A method of synthesizing multilayer heterostructures including an inorganic oxide layer residing on a solid substrate is described. Exemplary embodiments include producing an inorganic oxide layer on a solid substrate by a liquid coating process under relatively mild conditions. The relatively mild conditions include temperatures below 225.degree. C. and pressures above 9.4 mb. In an exemplary embodiment, a solution of diethyl aluminum ethoxide in anhydrous diglyme is applied to a flexible solid substrate by slot-die coating at ambient atmospheric pressure, and the diglyme removed by evaporation. An AlO.sub.x layer is formed by subjecting material remaining on the solid substrate to a relatively mild oven temperature of approximately 150.degree. C. The resulting AlO.sub.x layer exhibits relatively high light transmittance and relatively low vapor transmission rates for water. An exemplary embodiment of a flexible solid substrate is polyethylene napthalate (PEN). The PEN is not substantially adversely affected by exposure to 150.degree. C

  19. Edge Dislocations Triggered Surface Instability in Tensile Epitaxial Hexagonal Nitride Semiconductor.

    Science.gov (United States)

    Cheng, Jianpeng; Yang, Xuelin; Zhang, Jie; Hu, Anqi; Ji, Panfeng; Feng, Yuxia; Guo, Lei; He, Chenguang; Zhang, Lisheng; Xu, Fujun; Tang, Ning; Wang, Xinqiang; Shen, Bo

    2016-12-14

    Understanding the semiconductor surface and its properties including surface stability, atomic morphologies, and even electronic states is of great importance not only for understanding surface growth kinetics but also for evaluating the degree to which they affect the devices' performance. Here, we report studies on the nanoscale fissures related surface instability in AlGaN/GaN heterostructures. Experimental results reveal that edge dislocations are actually the root cause of the surface instability. The nanoscale fissures are initially triggered by the edge dislocations, and the subsequent evolution is associated with tensile lattice-mismatch stress and hydrogen etching. Our findings resolve a long-standing problem on the surface instability in AlGaN/GaN heterostructures and will also lead to new understandings of surface growth kinetics in other hexagonal semiconductor systems.

  20. Ge/GaAs heterostructure matrix detector

    Energy Technology Data Exchange (ETDEWEB)

    Kostamo, P. [Optoelectronics Laboratory, Helsinki University of Technology, P.O. Box 3500, 02015 HUT (Finland)]. E-mail: pasi.kostamo@hut.fi; Saeynaetjoki, A. [Optoelectronics Laboratory, Helsinki University of Technology, P.O. Box 3500, 02015 HUT (Finland); Knuuttila, L. [Optoelectronics Laboratory, Helsinki University of Technology, P.O. Box 3500, 02015 HUT (Finland); Lipsanen, H. [Optoelectronics Laboratory, Helsinki University of Technology, P.O. Box 3500, 02015 HUT (Finland); Andersson, H. [Oxford Instruments Analytical Oy (United Kingdom); Banzuzi, K. [Oxford Instruments Analytical Oy (United Kingdom); Nenonen, S. [Oxford Instruments Analytical Oy (United Kingdom); Sipilae, H. [Oxford Instruments Analytical Oy (United Kingdom); Vaijaervi, S. [Oxford Instruments Analytical Oy (United Kingdom); Lumb, D. [Science Payload and Advanced Concepts Office, ESA/ESTEC, Nordwijk (Netherlands)

    2006-07-01

    In this paper we present a novel germanium/gallium arsenide heterostructure X-ray detector with the active volume of germanium. The heterostructure is fabricated by depositing a gallium arsenide layer on a high-purity germanium wafer in a vertical metalorganic vapor-phase epitaxy system. This approach provides a new alternative to traditional lithium diffused n+ contact which is not easily applicable for finely pixelated detectors. The detector chip fabrication utilizing this kind of heterostructure is straightforward and only standard lithographic processes need to be applied. Electrical properties of the small format detector matrices are studied. Very low reverse biased current at 77 K is observed. It is concluded that the diffusion of arsenic in germanium results in an n-type germanium layer under the epitaxial gallium arsenide.

  1. Two-dimensional heterostructures for energy storage

    Science.gov (United States)

    Pomerantseva, Ekaterina; Gogotsi, Yury

    2017-07-01

    Two-dimensional (2D) materials provide slit-shaped ion diffusion channels that enable fast movement of lithium and other ions. However, electronic conductivity, the number of intercalation sites, and stability during extended cycling are also crucial for building high-performance energy storage devices. While individual 2D materials, such as graphene, show some of the required properties, none of them can offer all properties needed to maximize energy density, power density, and cycle life. Here we argue that stacking different 2D materials into heterostructured architectures opens an opportunity to construct electrodes that would combine the advantages of the individual building blocks while eliminating the associated shortcomings. We discuss characteristics of common 2D materials and provide examples of 2D heterostructured electrodes that showed new phenomena leading to superior electrochemical performance. We also consider electrode fabrication approaches and finally outline future steps to create 2D heterostructured electrodes that could greatly expand current energy storage technologies.

  2. 2D semiconductor optoelectronics

    Science.gov (United States)

    Novoselov, Kostya

    The advent of graphene and related 2D materials has recently led to a new technology: heterostructures based on these atomically thin crystals. The paradigm proved itself extremely versatile and led to rapid demonstration of tunnelling diodes with negative differential resistance, tunnelling transistors, photovoltaic devices, etc. By taking the complexity and functionality of such van der Waals heterostructures to the next level we introduce quantum wells engineered with one atomic plane precision. Light emission from such quantum wells, quantum dots and polaritonic effects will be discussed.

  3. Unitary lens semiconductor device

    Science.gov (United States)

    Lear, Kevin L.

    1997-01-01

    A unitary lens semiconductor device and method. The unitary lens semiconductor device is provided with at least one semiconductor layer having a composition varying in the growth direction for unitarily forming one or more lenses in the semiconductor layer. Unitary lens semiconductor devices may be formed as light-processing devices such as microlenses, and as light-active devices such as light-emitting diodes, photodetectors, resonant-cavity light-emitting diodes, vertical-cavity surface-emitting lasers, and resonant cavity photodetectors.

  4. One-dimensional Z-scheme TiO2/WO3/Pt heterostructures for enhanced hydrogen generation

    Science.gov (United States)

    Gao, Hongqing; Zhang, Peng; Hu, Junhua; Pan, Jimin; Fan, Jiajie; Shao, Guosheng

    2017-01-01

    One-dimensional Z-scheme TiO2/WO3/Pt heterostructures were fabricated by integrating a facile electrospinning technique and subsequent annealing in air. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and UV-vis diffuse reflectance spectroscopy, were used to characterize the as-fabricated samples. The results showed that the H2-generation of the as-fabricated one-dimensional Z-scheme TiO2/WO3/Pt heterostructures (S2) was greatly enhanced compared with pure TiO2 nanofibers (S0) and TiO2/WO3 nanofibers (S1). The enhanced photocatalyst activities were mainly attributed to the solid-state Z-scheme photosynthetic heterojunction system with Pt nanoparticle as an electron collector and WO3 as a hole collector, leading to effective charge separation on these semiconductors, which were evidenced by electrochemical impedance spectroscopy (EIS) and photocurrent analysis.

  5. Efficient Ab-Initio Electron Transport Calculations for Heterostructures by the Nonequilibrium Green’s Function Method

    Directory of Open Access Journals (Sweden)

    Hirokazu Takaki

    2014-01-01

    Full Text Available We present an efficient computation technique for ab-initio electron transport calculations based on density functional theory and the nonequilibrium Green’s function formalism for application to heterostructures with two-dimensional (2D interfaces. The computational load for constructing the Green’s functions, which depends not only on the energy but also on the 2D Bloch wave vector along the interfaces and is thus catastrophically heavy, is circumvented by parallel computational techniques with the message passing interface, which divides the calculations of the Green’s functions with respect to energy and wave vectors. To demonstrate the computational efficiency of the present code, we perform ab-initio electron transport calculations of Al(100-Si(100-Al(100 heterostructures, one of the most typical metal-semiconductor-metal systems, and show their transmission spectra, density of states (DOSs, and dependence on the thickness of the Si layers.

  6. Gate-defined quantum dot devices in undoped Si/SiGe heterostructures for spin qubit applications

    Science.gov (United States)

    Volk, Christian; Martins, Frederico; Marcus, Charles M.; Kuemmeth, Ferdinand

    Spin qubits based on few electron quantum dots in semiconductor heterostructures are among the most promising systems for realizing quantum computation. Due to its low concentration of nuclear-spin-carrying isotopes, silicon is of special interest as a host material. We characterize gate-defined double and triple quantum dot devices fabricated from undoped Si/Si0.7Ge0.3 heterostructures. Our device architecture is based on integrating all accumulation and depletion mode gates in a single gate layer. This allows us to omit the commonly used global accumulation gate in order to achieve a more local control of the potential landscape in the device. We present our recent progress towards implementing spin qubits in these structures. Support through the EC FP7- ICT project SiSPIN no. 323841, and the Danish National Research Foundation is acknowledged.

  7. Features of Formation of Ohmic Contacts and Gate on Epitaxial Heterostructure of AlGaN / GaN High Electron Mobility Transistor

    Directory of Open Access Journals (Sweden)

    I.A. Rogachev

    2016-06-01

    Full Text Available Reported about study of processes of formation of Ti / Al / Ni / Au ohmic contacts to heterostructures AlGaN / GaN and gate Ni / Au. Investigated of process recess the semiconductor layer for minimum resistance of ohmic contact – 0.4 Ohm·mm. Studied influence of encapsulation ohmic contacts on their surface morphology.

  8. Mechanism of the double heterostructure TiO$_2$/ZnO/TiO$_2$ for photocatalytic and photovoltaic applications: A theoretical study

    OpenAIRE

    Haffad, Slimane

    2017-01-01

    Understanding the mechanism of the heterojunction is an important step towards controllable and tunable interfaces for photocatalytic and photovoltaic based devices. To this aim, we propose a thorough study of a double heterostructure system consisting of two semiconductors with large band gap, namely, wurtzite ZnO and anatase TiO$_2$. We demonstrate via first-principle calculations two stable configurations of ZnO/TiO$_2$ interfaces. Our structural study provides a key information on the nat...

  9. Narrow linewidth single-mode semiconductor laser development for coherent detection lidar

    Science.gov (United States)

    Mansour, Kamjou; Ksendzov, Alexander; Menzies, Robert T.; Maker, Paul D.; Muller, Richard E.; Manfra, M. J.; Turner, George W.

    2003-01-01

    High power, tunable, single mode, narrow linewidth semiconductor lasers in the 2.05-(micro)m wavelength region are needed to develop semiconductor laser reference oscillators for optical remote sensing from Earth orbit. 2.05-I1/4m narrow linewidth monolithic distributed feedback (DFB) and distributed Bragg reflector (DBR) with the external grating ridge waveguide lasers fabricated from epitaxially grown InGaAs/InGaAsP/InP and in InGaAsSb/AlGaAsSb/GaSb heterostructures are reported.

  10. Optical sensors of gas on the basis of semiconductor sources of infrared emission

    Directory of Open Access Journals (Sweden)

    Kabatsiy V. N.

    2008-08-01

    Full Text Available Various constructions of optic sensors of gas and gas analyzers on their basis with the use of low-powered semiconductor sources of infrared emission for wave-length of 2,5–5,0 mm made on basis of InGaAs/InAs and InAsSbP/InAs heterostructures are worked out. The experimental results demonstrating the ability of application of semiconductor sources of infrared emission in optic sensors for measuring of metan concentration (CH4 and carbon dioxide (CO2 are given. The availability of use of such sensors in the gas analysis equipment of new generation is shown.

  11. Narrow linewidth single-mode semiconductor laser development for coherent detection lidar

    Science.gov (United States)

    Mansour, Kamjou; Ksendzov, Alexander; Menzies, Robert T.; Maker, Paul D.; Muller, Richard E.; Manfra, M. J.; Turner, George W.

    2003-01-01

    High power, tunable, single mode, narrow linewidth semiconductor lasers in the 2.05-(micro)m wavelength region are needed to develop semiconductor laser reference oscillators for optical remote sensing from Earth orbit. 2.05-I1/4m narrow linewidth monolithic distributed feedback (DFB) and distributed Bragg reflector (DBR) with the external grating ridge waveguide lasers fabricated from epitaxially grown InGaAs/InGaAsP/InP and in InGaAsSb/AlGaAsSb/GaSb heterostructures are reported.

  12. Advanced Semiconductor Devices

    Science.gov (United States)

    Shur, Michael S.; Maki, Paul A.; Kolodzey, James

    2007-06-01

    I. Wide band gap devices. Wide-Bandgap Semiconductor devices for automotive applications / M. Sugimoto ... [et al.]. A GaN on SiC HFET device technology for wireless infrastructure applications / B. Green ... [et al.]. Drift velocity limitation in GaN HEMT channels / A. Matulionis. Simulations of field-plated and recessed gate gallium nitride-based heterojunction field-effect transistors / V. O. Turin, M. S. Shur and D. B. Veksler. Low temperature electroluminescence of green and deep green GaInN/GaN light emitting diodes / Y. Li ... [et al.]. Spatial spectral analysis in high brightness GaInN/GaN light emitting diodes / T. Detchprohm ... [et al.]. Self-induced surface texturing of Al2O3 by means of inductively coupled plasma reactive ion etching in Cl2 chemistry / P. Batoni ... [et al.]. Field and termionic field transport in aluminium gallium arsenide heterojunction barriers / D. V. Morgan and A. Porch. Electrical characteristics and carrier lifetime measurements in high voltage 4H-SiC PiN diodes / P. A. Losee ... [et al.]. Geometry and short channel effects on enhancement-mode n-Channel GaN MOSFETs on p and n- GaN/sapphire substrates / W. Huang, T. Khan and T. P. Chow. 4H-SiC Vertical RESURF Schottky Rectifiers and MOSFETs / Y. Wang, P. A. Losee and T. P. Chow. Present status and future Directions of SiGe HBT technology / M. H. Khater ... [et al.]Optical properties of GaInN/GaN multi-quantum Wells structure and light emitting diode grown by metalorganic chemical vapor phase epitaxy / J. Senawiratne ... [et al.]. Electrical comparison of Ta/Ti/Al/Mo/Au and Ti/Al/Mo/Au Ohmic contacts on undoped GaN HEMTs structure with AlN interlayer / Y. Sun and L. F. Eastman. Above 2 A/mm drain current density of GaN HEMTs grown on sapphire / F. Medjdoub ... [et al.]. Focused thermal beam direct patterning on InGaN during molecular beam epitaxy / X. Chen, W. J. Schaff and L. F. Eastman -- II. Terahertz and millimeter wave devices. Temperature-dependent microwave performance of

  13. One-Dimensional Nanostructures and Devices of II–V Group Semiconductors

    Directory of Open Access Journals (Sweden)

    Shen Guozhen

    2009-01-01

    Full Text Available Abstract The II–V group semiconductors, with narrow band gaps, are important materials with many applications in infrared detectors, lasers, solar cells, ultrasonic multipliers, and Hall generators. Since the first report on trumpet-like Zn3P2nanowires, one-dimensional (1-D nanostructures of II–V group semiconductors have attracted great research attention recently because these special 1-D nanostructures may find applications in fabricating new electronic and optoelectronic nanoscale devices. This article covers the 1-D II–V semiconducting nanostructures that have been synthesized till now, focusing on nanotubes, nanowires, nanobelts, and special nanostructures like heterostructured nanowires. Novel electronic and optoelectronic devices built on 1-D II–V semiconducting nanostructures will also be discussed, which include metal–insulator-semiconductor field-effect transistors, metal-semiconductor field-effect transistors, andp–nheterojunction photodiode. We intent to provide the readers a brief account of these exciting research activities.

  14. Quantum devices using SiGe/Si heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Karunasiri, R.P.G.; Wang, K.L. (Univ. of California, Los Angeles (United States))

    Strained-layer Si{sub 1-x}Ge{sub x}/Si heterostructures have created a great deal of interest due to the potential of integration with the conventional silicon very large scale integrated technology. With the current advances in silicon molecular beam epitaxy (Si-MBE) and other low-temperature epitaxial techniques, many Si{sub 1-x}Ge{sub x}/Si heterojunction devices have been realized. For example, among those realized are avalanche photodiodes, modulation-doped field-effect transistors, heterojunction bipolar transistors, and more recently, resonant tunneling structures, hot-carrier transistors, and quantum well metal-oxide-semiconductor field-effect transistors. In this paper several quantum size effects in strained Si{sub 1-x}Ge{sub x} layers and their potential in device applications will be reviewed. Among those to be discussed are resonant tunneling, miniband transport, and intersubband absorption in Si{sub 1-x}Ge{sub x}/Si superlattice structures, optical properties of monolayer Si{sub m}Ge{sub n} superlattices, and observation of large Stark effect associated with interband transition between quantized states in Si{sub 1-x}Ge{sub x}/Si quantum well structures.

  15. Cu2ZnSnS4-Au heterostructures: Toward green photocatalytic materials active under visible light

    Science.gov (United States)

    Dilsaver, Patrick Steven

    Solar energy is a potentially limitless source of clean power, but needs an effective means of conversion and storage to be feasible. Semiconductor-metal heterostructures have been studied as potential photocatalysts for use in solar-to-chemical energy conversion as a way of converting solar energy. This thesis examines pathways towards the synthesis of Cu2ZnSnS 4-Au, a novel semiconductor-metal heterostructure. Cu2ZnSnS 4 (CZTS) is attractive for use in this area because it has a narrow bandgap (1.5 eV) and is made of relatively earth-abundant and non-toxic elements. There are four methods studied in this thesis for the fabrication of CZTS-Au, two use AuCl3 as a precursor and two utilize pre-formed Au nanoparticles. Both precursors were studied under thermal and photochemical deposition conditions. The resulting products were characterized to determine the most effective pathway to fabricate these heterostructures. AuCl 3 under thermal deposition conditions proved to be the best pathway due to the well-defined monodisperse product. We also studied whether Au metal islands could be effectively removed while leaving the CZTS nanocrystals intact. The results of this experiment were mixed. It does seem that smaller Au nanoparticles are removed, but larger amalgams remain attached to the CZTS nanorods and remain inseparable despite numerous efforts. Finally, CZTS-Au was tested for photocatalytic activity using the model system of methylene blue reduction. CZTS-Au was found to convert methylene blue to leucomethylene blue at a much higher rate than bare CZTS. These results open up a new area of CZTS-metal heterostructures for the purpose of finding greener photocatalysts for solar-to-chemical energy conversion.

  16. Virtual environmental applications for buried waste characterization technology evaluation report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-05-01

    The project, Virtual Environment Applications for Buried Waste Characterization, was initiated in the Buried Waste Integrated Demonstration Program in fiscal year 1994. This project is a research and development effort that supports the remediation of buried waste by identifying and examining the issues, needs, and feasibility of creating virtual environments using available characterization and other data. This document describes the progress and results from this project during the past year.

  17. Controlling Carrier Dynamics using Quantum-Confined Semiconductor Nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Beard, Matthew C.; Klimov, Victor I.

    2016-06-01

    The articles included in this special issue of Chemical Physics explore the use of quantum-confined semiconductor nanocrystals to control the flow of energy and/or charge. Colloidal quantum-confined semiconductor nanostructures are an emerging class of functional materials being developed for novel opto-electronic applications. In the last few years numerous examples in the literature have emerged where novel nanostructures have been tailored such as to achieve a specific function thus moving the field from the stage of discovery of novel behaviors to that of control of nanostructure properties. In addition to the internal structure of the NCs their assemblies can be tailored to achieve emergent properties and add additional control parameters that determine the final opto-electronic properties. These principles are explored via variations in shape, size, surface ligands, heterostructuring, morphology, composition, and assemblies and are demonstrated through measurements of excited state processes, such as Auger recombination; photoluminescence; charge separation and charge transport.

  18. Manipulation of Carrier Density near Ferroelectric/Semiconductor Interfaces

    Science.gov (United States)

    Kesim, Mehmet; Misirlioglu, I. Burc; Mantese, Joseph; Alpay, S. Pamir

    Switchable polarization of a ferroelectric (FE) opens up the opportunity to control the charge density and transport characteristics at the FE/metal and FE/semiconductor (SC) heterointerfaces. Carrier manipulation near such regions can be used in high density non-volatile memories, switchable diodes, and photovoltaic devices. FEs can be utilized as gate oxides in a metal oxide field-effect transistor configuration for non-volatile memory applications with lower gate voltages compared to that of transistors with linear dielectrics. The channel conductance can be modulated reversibly, for instance, by tuning the magnitude and spatial distribution of polarization in the FE. In this study, we show that FE heterostructures can be used to manipulate the conductivity of a FE/SC interface. We employ a non-linear thermodynamic model based on Landau-Ginzburg-Devonshire (LGD) theory to obtain the equilibrium polarization of heterostructures. The carriers along the heterostructures are mapped through coupling the LGD equation with the Maxwell equations and Fermi - Dirac distribution of charged carriers/ionized dopants in the FE and SC. We consider various configurations including FE/SC/paraelectric and FE/SC/FE stacks to investigate the carrier distribution and band bending near such interfaces. The resulting properties are explained through the phase transition characteristics and domain structure of the stacks.

  19. Buried Waste Integrated Demonstration Plan. Revision 1

    Energy Technology Data Exchange (ETDEWEB)

    Kostelnik, K.M.

    1991-12-01

    This document presents the plan of activities for the Buried Waste Integrated Demonstration (BWID) program which supports the environmental restoration (ER) objectives of the Department of Energy (DOE) Complex. Discussed in this plan are the objectives, organization, roles and responsibilities, and the process for implementing and managing BWID. BWID is hosted at the Idaho National Engineering Laboratory (INEL), but involves participants from throughout the DOE Complex, private industry, universities, and the international community. These participants will support, demonstrate, and evaluate a suite of advanced technologies representing a comprehensive remediation system for the effective and efficient remediation of buried waste. The processes for identifying technological needs, screening candidate technologies for applicability and maturity, selecting appropriate technologies for demonstration, field demonstrating, evaluation of results and transferring technologies to environmental restoration programs are also presented. This document further describes the elements of project planning and control that apply to BWID. It addresses the management processes, operating procedures, programmatic and technical objectives, and schedules. Key functions in support of each demonstration such as regulatory coordination, safety analyses, risk evaluations, facility requirements, and data management are presented.

  20. Quantum transport in semiconductor nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Kubis, Tillmann Christoph

    2009-11-15

    several controversially discussed questions on the nature of transport in this type of nanodevices. In contrast to previous approximate approaches, we show that the nature of transport in QCLs is sensitive to the applied bias voltage and can be tuned from the coherent to the incoherent regime. We point out that the elastic scattering at rough interfaces is among the most efficient incoherent scattering mechanisms in THz-QCLs and significantly influences the laser performance. Up to now, this has been utterly underestimated in approximate studies of THz-QCLs with direct optical transitions. All current theoretical models apply periodic (or field-periodic) boundary conditions on the transport in QCLs. Our revision of the open boundary conditions allows us to consider the QCL as an open quantum devices, instead. In this way, we illustrate that charge distributions in QCLs can develop periodicities that are only commensurable or even incommensurable with the QCL periodicity. This effect leads to efficient non-radiative transitions between the laser levels and is - due to the common periodic boundary conditions - completely missed in literature. We also propose several novel THz-QCLs with larger optical gain, lower thermal load and a higher resistivity against growth imperfections. The third part of this thesis is dedicated to the spin transport in two-dimensional semicon- ductor heterostructures. It is common to apply an approximate envelope function model (EFT) for the spin-orbit interaction in such devices, in spite of the well-known fact that EFT calculations typically incorrectly predict the spin-splitting in semiconductor heterostructures. For this reason, we represent the NEGF method in the EFT model as well as in a microscopic atomistic tight binding model. In the later model, the spin-orbit interaction is treated nonperturbatively going far beyond the approximate EFT model. We show that the numerically efficient EFT model yields results that qualitatively agree with

  1. Stabilized thin film heterostructure for electrochemical applications

    DEFF Research Database (Denmark)

    2015-01-01

    The invention provides a method for the formation of a thin film multi-layered heterostructure upon a substrate, said method comprising the steps of: a. providing a substrate; b. depositing a buffer layer upon said substrate, said buffer layer being a layer of stable ionic conductor (B); c. depos...

  2. Surface and buried interfacial structures of epoxy resins used as underfills studied by sum frequency generation vibrational spectroscopy.

    Science.gov (United States)

    Vázquez, Anne V; Holden, Brad; Kristalyn, Cornelius; Fuller, Mike; Wilkerson, Brett; Chen, Zhan

    2011-05-01

    Flip chip technology has greatly improved the performance of semiconductor devices, but relies heavily on the performance of epoxy underfill adhesives. Because epoxy underfills are cured in situ in flip chip semiconductor devices, understanding their surface and interfacial structures is critical for understanding their adhesion to various substrates. Here, sum frequency generation (SFG) vibrational spectroscopy was used to study surface and buried interfacial structures of two model epoxy resins used as underfills in flip chip devices, bisphenol A digylcidyl ether (BADGE) and 1,4-butanediol diglycidyl ether (BDDGE). The surface structures of these epoxies were compared before and after cure, and the orientations of their surface functional groups were deduced to understand how surface structural changes during cure may affect adhesion properties. Further, the effect of moisture exposure, a known cause of adhesion failure, on surface structures was studied. It was found that the BADGE surface significantly restructured upon moisture exposure while the BDDGE surface did not, showing that BADGE adhesives may be more prone to moisture-induced delamination. Lastly, although surface structure can give some insight into adhesion, buried interfacial structures more directly correspond to adhesion properties of polymers. SFG was used to study buried interfaces between deuterated polystyrene (d-PS) and the epoxies before and after moisture exposure. It was shown that moisture exposure acted to disorder the buried interfaces, most likely due to swelling. These results correlated with lap shear adhesion testing showing a decrease in adhesion strength after moisture exposure. The presented work showed that surface and interfacial structures can be correlated to adhesive strength and may be helpful in understanding and designing optimized epoxy underfill adhesives.

  3. Semiconductor Physical Electronics

    CERN Document Server

    Li, Sheng

    2006-01-01

    Semiconductor Physical Electronics, Second Edition, provides comprehensive coverage of fundamental semiconductor physics that is essential to an understanding of the physical and operational principles of a wide variety of semiconductor electronic and optoelectronic devices. This text presents a unified and balanced treatment of the physics, characterization, and applications of semiconductor materials and devices for physicists and material scientists who need further exposure to semiconductor and photonic devices, and for device engineers who need additional background on the underlying physical principles. This updated and revised second edition reflects advances in semicondutor technologies over the past decade, including many new semiconductor devices that have emerged and entered into the marketplace. It is suitable for graduate students in electrical engineering, materials science, physics, and chemical engineering, and as a general reference for processing and device engineers working in the semicondi...

  4. Analysis of timing jitter in external-cavity mode-locked semiconductor lasers

    DEFF Research Database (Denmark)

    Mulet, Josep; Mørk, Jesper

    2006-01-01

    processes, self-phase modulation, and spontaneous emission noise. Fluctuations of the mode-locked pulses are characterized from the fully distributed model using direct integration of noise-skirts in the phase-noise spectrum and the soliton perturbations introduced by Haus. We implement the model in order...... to investigate the performance of a MQW buried heterostructure laser. Results from numerical simulations show that the optimum driving conditions for achieving the shortest pulses with minimum timing jitter occur for large reverse bias in the absorber section at an optimum optical bandwidth limited by Gordon...

  5. Lattice-matched heteroepitaxy of wide gap ternary compound semiconductors

    Science.gov (United States)

    Bachmann, Klaus J.

    1992-01-01

    A variety of applications are identified for heteroepitaxial structures of wide gap I-III-VI2 and II-IV-V2 semiconductors, and are assessed in comparison with ternary III-V alloys and other wide gap materials. Non-linear optical applications of the I-III-VI2 and II-IV-V2 compound heterostructures are discussed, which require the growth of thick epitaxial layers imposing stringent requirements on the conditions of heteroepitaxy. In particular, recent results concerning the MOCVD growth of ZnSi(x)Ge(1-x)P2 alloys lattice-matching Si or GaP substrates are reviewed. Also, heterostructures of Cu(z)Ag(1-z)GaS2 alloys that lattice-match Si, Ge, GaP or GaAs substrates are considered in the context of optoelectronic devices operating in the blue wavelength regime. Since under the conditions of MOCVD, metastable alloys of the II-IV-V2 compounds and group IV elements are realized, II-IV-V2 alloys may also serve as interlayers in the integration of silicon and germanium with exactly lattice-matched tetrahedrally coordinated compound semiconductors, e.g. ZnSi(x)Ge(1-x)P2.

  6. Semiconductor Electrical Measurements Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — The Semiconductor Electrical Measurements Laboratory is a research laboratory which complements the Optical Measurements Laboratory. The laboratory provides for Hall...

  7. Semiconductor bridge (SCB) detonator

    Science.gov (United States)

    Bickes, Jr., Robert W.; Grubelich, Mark C.

    1999-01-01

    The present invention is a low-energy detonator for high-density secondary-explosive materials initiated by a semiconductor bridge igniter that comprises a pair of electrically conductive lands connected by a semiconductor bridge. The semiconductor bridge is in operational or direct contact with the explosive material, whereby current flowing through the semiconductor bridge causes initiation of the explosive material. Header wires connected to the electrically-conductive lands and electrical feed-throughs of the header posts of explosive devices, are substantially coaxial to the direction of current flow through the SCB, i.e., substantially coaxial to the SCB length.

  8. Acoustic imaging of objects buried in soil.

    Science.gov (United States)

    Frazier, C H; Cadalli, N; Munson, D C; O'Brien, W D

    2000-07-01

    In this study, we demonstrate an acoustic system for high-resolution imaging of objects buried in soil. Our goal is to image cultural artifacts in order to assess in a rapid manner the historical significance of a potential construction site. We describe the imaging system and present preliminary images produced from data collected from a soil phantom. A mathematical model and associated computer software are developed in order to simulate the signals acquired by the system. We have built the imaging system, which incorporates a single element source transducer and a receiver array. The source and receiver array are moved together along a linear path to collect data. Using this system, we have obtained B-mode images of several targets by using delay-and-sum beamforming, and we have also applied synthetic aperture theory to this problem.

  9. Landslide Buries Valley of the Geysers

    Science.gov (United States)

    2007-01-01

    Geysers are a rare natural phenomena found only in a few places, such as New Zealand, Iceland, the United States (Yellowstone National Park), and on Russia's far eastern Kamchatka Peninsula. On June 3, 2007, one of these rare geyser fields was severely damaged when a landslide rolled through Russia's Valley of the Geysers. The landslide--a mix of mud, melting snow, trees, and boulders--tore a scar on the land and buried a number of geysers, thermal pools, and waterfalls in the valley. It also blocked the Geyser River, causing a new thermal lake to pool upstream. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite captured this infrared-enhanced image on June 11, 2007, a week after the slide. The image shows the valley, the landslide, and the new thermal lake. Even in mid-June, just days from the start of summer, the landscape is generally covered in snow, though the geologically heated valley is relatively snow free. The tree-covered hills are red (the color of vegetation in this false-color treatment), providing a strong contrast to the aquamarine water and the gray-brown slide. According to the Russian News and Information Agency (RIA) [English language], the slide left a path roughly a kilometer and a half (one mile) long and 200 meters (600 feet) wide. Within hours of the landslide, the water in the new lake inundated a number of additional geysers. The geysers directly buried under the landslide now lie under as much as 60 meters (180 feet) of material, according to RIA reports. It is unlikely that the geysers will be able to force a new opening through this thick layer, adds RIA. Among those directly buried is Pervenets (Firstborn), the first geyser found in the valley, in 1941. Other geysers, such as the Bolshoi (Greater) and Maly (Lesser) Geysers, were silenced when buried by water building up behind the new natural dam. According to Vladimir and Andrei Leonov of the Russian Federation Institute of

  10. Including Arbitrary Antenna Patterns in Microwave Imaging of Buried Objects

    DEFF Research Database (Denmark)

    Meincke, Peter; Kim, Oleksiy S.; Lenler-Eriksen, Hans-Rudolph

    2004-01-01

    A linear inversion scheme for microwave imaging of buried objects is presented in which arbitrary antennas are accounted for through their plane-wave transmitting and receiving spectra......A linear inversion scheme for microwave imaging of buried objects is presented in which arbitrary antennas are accounted for through their plane-wave transmitting and receiving spectra...

  11. A Buried Vertical Filter for Micro and Nanoparticle Filtration

    NARCIS (Netherlands)

    Li, S.J.; Shen, C.; Sarro, P.M.

    2011-01-01

    This paper presents a silicon micromachined filter for micro- and nanoparticles. The filter is vertical and completely buried beneath the surface. The buried aspect allows additional features to be integrated above the filter, while the vertical aspect allows the creation of highly uniform pores and

  12. VIPMOS-A novel buried injector structure for EPROM applications

    NARCIS (Netherlands)

    Wijburg, Rutger C.; Wijburg, R.C.M.; Hemink, Gertjan J.; Hemink, Gertjan; Middelhoek, J.; Middelhoek, Jan; Wallinga, Hans; Mouthaan, A.J.

    1991-01-01

    A buried injector is proposed as a source of electrons for substrate hot electrons injection. To enhance the compatibility with VLSI processing, the buried injector is formed by the local overlap of the n-well and p-well of a retrograde twin-well CMOS process. The injector is activated by means of p

  13. Buried injector logic, a vertical IIL using deep ion implantation

    NARCIS (Netherlands)

    Mouthaan, A.J.

    1987-01-01

    A vertically integrated alternative for integrated injection logic has been realized, named buried injector logic (BIL). 1 MeV ion implantations are used to create buried layers. The vertical pnp and npn transistors have thin base regions and exhibit a limited charge accumulation if a gate is satura

  14. Including Arbitrary Antenna Patterns in Microwave Imaging of Buried Objects

    DEFF Research Database (Denmark)

    Meincke, Peter; Kim, Oleksiy S.; Lenler-Eriksen, Hans-Rudolph

    2004-01-01

    A linear inversion scheme for microwave imaging of buried objects is presented in which arbitrary antennas are accounted for through their plane-wave transmitting and receiving spectra......A linear inversion scheme for microwave imaging of buried objects is presented in which arbitrary antennas are accounted for through their plane-wave transmitting and receiving spectra...

  15. VIPMOS-A novel buried injector structure for EPROM applications

    NARCIS (Netherlands)

    Wijburg, Rutger C.; Hemink, Gertjan J.; Middelhoek, Jan; Wallinga, Hans; Mouthaan, Ton J.

    1991-01-01

    A buried injector is proposed as a source of electrons for substrate hot electrons injection. To enhance the compatibility with VLSI processing, the buried injector is formed by the local overlap of the n-well and p-well of a retrograde twin-well CMOS process. The injector is activated by means of p

  16. Variable Temperature High-Frequency Response of Heterostructure Transistors

    Science.gov (United States)

    Laskar, Joy

    1992-01-01

    The development of high performance heterostructure transistors is essential for emerging opto-electronic integrated circuits (OEICs) and monolithic microwave integrated circuits (MMICs). Applications for OEICs and MMICs include the rapidly growing telecommunications and personal communications markets. The key to successful OEIC and MMIC chip sets is the development of high performance, cost-effective technologies. In this work, several different transistor structures are investigated to determine the potential for high speed performance and the physical mechanisms controlling the ultimate device operation. A cryogenic vacuum microwave measurement system has been developed to study the high speed operation of modulation doped field-effect transistors (MODFETs), doped channel metal insulator field-effect transistors (MISFETs), and metal semiconductor field-effect transistors (MESFETs). This study has concluded that the high field velocity and not the low field mobility is what controls high frequency operation of GaAs based field-effect transistors. Both Al_{rm x} Ga_{rm 1-x}As/GaAs and InP/In_{rm y}Ga _{rm 1-y}As heterostructure bipolar transistors (HBTs) have also been studied at reduced lattice temperatures to understand the role of diffusive transport in the Al_{rm x} Ga_{rm 1-x}As/GaAs HBT and nonequilibrium transport in the InP/In _{rm y}Ga_ {rm 1-y}As HBT. It is shown that drift/diffusion formulation must be modified to accurately estimate the base delay time in the conventional Al _{rm x}Ga_ {rm 1-x}As/GaAs HBT. The reduced lattice temperature operation of the InP/In_ {rm y}Ga_{rm 1-y}As HBT demonstrates extreme nonequilibrium transport in the neutral base and collector space charge region with current gain cut-off frequency exceeding 300 GHz, which is the fastest reported transistor to date. Finally, the MODFET has been investigated as a three-terminal negative differential resistance (NDR) transistor. The existence of real space transfer is confirmed by

  17. Heterostructures based on inorganic and organic van der Waals systems

    Directory of Open Access Journals (Sweden)

    Gwan-Hyoung Lee

    2014-09-01

    Full Text Available The two-dimensional limit of layered materials has recently been realized through the use of van der Waals (vdW heterostructures composed of weakly interacting layers. In this paper, we describe two different classes of vdW heterostructures: inorganic vdW heterostructures prepared by co-lamination and restacking; and organic-inorganic hetero-epitaxy created by physical vapor deposition of organic molecule crystals on an inorganic vdW substrate. Both types of heterostructures exhibit atomically clean vdW interfaces. Employing such vdW heterostructures, we have demonstrated various novel devices, including graphene/hexagonal boron nitride (hBN and MoS2 heterostructures for memory devices; graphene/MoS2/WSe2/graphene vertical p-n junctions for photovoltaic devices, and organic crystals on hBN with graphene electrodes for high-performance transistors.

  18. Design of lateral heterostructure from arsenene and antimonene

    Science.gov (United States)

    Sun, Qilong; Dai, Ying; Ma, Yandong; Yin, Na; Wei, Wei; Yu, Lin; Huang, Baibiao

    2016-09-01

    Lateral heterostructures fabricated by two-dimensional building blocks have opened up exciting realms in material science and device physics. Identifying suitable materials for creating such heterostructures is urgently needed for the next-generation devices. Here, we demonstrate a novel type of seamless lateral heterostructures with excellent stabilities formed within pristine arsenene and antimonene. We find that these heterostructures could possess direct and reduced energy gaps without any modulations. Moreover, the highly coveted type-II alignment and the high carrier mobility are also identified, marking the enhanced quantum efficiency. The tensile strain can result in efficient bandgap engineering. Besides, the proposed critical condition for favored direct energy gaps would have a guiding significance on the subsequent works. Generally, our predictions not only introduce new vitality into lateral heterostructures, enriching available candidate materials in this field, but also highlight the potential of these lateral heterostructures as appealing materials for future devices.

  19. Photodeposition of Pt on Colloidal CdS and CdSe/CdS Semiconductor Nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Dukovic, Gordana; Merkle, Maxwell G.; Nelson, James H.; Hughes, Steven M.; Alivisatos, A. Paul

    2008-08-06

    Semiconductor photocatalysis has been identified as a promising avenue for the conversion of solar energy into environmentally friendly fuels, most notably by the production of hydrogen from water.[1-5] Nanometer-scale materials in particular have attracted considerable scientific attention as the building blocks for light-harvesting applications.[6,7] Their desirable attributes include tunability of the optical properties with size, amenability to relatively inexpensive low-temperature processing, and a high degree of synthetic sophistication leading to increasingly complex and multi-functional architectures. For photocatalysis in particular, the high surface-to-volume ratios in nanoscale materials should lead to an increased availability of carriers for redox reactions on the nanoparticle surface. Recombination of photoexcited carriers directly competes with photocatalytic activity.[3] Charge separation is often achieved with multi-component heterostructures. An early example is the case of TiO2 powders functionalized with Pt and RuO2 particles, where photoexcited electrons are transferred to Pt (the reduction site) and holes to RuO2 (the oxidation site).[8] More recently, many colloidally synthesized nanometer-scale metal-semiconductor heterostructures have been reported.[7,9,10] A majority of these structures are made by thermal methods.[7,10] We have chosen to study photochemical formation of metal-semiconductor heterostructures. The detailed understanding of the mechanisms involved in photodeposition of metals on nanometer-scale semiconductors is necessary to enable a high degree of synthetic control. At the same time, because the results of metal deposition can be directly observed by electron microscopy, it can be used to understand how factors such as nanocrystal composition, shape, carrier dynamics, and surface chemistry influence the photochemical properties of semiconductor nanocrystals. In this communication, we report on the photodeposition of Pt on

  20. A NEW STRUCTURE AND ITS ANALYTICAL BREAKDOWN MODEL OF HIGH VOLTAGE SOI DEVICE WITH STEP UNMOVABLE SURFACE CHARGES OF BURIED OXIDE LAYER

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A new SOI (Silicon On Insulator) high voltage device with Step Unmovable Surface Charges(SUSC) of buried oxide layer and its analytical breakdown model are proposed in the paper. The unmovable charges are implemented into the upper surface of buried oxide layer to increase the vertical electric field and uniform the lateral one. The 2-D Poisson's equation is solved to demonstrate the modulation effect of the immobile interface charges and analyze the electric field and breakdown voltage with the various geometric parameters and step numbers. A new RESURF (REduce SURface Field) condition of the SOI device considering the interface charges and buried oxide is derived to maximize breakdown voltage. The analytical results are in good agreement with the numerical analysis obtained by the 2-D semiconductor devices simulator MEDICI. As a result, an 1200V breakdown voltage is firstly obtained in 3μm-thick top Si layer, 2μm-thick buried oxide layer and 70μm-length drift region using a linear doping profile of unmovable buried oxide charges.

  1. Pulsed terahertz emission from GaN/InN heterostructure

    Science.gov (United States)

    Reklaitis, Antanas

    2011-11-01

    Dynamics of the electron-hole plasma excited by the femtosecond optical pulse in wurtzite GaN/InN heterostructure is investigated by Monte Carlo simulations. The GaN/InN heterostructure for pulsed terahertz emission is suggested. The results of Monte Carlo simulations show that the power of terahertz emission from the GaN/InN heterostructure exceeds the power of terahertz emission from the surface of InN by one order of magnitude.

  2. Semiconductors data handbook

    CERN Document Server

    Madelung, Otfried

    2004-01-01

    This volume Semiconductors: Data Handbook contains frequently used data from the corresponding larger Landolt-Börnstein handbooks in a low price book for the individual scientist working in the laboratory. The Handbook contain important information about a large number of semiconductors

  3. Applications of Semiconductor Lasers

    Institute of Scientific and Technical Information of China (English)

    LI Te; SUN Yan-fang; NING Yong-qiang; WANG Li-jun

    2005-01-01

    An overview of the applications of semiconductor lasers is presented. Diode lasers are widely used today,and the most prevalent use of the laser is probably in CD and DVD drives for computers and audio/video media systems. Semiconductor lasers are also used in many other fields ranging from optical fiber communications to display,medicine and pumping sources.

  4. Semiconductor Research Experimental Techniques

    CERN Document Server

    Balkan, Naci

    2012-01-01

    The book describes the fundamentals, latest developments and use of key experimental techniques for semiconductor research. It explains the application potential of various analytical methods and discusses the opportunities to apply particular analytical techniques to study novel semiconductor compounds, such as dilute nitride alloys. The emphasis is on the technique rather than on the particular system studied.

  5. Semiconductor radiation detection systems

    CERN Document Server

    2010-01-01

    Covers research in semiconductor detector and integrated circuit design in the context of medical imaging using ionizing radiation. This book explores other applications of semiconductor radiation detection systems in security applications such as luggage scanning, dirty bomb detection and border control.

  6. Photonic crystal heterostructures from self-assembled opals

    Science.gov (United States)

    Khokhar, Ali Z.; Rahman, Faiz; Johnson, Nigel P.

    2011-02-01

    This paper describes the fabrication of opal-based photonic crystal heterostructures. These heterostructures were created by using multilayer deposition of silica and polystyrene spheres. The fabricated structures involved both different lattice constants and different dielectric constants. Single and double heterostructures working in the visible region were fabricated by using techniques described here. The optical properties of these heterostructures were investigated experimentally and showed the superposition of the properties of each individual crystal region as well as optical signatures due to inter-layer defects.

  7. Quantum transport in semiconductor nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Kubis, Tillmann Christoph

    2009-11-15

    several controversially discussed questions on the nature of transport in this type of nanodevices. In contrast to previous approximate approaches, we show that the nature of transport in QCLs is sensitive to the applied bias voltage and can be tuned from the coherent to the incoherent regime. We point out that the elastic scattering at rough interfaces is among the most efficient incoherent scattering mechanisms in THz-QCLs and significantly influences the laser performance. Up to now, this has been utterly underestimated in approximate studies of THz-QCLs with direct optical transitions. All current theoretical models apply periodic (or field-periodic) boundary conditions on the transport in QCLs. Our revision of the open boundary conditions allows us to consider the QCL as an open quantum devices, instead. In this way, we illustrate that charge distributions in QCLs can develop periodicities that are only commensurable or even incommensurable with the QCL periodicity. This effect leads to efficient non-radiative transitions between the laser levels and is - due to the common periodic boundary conditions - completely missed in literature. We also propose several novel THz-QCLs with larger optical gain, lower thermal load and a higher resistivity against growth imperfections. The third part of this thesis is dedicated to the spin transport in two-dimensional semicon- ductor heterostructures. It is common to apply an approximate envelope function model (EFT) for the spin-orbit interaction in such devices, in spite of the well-known fact that EFT calculations typically incorrectly predict the spin-splitting in semiconductor heterostructures. For this reason, we represent the NEGF method in the EFT model as well as in a microscopic atomistic tight binding model. In the later model, the spin-orbit interaction is treated nonperturbatively going far beyond the approximate EFT model. We show that the numerically efficient EFT model yields results that qualitatively agree with

  8. Physical mechanism of surface roughening of the radial Ge-core/Si-shell nanowire heterostructure and thermodynamic prediction of surface stability of the InAs-core/GaAs-shell nanowire structure.

    Science.gov (United States)

    Cao, Y Y; Ouyang, G; Wang, C X; Yang, G W

    2013-02-13

    As a promising and typical semiconductor heterostructure at the nanoscale, the radial Ge/Si NW heterostructure, that is, the Ge-core/Si-shell NW structure, has been widely investigated and used in various nanodevices such as solar cells, lasers, and sensors because of the strong changes in the band structure and increased charge carrier mobility. Therefore, to attain high quality radial semiconductor NW heterostructures, controllable and stable epitaxial growth of core-shell NW structures has become a major challenge for both experimental and theoretical evaluation. Surface roughening is usually undesirable for the epitaxial growth of high quality radial semiconductor NW heterostructures, because it would destroy the core-shell NW structures. For example, the surface of the Ge-core/Si-shell NWs always exhibits a periodic modulation with island-like morphologies, that is, surface roughening, during epitaxial growth. Therefore, the physical understanding of the surface roughening behavior during the epitaxial growth of core-shell NW structures is essential and urgent for theoretical design and experimentally controlling the growth of high quality radial semiconductor NW heterostructures. Here, we proposed a quantitative thermodynamic theory to address the physical process of epitaxial growth of core-shell NW structures and surface roughening. We showed that the transformation from the Frank-van der Merwe mode to the Stranski-Krastanow mode during the epitaxial growth of radial semiconductor NW heterostructures is the physical origin of surface roughening. We deduced the thermodynamic criterion for the formation of the surface roughening and the phase diagram of growth and showed that the radius of the NWs and the thickness of the shell layer can not only determine the formation of the surface roughening in a core-shell NW structure, but also control the periodicity and amplitude of the surface roughness. The agreement between the theoretical results and the

  9. Compound Semiconductor Radiation Detectors

    CERN Document Server

    Owens, Alan

    2012-01-01

    Although elemental semiconductors such as silicon and germanium are standard for energy dispersive spectroscopy in the laboratory, their use for an increasing range of applications is becoming marginalized by their physical limitations, namely the need for ancillary cooling, their modest stopping powers, and radiation intolerance. Compound semiconductors, on the other hand, encompass such a wide range of physical and electronic properties that they have become viable competitors in a number of applications. Compound Semiconductor Radiation Detectors is a consolidated source of information on all aspects of the use of compound semiconductors for radiation detection and measurement. Serious Competitors to Germanium and Silicon Radiation Detectors Wide-gap compound semiconductors offer the ability to operate in a range of hostile thermal and radiation environments while still maintaining sub-keV spectral resolution at X-ray wavelengths. Narrow-gap materials offer the potential of exceeding the spectral resolutio...

  10. Designing heterostructures -- a route towards new superconductors

    Science.gov (United States)

    Kopp, Thilo

    2013-03-01

    By now it has become technologically feasible to grow controllably transition metal oxides layer by layer. In effect, the achieved progress allows to design heterostructures with optimized electronic properties. The talk will specifically address scenarios for interface superconductivity and the possibility to raise the transition temperature of bulk superconductors by layer design. Heterostructures offer a complexity beyond that of bulk materials. The nature of the superconducting states formed in layered materials and at interfaces is a fascinating topic of recent research which will be in the focus of this presentation. This work was supported by the DFG (TRR 80). I thankfully acknowledge the collaboration with Natalia Pavlenko, Peter Hirschfeld, Cyril Stephanos, Florian Loder, Arno Kampf, and Jochen Mannhart.

  11. Graphene nano-heterostructures for quantum devices

    Directory of Open Access Journals (Sweden)

    D. Bischoff

    2016-09-01

    Full Text Available Ten years ago, the exfoliation of graphene started the field of layered two-dimensional materials. Today, there is a huge variety of two-dimensional materials available for both research and applications. The different dimensionality compared to their bulk relatives is responsible for a wealth of novel properties of these layered two-dimensional materials. The true strength of two-dimensional materials is however the possibility to stack different layers on top of each other to engineer new heterostructures with specifically tailored properties. Known as van-der-Waals heterostructures, they enable the experimental observation of a variety of new phenomena. By patterning the individual layers laterally into nanostructures, additional functionality can be added to the devices. This review provides a glimpse at the future opportunities offered by van-der-Waals stacked nanodevices.

  12. Thermal response in van der Waals heterostructures

    Science.gov (United States)

    Naidu Gandi, Appala; Alshareef, Husam N.; Schwingenschlögl, Udo

    2017-01-01

    We solve numerically the Boltzmann transport equations of the phonons and electrons to understand the thermoelectric response in heterostructures of M2CO2 (M: Ti, Zr, Hf) MXenes with transition metal dichalcogenide monolayers. Low frequency optical phonons are found to occur as a consequence of the van der Waals bonding, contribute significantly to the thermal transport, and compensate for the reduced contributions of the acoustic phonons (increased scattering cross-sections in heterostructures), such that the thermal conductivities turn out to be similar to those of the bare MXenes. Our results indicate that the important superlattice design approach of thermoelectrics (to reduce the thermal conductivity) may be effective for two-dimensional van der Waals materials when used in conjunction with intercalation.

  13. Electron mobility in modulation-doped heterostructures

    Science.gov (United States)

    Walukiewicz, W.; Ruda, H. E.; Lagowski, J.; Gatos, H. C.

    1984-01-01

    A model for electron mobility in a two-dimensional electron gas confined in a triangular well was developed. All major scattering processes (deformation potential and piezoelectric acoustic, polar optical, ionized impurity, and alloy disorder) were included, as well as intrasubband and intersubband scattering. The model is applied to two types of modulation-doped heterostructures, namely GaAs-GaAlAs and In(0.53)Ga(0.47)As-Al(0.52)In(0.48)As. In the former case, phonons and remote ionized impurities ultimately limit the mobility, whereas in the latter, alloy disorder is a predominant scattering process at low temperatures. The calculated mobilities are in very good agreement with recently reported experimental characteristics for both GaAs-Ga(1-x)Al(x)As and In(0.53)Ga(0.47)As-Al(0.52)In(0.48)As modulation-doped heterostructures.

  14. Low energy consumption spintronics using multiferroic heterostructures.

    Science.gov (United States)

    Trassin, Morgan

    2016-01-27

    We review the recent progress in the field of multiferroic magnetoelectric heterostructures. The lack of single phase multiferroic candidates exhibiting simultaneously strong and coupled magnetic and ferroelectric orders led to an increased effort into the development of artificial multiferroic heterostructures in which these orders are combined by assembling different materials. The magnetoelectric coupling emerging from the created interface between the ferroelectric and ferromagnetic layers can result in electrically tunable magnetic transition temperature, magnetic anisotropy or magnetization reversal. The full potential of low energy consumption magnetic based devices for spintronics lies in our understanding of the magnetoelectric coupling at the scale of the ferroic domains. Although the thin film synthesis progresses resulted into the complete control of ferroic domain ordering using epitaxial strain, the local observation of magnetoelectric coupling remains challenging. The ability to imprint ferroelectric domains into ferromagnets and to manipulate those solely using electric fields suggests new technological advances for spintronics such as magnetoelectric memories or memristors.

  15. Thermal response in van der Waals heterostructures

    KAUST Repository

    Gandi, Appala

    2016-11-21

    We solve numerically the Boltzmann transport equations of the phonons and electrons to understand the thermoelectric response in heterostructures of M2CO2 (M: Ti, Zr, Hf) MXenes with transition metal dichalcogenide monolayers. Low frequency optical phonons are found to occur as a consequence of the van der Waals bonding, contribute significantly to the thermal transport, and compensate for the reduced contributions of the acoustic phonons (increased scattering cross-sections in heterostructures), such that the thermal conductivities turn out to be similar to those of the bare MXenes. Our results indicate that the important superlattice design approach of thermoelectrics (to reduce the thermal conductivity) may be effective for two-dimensional van der Waals materials when used in conjunction with intercalation. © 2016 IOP Publishing Ltd.

  16. Voltage control of magnetism in multiferroic heterostructures

    OpenAIRE

    LIU, MING; Sun, Nian X.

    2014-01-01

    Electrical tuning of magnetism is of great fundamental and technical importance for fast, compact and ultra-low power electronic devices. Multiferroics, simultaneously exhibiting ferroelectricity and ferromagnetism, have attracted much interest owing to the capability of controlling magnetism by an electric field through magnetoelectric (ME) coupling. In particular, strong strain-mediated ME interaction observed in layered multiferroic heterostructures makes it practically possible for realiz...

  17. Graphene-Boron Nitride Heterostructure Based Optoelectronic Devices for On-Chip Optical Interconnects

    Science.gov (United States)

    Gao, Yuanda

    Graphene has emerged as an appealing material for a variety of optoelectronic applications due to its unique electrical and optical characteristics. In this thesis, I will present recent advances in integrating graphene and graphene-boron nitride (BN) heterostructures with confined optical architectures, e.g. planar photonic crystal (PPC) nanocavities and silicon channel waveguides, to make this otherwise weakly absorbing material optically opaque. Based on these integrations, I will further demonstrate the resulting chip-integrated optoelectronic devices for optical interconnects. After transferring a layer of graphene onto PPC nanocavities, spectral selectivity at the resonance frequency and orders-of-magnitude enhancement of optical coupling with graphene have been observed in infrared spectrum. By applying electrostatic potential to graphene, electro-optic modulation of the cavity reflection is possible with contrast in excess of 10 dB. And furthermore, a novel and complex modulator device structure based on the cavity-coupled and BN-encapsulated dual-layer graphene capacitor is demonstrated to operate at a speed of 1.2 GHz. On the other hand, an enhanced broad-spectrum light-graphene interaction coupled with silicon channel waveguides is also demonstrated with ?0.1 dB/?m transmission attenuation due to graphene absorption. A waveguide-integrated graphene photodetector is fabricated and shown 0.1 A/W photoresponsivity and 20 GHz operation speed. An improved version of a similar photodetector using graphene-BN heterostructure exhibits 0.36 A/W photoresponsivity and 42 GHz response speed. The integration of graphene and graphene-BN heterostructures with nanophotonic architectures promises a new generation of compact, energy-efficient, high-speed optoelectronic device concepts for on-chip optical communications that are not yet feasible or very difficult to realize using traditional bulk semiconductors.

  18. Graphene diamond-like carbon films heterostructure

    Science.gov (United States)

    Zhao, Fang; Afandi, Abdulkareem; Jackman, Richard B.

    2015-03-01

    A limitation to the potential use of graphene as an electronic material is the lack of control over the 2D materials properties once it is deposited on a supporting substrate. Here, the use of Diamond-like Carbon (DLC) interlayers between the substrate and the graphene is shown to offer the prospect of overcoming this problem. The DLC films used here, more properly known as a-C:H with ˜25% hydrogen content, have been terminated with N or F moieties prior to graphene deposition. It is found that nitrogen terminations lead to an optical band gap shrinkage in the DLC, whilst fluorine groups reduce the DLC's surface energy. CVD monolayer graphene subsequently transferred to DLC, N terminated DLC, and F terminated DLC has then been studied with AFM, Raman and XPS analysis, and correlated with Hall effect measurements that give an insight into the heterostructures electrical properties. The results show that different terminations strongly affect the electronic properties of the graphene heterostructures. G-F-DLC samples were p-type and displayed considerably higher mobility than the other heterostructures, whilst G-N-DLC samples supported higher carrier densities, being almost metallic in character. Since it would be possible to locally pattern the distribution of these differing surface terminations, this work offers the prospect for 2D lateral control of the electronic properties of graphene layers for device applications.

  19. Voltage control of magnetism in multiferroic heterostructures.

    Science.gov (United States)

    Liu, Ming; Sun, Nian X

    2014-02-28

    Electrical tuning of magnetism is of great fundamental and technical importance for fast, compact and ultra-low power electronic devices. Multiferroics, simultaneously exhibiting ferroelectricity and ferromagnetism, have attracted much interest owing to the capability of controlling magnetism by an electric field through magnetoelectric (ME) coupling. In particular, strong strain-mediated ME interaction observed in layered multiferroic heterostructures makes it practically possible for realizing electrically reconfigurable microwave devices, ultra-low power electronics and magnetoelectric random access memories (MERAMs). In this review, we demonstrate this remarkable E-field manipulation of magnetism in various multiferroic composite systems, aiming at the creation of novel compact, lightweight, energy-efficient and tunable electronic and microwave devices. First of all, tunable microwave devices are demonstrated based on ferrite/ferroelectric and magnetic-metal/ferroelectric composites, showing giant ferromagnetic resonance (FMR) tunability with narrow FMR linewidth. Then, E-field manipulation of magnetoresistance in multiferroic anisotropic magnetoresistance and giant magnetoresistance devices for achieving low-power electronic devices is discussed. Finally, E-field control of exchange-bias and deterministic magnetization switching is demonstrated in exchange-coupled antiferromagnetic/ferromagnetic/ferroelectric multiferroic hetero-structures at room temperature, indicating an important step towards MERAMs. In addition, recent progress in electrically non-volatile tuning of magnetic states is also presented. These tunable multiferroic heterostructures and devices provide great opportunities for next-generation reconfigurable radio frequency/microwave communication systems and radars, spintronics, sensors and memories.

  20. Magnetoelectric Heterostructures for Spintronics and Magnetic Sensing

    Science.gov (United States)

    Nan, Tianxiang

    Magnetoelectric heterostructures with coupled magnetization and electric polarization across their interfaces enable significantly improvement of performance of many devices such as magnetic sensors, microwave magnetic devices, and spintronics. I will first show that by utilizing a unique ferroelastic polarization switching pathway, one can achieve non-volatile electric-field-switching of magnetism in multiferroic heterostructures with different ferroelectric single crystals through a strain-mediated magnetoelectric coupling. In the same system, with atomically-thin ferromagnets, the interfacial charge-mediated should also be taken into account. The charge- and strain-mediated coupling mechanisms are demonstrated and precisely quantified by the electric-field-tuning of ferromagnetic resonance. With the same technique, magnetic relaxation including intrinsic and extrinsic damping has also been shown to be strongly correlated to the strain, which is attributed to the electric-field-modification of spin-orbit coupling. Moreover, I will also show the tuning of spin-orbit torques from the spin-Hall effect with applied voltage probed with spin-torque ferromagnetic resonance and show the possible application on voltage tunable spin-Hall nano-oscillators. In the second part of my thesis, I will show an ultra-miniaturized magnetoelectric nano-electromechanical system (NEMS) resonator based on an AlN/FeGaB magnetoelectric heterostructure for detecting wide band magnetic fields. With the high Quality factor and the ultra-high resonance frequency, a low DC magnetic field detection limit of 300 pT has been demonstrated.

  1. Graphene diamond-like carbon films heterostructure

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Fang; Afandi, Abdulkareem; Jackman, Richard B., E-mail: r.jackman@ucl.ac.uk [London Centre for Nanotechnology, Electronic and Electrical Engineering Department, University College London, 17-19 Gordon Street, London WC1H 0AH (United Kingdom)

    2015-03-09

    A limitation to the potential use of graphene as an electronic material is the lack of control over the 2D materials properties once it is deposited on a supporting substrate. Here, the use of Diamond-like Carbon (DLC) interlayers between the substrate and the graphene is shown to offer the prospect of overcoming this problem. The DLC films used here, more properly known as a-C:H with ∼25% hydrogen content, have been terminated with N or F moieties prior to graphene deposition. It is found that nitrogen terminations lead to an optical band gap shrinkage in the DLC, whilst fluorine groups reduce the DLC's surface energy. CVD monolayer graphene subsequently transferred to DLC, N terminated DLC, and F terminated DLC has then been studied with AFM, Raman and XPS analysis, and correlated with Hall effect measurements that give an insight into the heterostructures electrical properties. The results show that different terminations strongly affect the electronic properties of the graphene heterostructures. G-F-DLC samples were p-type and displayed considerably higher mobility than the other heterostructures, whilst G-N-DLC samples supported higher carrier densities, being almost metallic in character. Since it would be possible to locally pattern the distribution of these differing surface terminations, this work offers the prospect for 2D lateral control of the electronic properties of graphene layers for device applications.

  2. Voltage control of magnetism in multiferroic heterostructures

    Science.gov (United States)

    Liu, Ming; Sun, Nian X.

    2014-01-01

    Electrical tuning of magnetism is of great fundamental and technical importance for fast, compact and ultra-low power electronic devices. Multiferroics, simultaneously exhibiting ferroelectricity and ferromagnetism, have attracted much interest owing to the capability of controlling magnetism by an electric field through magnetoelectric (ME) coupling. In particular, strong strain-mediated ME interaction observed in layered multiferroic heterostructures makes it practically possible for realizing electrically reconfigurable microwave devices, ultra-low power electronics and magnetoelectric random access memories (MERAMs). In this review, we demonstrate this remarkable E-field manipulation of magnetism in various multiferroic composite systems, aiming at the creation of novel compact, lightweight, energy-efficient and tunable electronic and microwave devices. First of all, tunable microwave devices are demonstrated based on ferrite/ferroelectric and magnetic-metal/ferroelectric composites, showing giant ferromagnetic resonance (FMR) tunability with narrow FMR linewidth. Then, E-field manipulation of magnetoresistance in multiferroic anisotropic magnetoresistance and giant magnetoresistance devices for achieving low-power electronic devices is discussed. Finally, E-field control of exchange-bias and deterministic magnetization switching is demonstrated in exchange-coupled antiferromagnetic/ferromagnetic/ferroelectric multiferroic hetero-structures at room temperature, indicating an important step towards MERAMs. In addition, recent progress in electrically non-volatile tuning of magnetic states is also presented. These tunable multiferroic heterostructures and devices provide great opportunities for next-generation reconfigurable radio frequency/microwave communication systems and radars, spintronics, sensors and memories. PMID:24421373

  3. Exotic topological insulator states and topological phase transitions in Sb2Se3-Bi2Se3 heterostructures

    KAUST Repository

    Zhang, Qianfan

    2012-03-27

    Topological insulator is a new state of matter attracting tremendous interest due to its gapless linear dispersion and spin momentum locking topological states located near the surface. Heterostructures, which have traditionally been powerful in controlling the electronic properties of semiconductor devices, are interesting for topological insulators. Here, we studied the spatial distribution of the topological state in Sb 2Se 3-Bi 2Se 3 heterostructures by first-principle simulation and discovered that an exotic topological state exists. Surprisingly, the state migrates from the nontrivial Bi 2Se 3 into the trivial Sb 2Se 3 region and spreads across the entire Sb 2Se 3 slab, extending beyond the concept of "surface" state while preserving all of the topological surface state characteristics. This unusual topological state arises from the coupling between different materials and the modification of electronic structure near Fermi energy. Our study demonstrates that heterostructures can open up opportunities for controlling the real-space distribution of the topological state and inducing quantum phase transitions between topologically trivial and nontrivial states. © 2012 American Chemical Society.

  4. Compact Buried Ducts in a Hot-Humid Climate House

    Energy Technology Data Exchange (ETDEWEB)

    Mallay, Dave [Home Innovation Research Labs, Upper Marlboro, MD (United States)

    2016-01-07

    "9A system of compact, buried ducts provides a high-performance and cost-effective solution for delivering conditioned air throughout the building. This report outlines research activities that are expected to facilitate adoption of compact buried duct systems by builders. The results of this research would be scalable to many new house designs in most climates and markets, leading to wider industry acceptance and building code and energy program approval. The primary research question with buried ducts is potential condensation at the outer jacket of the duct insulation in humid climates during the cooling season. Current best practices for buried ducts rely on encapsulating the insulated ducts with closed-cell spray polyurethane foam insulation to control condensation and improve air sealing. The encapsulated buried duct concept has been analyzed and shown to be effective in hot-humid climates. The purpose of this project is to develop an alternative buried duct system that performs effectively as ducts in conditioned space - durable, energy efficient, and cost-effective - in a hot-humid climate (IECC warm-humid climate zone 3A) with three goals that distinguish this project: 1) Evaluation of design criteria for buried ducts that use common materials and do not rely on encapsulation using spray foam or disrupt traditional work sequences; 2) Establishing design criteria for compact ducts and incorporate those with the buried duct criteria to further reduce energy losses and control installed costs; 3) Developing HVAC design guidance for performing accurate heating and cooling load calculations for compact buried ducts.

  5. Step-Tapered Active-Region Mid-Infrared Quantum Cascade Lasers and Novel Fabrication Processes for Buried Heterostructures

    Science.gov (United States)

    2015-07-28

    83 shorter cavity length (~ 1.5 mm) and narrower width (≤ 10 m) were fabricated, and mounted epi-side down on the copper heatsink, with high...mounted QCLs at a longer wavelength (= 9.3 m). Furthermore, by mounting the device junction-down on the copper heatsink, shorter devices (1.5 mm...a fundamental hexagonal symmetry, a high pillar density of ~ 1011/cm2, and a uniform size of ~24 nm in diameter or smaller over an entire employed

  6. Monolithic integration of GaAs/GaAlAs buried-heterostructure orthogonal facet laser and optical waveguide

    Energy Technology Data Exchange (ETDEWEB)

    Ribot, H.; Sansonetti, P.; Brandon, J.; Carre, M.; Menigaux, L.; Azoulay, R.; Bouadma, N.

    1989-02-06

    Monolithic integration of a quarter-circle laser evanescently coupled to an optical waveguide located below the active layer is demonstrated on GaAs. The curved resonator consists of a 45-..mu..m-long straight part and a quarter circle with a curvature radius of 150 ..mu..m. The component exhibits a threshold current of 50 mA in a pulsed regime. A 10 mW emission is measured from a 415-..mu..m-long tangential straight waveguide for an injection current of 140 mA.

  7. Microstructural evolution of a recrystallized Fe-implanted InGaAsP/InP heterostructure

    Energy Technology Data Exchange (ETDEWEB)

    Fekecs, Andre; Ilahi, Bouraoui [Institut Interdisciplinaire d' Innovation Technologique (3IT), and Laboratoire Nanotechnologies Nanosystemes (LN2)-CNRS UMI-3463, Universite de Sherbrooke, QC (Canada); Korinek, Andreas [Department of Materials Science and Engineering, and Canadian Centre for Electron Microscopy, McMaster University, Hamilton, ON (Canada); Chicoine, Martin; Schiettekatte, Francois [Departement de Physique, Universite de Montreal, Succursale Centre-Ville, Montreal, QC (Canada); Regroupement Quebecois sur les Materiaux de Pointe (RQMP), QC (Canada); Morris, Denis; Ares, Richard [Institut Interdisciplinaire d' Innovation Technologique (3IT), and Laboratoire Nanotechnologies Nanosystemes (LN2)-CNRS UMI-3463, Universite de Sherbrooke, QC (Canada); Regroupement Quebecois sur les Materiaux de Pointe (RQMP), QC (Canada)

    2015-09-15

    Through the recrystallization of an amorphous heterostructure, obtained by MeV Fe ion implantation, we are able to tailor a standard epitaxial semiconductor material, a small gap InGaAsP/InP alloy, for photoconductive terahertz optoelectronics. Here, we report on microstructural changes occurring in the material over a broad range of rapid thermal annealing temperatures, using X-ray diffraction line profile analysis and transmission electron microscopy. Results show a complete amorphous transition of the heterostructure after multiple-energy implantations done at 83 K. Upon thermal annealing, multiple structural layers develop via solid phase epitaxy and solid phase recrystallization. The photoconductive InGaAsP layer becomes polycrystalline and submicron grained, with high crystalline volume fraction and apparent (110) texture. Many grains are elongated and internally faulted, with high densities of planar faults occurring on closed-packed (111) planes. The X-ray diffraction line broadening is anisotropic and evolves with rapid thermal annealing temperatures. At 500 °C, the X-ray coherent domain size estimate of 10 nm is aligned reasonably with electron microscopy made in faulted areas. Above 500 °C, a significant decrease of the planar fault density is detected. We discuss the influence of these microstructural changes happening with recrystallization temperatures on the ultrafast photoconductive response of Fe-implanted InGaAsP/InP. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Vertical field effect tunneling transistor based on graphene-ultrathin Si nanomembrane heterostructures

    Science.gov (United States)

    Das, Tanmoy; Jang, Houk; Bok Lee, Jae; Chu, Hyunwoo; Kim, Seong Dae; Ahn, Jong-Hyun

    2015-12-01

    Graphene-based heterostructured vertical transistors have attracted a great deal of research interest. Herein we propose a Si-based technology platform for creating graphene/ultrathin semiconductor/metal (GSM) junctions, which can be applied to large-scale and low-power electronics compatible with a variety of substrates. We fabricated graphene/Si nanomembrane (NM)/metal vertical heterostructures by using a dry transfer technique to transfer Si NMs onto chemical vapor deposition-grown graphene layers. The resulting van der Waals interfaces between graphene and p-Si NMs exhibited nearly ideal Schottky barrier behavior. Due to the low density of states of graphene, the graphene/Si NM Schottky barrier height can be modulated by modulating the band profile in the channel region, yielding well-defined current modulation. We obtained a maximum current on/off ratio (Ion/Ioff) of up to ˜103, with a current density of 102 A cm-2. We also observed significant dependence of Schottky barrier height Δφb on the thickness of the Si NMs. We confirmed that the transport in these devices is dominated by the effects of the graphene/Si NM Schottky barrier.

  9. Optical response of confined excitons in GaInAsSb/GaSb Quantum Dots heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez-Cano, R [Departamento de Fisica, Universidad Autonoma de Occidente, A.A. 2790, Cali (Colombia); Tirado-Mejia, L; Fonthal, G; Ariza-Calderon, H [Laboratorio de Optoelectronica, Universidad del Quindio, A.A. 4603 Armenia (Colombia); Porras-Montenegro, N, E-mail: rsanchez40@gmail.co [Departamento de Fisica, Universidad del Valle, A.A. 25360, Cali (Colombia)

    2009-05-01

    The narrow-gap Ga{sub 1-x}In{sub x}As{sub y}Sb{sub 1-y} compounds are suitable materials for heterostructure devices operating in the infrared wavelength range. In these compounds grown by liquid phase epitaxy over GaSb single crystals, for x and y values in the range of 0.10 to 0.14 for both variables, the photoluminescence optical response at 12K is blue-shifted by 20 meV related to the photoreflectance response. We believe this behavior is due to possible higher electronic confinement in some places of the heterostructure, possibly formed in the interface during the growth process. In order to explain this behavior, in this work we study the exciton recombination energy in spherical Quantum Dots (QDs) on Ga{sub 1-x}In{sub x}As{sub y}Sb{sub 1-y}/GaSb, using the variational procedure within the effective-mass approximation and considering an electron in a Type I band alignment formed by two semiconductors with similar parabolic conduction bands. Our results are in good agreement with recent experimental results.

  10. Fabrication and Photocatalytic Activity of Ag3PO4-TiO2 Heterostructural Nanotube Arrays

    Institute of Scientific and Technical Information of China (English)

    MO Yanping; CHEN Feng; YANG Yunyun; SONG Jia; XU Qiong; XU Ying

    2016-01-01

    To extend the absorption capability of TiO2 into visible light region and inhibit the recombination of photogenerated electrons and holes, we put forward an effective strategy of the coupling of TiO2 with a suitable semiconductor that possesses a narrow band gap. Meanwhile, Ag3PO4-TiO2 heterostructural nanotube arrays were prepared by the two-step anodic oxidation to obtain the TiO2 nanotube arrays and then by a deposition-precipitation method to load Ag3PO4. The samples were characterized by ifeld emission scanning electron microscopy (FESEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD), and UV-vis diffuse relfectance spectroscopy (UV-vis DRS). The experimental results showed that Ag3PO4nanoparticles were uniformly dispersed on the highly ordered TiO2 nanotube arrays, which increased the visible-light absorption of TiO2 photocatalyst. The photocurrent density and photocatalytic degradation of methyl orange indicated that the performance of Ag3PO4-TiO2 heterostructural nanotube arrays was better than that of the TiO2 nanotube arrays, which could be attributed to the effective electron-hole separation and the improved utilization of visible light.

  11. Polarization-dependent interfacial coupling modulation of ferroelectric photovoltaic effect in PZT-ZnO heterostructures.

    Science.gov (United States)

    Pan, Dan-Feng; Bi, Gui-Feng; Chen, Guang-Yi; Zhang, Hao; Liu, Jun-Ming; Wang, Guang-Hou; Wan, Jian-Guo

    2016-03-08

    Recently, ferroelectric perovskite oxides have drawn much attention due to potential applications in the field of solar energy conversion. However, the power conversion efficiency of ferroelectric photovoltaic effect currently reported is far below the expectable value. One of the crucial problems lies in the two back-to-back Schottky barriers, which are formed at the ferroelectric-electrode interfaces and blocking most of photo-generated carriers to reach the outside circuit. Herein, we develop a new approach to enhance the ferroelectric photovoltaic effect by introducing the polarization-dependent interfacial coupling effect. Through inserting a semiconductor ZnO layer with spontaneous polarization into the ferroelectric ITO/PZT/Au film, a p-n junction with strong polarization-dependent interfacial coupling effect is formed. The power conversion efficiency of the heterostructure is improved by nearly two orders of magnitude and the polarization modulation ratio is increased about four times. It is demonstrated that the polarization-dependent interfacial coupling effect can give rise to a great change in band structure of the heterostructure, not only producing an aligned internal electric field but also tuning both depletion layer width and potential barrier height at PZT-ZnO interface. This work provides an efficient way in developing highly efficient ferroelectric-based solar cells and novel optoelectronic memory devices.

  12. Buried waste containment system materials. Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Weidner, J.R.; Shaw, P.G.

    1997-10-01

    This report describes the results of a test program to validate the application of a latex-modified cement formulation for use with the Buried Waste Containment System (BWCS) process during a proof of principle (POP) demonstration. The test program included three objectives. One objective was to validate the barrier material mix formulation to be used with the BWCS equipment. A basic mix formula for initial trials was supplied by the cement and latex vendors. The suitability of the material for BWCS application was verified by laboratory testing at the Idaho National Engineering and Environmental Laboratory (INEEL). A second objective was to determine if the POP BWCS material emplacement process adversely affected the barrier material properties. This objective was met by measuring and comparing properties of material prepared in the INEEL Materials Testing Laboratory (MTL) with identical properties of material produced by the BWCS field tests. These measurements included hydraulic conductivity to determine if the material met the US Environmental Protection Agency (EPA) requirements for barriers used for hazardous waste sites, petrographic analysis to allow an assessment of barrier material separation and segregation during emplacement, and a set of mechanical property tests typical of concrete characterization. The third objective was to measure the hydraulic properties of barrier material containing a stop-start joint to determine if such a feature would meet the EPA requirements for hazardous waste site barriers.

  13. A diphtheria outbreak in Buri Ram, Thailand.

    Science.gov (United States)

    Pantukosit, Pantavee; Arpornsuwan, Manote; Sookananta, Kanokporn

    2008-07-01

    In May 1996 there was an outbreak of diphtheria in Buri Ram, Thailand which infected 31 patients, 8 males and 23 females. The mean age of the patients was 8 +/- 5 years. Seventy-four percent had a history of childhood vaccinations. Common signs and symptoms included fever (100%) which was low grade in 61%, sore throat (90%), upper airway obstruction (3%), and hoarseness (10%). Pseudomembranes (seen in 100%) were located on the tonsils (71%), pharynx (22%), larynx (9.6%), and uvula (6%). The mean duration of symptoms prior to admission was 2 days with a range of 1 to 5 days. Complications included upper airway obstruction (10%) and cardiac complications (10%). There were no neurological complication or deaths. There were negative associations between cardiac complications, severity of disease and previous diphtheria vaccination. The ages varied from children to adults. Early recognition and prompt treatment decreased complications and mortality in this group of patients when compared with Chiang Mai and Queen Sirikit National Institute of Child Health (QSNICH) studies.

  14. Buried nanoantenna arrays: versatile antireflection coating.

    Science.gov (United States)

    Kabiri, Ali; Girgis, Emad; Capasso, Federico

    2013-01-01

    Reflection is usually a detrimental phenomenon in many applications such as flat-panel-displays, solar cells, photodetectors, infrared sensors, and lenses. Thus far, to control and suppress the reflection from a substrate, numerous techniques including dielectric interference coatings, surface texturing, adiabatic index matching, and scattering from plasmonic nanoparticles have been investigated. A new technique is demonstrated to manage and suppress reflection from lossless and lossy substrates. It provides a wider flexibility in design versus previous methods. Reflection from a surface can be suppressed over a narrowband, wideband, or multiband frequency range. The antireflection can be dependent or independent of the incident wave polarization. Moreover, antireflection at a very wide incidence angle can be attained. The reflection from a substrate is controlled by a buried nanoantenna array, a structure composed of (1) a subwavelength metallic array and (2) a dielectric cover layer referred to as a superstrate. The material properties and thickness of the superstrate and nanoantennas' geometry and periodicity control the phase and intensity of the wave circulating inside the superstrate cavity. A minimum reflectance of 0.02% is achieved in various experiments in the mid-infrared from a silicon substrate. The design can be integrated in straightforward way in optical devices. The proposed structure is a versatile AR coating to optically impedance matches any substrate to free space in selected any narrow and broadband spectral response across the entire visible and infrared spectrum.

  15. Buried plastic scintillator muon telescope (BATATA)

    Energy Technology Data Exchange (ETDEWEB)

    Alfaro, R. [Inst. de Fisica, Universidad Nacional Autonoma de Mexico, Mexico, D.F., C.P. 04510 (Mexico); De Donato, C.; D' Olivo, J.C.; Guzman, A.; Medina-Tanco, G. [Inst. de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Mexico, D.F., C.P. 04510 (Mexico); Moreno Barbosa, E. [Fac. de Ciencias Fisico Matematicas, Benemerita Universidad Autonoma de Puebla, Puebla (Mexico); Paic, G.; Patino Salazar, E. [Inst. de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Mexico, D.F., C.P. 04510 (Mexico); Salazar Ibarguen, H. [Fac. de Ciencias Fisico Matematicas, Benemerita Universidad Autonoma de Puebla, Puebla (Mexico); Sanchez, F.A., E-mail: federico.sanchez@nucleares.unam.m [Inst. de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Mexico, D.F., C.P. 04510 (Mexico); Supanitsky, A.D. [Inst. de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Mexico, D.F., C.P. 04510 (Mexico); Valdes-Galicia, J.F. [Inst. de Geofisica, Universidad Nacional Autonoma de Mexico, Mexico, D.F., C.P. 04510 (Mexico); Vargas Trevino, A.D.; Vergara Limon, S. [Fac. de Ciencias de la Electronica, Benemerita Universidad Autonoma de Puebla, Puebla (Mexico); Villasenor, L.M. [Inst. de Fisica y Matematicas, Universidad Michoacana de San Nicolas Hidalgo Morelia (Mexico); Observatorio Pierre Auger, Av. San Martin Norte 304 (5613) Malarguee, Prov. Mendoza (Argentina)

    2010-05-21

    Muon telescopes have multiple applications in the area of cosmic ray research. We are currently building such a detector with the objective of comparing the ground penetration of muon vs. electron-gamma signals originated in cosmic ray showers. The detector is composed by a set of three parallel dual-layer scintillator planes, buried at fixed depths ranging from 120 to 600g/cm{sup 2}. Each layer is 4m{sup 2} and is composed by 49 rectangular strips of 4cmx2m, oriented at a 90{sup 0} angle with respect to its companion layer, which gives an xy-coincidence pixel of 4x4cm{sup 2}. The scintillators are MINOS extruded polystyrene strips, with an embedded Bicron BC92 wavelength shifting (WLS) fibers, of 1.5 mm in diameter. Light is collected by Hamamatsu H7546B multi-anode PMTs of 64 pixels. The front-end (FE) electronics works in counting mode and signals are transmitted to the surface DAQ stage using low-voltage differential signaling (LVDS). Any strip signal above threshold opens a GPS-tagged 2{mu}s data collection window. Data, including signal and background, are acquired by a system of FPGA (Spartan 2E) boards and a single-board computer (TS7800).

  16. Buried plastic scintillator muon telescope (BATATA)

    Science.gov (United States)

    Alfaro, R.; de Donato, C.; D'Olivo, J. C.; Guzmán, A.; Medina-Tanco, G.; Moreno Barbosa, E.; Paic, G.; Patiño Salazar, E.; Salazar Ibarguen, H.; Sánchez, F. A.; Supanitsky, A. D.; Valdés-Galicia, J. F.; Vargas Treviño, A. D.; Vergara Limón, S.; Villaseñor, L. M.; Auger Collaboration

    2010-05-01

    Muon telescopes have multiple applications in the area of cosmic ray research. We are currently building such a detector with the objective of comparing the ground penetration of muon vs. electron-gamma signals originated in cosmic ray showers. The detector is composed by a set of three parallel dual-layer scintillator planes, buried at fixed depths ranging from 120 to 600g/cm2. Each layer is 4m2 and is composed by 49 rectangular strips of 4cm×2m, oriented at a 90∘ angle with respect to its companion layer, which gives an xy-coincidence pixel of 4×4cm2. The scintillators are MINOS extruded polystyrene strips, with an embedded Bicron BC92 wavelength shifting (WLS) fibers, of 1.5 mm in diameter. Light is collected by Hamamatsu H7546B multi-anode PMTs of 64 pixels. The front-end (FE) electronics works in counting mode and signals are transmitted to the surface DAQ stage using low-voltage differential signaling (LVDS). Any strip signal above threshold opens a GPS-tagged 2μs data collection window. Data, including signal and background, are acquired by a system of FPGA (Spartan 2E) boards and a single-board computer (TS7800).

  17. Photoelastic Effect and Optimal Waveguide Structure in InGaAsP/InP Double Heterostructures

    Institute of Scientific and Technical Information of China (English)

    邢启江

    2002-01-01

    Stress field profiles and dielectric constant variations in In GaAsP/InP double heterostruct ures caused by a 110 nm thick W0.95Ni0.05 metal thin-film strain stripe are calculated. Both theoretical and experimental results demonstrate the form of the photoelastic waveguide structure in the InGaAsP/InP double heterostructures. For a 4bμm width W0.95Ni0.05 thin-film strain stripe, the difference between dielectric constants of the waveguide at the centre and the edge of the stripe is 9 × l0-2 - 2 × 10-2 in the depth range from 0.2 to 2 tm of the semiconductor. At a given depth, the width of the strain stripe for the optimal waveguide structure is determined. The maximal change of dielectric constant for the waveguide is an inverse proportion of the depth.

  18. Experimental evidence of hot carriers solar cell operation in multi-quantum wells heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Rodière, Jean; Lombez, Laurent, E-mail: laurent.lombez@chimie-paristech.fr [IRDEP, Institute of R and D on Photovoltaic Energy, UMR 7174, CNRS-EDF-Chimie ParisTech, 6 Quai Watier-BP 49, 78401 Chatou Cedex (France); Le Corre, Alain; Durand, Olivier [INSA, FOTON-OHM, UMR 6082, F-35708 Rennes (France); Guillemoles, Jean-François [IRDEP, Institute of R and D on Photovoltaic Energy, UMR 7174, CNRS-EDF-Chimie ParisTech, 6 Quai Watier-BP 49, 78401 Chatou Cedex (France); NextPV, LIA CNRS-RCAST/U. Tokyo-U. Bordeaux, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904 (Japan)

    2015-05-04

    We investigated a semiconductor heterostructure based on InGaAsP multi quantum wells (QWs) using optical characterizations and demonstrate its potential to work as a hot carrier cell absorber. By analyzing photoluminescence spectra, the quasi Fermi level splitting Δμ and the carrier temperature are quantitatively measured as a function of the excitation power. Moreover, both thermodynamics values are measured at the QWs and the barrier emission energy. High values of Δμ are found for both transition, and high carrier temperature values in the QWs. Remarkably, the quasi Fermi level splitting measured at the barrier energy exceeds the absorption threshold of the QWs. This indicates a working condition beyond the classical Shockley-Queisser limit.

  19. Transfer matrix theory of monolayer graphene/bilayer graphene heterostructure superlattice

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yu, E-mail: ywang@semi.ac.cn [Department of Physics, Faculty of Science, Kunming University of Science and Technology, Kunming 650500 (China)

    2014-10-28

    We have formulated a transfer matrix method to investigate electronic properties of graphene heterostructure consisting of monolayer graphene and bilayer counterpart. By evaluating transmission, conductance, and band dispersion, we show that, irrespective of the different carrier chiralities in monolayer graphene and bilayer graphene, superlattice consisting of biased bilayer graphene barrier and monolayer graphene well can mimic the electronic properties of conventional semiconductor superlattice, displaying the extended subbands in the quantum tunneling regime and producing anisotropic minigaps for the classically allowed transport. Due to the lateral confinement, the lowest mode has shifted away from the charge neutral point of monolayer graphene component, opening a sizeable gap in concerned structure. Following the gate-field and geometry modulation, all electronic states and gaps between them can be externally engineered in an electric-controllable strategy.

  20. Transfer matrix theory of monolayer graphene/bilayer graphene heterostructure superlattice

    Science.gov (United States)

    Wang, Yu

    2014-10-01

    We have formulated a transfer matrix method to investigate electronic properties of graphene heterostructure consisting of monolayer graphene and bilayer counterpart. By evaluating transmission, conductance, and band dispersion, we show that, irrespective of the different carrier chiralities in monolayer graphene and bilayer graphene, superlattice consisting of biased bilayer graphene barrier and monolayer graphene well can mimic the electronic properties of conventional semiconductor superlattice, displaying the extended subbands in the quantum tunneling regime and producing anisotropic minigaps for the classically allowed transport. Due to the lateral confinement, the lowest mode has shifted away from the charge neutral point of monolayer graphene component, opening a sizeable gap in concerned structure. Following the gate-field and geometry modulation, all electronic states and gaps between them can be externally engineered in an electric-controllable strategy.

  1. Preparation and Transparent Property of the n-ZnO/p-Diamond Heterostructure

    Institute of Scientific and Technical Information of China (English)

    WANG Cheng-Xin; GAO Chun-Xiao; LIU Hong-Wu; HAN Yong-Hao; LUO Ji-Feng; SEEN Cai-Xia

    2003-01-01

    Heterostructures of an n-type ZnO Glm/p-type diamond Elm on the {111} crystalline diamond substrate have been prepared for the first time. The electrodes of the n- and p-type semiconductors are experimentally verified to be ohmic. The diode shows a good rectification characteristic and the ratio of forward current to the reverse current exceeded 200 within the range of applied voltages of -2 to +2 V. The turn-on voltage of the diode is 0.34 V and the highest current is about 5.0mA as the forward voltage reaches 2 V. Moreover, the diode is optically transparent in the region of 500-700 nm wavelength.

  2. Tunable electronic structure in stained two dimensional van der Waals g-C2N/XSe2 (X = Mo, W) heterostructures

    Science.gov (United States)

    Zheng, Z. D.; Wang, X. C.; Mi, W. B.

    2017-10-01

    The electronic structure of the strained g-C2N/XSe2 (X=Mo, W) van der Waals heterostructures are investigated by first-principles calculations. The g-C2N/MoSe2 heterostructure is an indirect band gap semiconductor at a strain from 0% to 8%, where its band gap is 0.66, 0.61, 0.73, 0.60 and 0.33 eV. At K point, the spin splitting is 186, 181, 39, 13 and 9 meV, respectively. For g-C2N/WSe2 heterostructures, the band gap is 0.32, 0.37, 0.42, 0.45 and 0.36 eV, and the conduction band minimum is shifted from Г-M region to K-Г region as the strain increases from 0% to 8%. Its spin splitting monotonically decreases as a strain raises to 8%, which is 445, 424, 261, 111 and 96 meV, respectively. Moreover, at a strain less than 4%, the conduction band mainly comes from g-C2N, but it comes from XSe2 (X=Mo, W) above 6%. Our results show that the g-C2N/XSe2 heterostructures have tunable electronic structures, which makes it a potential candidate for novel electronic devices.

  3. Coherent dynamics in semiconductors

    DEFF Research Database (Denmark)

    Hvam, Jørn Märcher

    1998-01-01

    Ultrafast nonlinear optical spectroscopy is used to study the coherent dynamics of optically excited electron-hole pairs in semiconductors. Coulomb interaction implies that the optical inter-band transitions are dominated, at least at low temperatures, by excitonic effects. They are further...... and molecular systems are found and studied in the exciton-biexciton system of semiconductors. At densities where strong exciton interactions, or many-body effects, become dominant, the semiconductor Bloch equations present a more rigorous treatment of the phenomena Ultrafast degenerate four-wave mixing is used...

  4. Defects in semiconductors

    CERN Document Server

    Romano, Lucia; Jagadish, Chennupati

    2015-01-01

    This volume, number 91 in the Semiconductor and Semimetals series, focuses on defects in semiconductors. Defects in semiconductors help to explain several phenomena, from diffusion to getter, and to draw theories on materials' behavior in response to electrical or mechanical fields. The volume includes chapters focusing specifically on electron and proton irradiation of silicon, point defects in zinc oxide and gallium nitride, ion implantation defects and shallow junctions in silicon and germanium, and much more. It will help support students and scientists in their experimental and theoret

  5. Physics of semiconductor lasers

    CERN Document Server

    Mroziewicz, B; Nakwaski, W

    2013-01-01

    Written for readers who have some background in solid state physics but do not necessarily possess any knowledge of semiconductor lasers, this book provides a comprehensive and concise account of fundamental semiconductor laser physics, technology and properties. The principles of operation of these lasers are therefore discussed in detail with the interrelations between their design and optical, electrical and thermal properties. The relative merits of a large number of laser structures and their parameters are described to acquaint the reader with the various aspects of the semiconductor l

  6. Slow Light Semiconductor Laser

    Science.gov (United States)

    2015-02-02

    we demonstrate a semiconductor laser with a spectral linewidth of 18 kHz in the telecom band around 1:55um. The views, opinions and/or findings...we demonstrate a semiconductor laser with a spectral linewidth of 18 kHz in the telecom band around 1:55um. Further, the large intracavity field...hybrid Si/III- V platforms Abstract The semiconductor laser is the principal light source powering the world-wide optical fiber network . Ever

  7. Semiconductors bonds and bands

    CERN Document Server

    Ferry, David K

    2013-01-01

    As we settle into this second decade of the twenty-first century, it is evident that the advances in micro-electronics have truly revolutionized our day-to-day lifestyle. The technology is built upon semiconductors, materials in which the band gap has been engineered for special values suitable to the particular application. This book, written specifically for a one semester course for graduate students, provides a thorough understanding of the key solid state physics of semiconductors. It describes how quantum mechanics gives semiconductors unique properties that enabled the micro-electronics revolution, and sustain the ever-growing importance of this revolution.

  8. Physics and technology of antimonide heterostructure devices at SCD

    Science.gov (United States)

    Klipstein, Philip

    2015-01-01

    SCD has developed a range of advanced infrared detectors based on III-V semiconductor heterostructures, grown on GaSb. The XBn/XBp family of detectors enables diffusion limited behavior with dark currents comparable with MCT Rule-07 and with high quantum efficiencies. InAsSb/AlSbAs based XBn focal plane array detectors with a cut-off wavelength of ~ 4.1 μm and formats presently up to 1024×1280 / 15 μm, operate with background limited performance up to ~175 K at F/3. They have a sensitivity and image quality comparable with those of standard InSb detectors working at 77K. In an XBp configuration, the same concept has been applied to an InAs/GaSb type II superlattice (T2SL) detector with a cut-off wavelength of ~ 9.5 μm, which operates with background limited performance up to ~100 K at F/2. In order to design our detectors effectively, a suite of simulation algorithms was developed based on the k ṡ p and optical transfer matrix methods. In a given T2SL detector, the complete spectral response curve can be predicted essentially from a knowledge of the InAs and GaSb layer widths in a single period of the superlattice. Gallium free T2SL detectors in which the GaSb layer is replaced with InAs1-xSbx (x ~ 0.15-0.5) have also been simulated and the predicted spectral response compared for the two detector types.

  9. A low on-resistance buried current path SOI p-channel LDMOS compatible with n-channel LDMOS

    Institute of Scientific and Technical Information of China (English)

    Zhou Kun; Luo Xiao-Rong; Fan Yuan-Hang; Luo Yin-Chun; Hu Xia-Rong; Zhang Bo

    2013-01-01

    A novel low specific on-resistance (Ron,sp) silicon-on-insulator (SOI) p-channel lateral double-diffused metal-oxide semiconductor (pLDMOS) compatible with high voltage (HV) n-channel LDMOS (nLDMOS) is proposed.The pLDMOS is built in the N-type SOI layer with a buried P-type layer acting as a current conduction path in the on-state (BP SOI pLDMOS).Its superior compatibility with the HV nLDMOS and low voltage (LV) complementary metal-oxide semiconductor (CMOS) circuitry which are formed on the N-SOI layer can be obtained.In the off-state the P-buried layer built in the N-SOI layer causes multiple depletion and electric field reshaping,leading to an enhanced (reduced) surface field (RESURF)effect.The proposed BP SOI pLDMOS achieves not only an improved breakdown voltage (BV) but also a significantly reduced Ron,sp.The BV of the BP SOI pLDMOS increases to 319 V from 215 V of the conventional SOI pLDMOS at the same half cell pitch of 25 μm,and Ron,sp decreases from 157 mΩ·cm2 to 55 mΩ·cm2.Compared with the PW SOI pLDMOS,the BP SOI pLDMOS also reduces the Ron,sp by 34% with almost the same BV.

  10. Gallium Nitride, Indium Nitride, and Heterostructure Development Using The MEAglow Growth System

    Science.gov (United States)

    Binsted, Peter W.

    This thesis presents an in depth study of semiconductor development using a new process termed Migration Enhanced Afterglow (MEAglow). The MEAglow growth reactor is housed in the Lakehead University Semiconductor Research Lab. Thin films of gallium nitride and indium nitride are produced as well as heterostructures comprised of these two films and their ternary alloy InGaN. MEAglow is a form of plasma enhanced chemical vapour deposition (PECVD) employing migration enhanced epitaxy (MEE). The heterostructure is being developed for a novel field effect transistor (FET) based on the tunnelling of charge carriers which alter the channel conductivity. The configuration of this unique III-Nitride device should allow the FET to function as normally off in either n-type or p-type operation. Due to the difficulties in growing low temperature GaN, test devices of this abstract design were not previously possible. Further details on the device operation and growth parameters are included. Samples produced by the research reactor were characterised through x-ray diffraction (XRD), ultraviolet-near infrared-visible spectroscopy (UV-Vis-NIR), Auger spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM). Film growth is accomplished by an improved form of pulsed delivery Plasma Enhanced Chemical Vapour Deposition (PECVD). The reactor features a scalable hollow cathode type plasma source. Data obtained through characterisation is subjected to theoretical treatment which explains much not previously understood behaviour of the GaN films. Many challenges in III-Nitride film growth have been overcome during this research project. A method of developing structures consisting of InN and GaN within the same system has been proven.

  11. Integration of carbon nanotubes with semiconductor technology: fabrication of hybrid devices by III–V molecular beam epitaxy

    DEFF Research Database (Denmark)

    Stobbe, Søren; Lindelof, P. E.; Nygård, J.

    2006-01-01

    on incorporation of singlewall nanotubes in III–V semiconductor heterostructures grown by molecular beam epitaxy (MBE). We demonstrate that singlewall carbon nanotubes can be overgrown using MBE; electrical contacts to the nanotubes are obtained by GaMnAs grown at 250 °C. The resulting devices can exhibit field......We review a number of essential issues regarding the integration of carbon nanotubes in semiconductor devices for electronics: material compatibility, electrical contacts, functionalities, circuit architectures and reliability. In the second part of the paper, we present our own recent results...

  12. Numerical analysis of the self-heating effect in SGOI with a double step buried oxide

    Energy Technology Data Exchange (ETDEWEB)

    Li Bin; Liu Hongxia; Li Jin; Yuan Bo; Cao Lei, E-mail: 13389232181@189.cn [Key Laboratory for Wide Band Gap Semiconductor Materials and Devices of Education, School of Microelectronics, Xidian University, Xi' an 710071 (China)

    2011-03-15

    To reduce the self-heating effect of strained Si grown on relaxed SiGe-on-insulator (SGOI) n-type metal-oxide-semiconductor field-effect transistors (nMOSFETs), this paper proposes a novel device called double step buried oxide (BOX) SGOI, investigates its electrical and thermal characteristics, and analyzes the effect of self-heating on its electrical parameters. During the simulation of the device, a low field mobility model for strained Si MOSFETs is established and reduced thermal conductivity resulting from phonon boundary scattering is considered. A comparative study of SGOI nMOSFETs with different BOX thicknesses under channel and different channel strains has been performed. By reducing moderately the BOX thickness under the channel, the channel temperature caused by the self-heating effect can be effectively reduced. Moreover, mobility degradation, off state current and a short-channel effect such as drain induced barrier lowering can be well suppressed. Therefore, SGOI MOSFETs with a thinner BOX under the channel can improve the overall performance and long-term reliability efficiently. (semiconductor devices)

  13. Growth and characterization of VO{sub 2}/p-GaN/sapphire heterostructure with phase transition properties

    Energy Technology Data Exchange (ETDEWEB)

    Bian, Jiming, E-mail: jmbian@dlut.edu.cn [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); Key Laboratory of Inorganic Coating Materials, Chinese Academy of Sciences, Shanghai 200050. China (China); Wang, Minhuan; Miao, Lihua; Li, Xiaoxuan; Luo, Yingmin [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); Zhang, Dong [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); New Energy Source Research Center of Shenyang Institute of Engineering, Shenyang 110136 (China); Zhang, Yuzhi [Key Laboratory of Inorganic Coating Materials, Chinese Academy of Sciences, Shanghai 200050. China (China)

    2015-12-01

    Highlights: • VO{sub 2} films were deposited on p-GaN/sapphire substrates by PLD. • A well-defined VO{sub 2}/p-GaN/sapphire interface was observed. • The valence state of V in VO{sub 2} films was confirmed by XPS analyses. • A distinct reversible SMT phase transition behavior was observed. - Abstract: High quality pure phase VO{sub 2} films were deposited on p-GaN/sapphire substrates by pulsed laser deposition (PLD). A well-defined interface with dense and uniform morphology was observed in the as-grown VO{sub 2}/p-GaN/sapphire heterostructure. The X-ray photoelectron spectroscopy (XPS) analyses confirmed the valence state of vanadium (V) in VO{sub 2} films was principally composed of V{sup 4+} with trace amount of V{sup 5+}, no other valence state of V was detected. Meanwhile, a distinct reversible semiconductor-to-metal (SMT) phase transition with resistance change up to nearly three orders of magnitude was observed in the temperature dependent electrical resistance measurement, which was comparable to the high quality VO{sub 2} film grown directly on sapphire substrates. Our present findings will give a deeper insight into the physical mechanism behind the exotic characteristics of VO{sub 2}/p-GaN heterostructure, and further motivate research in novel devices with combined functional properties of both correlated oxide and wide bandgap nitride semiconductors.

  14. Forming openings to semiconductor layers of silicon solar cells by inkjet printing

    Energy Technology Data Exchange (ETDEWEB)

    Lennon, Alison J.; Utama, Roland Y.; Lenio, Martha A.T.; Ho-Baillie, Anita W.Y.; Kuepper, Nicole B.; Wenham, Stuart R. [The University of New South Wales, ARC Photovoltaics Centre of Excellence, Sydney 2052 (Australia)

    2008-11-15

    An inkjet printing method for forming openings to buried semiconductor layers of silicon solar cells is described. The method uses an overlying resist as a sacrificial layer onto which a plasticiser for the resist polymer is deposited in a programmed pattern using inkjet printing. At the locations where the plasticiser is printed, the resist becomes permeable to aqueous etching solutions, enabling openings to be created in underlying dielectric or silicon layer(s). The formed openings can be used to create metal contacts to the buried silicon layers of the solar cell. The permeability of the resist to aqueous etchants can be reversed, thus enabling a single resist layer to be used to create more than one set of openings in the underlying layers. The proposed method may also be applied more generally to the formation of patterns of openings in layers of semiconductor or microelectromechanical devices. (author)

  15. 49 CFR 195.248 - Cover over buried pipeline.

    Science.gov (United States)

    2010-10-01

    ... HAZARDOUS LIQUIDS BY PIPELINE Construction § 195.248 Cover over buried pipeline. (a) Unless specifically... (457) Any other area 30 (762) 18 (457) 1 Rock excavation is any excavation that requires blasting or...

  16. A Review of Celestial Burying Ground in Tibet

    Institute of Scientific and Technical Information of China (English)

    YUQIAN

    2005-01-01

    Celestial burying ground ,also called “Mandala”,is where life leaves and comes.A huge piece of stone hidden in high mountains is surrounded by burning plants that give up smoke going up into the air.

  17. Fabrication of MgFe2O4/MoS2 Heterostructure Nanowires for Photoelectrochemical Catalysis.

    Science.gov (United States)

    Fan, Weiqiang; Li, Meng; Bai, Hongye; Xu, Dongbo; Chen, Chao; Li, Chunfa; Ge, Yilin; Shi, Weidong

    2016-02-16

    A novel one-dimensional MgFe2O4/MoS2 heterostructure has been successfully designed and fabricated. The bare MgFe2O4 was obtained as uniform nanowires through electrospinning, and MoS2 thin film appeared on the surface of MgFe2O4 after further chemical vapor deposition. The structure of the MgFe2O4/MoS2 heterostructure was systematic investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectrometry (XPS), and Raman spectra. According to electrochemical impedance spectroscopy (EIS) results, the MgFe2O4/MoS2 heterostructure showed a lower charge-transfer resistance compared with bare MgFe2O4, which indicated that the MoS2 played an important role in the enhancement of electron/hole mobility. MgFe2O4/MoS2 heterostructure can efficiently degrade tetracycline (TC), since the superoxide free-radical can be produced by sample under illumination due to the active species trapping and electron spin resonance (ESR) measurement, and the optimal photoelectrochemical degradation rate of TC can be achieved up to 92% (radiation intensity: 47 mW/cm(2), 2 h). Taking account of its unique semiconductor band gap structure, MgFe2O4/MoS2 can also be used as an photoelectrochemical anode for hydrogen production by water splitting, and the hydrogen production rate of MgFe2O4/MoS2 was 5.8 mmol/h·m(2) (radiation intensity: 47 mW/cm(2)), which is about 1.7 times that of MgFe2O4.

  18. Physics of semiconductor devices

    CERN Document Server

    Rudan, Massimo

    2015-01-01

    This book describes the basic physics of semiconductors, including the hierarchy of transport models, and connects the theory with the functioning of actual semiconductor devices.  Details are worked out carefully and derived from the basic physics, while keeping the internal coherence of the concepts and explaining various levels of approximation. Examples are based on silicon due to its industrial importance. Several chapters are included that provide the reader with the quantum-mechanical concepts necessary for understanding the transport properties of crystals. The behavior of crystals incorporating a position-dependent impurity distribution is described, and the different hierarchical transport models for semiconductor devices are derived (from the Boltzmann transport equation to the hydrodynamic and drift-diffusion models). The transport models are then applied to a detailed description of the main semiconductor-device architectures (bipolar, MOS). The final chapters are devoted to the description of s...

  19. Biggest semiconductor installed

    CERN Multimedia

    2008-01-01

    Scientists and technicians at the European Laboratory for Particle Physics, commonly known by its French acronym CERN (Centre Europen pour la Recherche Nuclaire), have completed the installation of the largest semiconductor silicon detector.

  20. Defects in semiconductor nanostructures

    Indian Academy of Sciences (India)

    Vijay A Singh; Manoj K Harbola; Praveen Pathak

    2008-02-01

    Impurities play a pivotal role in semiconductors. One part in a million of phosphorous in silicon alters the conductivity of the latter by several orders of magnitude. Indeed, the information age is possible only because of the unique role of shallow impurities in semiconductors. Although work in semiconductor nanostructures (SN) has been in progress for the past two decades, the role of impurities in them has been only sketchily studied. We outline theoretical approaches to the electronic structure of shallow impurities in SN and discuss their limitations. We find that shallow levels undergo a SHADES (SHAllow-DEep-Shallow) transition as the SN size is decreased. This occurs because of the combined effect of quantum confinement and reduced dielectric constant in SN. Level splitting is pronounced and this can perhaps be probed by ESR and ENDOR techniques. Finally, we suggest that a perusal of literature on (semiconductor) cluster calculations carried out 30 years ago would be useful.

  1. Isotopically controlled semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Haller, E.E.

    2004-11-15

    A review of recent research involving isotopically controlled semiconductors is presented. Studies with isotopically enriched semiconductor structures experienced a dramatic expansion at the end of the Cold War when significant quantities of enriched isotopes of elements forming semiconductors became available for worldwide collaborations. Isotopes of an element differ in nuclear mass, may have different nuclear spins and undergo different nuclear reactions. Among the latter, the capture of thermal neutrons which can lead to neutron transmutation doping, can be considered the most important one for semiconductors. Experimental and theoretical research exploiting the differences in all the properties has been conducted and will be illustrated with selected examples. Manuel Cardona, the longtime editor-in-chief of Solid State Communications has been and continues to be one of the major contributors to this field of solid state physics and it is a great pleasure to dedicate this review to him.

  2. A semiconductor laser

    Energy Technology Data Exchange (ETDEWEB)

    Naoko, O.; Masaru, K.

    1984-04-20

    A semiconductor laser with enhanced characteristics is patented in which bleaching coatings are generated on the outcoupling mirrors by sputtering alternating coating layers made from A1203 and A10, with high and low indices of refraction.

  3. Vertical-Cavity In-plane Heterostructures: Physics and Applications

    CERN Document Server

    Taghizadeh, Alireza; Chung, Il-Sug

    2015-01-01

    We show that the in-plane heterostructures realized in vertical cavities with high contrast grating(HCG) reflector enables exotic configurations of heterostructure and photonic wells. In photonic crystal heterostructures forming a photonic well, the property of a confined mode is determined by the well width and barrier height. We show that in vertical-cavity in-plane heterostructures, anisotropic dispersion curvatures plays a key role as well, leading to exotic effects such as a photonic well with conduction band like well and a valence band like barrier. We investigate three examples to discuss the rich potential of this heterostructure as a platform for various physics studies and propose a system of two laterally coupled cavities which shows the breaking of parity-time symmetry as an example.

  4. Data fusion for the detection of buried land mines

    Energy Technology Data Exchange (ETDEWEB)

    Clark, G.A.; Sengupta, S.K.; Schaich, P.C.; Sherwood, R.J.; Buhl, M.R.; Hernandez, J.E.; Kane, R.J.; Barth, M.J.; Fields, D.J.; Carter, M.R.

    1993-10-01

    The authors conducted experiments to demonstrate the enhanced delectability of buried land mines using sensor fusion techniques. Multiple sensors, including imagery, infrared imagery, and ground penetrating radar, have been used to acquire data on a number of buried mines and mine surrogates. The authors present this data along with a discussion of the application of sensor fusion techniques for this particular detection problem. The authors describe the data fusion architecture and discuss some relevant results of these classification methods.

  5. Compact Buried Ducts in a Hot-Humid Climate House

    Energy Technology Data Exchange (ETDEWEB)

    Mallay, D. [Home Innovation Research Labs, Upper Marlboro, MD (United States)

    2016-01-01

    A system of compact, buried ducts provides a high-performance and cost-effective solution for delivering conditioned air throughout the building. This report outlines research activities that are expected to facilitate adoption of compact buried duct systems by builders. The results of this research would be scalable to many new house designs in most climates and markets, leading to wider industry acceptance and building code and energy program approval.

  6. Classification of Target Buried in the Underground by Radar Polarimetry

    OpenAIRE

    Moriyama, Toshifumi; Nakamura, Masafumi; Yamaguchi, Yoshio; Yamada, Hiroyoshi; Boerner, Wolfgang-M.

    1999-01-01

    This paper discusses the classification of targets buried in the underground by radar polarimetry. The subsurface radar is used for the detection of objects buried beneath the ground surface, such as gas pipes, cables and cavities, or in archeological exploration operation. In addition to target echo, the subsurface radar receives various other echoes, because the underground is inhomogeneous medium. Therefore, the subsurface radar needs to distinguish these echoes. In order to enhance the di...

  7. Dynamic Pressure of Seabed around Buried Pipelines in Shallow Water

    OpenAIRE

    Changjing Fu; Guoying Li; Tianlong Zhao; Donghai Guan

    2015-01-01

    Due to the obvious nonlinear effect caused by the shallow waves, the nonlinear wave loads have a great influence on the buried pipelines in shallow water. In order to ensure their stability, the forces on the pipelines that resulted from nonlinear waves should be considered thoroughly. Based on the Biot consolidation theory and the first-order approximate cnoidal wave theory, analytical solutions of the pore water pressure around the buried pipelines in shallow water caused by waves are first...

  8. Radiation effects in semiconductors

    CERN Document Server

    2011-01-01

    There is a need to understand and combat potential radiation damage problems in semiconductor devices and circuits. Written by international experts, this book explains the effects of radiation on semiconductor devices, radiation detectors, and electronic devices and components. These contributors explore emerging applications, detector technologies, circuit design techniques, new materials, and innovative system approaches. The text focuses on how the technology is being used rather than the mathematical foundations behind it. It covers CMOS radiation-tolerant circuit implementations, CMOS pr

  9. SILICON CARBIDE FOR SEMICONDUCTORS

    Science.gov (United States)

    This state-of-the-art survey on silicon carbide for semiconductors includes a bibliography of the most important references published as of the end...of 1964. The various methods used for growing silicon carbide single crystals are reviewed, as well as their properties and devices fabricated from...them. The fact that the state of-the-art of silicon carbide semiconductors is not further advanced may be attributed to the difficulties of growing

  10. Heterostructure-based high-speed/high-frequency electronic circuit applications

    Science.gov (United States)

    Zampardi, P. J.; Runge, K.; Pierson, R. L.; Higgins, J. A.; Yu, R.; McDermott, B. T.; Pan, N.

    1999-08-01

    With the growth of wireless and lightwave technologies, heterostructure electronic devices are commodity items in the commercial marketplace [Browne J. Power-amplifier MMICs drive commercial circuits. Microwaves & RF, 1998. p. 116-24.]. In particular, HBTs are an attractive device for handset power amplifiers at 900 MHz and 1.9 GHz for CDMA applications [Lum E. GaAs technology rides the wireless wave. Proceedings of the 1997 GaAs IC Symposium, 1997. p. 11-13; "Rockwell Ramps Up". Compound Semiconductor, May/June 1997.]. At higher frequencies, both HBTs and p-HEMTs are expected to dominate the marketplace. For high-speed lightwave circuit applications, heterostructure based products on the market for OC-48 (2.5 Gb/s) and OC-192 (10 Gb/s) are emerging [http://www.nb.rockwell.com/platforms/network_access/nahome.html#5.; http://www.nortel.com/technology/opto/receivers/ptav2.html.]. Chips that operate at 40 Gb/ have been demonstrated in a number of research laboratories [Zampardi PJ, Pierson RL, Runge K, Yu R, Beccue SM, Yu J, Wang KC. hybrid digital/microwave HBTs for >30 Gb/s optical communications. IEDM Technical Digest, 1995. p. 803-6; Swahn T, Lewin T, Mokhtari M, Tenhunen H, Walden R, Stanchina W. 40 Gb/s 3 Volt InP HBT ICs for a fiber optic demonstrator system. Proceedings of the 1996 GaAs IC Symposium, 1996. p. 125-8; Suzuki H, Watanabe K, Ishikawa K, Masuda H, Ouchi K, Tanoue T, Takeyari R. InP/InGaAs HBT ICs for 40 Gbit/s optical transmission systems. Proceedings of the 1997 GaAs IC Symposium, 1997. p. 215-8]. In addition to these two markets, another area where heterostructure devices are having significant impact is for data conversion [Walden RH. Analog-to digital convertor technology comparison. Proceedings of the 1994 GaAs IC Symposium, 1994. p. 217-9; Poulton K, Knudsen K, Corcoran J, Wang KC, Nubling RB, Chang M-CF, Asbeck PM, Huang RT. A 6-b, 4 GSa/s GaAs HBT ADC. IEEE J Solid-State Circuits 1995;30:1109-18; Nary K, Nubling R, Beccue S, Colleran W

  11. Extreme Band Engineering of III-Nitride Nanowire Heterostructures for Electronic and Photonic Application

    Science.gov (United States)

    Sarwar, ATM Golam

    Bottom-up nanowires are attractive for realizing semiconductor devices with extreme heterostructures because strain relaxation through the nanowire sidewalls allows the combination of highly lattice mismatched materials without creating dislocations. The resulting nanowires are used to fabricate light-emitting diodes (LEDs), lasers, solar cells, and sensors. The aim of this work is to investigate extreme heterostructures, which are impossible or very hard to realize in conventional planar films, exploiting the strain accommodation property of nanowires and engineer their band structure for novel electronic and photonic applications. To this end, in this thesis, III-Nitride semiconductor nanowires are investigated. In the first part of this work, a complete growth phase diagram of InN nanowires on silicon using plasma assisted molecular beam epitaxy is developed, and structural and optical characteristics are mapped as a function of growth parameters. Next, a novel up-side down pendeoepitaxial growth of InN forming mushroom-like microstructures is demonstrated and detail structural and optical characterizations are performed. Based on this, a method to grow strain-free large area single crystalline InN or thin film is proposed and the growth of InN on patterned GaN is investigated. The optimized growth conditions developed for InN are further used to grow InGaN nanowires graded over the whole composition range. Numerical energy band simulation is performed to better understand the effect of polarization charge on photo-carrier transport in these extremely graded nanowires. A novel photodetector device with negative differential photocurrent is demonstrated using the graded InGaN nanowires. In the second part of this thesis, polarization-induced nanowire light emitting diodes (PINLEDs) are investigated. The electrical and optical properties of the nanowire heterostructure are engineered and optimized for ultraviolet and deep ultraviolet applications. The electrical

  12. Scanning probe characterization of novel semiconductor materials and devices

    Science.gov (United States)

    Zhou, Xiaotian

    As semiconductor devices shrink in size, it becomes more important to characterize and understand electronic properties of the materials and devices at the nanoscale. Scanning probe techniques offers numerous advantages over traditional tools used for semiconductor materials and devices characterization including high spatial resolution, ease of use and multi-functionality for electrical characterization, such as current, potential and capacitance, etc. In the first chapter, the basic principle of atomic force microscopy (AFM), and its application to characterization of semiconductor materials and devices are discussed. In the second part of the thesis, scanning capacitance microscopy (SCM), spectroscopy (SCS) and scanning Kelvin probe microscopy (SKPM) are used to investigate the structure and electronic properties of nitride based materials and devices, specifically doping in p-type GaN and electronic structure and morphology of InxGa1-xN/GaN quantum wells. In this work, AFM is used to characterize the local electronic structure in nitride thin film and heterostructures devices. In next part the thesis, AFM is used as an active part of the device, in conductive atomic force microscopy (C-AFM) and scanning gate microscopy (SGM), to study the transport properties and gating effect of InAs semiconductor nanowire based field effect transistor. This is made possible because the nanowire, as a potential one-dimension building block for high performance electronics and optoelectronics, has a diameter comparable to the size of AFM tips. In the last part of the thesis (appendix), SKPM is used to characterize semiconductor-like organic thin films, where measurements of the potential profile along the channel of an organic thin film transistor (OTFT) at different gate bias are presented to illustrate the unique transport property of such devices.

  13. External electric field effects on AAS oscillations in narrow gap semiconductors

    Science.gov (United States)

    Lillianfeld, R. B.; Kallaher, R. L.; Davis, D. E.; Heremans, J. J.; Chen, Hong; Goel, N.; Chung, S. J.; Santos, M. B.; van Roy, W.; Borghs, G.

    2008-03-01

    We present experiments on quantum interference phenomena in semiconductors with strong spin-orbit interaction, using mesoscopic parallel ring arrays fabricated on InSb/InAlSb and InAs/AlGaSb heterostructures. A front gate modulates the spin-orbit interaction, which in turn affects the oscillatory interference phenomena. The experiments investigate the low temperature resistance of the ring arrays as a function of weak perpendicularly applied magnetic fields as well as applied gate voltage. The low field magnetoresistance in the arrays has the h/2e periodicity characteristic of Altshuler-Aronov-Spivak (AAS) oscillations. Despite reduced gate action typical of narrow-gap heterostructures (characterized by Hall measurements), we note an effect on the oscillatory magnetoresistance. The AAS oscillation magnitudes acquire a quasi-periodic modulation as function of gate voltage, and the localization background broadens at higher electron densities. The nature of these influences is examined. (NSF DMR-0618235, DMR-0080054, DMR-0209371)

  14. Nanoscale Semiconductor Electronics

    Science.gov (United States)

    2015-02-25

    create a brand -new process technology for the nano- fabrication of III-V devices. The radiation effects on these devices has been tested in AFRL...34Hydrolization oxidation of AlxGa1-xAs/GaAs quantum well heterostructures and superlattices," Appl . Phys. Lett. 57, 2844, 1990. [7] H. Wada and T. Kamijoh...942, Jun 1997. [8] H. Wada and T. Kamijoh, “Effects of Heat Treatment on Bonding Properties in InP-to- Si Direct Wafer Bonding,” Jpn. J. Appl

  15. van der Waals Heterostructures Grown by MBE

    Science.gov (United States)

    Hinkle, Christopher

    In this work, we demonstrate the high-quality MBE heterostructure growth of various layered 2D materials by van der Waals epitaxy (VDWE). The coupling of different types of van der Waals materials including transition metal dichalcogenide thin films (e.g., WSe2, WTe2, HfSe2) , insulating hexagonal boron nitride (h-BN), and topological insulators (e.g., Bi2Se3) allows for the fabrication of novel electronic devices that take advantage of unique quantum confinement and spin-based characteristics. The relaxed lattice-matching criteria of van der Waals epitaxy has allowed for high-quality heterostructure growth with atomically abrupt interfaces, allowing us to couple these materials based primarily on their band alignment and electronic properties. We will discuss the impact of sample preparation, surface reactivity, and lattice mismatch of various substrates (sapphire, graphene, TMDs, Bi2Se3) on the growth mode and quality of the films and will discuss our studies of substrate temperature and flux rates on the resultant growth and grain size. Structural and chemical characterization was conducted via reflection high energy electron diffraction (RHEED, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning tunneling microscopy/spectroscopy (STM/S), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Experimentally determined band alignments have been determined and compared with first-principles calculations allowing the design of novel low-power logic and magnetic memory devices. Initial results from the electrical characterization of these grown thin films and some simple devices will also be presented. These VDWE grown layered 2D materials show significant potential for fabricating novel heterostructures with tunable band alignments and magnetic properties for a variety of nanoelectronic and optoelectronic applications.

  16. Growth and Device Performance of AlGaN/GaN Heterostructure with AlSiC Precoverage on Silicon Substrate

    Directory of Open Access Journals (Sweden)

    Jae-Hoon Lee

    2014-01-01

    Full Text Available A crack-free AlGaN/GaN heterostructure was grown on 4-inch Si (111 substrate with initial dot-like AlSiC precoverage layer. It is believed that introducing the AlSiC layer between AlN wetting layer and Si substrate is more effective in obtaining a compressively stressed film growth than conventional Al precoverage on Si surface. The metal semiconductor field effect transistor (MESFET, fabricated on the AlGaN/GaN heterostructure grown with the AlSiC layer, exhibited normally on characteristics, such as threshold voltage of −2.3 V, maximum drain current of 370 mA/mm, and transconductance of 124 mS/mm.

  17. Structure, chemical bonding states, and optical properties of the hetero-structured ZnO/CuO prepared by using the hydrothermal and the electrospinning methods

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Kyong-Soo; Kim, Jong Wook; Bae, Jong-Seong; Hong, Tae Eun; Jeong, Euh Duck; Jin, Jong Sung; Ha, Myoung Gyu; Kim, Jong-Pil, E-mail: jpkim@kbsi.re.kr

    2017-01-01

    ZnO-branched nanostructures have recently attracted considerable attention due to their rich architectures and promising applications in the field of optoelectronics. Contrary to n-type semiconducting metal oxides, cupric oxide is a p-type semiconductor which can be applied to high-critical-temperature superconductors, photovoltaic materials, field emission, and catalysis. We report the synthesis of the ZnO nanorods on the CuO nanofibers prepared by using the electrospinning method along with the hydrothermal method. As the growing time increases, emission spectra of the hetero-structured ZnO/CuO show that the observed band in the UV region is slightly increased, while the intensity of the green emission is highly enhanced. The hetero-structured ZnO/CuO is found to be a promising candidate for developing renewable devices with photoluminescent behavior and the increased surface to volume ratio.

  18. Pseudomorphic GeSn/Ge (001) heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Tonkikh, A. A., E-mail: tonkikh@mpi-halle.de [Max Planck Institute of Microstructure Physics (Germany); Talalaev, V. G. [Martin Luther University Halle-Wittenberg, ZIK SiLi-nano (Germany); Werner, P. [Max Planck Institute of Microstructure Physics (Germany)

    2013-11-15

    The synthesis of pseudomorphic GeSn heterostructures on a Ge (001) substrate by molecular-beam epitaxy is described. Investigations by transmission electron microscopy show that the GeSn layers are defect free and possess cubic diamondlike structure. Photoluminescence spectroscopy reveals interband radiative recombination in the GeSn quantum wells, which is identified as indirect transitions between the subbands of heavy electrons and heavy holes. On the basis of experimental data and modeling of the band structure of pseudomorphic GeSn compounds, the lower boundary of the bowing parameter for the indirect band gap is estimated as b{sub L} {>=} 1.47 eV.

  19. Anomalous Fraunhofer interference in epitaxial superconductor-semiconductor Josephson junctions

    Science.gov (United States)

    Suominen, H. J.; Danon, J.; Kjaergaard, M.; Flensberg, K.; Shabani, J.; Palmstrøm, C. J.; Nichele, F.; Marcus, C. M.

    2017-01-01

    We investigate patterns of critical current as a function of perpendicular and in-plane magnetic fields in superconductor-semiconductor-superconductor (SNS) junctions based on InAs/InGaAs heterostructures with an epitaxial Al layer. This material system is of interest due to its exceptionally good superconductor-semiconductor coupling, as well as large spin-orbit interaction and g factor in the semiconductor. Thin epitaxial Al allows the application of large in-plane field without destroying superconductivity. For fields perpendicular to the junction, flux focusing results in aperiodic node spacings in the pattern of critical currents known as Fraunhofer patterns by analogy to the related interference effect in optics. Adding an in-plane field yields two further anomalies in the pattern. First, higher-order nodes are systematically strengthened, indicating current flow along the edges of the device, as a result of confinement of Andreev states driven by an induced flux dipole; second, asymmetries in the interference appear that depend on the field direction and magnitude. A model is presented, showing good agreement with experiment, elucidating the roles of flux focusing, Zeeman and spin-orbit coupling, and disorder in producing these effects.

  20. Inelastic light scattering in low dimensional semiconductors

    CERN Document Server

    Watt, M

    1988-01-01

    frequencies of the surface phonon peaks showed good agreement with calculated frequencies based on vibrations in small, geometrically-regular crystals. The main contribution of this work is the study of the surface phonons of the GaAs quantum cylinders. This is the first time that surface phonons have been observed in small fabricated samples: all previous work has involved specially-prepared crystalline powders or else comparatively large slab geometries. The conclusion that can be drawn from this work is that the cylinders are not only well-defined (as observed from the SEM micrographs) but they are also crystalline. The implication is that such structures can now be fabricated at a sufficiently high level to allow progress in prototype devices such as the quantum dot laser. Raman scattering is a powerful technique with which to study the lattice vibrations of semiconductors. Investigations of the phonons of GalnAs-InP heterostructures have shown that although the phonons in GalnAs quantum wells resembled t...

  1. EDITORIAL: Non-polar and semipolar nitride semiconductors Non-polar and semipolar nitride semiconductors

    Science.gov (United States)

    Han, Jung; Kneissl, Michael

    2012-02-01

    Throughout the history of group-III-nitride materials and devices, scientific breakthroughs and technological advances have gone hand-in-hand. In the late 1980s and early 1990s, the discovery of the nucleation of smooth (0001) GaN films on c-plane sapphire and the activation of p-dopants in GaN led very quickly to the realization of high-brightness blue and green LEDs, followed by the first demonstration of GaN-based violet laser diodes in the mid 1990s. Today, blue InGaN LEDs boast record external quantum efficiencies exceeding 80% and the emission wavelength of the InGaN-based laser diode has been pushed into the green spectral range. Although these tremenduous advances have already spurred multi-billion dollar industries, there are still a number of scientific questions and technological issues that are unanswered. One key challenge is related to the polar nature of the III-nitride wurtzite crystal. Until a decade ago all research activities had almost exclusively concentrated on (0001)-oriented polar GaN layers and heterostructures. Although the device characteristics seem excellent, the strong polarization fields at GaN heterointerfaces can lead to a significant deterioration of the device performance. Triggered by the first demonstration non-polar GaN quantum wells grown on LiAlO2 by Waltereit and colleagues in 2000, impressive advances in the area of non-polar and semipolar nitride semiconductors and devices have been achieved. Today, a large variety of heterostructures free of polarization fields and exhibiting exceptional electronic and optical properties have been demonstrated, and the fundamental understanding of polar, semipolar and non-polar nitrides has made significant leaps forward. The contributions in this Semiconductor Science and Technology special issue on non-polar and semipolar nitride semiconductors provide an impressive and up-to-date cross-section of all areas of research and device physics in this field. The articles cover a wide range of

  2. Buried Quaternary Valleys In NW Europe - Aquifers and Drilling Hazards

    Science.gov (United States)

    Huuse, M.; Lykke-Andersen, H.; Piotrowski, J.

    Buried Quaternary valleys are extremely widespread in the formerly glaciated, low- land areas of NW Europe (Huuse &Lykke-Andersen 2000, Fig. 4). The valleys may be several hundred metres deep, some kilometres across and few to several tens of kilometres long. Most of the deep valleys have irregular length profiles with sills and basins, unlike standard subaerial river systems. We interpret these as overdeepened valleys, formed mainly by subglacial meltwater erosion. Buried valleys located on- shore often provide sheltered reservoirs of clean groundwater, and much attention is presently focused on locating onshore valleys and quantifying their potential as groundwater aquifers. In nearshore areas, buried valleys may be a risk factor by pro- viding pathways of salt-water intrusion of onshore groundwater aquifers. Far offshore, buried valleys are located in the shallow subsurface above the prolific oil and gas fields of the central North Sea. Here, the valleys pose a risk for drilling operations by hosting shallow gas and potentially unstable sediments. The central North Sea is now largely covered by 3D seismic data, which often image the buried valleys in a level of de- tail much greater than that available onshore. Hence offshore valleys imaged by 3D seismic data may be used as analogues for groundwater reservoirs onshore NW Eu- rope. Here, we present examples of buried valleys from onshore, nearshore and far offshore locations, to illustrate how genetically and morphologically identical valleys may benefit or hamper the exploitation of subsurface accummulations of groundwater and hydrocarbons. Huuse, M. &Lykke-Andersen, H. 2000. Buried Quaternary valleys in the eastern Dan- ish North Sea: morphology and origin. Quaternary Science Reviews 19, 1233-1253.

  3. Semiconductor Nanowires from Materials Science and Device Physics Perspectives

    Science.gov (United States)

    Samuelson, Lars

    2005-03-01

    Realization of extremely down-scaled devices gives tough challenges related to technology and materials science. One reason for the concern is that top-down fabricated nano-devices tend to have their properties dominated by process-induced damage, rendering ultra-small devices not so useful. Alternatively, bottom-up fabrication methods may allow dimensions on the scale even below 10 nm, still with superb device properties. I will in this talk describe our research on catalytically induced growth of semiconductor nanowires. Our method uses catalytic gold nanoparticles, allowing tight control of diameter as well as position of where the nanowire grows, with our work completely focused on epitaxially nucleated nanowires in which the nanowire structure can be seen as a coherent, monolithic extension of the crystalline substrate material. One of the most important achievements in this field of research is the realization of atomically abrupt heterostructures within nanowires, in which the material composition can be altered within only one or a few monolayers, thus allowing 1D heterostructure devices to be realized. This has allowed a variety of quantum devices to be realized, such as single-electron transistors, resonant tunneling devices as well as memory storage devices. A related recent field of progress has been the realization of ideally nucleated III-V nanowires on Si substrates, cases where we have also reported functioning III-V heterostructure device structures on Si. All of these device related challenges evolve from an improved understanding of the materials science involved in nucleation of nanowires, in altering of composition of the growing nanowire, in control of the growth direction etc. I will give examples of these materials science issues and will especially dwell on the opportunities to form new kinds of materials, e.g. as 3D complex nanowire structures, resembling nanotrees or nanoforests.

  4. Method of doping a semiconductor

    Science.gov (United States)

    Yang, Chiang Y.; Rapp, Robert A.

    1983-01-01

    A method for doping semiconductor material. An interface is established between a solid electrolyte and a semiconductor to be doped. The electrolyte is chosen to be an ionic conductor of the selected impurity and the semiconductor material and electrolyte are jointly chosen so that any compound formed from the impurity and the semiconductor will have a free energy no lower than the electrolyte. A potential is then established across the interface so as to allow the impurity ions to diffuse into the semiconductor. In one embodiment the semiconductor and electrolyte may be heated so as to increase the diffusion coefficient.

  5. The control of stoichiometry in Epitaxial semiconductor structures. Interfacial Chemistry: Property relations. A workshop review

    Science.gov (United States)

    Bachmann, Klaus J.

    1995-01-01

    A workshop on the control of stoichiometry in epitaxial semiconductor structures was held on August 21-26, 1995 in the hotel Stutenhaus at Vesser in Germany. The secluded location of the workshop in the forest of Thuringia and its informal style stimulated extensive private discussions among the participants and promoted new contacts between young scientists from Eastern and Western Europe and the USA. Topics addressed by the presentations were interactions of precursors to heteroepitaxy and doping with the substrate surface, the control of interfacial properties under the conditions of heteroepitaxy for selected materials systems, methods of characterization of interfaces and native point defects in semiconductor heterostructures and an in depth evaluation of the present status of the control and characterization of the point defect chemistry for one specific semiconductor (ZnGeP2), including studies of both heterostructures and bulk single crystals. The selected examples of presentations and comments given here represent individual choices - made by the author to highlight major points of the discussions.

  6. Military applications for heterostructure microelectronics technology

    Science.gov (United States)

    Greiling, Paul; Kirkpatrick, Conilee; Valentine, Gary

    1995-09-01

    Military systems, whether radar, communications, electronic warfare (EW) or smart munitions, require superior device and IC performance. The performance advantages of heterostructure devices over standard Si CMOS, Si bipolar transistors or GaAs MESFETs has motivated major aerospace firms in the United States to develop Si, GaAs and InP-based heterojunction bipolar (HBT) and high electron mobility transistor (HEMT) technologies. In response to advanced system performance requirements, technology efforts are being pushed toward devices which can yield {T}/{R} modules with octave bandwidths, noise figures under 3 dB, output power of 20 W and power greater than 30%. Device technology development for satellite communications is being driven in part by the need for ultra low noise high output power with high power added efficiency with high MMTF. For these systems as well as EW applications, designers want to digitize the signal as close to the front end as possible. This is driving the development of a 100 GHz IC technology for A/D converters, synthesizers, MUX/DEMUXs, DDSs. and PRNs. Requirements for A/D converters with 16 bits @ 100-200 MHz up to 8-10 bits @ 10 GHz are appearing for advanced radars and EW systems. The military system requirements continue to drive the development of the newer, better and higher performance heterostructure device technologies.

  7. Tunnel-injection quantum dot deep-ultraviolet light-emitting diodes with polarization-induced doping in III-nitride heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Verma, Jai, E-mail: jverma@nd.edu; Islam, S. M.; Protasenko, Vladimir; Kumar Kandaswamy, Prem; Xing, Huili; Jena, Debdeep [Department of Electrical Engineering, University of Notre Dame, Notre Dame, Indiana 46556 (United States)

    2014-01-13

    Efficient semiconductor optical emitters in the deep-ultraviolet spectral window are encountering some of the most deep rooted problems of semiconductor physics. In III-Nitride heterostructures, obtaining short-wavelength photon emission requires the use of wide bandgap high Al composition AlGaN active regions. High conductivity electron (n-) and hole (p-) injection layers of even higher bandgaps are necessary for electrical carrier injection. This approach requires the activation of very deep dopants in very wide bandgap semiconductors, which is a difficult task. In this work, an approach is proposed and experimentally demonstrated to counter the challenges. The active region of the heterostructure light emitting diode uses ultrasmall epitaxially grown GaN quantum dots. Remarkably, the optical emission energy from GaN is pushed from 365 nm (3.4 eV, the bulk bandgap) to below 240 nm (>5.2 eV) because of extreme quantum confinement in the dots. This is possible because of the peculiar bandstructure and band alignments in the GaN/AlN system. This active region design crucially enables two further innovations for efficient carrier injection: Tunnel injection of carriers and polarization-induced p-type doping. The combination of these three advances results in major boosts in electroluminescence in deep-ultraviolet light emitting diodes and lays the groundwork for electrically pumped short-wavelength lasers.

  8. Growth, Characterization, and Simulation of Novel Semiconductor Tunnel Structures.

    Science.gov (United States)

    Chow, David Hsingkuo

    This thesis presents investigations of novel semiconductor heterostructure devices based on quantum mechanical tunneling. Due to their small characteristic dimensions, these devices have extremely fast charge transport properties. Thus, it is expected that tunnel structure devices will be well -suited to high frequency and optoelectronic applications. In chapter 2, a theoretical model is developed to simulate tunneling currents in single barrier heterostructures. The model includes band bending effects and a two band treatment of electron attenuation coefficients in the barrier. It is proposed that certain material systems have the appropriate band alignments to realize a novel single barrier negative differential resistance (NDR) mechanism. A thorough theoretical analysis of these single barrier NDR structures is presented. The first experimental demonstration of the single barrier NDR mechanism is reported in chapter 3. The HgTe/CdTe material system was selected for the demonstration. In this material system, low temperatures (Triple barrier GaAs/AlAs tunnel structures are found to display strong NDR, indicating that the tunneling process is coherent (as opposed to sequential) in nature. Finally, a technique for depositing high quality InAs buffer layers on GaAs substrates is developed.

  9. Nanoelectronics and quantum transport based on semiconductor nanowires

    Science.gov (United States)

    Lieber, Charles

    2010-03-01

    Semiconductor nanowires represent a uniquely powerful platform for exploring a diverse range of physical phenomena at the nanoscale due to the demonstrated capabilities of rational design and precise control of diameter, composition, morphology electronic properties during synthesis. In this talk, we will review advances of nanowires as high performance transistor and quantum devices with a focus on the prototypical Ge/Si core/shell nanowire heterostructure model system. First, a clean one-dimensional hole gas is formed due to band structure design, which sustains ballistic transport up to room temperature. Large subband spacing indicates a truly one-dimensional channel. Second, field-effect transistors utilizing Ge/Si nanowire heterostructure as the active channel are discussed with results demonstrating that these devices can outperform state-of-the-art Si MOSFETs. Third, the scaling of transistors with sub-100 nm channels are discussed with respect to pushing performance limit. Measurements and analyses show that devices with channel lengths down to 40 nm operate close to the ballistic limit and provide an intrinsic speed of 2 THz. Finally, advances in top-gate defined multi-quantum dot devices are reviewed, where control of contact transparency is used to enable studies in different quantum regimes. A fully tunable double quantum dot with integrated charge sensor is demonstrated. The characterization of charge transport and spin states, as well as its promise as a long coherence time spin qubit will be discussed.

  10. Low Dimensional Semiconductor Structures Characterization, Modeling and Applications

    CERN Document Server

    Horing, Norman

    2013-01-01

    Starting with the first transistor in 1949, the world has experienced a technological revolution which has permeated most aspects of modern life, particularly over the last generation. Yet another such revolution looms up before us with the newly developed capability to control matter on the nanometer scale. A truly extraordinary research effort, by scientists, engineers, technologists of all disciplines, in nations large and small throughout the world, is directed and vigorously pressed to develop a full understanding of the properties of matter at the nanoscale and its possible applications, to bring to fruition the promise of nanostructures to introduce a new generation of electronic and optical devices. The physics of low dimensional semiconductor structures, including heterostructures, superlattices, quantum wells, wires and dots is reviewed and their modeling is discussed in detail. The truly exceptional material, Graphene, is reviewed; its functionalization and Van der Waals interactions are included h...

  11. Charge separation sensitized by advanced II-VI semiconductor nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Kelley, David F. [Univ.of California, Merced, CA (United States)

    2017-04-11

    This proposal focuses on how the composition and morphology of pure and alloyed II-VI semiconductor heterostructures control their spectroscopic and dynamical properties. The proposed research will use a combination of synthesis development, electron microscopy, time-resolved electronic spectroscopy and modeling calculations to study these nanostructures. The proposed research will examine the extent to which morphology, compression due to lattice mismatch and alloy effects can be used to tune the electron and hole energies and the spectroscopic properties of II-VI heterojunctions. It will also use synthesis, optical spectroscopy and HRTEM to examine the role of lattice mismatch and hence lattice strain in producing interfacial defects, and the extent to which defect formation can be prevented by controlling the composition profile through the particles and across the interfaces. Finally, we will study the magnitude of the surface roughness in core/shell nanostructures and the role of shell thickness variability on the inhomogeneity of interfacial charge transfer rates.

  12. Amorphous semiconductor sample preparation for transmission EXAFS measurements

    Energy Technology Data Exchange (ETDEWEB)

    Ridgway, M.C.; Glover, C.J.; Tan, H.H. [Australian National Univ., Canberra (Australia). Dept. of Electronic Materials Engineering] [and others

    1998-12-31

    A novel methodology has been developed for the preparation of amorphous semiconductor samples for use in transmission extended x-ray absorption fine structure (EXAFS) measurements. Epitaxial heterostructures were fabricated by metal organic chemical vapor deposition (group III-Vs) or molecular beam epitaxy (group IVs). An epitaxial layer of {approximately} 2 {micro}m thickness was separated from the underlying substrate by selective chemical etching of an intermediate sacrificial layer. Ion implantation was utilized to amorphize the epitaxial layer either before or after selective chemical etching. The resulting samples were both stoichiometric and homogeneous in contrast to those produced by conventional techniques. The fabrication of amorphous GaAs, InP, In{sub 0.53}Ga{sub 0.47}As and Si{sub x}Ge{sub 1{minus}x} samples is described. Furthermore, EXAFS measurements comparing both fluorescence and transmission detection, and crystalline and amorphized GaAs, are shown.

  13. Beyond amorphous organic semiconductors

    Science.gov (United States)

    Hanna, Jun-ichi

    2003-07-01

    Recently it has been discovered that some types of liquid crystals, which believed to be governed by ionic conduction, exhibit a very fast electronic conduction. Their charge carrier transport is characterized by high mobility over 10-2 cm2/Vs independent of electric field and temperature. Now, the liquid crystals are being recognized as a new class of organic semiconductors. In this article, a new aspect of liquid crystals as a self-organizing molecular semiconductor are reviewed, focused on their basic charge carrier transport properties and discussed in comparison with those of molecular crystals and amorphous materials. And it is concluded that the liquid crystal is promising as a quality organic semiconductor for the devices that require a high mobility.

  14. Photoelectronic properties of semiconductors

    CERN Document Server

    Bube, Richard H

    1992-01-01

    The interaction between light and electrons in semiconductors forms the basis for many interesting and practically significant properties. This book examines the fundamental physics underlying this rich complexity of photoelectronic properties of semiconductors, and will familiarise the reader with the relatively simple models that are useful in describing these fundamentals. The basic physics is also illustrated with typical recent examples of experimental data and observations. Following introductory material on the basic concepts, the book moves on to consider a wide range of phenomena, including photoconductivity, recombination effects, photoelectronic methods of defect analysis, photoeffects at grain boundaries, amorphous semiconductors, photovoltaic effects and photoeffects in quantum wells and superlattices. The author is Professor of Materials Science and Electrical Engineering at Stanford University, and has taught this material for many years. He is an experienced author, his earlier books having fo...

  15. Semiconductors for organic transistors

    Directory of Open Access Journals (Sweden)

    Antonio Facchetti

    2007-03-01

    Full Text Available Organic molecules/polymers with a π-conjugated (heteroaromatic backbone are capable of transporting charge and interact efficiently with light. Therefore, these systems can act as semiconductors in opto-electronic devices similar to inorganic materials. However, organic chemistry offers tools for tailoring materials' functional properties via modifications of the molecular/monomeric units, opening new possibilities for inexpensive device manufacturing. This article reviews the fundamental aspects behind the structural design/realization of p- (hole transporting and n-channel (electron-transporting semiconductors for organic field-effect transistors (OFETs. An introduction to OFET principles and history, as well as of the state-of-the-art organic semiconductor structure and performance of OFETs is provided.

  16. Fundamentals of semiconductor lasers

    CERN Document Server

    Numai, Takahiro

    2015-01-01

    This book explains physics under the operating principles of semiconductor lasers in detail based on the experience of the author, dealing with the first manufacturing of phase-shifted DFB-LDs and recent research on transverse modes.   The book also bridges a wide gap between journal papers and textbooks, requiring only an undergraduate-level knowledge of electromagnetism and quantum mechanics, and helps readers to understand journal papers where definitions of some technical terms vary, depending on the paper. Two definitions of the photon density in the rate equations and two definitions of the phase-shift in the phase-shifted DFB-LD are explained, and differences in the calculated results are indicated, depending on the definitions.    Readers can understand the physics of semiconductor lasers and analytical tools for Fabry-Perot LDs, DFB-LDs, and VCSELs and will be stimulated to develop semiconductor lasers themselves.

  17. Basic Semiconductor Physics

    CERN Document Server

    Hamaguchi, Chihiro

    2010-01-01

    This book presents a detailed description of the basic semiconductor physics. The reader is assumed to have a basic command of mathematics and some elementary knowledge of solid state physics. The text covers a wide range of important phenomena in semiconductors, from the simple to the advanced. The reader can understand three different methods of energy band calculations, empirical pseudo-potential, k.p perturbation and tight-binding methods. The effective mass approximation and electron motion in a periodic potential, Boltzmann transport equation and deformation potentials used for full band Monte Carlo simulation are discussed. Experiments and theoretical analysis of cyclotron resonance are discussed in detail because the results are essential to the understanding of semiconductor physics. Optical and transport properties, magneto-transport, two dimensional electron gas transport (HEMT and MOSFET), and quantum transport are reviewed, explaining optical transition, electron phonon interactions, electron mob...

  18. Quantized conductance doubling and hard gap in a two-dimensional semiconductor–superconductor heterostructure

    Science.gov (United States)

    Kjaergaard, M.; Nichele, F.; Suominen, H. J.; Nowak, M. P.; Wimmer, M.; Akhmerov, A. R.; Folk, J. A.; Flensberg, K.; Shabani, J.; Palmstrøm, C. J.; Marcus, C. M.

    2016-01-01

    Coupling a two-dimensional (2D) semiconductor heterostructure to a superconductor opens new research and technology opportunities, including fundamental problems in mesoscopic superconductivity, scalable superconducting electronics, and new topological states of matter. One route towards topological matter is by coupling a 2D electron gas with strong spin–orbit interaction to an s-wave superconductor. Previous efforts along these lines have been adversely affected by interface disorder and unstable gating. Here we show measurements on a gateable InGaAs/InAs 2DEG with patterned epitaxial Al, yielding devices with atomically pristine interfaces between semiconductor and superconductor. Using surface gates to form a quantum point contact (QPC), we find a hard superconducting gap in the tunnelling regime. When the QPC is in the open regime, we observe a first conductance plateau at 4e2/h, consistent with theory. The hard-gap semiconductor–superconductor system demonstrated here is amenable to top-down processing and provides a new avenue towards low-dissipation electronics and topological quantum systems. PMID:27682268

  19. Transferable tight binding model for strained group IV and III-V heterostructures

    Science.gov (United States)

    Tan, Yaohua; Povolotskyi, Micheal; Kubis, Tillmann; Boykin, Timothy; Klimeck, Gerhard

    Modern semiconductor devices have reached critical device dimensions in the range of several nanometers. For reliable prediction of device performance, it is critical to have a numerical efficient model that are transferable to material interfaces. In this work, we present an empirical tight binding (ETB) model with transferable parameters for strained IV and III-V group semiconductors. The ETB model is numerically highly efficient as it make use of an orthogonal sp3d5s* basis set with nearest neighbor inter-atomic interactions. The ETB parameters are generated from HSE06 hybrid functional calculations. Band structures of strained group IV and III-V materials by ETB model are in good agreement with corresponding HSE06 calculations. Furthermore, the ETB model is applied to strained superlattices which consist of group IV and III-V elements. The ETB model turns out to be transferable to nano-scale hetero-structure. The ETB band structures agree with the corresponding HSE06 results in the whole Brillouin zone. The ETB band gaps of superlattices with common cations or common anions have discrepancies within 0.05eV.

  20. Superior Plasmonic Photodetectors Based on Au@MoS2 Core-Shell Heterostructures.

    Science.gov (United States)

    Li, Yuan; DiStefano, Jennifer G; Murthy, Akshay A; Cain, Jeffrey D; Hanson, Eve D; Li, Qianqian; Castro, Fernando C; Chen, Xinqi; Dravid, Vinayak P

    2017-09-21

    Integrating plasmonic materials into semiconductor media provides a promising approach for applications such as photo-sensing and solar energy conversion. The resulting structures introduce enhanced light-matter interactions, additional charge trap states, and efficient charge-transfer pathways for light-harvesting devices, especially when an intimate interface is built between the plasmonic nanostructure and semiconductor. Herein, we report the development of plasmonic photodetectors using Au@MoS2 heterostructures - an Au nanoparticle core that is encapsulated by a CVD-grown multilayer MoS2 shell, which perfectly realizes the intimate and direct interfacing of Au and MoS2. We explored their favorable applications in different types of photo-sensing devices. The first involves the development of a large-area interdigitated field-effect phototransistor, which shows a photoresponsivity of ~10 times higher than that of planar MoS2 transistors. The other type of device geometry is a Si-supported Au@MoS2 heterojunction gateless photodiode. We demonstrated its superior photo-response and recovery ability, with a photoresponsivity as high as 22.3 A/W, which is beyond the most distinguished values of previously reported similar gateless photodetectors. The improvement of photo-sensing performance can be a combined result of multiple factors, including enhanced light absorption, creation of more trap states, and, possibly, the formation of interfacial charge-transfer transition, benefiting from the intimate connection of Au and MoS2.

  1. Optical processes in semiconductors

    CERN Document Server

    Pankove, Jacques I

    1975-01-01

    Based on a series of lectures at Berkeley, 1968-1969, this is the first book to deal comprehensively with all of the phenomena involving light in semiconductors. The author has combined, for the graduate student and researcher, a great variety of source material, journal research, and many years of experimental research, adding new insights published for the first time in this book.Coverage includes energy states in semiconductors and their perturbation by external parameters, absorption, relationships between optical constants, spectroscopy, radiative transitions, nonradiative recombination

  2. Compound semiconductor device physics

    CERN Document Server

    Tiwari, Sandip

    2013-01-01

    This book provides one of the most rigorous treatments of compound semiconductor device physics yet published. A complete understanding of modern devices requires a working knowledge of low-dimensional physics, the use of statistical methods, and the use of one-, two-, and three-dimensional analytical and numerical analysis techniques. With its systematic and detailed**discussion of these topics, this book is ideal for both the researcher and the student. Although the emphasis of this text is on compound semiconductor devices, many of the principles discussed will also be useful to those inter

  3. Ternary chalcopyrite semiconductors

    CERN Document Server

    Shay, J L; Pamplin, B R

    2013-01-01

    Ternary Chalcopyrite Semiconductors: Growth, Electronic Properties, and Applications covers the developments of work in the I-III-VI2 and II-IV-V2 ternary chalcopyrite compounds. This book is composed of eight chapters that focus on the crystal growth, characterization, and applications of these compounds to optical communications systems. After briefly dealing with the status of ternary chalcopyrite compounds, this book goes on describing the crystal growth of II-IV-V2 and I-III-VI2 single crystals. Chapters 3 and 4 examine the energy band structure of these semiconductor compounds, illustrat

  4. Advances in semiconductor lasers

    CERN Document Server

    Coleman, James J; Jagadish, Chennupati

    2012-01-01

    Semiconductors and Semimetals has distinguished itself through the careful selection of well-known authors, editors, and contributors. Originally widely known as the ""Willardson and Beer"" Series, it has succeeded in publishing numerous landmark volumes and chapters. The series publishes timely, highly relevant volumes intended for long-term impact and reflecting the truly interdisciplinary nature of the field. The volumes in Semiconductors and Semimetals have been and will continue to be of great interest to physicists, chemists, materials scientists, and device engineers in academia, scien

  5. Semiconductor opto-electronics

    CERN Document Server

    Moss, TS; Ellis, B

    1972-01-01

    Semiconductor Opto-Electronics focuses on opto-electronics, covering the basic physical phenomena and device behavior that arise from the interaction between electromagnetic radiation and electrons in a solid. The first nine chapters of this book are devoted to theoretical topics, discussing the interaction of electromagnetic waves with solids, dispersion theory and absorption processes, magneto-optical effects, and non-linear phenomena. Theories of photo-effects and photo-detectors are treated in detail, including the theories of radiation generation and the behavior of semiconductor lasers a

  6. Quantum Transport in Semiconductors

    Science.gov (United States)

    1991-10-01

    SRS i 91 4. TITLE AND SUBTITLE Quantum Transport in Semiconductors 5. FUNDING NUMBER söMtos-rizk-ooss 6. AUTHOR(S) D. K. Ferry ©fte ELECTE...OF ABSTRACT UL NSN 7540-01-280-5500 O 1 9 Standard Form 298 (Rev. 2-89) Presented by ANSI Std «9-18 298-102 Final Report Quantum Transport in... Quantum Transport in Semiconductor Devices This final report describes a program of research investigating quantum effects which become important in

  7. Introductory semiconductor device physics

    CERN Document Server

    Parker, Greg

    2004-01-01

    ATOMS AND BONDINGThe Periodic TableIonic BondingCovalent BondingMetallic bondingvan der Waals BondingStart a DatabaseENERGY BANDS AND EFFECTIVE MASSSemiconductors, Insulators and MetalsSemiconductorsInsulatorsMetalsThe Concept of Effective MassCARRIER CONCENTRATIONS IN SEMICONDUCTORSDonors and AcceptorsFermi-LevelCarrier Concentration EquationsDonors and Acceptors Both PresentCONDUCTION IN SEMICONDUCTORSCarrier DriftCarrier MobilitySaturated Drift VelocityMobility Variation with TemperatureA Derivation of Ohm's LawDrift Current EquationsSemiconductor Band Diagrams with an Electric Field Presen

  8. Single semiconductor quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Michler, Peter (ed.) [Stuttgart Univ. (Germany). Inst. fuer Halbleiteroptik und Funktionelle Grenzflaechen

    2009-07-01

    This book reviews recent advances in the exciting and rapidly growing field of semiconductor quantum dots via contributions from some of the most prominent researchers in the scientific community. Special focus is given to optical, quantum optical, and spin properties of single quantum dots due to their potential applications in devices operating with single electron spins and/or single photons. This includes single and coupled quantum dots in external fields, cavity-quantum electrodynamics, and single and entangled photon pair generation. Single Semiconductor Quantum Dots also addresses growth techniques to allow for a positioned nucleation of dots as well as applications of quantum dots in quantum information technologies. (orig.)

  9. Engineering magnetism in semiconductors

    Directory of Open Access Journals (Sweden)

    Tomasz Dietl

    2006-11-01

    Full Text Available Transition metal doped III-V, II-VI, and group IV compounds offer an unprecedented opportunity to explore ferromagnetism in semiconductors. Because ferromagnetic spin-spin interactions are mediated by holes in the valence band, changing the Fermi level using co-doping, electric fields, or light can directly manipulate the magnetic ordering. Moreover, engineering the Fermi level position by co-doping makes it possible to modify solubility and self-compensation limits, affecting magnetic characteristics in a number of surprising ways. The Fermi energy can even control the aggregation of magnetic ions, providing a new route to self-organization of magnetic nanostructures in a semiconductor host.

  10. Semiconductor surface protection material

    Science.gov (United States)

    Packard, R. D. (Inventor)

    1973-01-01

    A method and a product for protecting semiconductor surfaces is disclosed. The protective coating material is prepared by heating a suitable protective resin with an organic solvent which is solid at room temperature and converting the resulting solution into sheets by a conventional casting operation. Pieces of such sheets of suitable shape and thickness are placed on the semiconductor areas to be coated and heat and vacuum are then applied to melt the sheet and to drive off the solvent and cure the resin. A uniform adherent coating, free of bubbles and other defects, is thus obtained exactly where it is desired.

  11. 16th Russian Youth Conference on Physics of Semiconductors and Nanostructures, Opto- and Nanoelectronics

    Science.gov (United States)

    Suris, Robert A.; Vorobjev, Leonid E.; Firsov, Dmitry A.

    2015-01-01

    The 16th Russian Youth Conference on Physics of Semiconductors and Nanostructures, Opto- and Nanoelectronics was held on November 24 - 28 at St. Petersburg Polytechnic University. The program of the Conference included semiconductor technology, heterostructures with quantum wells and quantum dots, opto- and nanoelectronic devices, and new materials. A large number of participants with about 200 attendees from many regions of Russia provided a perfect platform for the valuable discussions between students and experienced scientists. The Conference included two invited talks given by a corresponding member of RAS P.S. Kopyev ("Nitrides: the 4th Nobel Prize on semiconductor heterostructures") and Dr. A.V. Ivanchik ("XXI century is the era of precision cosmology"). Students, graduate and postgraduate students presented their results on plenary and poster sessions. The total number of accepted papers published in Russian (the official conference language) was 92. Here we publish 18 of them in English. Like previous years, the participants were involved in the competition for the best report. Certificates and cash prizes were awarded to a number of participants for the presentations selected by the Program Committee. Two special E.F. Gross Prizes were given for the best presentations in semiconductor optics. Works with potential applications were recommended for participation in the following competition for support from the Russian Foundation for Assistance to Small Innovative Enterprises in Science and Technology. The Conference was supported by the Russian Foundation for Basic Research, the "Dynasty" foundation and the innovation company "ATC - Semiconductor Devices", St. Petersburg. The official Conference website is http://www.semicond.spbstu.ru/conf2014-eng.html

  12. Metal semiconductor contacts and devices

    CERN Document Server

    Cohen, Simon S; Einspruch, Norman G

    1986-01-01

    VLSI Electronics Microstructure Science, Volume 13: Metal-Semiconductor Contacts and Devices presents the physics, technology, and applications of metal-semiconductor barriers in digital integrated circuits. The emphasis is placed on the interplay among the theory, processing, and characterization techniques in the development of practical metal-semiconductor contacts and devices.This volume contains chapters that are devoted to the discussion of the physics of metal-semiconductor interfaces and its basic phenomena; fabrication procedures; and interface characterization techniques, particularl

  13. Handbook of luminescent semiconductor materials

    CERN Document Server

    Bergman, Leah

    2011-01-01

    Photoluminescence spectroscopy is an important approach for examining the optical interactions in semiconductors and optical devices with the goal of gaining insight into material properties. With contributions from researchers at the forefront of this field, Handbook of Luminescent Semiconductor Materials explores the use of this technique to study semiconductor materials in a variety of applications, including solid-state lighting, solar energy conversion, optical devices, and biological imaging. After introducing basic semiconductor theory and photoluminescence principles, the book focuses

  14. Buried waste integrated demonstration FY 94 deployment plan

    Energy Technology Data Exchange (ETDEWEB)

    Hyde, R.A.; Walker, S.; Garcia, M.M.

    1994-05-01

    The Buried Waste Integrated Demonstration (BWID) is a program funded by the U.S. Department of Energy Office of Technology Development. BWID supports the applied research, development, demonstration, testing, and evaluation of a suite of advanced technologies that together form a comprehensive remediation system for the effective and efficient remediation of buried waste. The fiscal year (FY) 1994 effort will fund thirty-eight technologies in five areas of buried waste site remediation: site characterization, waste characterization, retrieval, treatment, and containment/stabilization. This document is the basic operational planning document for deployment of all BWID projects. Discussed in this document are the BWID preparations for INEL field demonstrations, INEL laboratory demonstrations, non-INEL demonstrations, and paper studies. Each technology performing tests will prepare a test plan to detail the specific procedures, objectives, and tasks of each test. Therefore, information specific to testing each technology is intentionally omitted from this document.

  15. Autonomous robotic platforms for locating radio sources buried under rubble

    Science.gov (United States)

    Tasu, A. S.; Anchidin, L.; Tamas, R.; Paun, M.; Danisor, A.; Petrescu, T.

    2016-12-01

    This paper deals with the use of autonomous robotic platforms able to locate radio signal sources such as mobile phones, buried under collapsed buildings as a result of earthquakes, natural disasters, terrorism, war, etc. This technique relies on averaging position data resulting from a propagation model implemented on the platform and the data acquired by robotic platforms at the disaster site. That allows us to calculate the approximate position of radio sources buried under the rubble. Based on measurements, a radio map of the disaster site is made, very useful for locating victims and for guiding specific rubble lifting machinery, by assuming that there is a victim next to a mobile device detected by the robotic platform; by knowing the approximate position, the lifting machinery does not risk to further hurt the victims. Moreover, by knowing the positions of the victims, the reaction time is decreased, and the chances of survival for the victims buried under the rubble, are obviously increased.

  16. End effectors and attachments for buried waste excavation equipment

    Energy Technology Data Exchange (ETDEWEB)

    King, R.H.

    1993-09-01

    The Buried Waste Integrated Demonstration (BWID) supports the applied research, development, demonstration, and evaluation of a suite of advanced technologies that form a comprehensive remediation system for the effective and efficient remediation of buried waste. Their efforts are identified and coordinated in support of the U.S. Department of Energy (DOE), Environmental Restoration and Waste Management (ER&WM) Department`s needs and objectives. The present focus of BWID is to support retrieval and ex-situ treatment configuration options. Future activities will explore and support containment, and stabilization efforts in addition to the retrieval/ex situ treatment options. This report presents a literature search on the state-of-the-art in end effectors and attachments in support of excavator of buried transuranic waste. Included in the report are excavator platforms and a discussion of the various attachments. Also included is it list of vendors and specifications.

  17. Heating and cooling potential of buried pipes in southern Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Abadie, Marc O.; Santos, Gerson H. dos; Freire, Roberto Z.; Mendes, Nathan [Pontificia Universidade Catolica do Parana (PUC-PR), Curitiba, PR (Brazil). Lab. de Sistemas Termicos], e-mail: mabadie@univ-lr.fr, e-mail: gerson.santos@pucpr.br, e-mail: rozafre@terra.com.br; Mendes, Nathan [Pontifical Catholic University of Parana (PUCPR/CCET), Curitiba, PR (Brazil). Thermal Systems Laboratory - LST], e-mail: nathan.mendes@pucpr.br

    2006-07-01

    The present numerical study aims to evaluate the heating and cooling potential of buried pipes in three cities of South Brazil i.e. Curitiba, Florianopolis and Porto-Alegre. In a first part, ground temperatures at the buried pipe location (between 1 and 3 m depth) are calculated by both a simplified model and a three-dimensional volume-finite code (SOLUM). Then, a prototypical house and its buried pipe are modeled with a building energy simulation tool (TRNSYS) to evaluate the positive and negative effects of such system on thermal comfort and heating and cooling energy. Results show that this passive system is particularly efficient in Curitiba, can reduce energy consumption in Porto Alegre and is not well-adapted to Florianopolis. (author)

  18. Damage Assessment for Buried Structures Against Internal Blast Load

    Institute of Scientific and Technical Information of China (English)

    MA Guowei; HUANG Xin; LI Jianchun

    2008-01-01

    The soil-structure interaction(SSI)decoupling is applied to simplify buried structure against internal blast lpad as spring effect.Shear failure.bending failure and Combined failure modes are considered based on five transverse velocity profiles for the rigid-plastic structural element.The critical equations for shear and bending failure are derived respectively.Pressure impulse diagrams are accordingly developed to assess damage of the buried structures against internal blast lpad.Cornparison is done to show influences of soil-structure interaction and shear to-bending strength ratio of a structural element.A case study is conducted to show the application of damage assessment to a reinforced concrete beam element of buried structure.

  19. Intense terahertz excitation of semiconductors

    CERN Document Server

    Ganichev, S D

    2006-01-01

    This work presents the first comprehensive treatment of high-power terahertz applications to semiconductors and low-dimensional semiconductor structures. Terahertz properties of semiconductors are in the centre of scientific activities because of the need of high-speed electronics.

  20. Semiconductor quantum wells with BenDaniel-Duke boundary conditions: approximate analytical results

    Science.gov (United States)

    Barsan, Victor; Ciornei, Mihaela-Cristina

    2017-01-01

    The Schrödinger equation for a particle moving in a square well potential with BenDaniel-Duke boundary conditions is solved. Using algebraic approximations for trigonometric functions, the transcendental equations of the bound states energy are transformed into tractable, algebraic equations. For the ground state and the first excited state, they are cubic equations; we obtain simple formulas for their physically interesting roots. The case of higher excited states is also analysed. Our results have direct applications in the physics of type I and type II semiconductor heterostructures.

  1. DLTS characterisation of defects in III-V compound semiconductors grown by MBE

    OpenAIRE

    2011-01-01

    The interest in the growth of III-V compound semiconductors such as GaAs and AlGaAs on high index planes has increased tremendously over the last few years. The structural, optical and electrical properties III-V based structures are found to improve by, growing on (nil) planes. For example the amphoteric nature of silicon (Si) facilitates the Molecular Beam Epitaxy (MBE) growth of p-type GaAs/AlGaAs heterostructures on (311)A that have higher hole mobilities than those based on the conventio...

  2. Practical Issues for Atom Probe Tomography Analysis of III-Nitride Semiconductor Materials

    OpenAIRE

    2015-01-01

    This is the author accepted manuscript. The final version is available from Cambridge University Press via http://dx.doi.org/10.1017/S1431927615000422 Various practical issues affecting atom probe tomography (APT) analysis of III-nitride semiconductors have been studied as part of an investigation using a c-plane InAlN/GaN heterostructure. Specimen preparation was undertaken using a focused ion beam microscope with a mono-isotopic Ga source. This enabled the unambiguous observation of impl...

  3. Quantum Wells, Wires and Dots Theoretical and Computational Physics of Semiconductor Nanostructures

    CERN Document Server

    Harrison, Paul

    2011-01-01

    Quantum Wells, Wires and Dots, 3rd Edition is aimed at providing all the essential information, both theoretical and computational, in order that the reader can, starting from essentially nothing, understand how the electronic, optical and transport properties of semiconductor heterostructures are calculated. Completely revised and updated, this text is designed to lead the reader through a series of simple theoretical and computational implementations, and slowly build from solid foundations, to a level where the reader can begin to initiate theoretical investigations or explanations of their

  4. Computer-automated tuning of semiconductor double quantum dots into the single-electron regime

    Science.gov (United States)

    Baart, T. A.; Eendebak, P. T.; Reichl, C.; Wegscheider, W.; Vandersypen, L. M. K.

    2016-05-01

    We report the computer-automated tuning of gate-defined semiconductor double quantum dots in GaAs heterostructures. We benchmark the algorithm by creating three double quantum dots inside a linear array of four quantum dots. The algorithm sets the correct gate voltages for all the gates to tune the double quantum dots into the single-electron regime. The algorithm only requires (1) prior knowledge of the gate design and (2) the pinch-off value of the single gate T that is shared by all the quantum dots. This work significantly alleviates the user effort required to tune multiple quantum dot devices.

  5. Ionic conductivity in oxide heterostructures: the role of interfaces

    Directory of Open Access Journals (Sweden)

    Emiliana Fabbri, Daniele Pergolesi and Enrico Traversa

    2010-01-01

    Full Text Available Rapidly growing attention is being directed to the investigation of ionic conductivity in oxide film heterostructures. The main reason for this interest arises from interfacial phenomena in these heterostructures and their applications. Recent results revealed that heterophase interfaces have faster ionic conduction pathways than the bulk or homophase interfaces. This finding can open attractive opportunities in the field of micro-ionic devices. The influence of the interfaces on the conduction properties of heterostructures is becoming increasingly important with the miniaturization of solid-state devices, which leads to an enhanced interface density at the expense of the bulk. This review aims to describe the main evidence of interfacial phenomena in ion-conducting film heterostructures, highlighting the fundamental and technological relevance and offering guidelines to understanding the interface conduction mechanisms in these structures.

  6. 2D materials and van der Waals heterostructures.

    Science.gov (United States)

    Novoselov, K S; Mishchenko, A; Carvalho, A; Castro Neto, A H

    2016-07-29

    The physics of two-dimensional (2D) materials and heterostructures based on such crystals has been developing extremely fast. With these new materials, truly 2D physics has begun to appear (for instance, the absence of long-range order, 2D excitons, commensurate-incommensurate transition, etc.). Novel heterostructure devices--such as tunneling transistors, resonant tunneling diodes, and light-emitting diodes--are also starting to emerge. Composed from individual 2D crystals, such devices use the properties of those materials to create functionalities that are not accessible in other heterostructures. Here we review the properties of novel 2D crystals and examine how their properties are used in new heterostructure devices.

  7. MgZnO/ZnO heterostructures with electron mobility exceeding 1 × 106 cm2/Vs

    Science.gov (United States)

    Falson, Joseph; Kozuka, Yusuke; Uchida, Masaki; Smet, Jurgen H.; Arima, Taka-Hisa; Tsukazaki, Atsushi; Kawasaki, Masashi

    2016-05-01

    The inherently complex chemical and crystallographic nature of oxide materials has suppressed the purities achievable in laboratory environments, obscuring the rich physical degrees of freedom these systems host. In this manuscript we provide a systematic approach to defect identification and management in oxide molecular beam epitaxy grown MgZnO/ZnO heterostructures which host two-dimensional electron systems. We achieve samples displaying electron mobilities in excess of 1 × 106 cm2/Vs. This data set for the MgZnO/ZnO system firmly establishes that the crystalline quality has become comparable to traditional semiconductor materials.

  8. Buried wire gage for wall shear stress measurements

    Science.gov (United States)

    Murthy, V. S.; Rose, W. C.

    1978-01-01

    A buried wire gage for measuring wall shear stress in fluid flow was studied and further developed. Several methods of making this relatively new type of gage were examined to arrive at a successful technique that is well-suited for wind-tunnel testing. A series of measurements was made to demonstrate the adequacy of a two-point calibration procedure for these gages. The buried wire gage is also demonstrated to be ideally suited for quantitative measurement of wall shear stress in wind-tunnel testing.

  9. Gnathostoma infection in Nakhon Nayok and Prachin Buri, Central Thailand.

    Science.gov (United States)

    Rojekittikhun, Wichit; Chaiyasith, Tossapon; Nuamtanong, Supaporn; Pubampen, Somchit; Maipanich, Wanna; Tungtrongchitr, Rungsunn

    2002-09-01

    Gnathostoma infection in Nakhon Nayok and Prachin Buri Provinces, Central Thailand, was investigated. The prevalence and intensity of infection of swamp eels were determined; dog fecal samples and fresh-water copepods were examined for evidence of infection. The overall prevalence of eel infection was 38.1% (117/307) in Nakhon Nayok and 24.0% (74/308) in Prachin Buri--the former rate being significantly higher than the latter. Most of the positive Nalkhon Nayok eels (53.8%) harbored only 1-9 larvae; only one eel bore more than 50 larvae. In Prachin Buri, 67.6% of the positive eels harbored 1-9 larvae; again, only one eel bore more than 50 larvae. The mean number of 11.0 +/- 10.4 larvae/eel in Nakhon Nayok was not significantly different from that of Prachin Buri (9.3 +/- 11.4). A total of 1,292 gnathostome larvae were recovered from 307 eels in Nakhon Nayok. Of these, 52.3% had accumulated in the liver and 47.7% had spread throughout the muscles. In eels from Prachin Buri, 50.6% and 49.4% of the total of 688 larvae (from 308 eels) were found in the liver and muscles, respectively. The larvae preferred encysting in ventral of muscles rather than dorsal part; they preferred the middle portion to the anterior and posterior portions. The average length of gnathostome larvae recovered from Nakhon Nayok eels was 4.0 +/- 0.5 mm (range 2.5-5.1 mm) and the average body width was 0.40 +/- 0.05 mm (range 0.29-0.51 mm). Those from eels in Prachin Buri were 3.9 +/- 0.5 mm (range 2.2-5.1 mm) and 0.34 +/- 0.05 mm (range 0.20-0.48 mm), respectively. The mean body length and width of the larvae from eels in Nakhon Nayok were significantly greater than those of the larvae from eels in Prachin Buri. In Ban Phrao, Nakhon Nayok, none of the first 44 fecal specimens examined was positive. Of the second (68) and the third (70) specimens, one (1.5%) and two (2.9%) samples were positive. However, six months after the third fecal collection, no eggs were found. In Tha Ngam, Prachin Buri, no

  10. Biexcitons in semiconductor microcavities

    DEFF Research Database (Denmark)

    Borri, P.; Langbein, W.; Woggon, U.

    2003-01-01

    In this paper, the present status of the experimental study of the optical properties of biexcitons in semiconductor microcavities is reviewed. In particular, a detailed investigation of a polariton-biexciton transition in a high-quality single quantum well GaAs/AlGaAs microcavity is reported...

  11. Semiconductor Nanocrystal Photonics

    Science.gov (United States)

    2005-08-31

    Hahn, H. Du, and T. D. Krauss, "Photoluminescence enhancement of colloidal semiconductor quantum dots embedded in a monolithic microcavity," Appl... DBRs ). The colloidal NC suspension was spun-coat into a 95-nm thick layer in the center of the cavity and then the other layers forming the top DBR

  12. Terahertz semiconductor nonlinear optics

    DEFF Research Database (Denmark)

    Turchinovich, Dmitry; Hvam, Jørn Märcher; Hoffmann, Matthias

    2013-01-01

    nonlinearity in doped semiconductors originates from the near-instantaneous heating of free electrons in the ponderomotive potential created by electric field of the THz pulse, leading to ultrafast increase of electron effective mass by intervalley scattering. Modification of effective mass in turn leads...

  13. Nonlinear properties of a graded-index photonic heterostructure

    Indian Academy of Sciences (India)

    B Tavakkoly Moghaddam; S Roshan Entezar; H Pashei Adl

    2013-05-01

    The optical properties of a one-dimensional (1D) photonic heterostructure with gradedindex nonlinear materials are demonstrated theoretically. The influence of the gradation profile of the graded-index nonlinear layers on the linear and nonlinear responses of the structure are analysed. It is shown that the -factor of the defect mode and the threshold input intensity to achieve the optical bistability in the used photonic heterostructure depend on the gradation profile of the gradedindex nonlinear layers.

  14. Growth And Characterization Studies Of Advanced Infrared Heterostructures

    Science.gov (United States)

    2015-06-30

    AFRL-RV-PS- TR-2015-0126 AFRL-RV-PS- TR-2015-0126 GROWTH AND CHARACTERIZATION STUDIES OF ADVANCED INFRARED HETEROSTRUCTURES Sanjay Krishna...To) 15 Feb 2013 – 09 May 2014 4. TITLE AND SUBTITLE Growth And Characterization Studies Of Advanced Infrared Heterostructures 5a. CONTRACT NUMBER...DISCUSSION After growth , the epitaxial wafers were characterized by x-ray diffraction to monitor crystal quality and layer thicknesses. The

  15. An investigation of dopping profile for a one dimensional heterostructure

    Science.gov (United States)

    Huang, Zhaohui

    2005-03-01

    A one-dimensional junction is formed by joining two silicon nanowires whose surfaces are terminated with capping groups of different electronegativity and polarizability. If this heterostructure is doped (with e.g. phosphorous) on the side with the higher bandgap, the system becomes a modulation doped heterostructure with novel one-dimensional electrostatics. We use density functional theory calculations in the pseudopotential approximation, plus empirical model calculations, to investigate doping profiles in this new class of nanostructures.

  16. Electron-hole pairing in graphene-GaAs heterostructures

    OpenAIRE

    Gamucci, A.; Spirito, D.; Carrega, M.; Karmakar, B.; Lombardo, A.; Bruna, M; Ferrari, A. C.; Pfeiffer, L.N.; West, K. W.; Polini, M.; V. Pellegrini

    2014-01-01

    Vertical heterostructures combining different layered materials offer novel opportunities for applications and fundamental studies of collective behavior driven by inter-layer Coulomb coupling. Here we report heterostructures comprising a single-layer (or bilayer) graphene carrying a fluid of massless (massive) chiral carriers, and a quantum well created in GaAs 31.5 nm below the surface, supporting a high-mobility two-dimensional electron gas. These are a new class of double-layer devices co...

  17. Excitons in van der Waals heterostructures

    DEFF Research Database (Denmark)

    Latini, Simone; Olsen, Thomas; Thygesen, Kristian Sommer

    2015-01-01

    The existence of strongly bound excitons is one of the hallmarks of the newly discovered atomically thin semiconductors. While it is understood that the large binding energy is mainly due to the weak dielectric screening in two dimensions, a systematic investigation of the role of screening on tw...

  18. Building Structural Complexity in Semiconductor Nanocrystals through Chemical Transformations

    Energy Technology Data Exchange (ETDEWEB)

    Sadtler, Bryce F [Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2009-05-01

    Methods are presented for synthesizing nanocrystal heterostructures comprised of two semiconductor materials epitaxially attached within individual nanostructures. The chemical transformation of cation exchange, where the cations within the lattice of an ionic nanocrystal are replaced with a different metal ion species, is used to alter the chemical composition at specific regions ofa nanocrystal. Partial cation exchange was performed in cadmium sulfide (CdS) nanorods of well-defined size and shape to examine the spatial organization of materials within the resulting nanocrystal heterostructures. The selectivity for cation exchange to take place at different facets of the nanocrystal plays an important role in determining the resulting morphology of the binary heterostructure. The exchange of copper (I) (Cu+) cations in CdS nanorods occurs preferentially at the ends of the nanorods. Theoretical modeling of epitaxial attachments between different facets of CdS and Cu2S indicate that the selectivity for cation exchange at the ends of the nanorods is a result of the low formation energy of the interfaces produced. During silver (I) (Ag+) cation exchange in CdS nanorods, non-selective nucleation of silver sulfide (Ag2S), followed by partial phase segregation leads to significant changes in the spatial arrangement of CdS and Ag2S regions at the exchange reaction proceeds through the nanocrystal. A well-ordered striped pattern of alternating CdS and Ag2S segments is found at intermediate fractions of exchange. The forces mediating this spontaneous process are a combination of Ostwald ripening to reduce the interfacial area along with a strain-induced repulsive interaction between Ag2S segments. To elucidate why Cu+ and Ag+ cation exchange with CdS nanorods produce different morphologies, models for epitaxial attachments between various facets of CdS with Cu2S or

  19. Rashba-Edelstein Magnetoresistance in Metallic Heterostructures

    Science.gov (United States)

    Nakayama, Hiroyasu; Kanno, Yusuke; An, Hongyu; Tashiro, Takaharu; Haku, Satoshi; Nomura, Akiyo; Ando, Kazuya

    2016-09-01

    We report the observation of magnetoresistance originating from Rashba spin-orbit coupling (SOC) in a metallic heterostructure: the Rashba-Edelstein (RE) magnetoresistance. We show that the simultaneous action of the direct and inverse RE effects in a Bi /Ag /CoFeB trilayer couples current-induced spin accumulation to the electric resistance. The electric resistance changes with the magnetic-field angle, reminiscent of the spin Hall magnetoresistance, despite the fact that bulk SOC is not responsible for the magnetoresistance. We further found that, even when the magnetization is saturated, the resistance increases with increasing the magnetic-field strength, which is attributed to the Hanle magnetoresistance in this system.

  20. Measuring thermoelectric property of nano-heterostructure

    Institute of Scientific and Technical Information of China (English)

    Lu Hong-Liang; Zhang Chen-Dong; Cai Jin-Ming; Gao Min; Zou Qiang; Guo Hai-Ming; Gao Hong-Jun

    2011-01-01

    A method of measuring the thermoelectric power of nano-heterostructures based on four-probe scanning tunneling microscopy is presented.The process is composed of the in-situ fabrication of a tungsten-indium tip,the precise control of the tip-sample contact and the identification of thermoelectric potential.When the temperature of the substrate is elevated,while that of the tip is kept at room temperature,a thermoelectric potential occurs and can be detected by a current-voltage measurement.As an example of its application,the method is demonstrated to be effective to measure the thermoelectric power in several systems.A Seebeck coefficient of tens of μV/K is obtained in graphene epitaxially grown on Ru (0001) substrate and the thermoelectric potential polarity of this system is found to be the reverse of that of bare Ru (0001) substrate.

  1. Organic heterostructures deposited by MAPLE on AZO substrate

    Science.gov (United States)

    Socol, M.; Preda, N.; Stanculescu, A.; Breazu, C.; Florica, C.; Stanculescu, F.; Iftimie, S.; Girtan, M.; Popescu-Pelin, G.; Socol, G.

    2017-09-01

    Organic heterostructures based on poly(3-hexylthiophene) (P3HT) and fullerene (C60) as blends or multilayer were deposited on Al:ZnO (AZO) by Matrix-Assisted Pulsed Laser Evaporation (MAPLE) technique. The AZO layers were obtained by Pulsed Laser Deposition (PLD) on glass substrate, the high quality of the films being reflected by the calculated figure of merit. The organic heterostructures were investigated from morphological, optical and electrical point of view by atomic force microscopy (AFM), UV-vis spectroscopy, photoluminescence (PL) and current-voltage (I-V) measurements, respectively. The increase of the C60 content in the blend heterostructure has as result a high roughness. Compared with the multilayer heterostructure, those based on blends present an improvement in the electrical properties. Under illumination, the highest current value was recorded for the heterostructure based on the blend with the higher C60 amount. The obtained results showed that MAPLE is a useful technique for the deposition of the organic heterostructures on AZO as transparent conductor electrode.

  2. Spectroscopy of Charge Carriers and Traps in Field-Doped Organic Semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Xiaoyang; Frisbie, C Daniel

    2012-08-13

    This research project aims to achieve quantitative and molecular level understanding of charge carriers and traps in field-doped organic semiconductors via in situ optical absorption spectroscopy, in conjunction with time-resolved electrical measurements. During the funding period, we have made major progress in three general areas: (1) probed charge injection at the interface between a polymeric semiconductor and a polymer electrolyte dielectric and developed a thermodynamic model to quantitatively describe the transition from electrostatic to electrochemical doping; (2) developed vibrational Stark effect to probe electric field at buried organic semiconductor interfaces; (3) used displacement current measurement (DCM) to study charge transport at organic/dielectric interfaces and charge injection at metal/organic interfaces.

  3. Temperature transformations of optical spectra in semiconductor flat heterostructures with quantum wells.

    Science.gov (United States)

    Kondryuk, D V; Derevyanchuk, A V; Kramar, V M

    2016-04-20

    The results of theoretical study of the temperature dependence of a long-wave range fundamental absorption edge in flat nanoheterostructures with a single quantum well (nanofilms) are adduced. The quantum well is assumed to be rectangular, of finite depth, and with unstrained heterojunctions as the nanofilm surface. Energies of electrons, holes, and excitons have been calculated within the framework of the effective mass model using the Green functions techniques, with account of their interaction with polar optical phonons confined within a quantum well. Numerical calculations are performed for nanofilms β-CdS/β-HgS/β-CdS and Al0.3Ga0.7As/GaAs/Al0.3Ga0.7As. It is shown that interaction with optical phonons causes a long-wave shift of the threshold frequency of the fundamental absorption band and a shift of exciton peaks by hundreds of Å for the first mentioned nanofilm and by dozens of Å for the second one, which is characterized by lower magnitudes of the constants of the electron-phonon coupling. The shift magnitude, as well as the height and half-width of the exciton absorption band, changes when the temperature exceeds 80 and 100 K, respectively.

  4. Chemistry and Defects in Semiconductor Heterostructures. Materials Research Society Symposium Proceedings. Volume 148

    Science.gov (United States)

    1990-05-01

    energ7y for an overomowtbh (141. This work was sapported by’he𔃿.lpartmest ofPCro-t-CC-’F D53) r. Jules Soatbort, contract monitor, for which muon...found, indicating a single crystalline material. The patterns, however, are verN sensitive to small non-uniform lattice strains which can be detected to

  5. MBE Growth, Characterization and Electronic Device Processing of Hg- Based Semiconductor Alloys and Heterostructures

    Science.gov (United States)

    1993-12-16

    028• 2 Approved for publ i c release; distribution unlimited. MBE GROWTH , CHARACTERIZATION AND ElECTRONIC DEVICE PROCESSING OF Hg-BASED SEMICONDUCTING...REPORT JEAN-PIERRE FAURIE PRINCIPAL INVESTIGATOR 94 337 94 5 12 041 2 DARPA contract F49620-90-C-0090 entitled, " MBE growth characterization and...All CdTe (111)B layers grown on misoriented is shown in Figs. 3a and 3b. For a layer with ingile- Si(001) are single domain. During the MBE growth , domain

  6. Controlling the Directional Emission of Light by Periodic Arrays of Heterostructured Semiconductor Nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Diedenhofen, S.L. [FOM Institute AMOLF, c/o Philips Research, High-Tech Campus 4, 5656 AE Eindhoven (Netherlands); Janssen, O.T.A.; Urbach, H.P. [Optics Research Group, Delft University of Technology, PO Box 5046, 2608 GA Delft (Netherlands); Hocevar, M. [Kavli Institute of Nanoscience, Quantum Transport, Delft University of Technology, 2600 GA Delft (Netherlands); Pierret, A.; Bakkers, E.P.A.M. [Philips Research Laboratories, High-Tech Campus 4, 5656 AE Eindhoven (Netherlands); Gomez Rivas, J. [Applied Physics, Photonics and Semiconductor Nanophysics, Eindhoven University of Technology, 5600 MB Eindhoven (Netherlands)

    2011-07-01

    We demonstrate experimentally the directional emission of light by InAsP segments embedded in InP nanowires. The nanowires are arranged in a periodic array, forming a 2D photonic crystal slab. The directionality of the emission is interpreted in terms of the preferential decay of the photoexcited nanowires and the InAsP segments into Bloch modes of the periodic structure. By simulating the emission of arrays of nanowires with the emitting segments located at different heights, we conclude that the position of this active region strongly influences the directionality and efficiency of the emission. Our results will help to improve the design of nanowire based LEDs and single photon sources.

  7. Controlling the directional emission of light by periodic arrays of heterostructured semiconductor nanowires.

    Science.gov (United States)

    Diedenhofen, Silke L; Janssen, Olaf T A; Hocevar, Moïra; Pierret, Aurélie; Bakkers, Erik P A M; Urbach, H Paul; Rivas, Jaime Gómez

    2011-07-26

    We demonstrate experimentally the directional emission of light by InAsP segments embedded in InP nanowires. The nanowires are arranged in a periodic array, forming a 2D photonic crystal slab. The directionality of the emission is interpreted in terms of the preferential decay of the photoexcited nanowires and the InAsP segments into Bloch modes of the periodic structure. By simulating the emission of arrays of nanowires with the emitting segments located at different heights, we conclude that the position of this active region strongly influences the directionality and efficiency of the emission. Our results will help to improve the design of nanowire based LEDs and single photon sources.

  8. The band gap and band offset in ultrathin oxide-semiconductor heterostructures

    Science.gov (United States)

    Schmeißer, D.; Henkel, K.; Bergholz, M.; Tallarida, M.

    2010-03-01

    In ultrathin high- k oxide layers knowledge of the band line up and band gap is essential for modeling the transport properties and to learn about a device's long term stability and reliability. However, such data are hard to determine in such ultrathin layers and usually are extrapolated from values for bulk samples or are taken from the literature. In our in situ approach we use electron energy loss spectroscopy, valence band photoelectron spectroscopy, X-ray absorption spectroscopy, and resonant inelastic X-ray scattering to obtain the loss function and the valence and conduction band densities of states. From such data we derive the values of the band offsets and of the band gap. We discuss the ability of this combination of different techniques for the analysis of such complex ultrathin dielectric systems and discuss in detail the properties of the native oxide in SiO 2/Si(001) and SiO 2/3C-SiC(001).

  9. Semiconductor/Piezoelectrics Hybrid Heterostructures with Highly Effective Gate-Tunable Electrotransport and Magnetic Behaviors.

    Science.gov (United States)

    Chen, Lei; Zhao, Wei-Yao; Wang, Jing; Gao, Guan-Yin; Zhang, Jin-Xing; Wang, Yu; Li, Xiao-Min; Cao, Shi-Xun; Li, Xiao-Guang; Luo, Hao-Su; Zheng, Ren-Kui

    2016-10-12

    We report the epitaxial growth of oxygen deficient titanium dioxide thin films on 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) single crystals and realized highly effective in situ electrostatic manipulation of electrotransport and magnetism of TiO2-δ films via gate voltages. Upon the polarization switching in the PMN-PT, the carrier density of the TiO2-δ film could be reversibly modified, resulting in a large nonvolatile resistivity modulation by ∼51% at T = 300 K, approximately 4-12 times larger than that of other transition-metal oxide film/PMN-PT structures. By taking advantage of in situ manipulation of the carrier density via gate voltages, we found that competition between the trap of electrons by the Ti(3+)-VO pairs and that by the positive polarization charges at the interface results in a significant resistivity relaxation upon the polarization switching, and revealed that magnetization is inversely correlated with the carrier density of the TiO2-δ film. Such hybrid structures combining materials with dissimilar functionalities may have potential applications in multifunctional devices which can take advantage of the useful and unique properties of both materials.

  10. Electric field dependence of junction magnetoresistance in magnetite/semiconductor heterostructure at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Aireddy, H.; Bhaumik, S.; Das, A. K., E-mail: amal@phy.iitkgp.ernet.in [Department of Physics, Indian Institute of Technology, Kharagpur 721 302 (India)

    2015-12-07

    We have fabricated Fe{sub 3}O{sub 4}/p-Si heterojunction using pulsed laser deposition technique and explored its electro-magnetic transport properties. The heterojunction exhibits backward rectifying property at all temperatures, and appraisal of giant junction magnetoresistance (JMR) is observed at room temperature (RT). Conspicuously, the variation and sign change of JMR as a function of electric field is observed at RT. The backward rectifying behavior of the device is ascribed to the highly doped p-type (p{sup ++}) semiconducting nature of Fe{sub 3}O{sub 4}, and the origin of electric field (voltage) dependence of magnetoresistance is explained proposing electronic band diagram of Fe{sub 3}O{sub 4}/SiO{sub 2}/p-Si heterojunction. This interesting result may have importance to integrate Si-based magnetoresistance sources in multifunctional spintronic devices.

  11. Valence-band offsets and Schottky barrier heights of layered semiconductors explained by interface-induced gap states

    Science.gov (United States)

    Mönch, Winfried

    1998-04-01

    Many metal chalcogenides are layered semiconductors. They consist of chalcogen-metal-chalcogen layers that are themselves bound by van der Waals forces. Hence, heterostructures involving layered compounds are abrupt and strain-free. Experimental valence-band offsets of heterostructures between GaSe, InSe, SnS2, SnSe2, MoS2, MoTe2, WSe2, and CuInSe2 and between some of these compounds and ZnSe, CdS, and CdTe as well as barrier heights of Au contacts on GaSe, InSe, MoS2, MoTe2, WSe2, ZnSe, CdS, and CdTe are analyzed. The valence-band discontinuities of the heterostructures and the barrier heights of the Schottky contact compounds are consistently described by the continuum of interface-induced gap states as the primary mechanism that governs the band lineup at semiconductor interfaces.

  12. Detection of Buried Mines and Unexploded Ordnance (UXO)

    Science.gov (United States)

    2007-04-20

    Confederate forces used black powder and buried artillery shells to attack advancing Union units. Major General William Tecumseh Sherman countered these...AK-2-2539 6. AUTHOR(S) David Heberlein, Bohdan Balko, Isaac Chappell , John Biddle 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S

  13. Identification of buried victims in natural disaster with GPR method

    Science.gov (United States)

    Dewi, Rianty Kusuma; Kurniawan, Adityo; Taqwantara, Reyhan Fariz; Iskandar, Farras M.; Naufal, Taufiq Ziyan; Widodo

    2017-07-01

    Indonesian is one of the most seismically active regions in the world and has very complicated plate convergence because there is meeting point of several tectonic plates. The complexity of tectonic features causes a lot of natural disasters such as landslides, tsunamis, earth quakes, volcanoes eruption, etc. Sometimes, the disasters occurs in high populated area and causing thousands to millions of victim been buried under the rumble. Unfortunately, the evacuation still uses the conventional method such using rescue dogs whereas the sensitivity of smell is decrease when the victims buried under the level of the ground. The purpose of this study is to detect buried bodies using GPR method, so it can enhance the effectiveness and the efficiency in looking for the disaster victims. GPR method is used because it can investigate things under the ground. A detailed GPR research has been done in Cikutra Graveyard, Bandung, with corpse buried two week until two years before the research. The radar profiles from this research showed amplitude contras anomaly between the new corpse and the old ones. We obtained the amplitude contras at 1.2-1.4 meters under the surface. This method proved to be effective but still need more attention on undulated surface and non-soil areas.

  14. Modeling of the Uplift Response of Buried Pipelines

    DEFF Research Database (Denmark)

    Choobbasti, Asskar Janalizadeh; Vahdatirad, Mohammadjavad; Firouzianbandpey, Sarah;

    2009-01-01

    Over the years, researchers have tried to understand the complex behavior of buried pipelines subjected to ground ruptures due to landslides, earthquakes, faults and uplift forces in shallow trenches. In an attempt to understand this complex behavior, an experimental investigation program has been...

  15. Buried nodules from the central Indian Ocean basin

    Digital Repository Service at National Institute of Oceanography (India)

    Pattan, J.N.; Parthiban, G.

    Indian Ocean. Mar. Geol.92, p. 115- 125. Usui, A. and Ito, T. (1994). Fossil manganese deposits buried within DSDP /ODP cores, Legs 1-126. Mar. geol. 119, p. 111-136. Von Stackelberg, U. (1984). Significance of bentic organisms for the growth...

  16. Ground Penetrating Radar Imaging of Buried Metallic Objects

    DEFF Research Database (Denmark)

    Polat, A. Burak; Meincke, Peter

    2001-01-01

    During the past decade there has been considerable research on ground penetrating radar (GPR) tomography for detecting objects such as pipes, cables, mines and barrels buried under the surface of the Earth. While the earlier researches were all based on the assumption of a homogeneous background...

  17. Buried Waste Integrated Demonstration Technology Preparedness and Status Report Guidance

    Energy Technology Data Exchange (ETDEWEB)

    Blacker, P.B.; Bonnenberg, R.W.; Cannon, P.G.; Hyde, R.A.; Watson, L.R.

    1994-04-01

    A Technology Preparedness and Status Report is required for each Technical Task Plan funded by the Buried Waste Integrated Demonstration. This document provides guidance for the preparation of that report. Major sections of the report will include a subset of the need for the technology, objectives of the demonstration, technology description and readiness evaluation, demonstration requirements, and preparedness checklist and action plan.

  18. Spin polarized transports through a narrow-gap semiconductor wire with ferromagnetic contacts formed on InAlAs step-graded buffer layers

    OpenAIRE

    Akabori, M; Yamada, S.

    2004-01-01

    We investigated the transport properties of ferromagnetic/semiconductor hybrid structures utilizing an InAs/In_Al_As modulation-doped heterostructures formed on a GaAs (001) substrate with In_xAl_As step-graded buffer layers. We used NiFe as ferromagnetic electrodes for injection/detection of spin-polarized electrons, which were formed on side walls of the semiconductor mesa to contact electron channel directly. We measured magneto-transport properties of the samples with current flow between...

  19. 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

  20. 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.

  1. Micromagnetic sensors and Dirac fermions in HgTe heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Buettner, Bastian

    2012-08-06

    Within the scope of this thesis two main topics have been investigated: the examination of micromagnetic sensors and transport of massive and massless Dirac fermions in HgTe quantum wells. For the investigation of localized, inhomogeneous magnetic fields, the fabrication and characterization of two different non-invasive and ultra sensitive sensors has been established at the chair ''Experimentelle Physik'' of the University of Wuerzburg. The first sensor is based on the young technique named micro-Hall magnetometry. The necessary semiconductor devices (Hall cross structures) were fabricated by high-resolution electron beam lithography based on two different two dimensional electron gases (2DEGs), namely InAs/(Al,Ga)Sb- and HgTe/(Hg,Cd)Te-heterostructures. The characteristics have been examined in two different ways. Measurements in homogeneous magnetic fields served for characterization of the sensors, whereas the investigation of artificially produced sub-{mu}m magnets substantiates the suitability of the devices for the study of novel nanoscale magnetic materials (e.g. nanowires). Systematic experiments with various magnets are in accordance with the theory of single-domain particles and anisotropic behavior due to shapes with high aspect ratio. The highest sensitivity for strongly localized fields was obtained at T=4.2 K for a (200.200) nm{sup 2} Hall cross - made from shallow, high mobility HgTe 2DEG. Although the field resolution was merely {delta}B{approx}100 {mu}T, the nanoscale sensor size yields an outstanding flux resolution of {delta}{Phi}=2.10{sup -3} {Phi}{sub 0}, where {Phi}{sub 0}=h/2e is the flux quantum. Translating this result in terms of magnetic moment, the sensitivity allows for the detection of magnetization changes of a particle centered on top of the sensor as low as {delta}M{approx}10{sup 2} {mu}{sub B}, with the magnetic moment of a single electron {mu}{sub B}, the Bohr magneton. The further examination of a permalloy

  2. Micromagnetic sensors and Dirac fermions in HgTe heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Buettner, Bastian

    2012-08-06

    Within the scope of this thesis two main topics have been investigated: the examination of micromagnetic sensors and transport of massive and massless Dirac fermions in HgTe quantum wells. For the investigation of localized, inhomogeneous magnetic fields, the fabrication and characterization of two different non-invasive and ultra sensitive sensors has been established at the chair ''Experimentelle Physik'' of the University of Wuerzburg. The first sensor is based on the young technique named micro-Hall magnetometry. The necessary semiconductor devices (Hall cross structures) were fabricated by high-resolution electron beam lithography based on two different two dimensional electron gases (2DEGs), namely InAs/(Al,Ga)Sb- and HgTe/(Hg,Cd)Te-heterostructures. The characteristics have been examined in two different ways. Measurements in homogeneous magnetic fields served for characterization of the sensors, whereas the investigation of artificially produced sub-{mu}m magnets substantiates the suitability of the devices for the study of novel nanoscale magnetic materials (e.g. nanowires). Systematic experiments with various magnets are in accordance with the theory of single-domain particles and anisotropic behavior due to shapes with high aspect ratio. The highest sensitivity for strongly localized fields was obtained at T=4.2 K for a (200.200) nm{sup 2} Hall cross - made from shallow, high mobility HgTe 2DEG. Although the field resolution was merely {delta}B{approx}100 {mu}T, the nanoscale sensor size yields an outstanding flux resolution of {delta}{Phi}=2.10{sup -3} {Phi}{sub 0}, where {Phi}{sub 0}=h/2e is the flux quantum. Translating this result in terms of magnetic moment, the sensitivity allows for the detection of magnetization changes of a particle centered on top of the sensor as low as {delta}M{approx}10{sup 2} {mu}{sub B}, with the magnetic moment of a single electron {mu}{sub B}, the Bohr magneton. The further examination of a permalloy

  3. Contribution to the study of electronic structure of crystalline semiconductors (Si, Ge, GaAs, Gap, ZnTe, ZnSe

    Directory of Open Access Journals (Sweden)

    Bouhafs B.

    2012-06-01

    Full Text Available The band structure of semiconductors was described by several theorists since the Fifties. The main objective of the present paper is to do a comparative study between various families of semi-conductors IV (Si,Ge, III-V (GaAs, GaP and II-VI (ZnSe, ZnTe with both methods; tight Binding1 method and pseudo potential method2. This work enables us to understand as well as the mechanism of conduction process in these semiconductors and powers and limits of the above methods. The obtained results allow to conclude that both methods are in a good agreement to describe the morphology of band structures of the cited semiconductors. This encourages us to study in the future the electronic behaviour through the structure of bands for more complex systems such as the heterostructures.

  4. Optics and Optoelectronics of Two-dimensional Semiconducting Monolayers and Heterostructures

    Science.gov (United States)

    Ross, Jason Solomon

    Until recently, the physics of truly two-dimensional (2D) excitons could only be explored theoretically. Following the discovery of graphene, many 2D materials were quickly identified and isolated, one system being the semiconducting Group VI-B transition metal dichalcogenides (TMDs). These semiconductors are the first air-stable materials that are atomically thin (three atomics thick), and yet can be produced in arbitrarily large lateral sheets. They have a direct band gap in which confinement leads to large spatial overlap of electrons and holes resulting in strongly coupled excitonic transitions that dominate light-matter interactions. The direct band-gap of monolayer TMDs occurs at the corners of the hexagonal Brillouin zone, referred to as the K valleys. Entirely unique to these materials, excitons in adjacent K valleys selectively couple to light of opposite circular polarization, i.e. the K (K') valley is selective to right (left) circularly polarized photons. This property offers the possible realization of novel devices that will manipulate the valley index, known as valleytronics. Further, creating a stacked heterostructure (HS) of two TMD monolayers of different molecular species can exhibit type-II band alignment leading to the first atomically sharp built-in p-n junction and a bright interlayer exciton with long lifetimes. Being flat 2D sheets, it is easy to couple these materials to nearby systems such as microfabricated electrodes and photonic crystal cavities allowing for unique modulation and device schemes. Here, I employ both optical and electronic techniques to study the unique physics of 2D excitons in TMDs as well as demonstrate some of their first optoelectronic and valleytronic devices. The most notable achievement is perhaps the first demonstrations of both atomically thin and 2D heterostructure light emitting diodes and photovoltaic devices. Other breakthroughs include the first demonstration of exciton charging tunability in a 2D system

  5. A novel partial SOI LDMOSFET with periodic buried oxide for breakdown voltage and self heating effect enhancement

    Science.gov (United States)

    Jamali Mahabadi, S. E.; Rajabi, Saba; Loiacono, Julian

    2015-09-01

    In this paper a partial silicon on insulator (PSOI) lateral double diffused metal oxide semiconductor field effect transistor (LDMOSFET) with periodic buried oxide layer (PBO) for enhancing breakdown voltage (BV) and self-heating effects (SHEs) is proposed for the first time. This new structure is called periodic buried oxide partial silicon on insulator (PBO-PSOI). In this structure, periodic small pieces of SiO2 were used as the buried oxide (BOX) layer in PSOI to modulate the electric field in the structure. It was demonstrated that the electric field is distributed more evenly by producing additional electric field peaks, which decrease the common peaks near the drain and gate junctions in the PBO-PSOI structure. Hence, the area underneath the electric field curve increases which leads to higher breakdown voltage. Also a p-type Si window was introduced in the source side to force the substrate to share the vertical voltage drop, leading to a higher vertical BV. Furthermore, the Si window under the source and those between periodic pieces of SiO2 create parallel conduction paths between the active layer and substrate thereby alleviating the SHEs. Simulations with the two dimensional ATLAS device simulator from the Silvaco suite of simulation tools show that the BV of PBO-PSOI is 100% higher than that of the conventional partial SOI (C-PSOI) structure. Furthermore the PBO-PSOI structure alleviates SHEs to a greater extent than its C-PSOI counterpart. The achieved drain current for the PBO-PSOI structure (100 μA), at drain-source voltage of VDS = 100 V and gate-source voltage of VGS = 25 V, is shown to be significantly larger than that in C-PSOI and fully depleted SOI (FD-SOI) structures (87 μA and 51 μA respectively). Drain current can be further improved at the expense of BV by increasing the doping of the drift region.

  6. A Versatile and Simple Approach to Generate Light Emission in Semiconductors Mediated by Electric Double Layers

    KAUST Repository

    Pu, Jiang

    2017-04-18

    The light-emitting device is the primary device for current light sources. In principle, conventional light-emitting devices need heterostructures and/or intentional carrier doping to form a p-n junction. This junction formation is, however, very difficult to achieve for most emerging semiconductors, and the fabrication of light-emitting devices is invariably a significant challenge. This study proposes a versatile and simple approach to realize light-emitting devices. This proposed device requires only a semiconducting film with two electrodes that are covered with an electrolyte. This unique structure achieves light emission at a voltage slightly larger than the bandgap energy of materials. This study applies this concept to emerging direct bandgap semiconductors, such as transition metal dichalcogenide monolayers and zinc oxide single crystals. These devices generate obvious light emission and provide sufficient evidence of the formation of a dynamic p-i-n junction or tunneling junction, presenting a versatile technique to develop optoelectronic devices.

  7. Progress towards Spin-Based Light Emission in Group IV Semiconductors

    Directory of Open Access Journals (Sweden)

    Sebastiano De Cesari

    2017-03-01

    Full Text Available Spin-optoelectronics is an emerging technology in which novel and advanced functionalities are enabled by the synergetic integration of magnetic, optical and electronic properties onto semiconductor-based devices. This article reviews the possible implementation and convergence of spintronics and photonics concepts on group IV semiconductors: the core materials of mainstream microelectronics. In particular, we describe the rapid pace of progress in the achievement of lasing action in the notable case of Ge-based heterostructures and devote special attention to the pivotal role played by optical investigations in advancing the understanding of the rich spin physics of group IV materials. Finally, we scrutinize recent developments towards the monolithic integration on Si of a new class of spin-based light emitting devices having prospects for applications in fields such as cryptography and interconnects.

  8. Goos–Hänchen effect for optical vibrational modes in a semiconductor structure

    Science.gov (United States)

    Villegas, Diosdado; Arriaga, J.; de León-Pérez, Fernando; Pérez-Álvarez, R.

    2017-03-01

    We study the tunneling of optical vibrational modes with transverse horizontal polarization that impinge, at a given angle, on a semiconductor heterostructure. We find a large influence of the Goos–Hänchen shift on tunneling times. In particular, a Goos–Hänchen shift larger than the barrier thickness is reported for the first time. The relation between Goos–Hänchen and Hartman effects is also discussed. The identity that equals the dwell time to the sum of transmission and interference times, previously derived for one-dimensional tunneling problems, is extended to the two-dimensional case. Closed-form expressions are developed for the relevant quantities. Instead of using the standard approach, the interference time is computed from the vibrational energy density. The present study could be useful for the design of semiconductor devices.

  9. Goos-Hänchen effect for optical vibrational modes in a semiconductor structure.

    Science.gov (United States)

    Villegas, Diosdado; Arriaga, J; de León-Pérez, Fernando; Pérez-Álvarez, R

    2017-03-29

    We study the tunneling of optical vibrational modes with transverse horizontal polarization that impinge, at a given angle, on a semiconductor heterostructure. We find a large influence of the Goos-Hänchen shift on tunneling times. In particular, a Goos-Hänchen shift larger than the barrier thickness is reported for the first time. The relation between Goos-Hänchen and Hartman effects is also discussed. The identity that equals the dwell time to the sum of transmission and interference times, previously derived for one-dimensional tunneling problems, is extended to the two-dimensional case. Closed-form expressions are developed for the relevant quantities. Instead of using the standard approach, the interference time is computed from the vibrational energy density. The present study could be useful for the design of semiconductor devices.

  10. Polymer semiconductor crystals

    Directory of Open Access Journals (Sweden)

    Jung Ah Lim

    2010-05-01

    Full Text Available One of the long-standing challenges in the field of polymer semiconductors is to figure out how long interpenetrating and entangled polymer chains self-assemble into single crystals from the solution phase or melt. The ability to produce these crystalline solids has fascinated scientists from a broad range of backgrounds including physicists, chemists, and engineers. Scientists are still on the hunt for determining the mechanism of crystallization in these information-rich materials. Understanding the theory and concept of crystallization of polymer semiconductors will undoubtedly transform this area from an art to an area that will host a bandwagon of scientists and engineers. In this article we describe the basic concept of crystallization and highlight some of the advances in polymer crystallization from crystals to nanocrystalline fibers.

  11. Stretchable Organic Semiconductor Devices.

    Science.gov (United States)

    Qian, Yan; Zhang, Xinwen; Xie, Linghai; Qi, Dianpeng; Chandran, Bevita K; Chen, Xiaodong; Huang, Wei

    2016-11-01

    Stretchable electronics are essential for the development of intensely packed collapsible and portable electronics, wearable electronics, epidermal and bioimplanted electronics, 3D surface compliable devices, bionics, prosthesis, and robotics. However, most stretchable devices are currently based on inorganic electronics, whose high cost of fabrication and limited processing area make it difficult to produce inexpensive, large-area devices. Therefore, organic stretchable electronics are highly attractive due to many advantages over their inorganic counterparts, such as their light weight, flexibility, low cost and large-area solution-processing, the reproducible semiconductor resources, and the easy tuning of their properties via molecular tailoring. Among them, stretchable organic semiconductor devices have become a hot and fast-growing research field, in which great advances have been made in recent years. These fantastic advances are summarized here, focusing on stretchable organic field-effect transistors, light-emitting devices, solar cells, and memory devices.

  12. Compound semiconductor device modelling

    CERN Document Server

    Miles, Robert

    1993-01-01

    Compound semiconductor devices form the foundation of solid-state microwave and optoelectronic technologies used in many modern communication systems. In common with their low frequency counterparts, these devices are often represented using equivalent circuit models, but it is often necessary to resort to physical models in order to gain insight into the detailed operation of compound semiconductor devices. Many of the earliest physical models were indeed developed to understand the 'unusual' phenomena which occur at high frequencies. Such was the case with the Gunn and IMPATI diodes, which led to an increased interest in using numerical simulation methods. Contemporary devices often have feature sizes so small that they no longer operate within the familiar traditional framework, and hot electron or even quantum­ mechanical models are required. The need for accurate and efficient models suitable for computer aided design has increased with the demand for a wider range of integrated devices for operation at...

  13. Semiconductor physics an introduction

    CERN Document Server

    Seeger, Karlheinz

    1999-01-01

    Semiconductor Physics - An Introduction - is suitable for the senior undergraduate or new graduate student majoring in electrical engineering or physics. It will also be useful to solid-state scientists and device engineers involved in semiconductor design and technology. The text provides a lucid account of charge transport, energy transport and optical processes, and a detailed description of many devices. It includes sections on superlattices and quantum well structures, the effects of deep-level impurities on transport, the quantum Hall effect and the calculation of the influence of a magnetic field on the carrier distribution function. This 6th edition has been revised and corrected, and new sections have been added to different chapters.

  14. Single frequency semiconductor lasers

    CERN Document Server

    Fang, Zujie; Chen, Gaoting; Qu, Ronghui

    2017-01-01

    This book systematically introduces the single frequency semiconductor laser, which is widely used in many vital advanced technologies, such as the laser cooling of atoms and atomic clock, high-precision measurements and spectroscopy, coherent optical communications, and advanced optical sensors. It presents both the fundamentals and characteristics of semiconductor lasers, including basic F-P structure and monolithic integrated structures; interprets laser noises and their measurements; and explains mechanisms and technologies relating to the main aspects of single frequency lasers, including external cavity lasers, frequency stabilization technologies, frequency sweeping, optical phase locked loops, and so on. It paints a clear, physical picture of related technologies and reviews new developments in the field as well. It will be a useful reference to graduate students, researchers, and engineers in the field.

  15. Three dimensional strained semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Voss, Lars; Conway, Adam; Nikolic, Rebecca J.; Leao, Cedric Rocha; Shao, Qinghui

    2016-11-08

    In one embodiment, an apparatus includes a three dimensional structure comprising a semiconductor material, and at least one thin film in contact with at least one exterior surface of the three dimensional structure for inducing a strain in the structure, the thin film being characterized as providing at least one of: an induced strain of at least 0.05%, and an induced strain in at least 5% of a volume of the three dimensional structure. In another embodiment, a method includes forming a three dimensional structure comprising a semiconductor material, and depositing at least one thin film on at least one surface of the three dimensional structure for inducing a strain in the structure, the thin film being characterized as providing at least one of: an induced strain of at least 0.05%, and an induced strain in at least 5% of a volume of the structure.

  16. Control of single photon emitters in semiconductor nanowires by surface acoustic waves

    Science.gov (United States)

    Lazić, S.; Hernández-Mínguez, A.; Santos, P. V.

    2017-08-01

    We report on an experimental study into the effects of surface acoustic waves on the optical emission of dot-in-a-nanowire heterostructures in III-V material systems. Under direct optical excitation, the excitonic energy levels in III-nitride dot-in-a-nanowire heterostructures oscillate at the acoustic frequency, producing a characteristic splitting of the emission lines in the time-integrated photoluminescence spectra. This acoustically induced periodic tuning of the excitonic transition energies is combined with spectral detection filtering and employed as a tool to regulate the temporal output of anti-bunched photons emitted from these nanowire quantum dots. In addition, the acoustic transport of electrons and holes along a III-arsenide nanowire injects the electric charges into an ensemble of quantum dot-like recombination centers that are spatially separated from the optical excitation area. The acoustic population and depopulation mechanism determines the number of carrier recombination events taking place simultaneously in the ensemble, thus allowing control of the anti-bunching degree of the emitted photons. The results presented are relevant for the dynamic control of single photon emission in III-V semiconductor heterostructures.

  17. Process dependency on threshold voltage of GaN MOSFET on AlGaN/GaN heterostructure

    Science.gov (United States)

    Wang, Qingpeng; Jiang, Ying; Miyashita, Takahiro; Motoyama, Shin-ichi; Li, Liuan; Wang, Dejun; Ohno, Yasuo; Ao, Jin-Ping

    2014-09-01

    GaN metal-oxide-semiconductor field-effect transistors (MOSFETs) with recessed gate on AlGaN/GaN heterostructure are reported in which the drain and source ohmic contacts were fabricated on the AlGaN/GaN heterostructure and the electron channel was formed on the GaN buffer layer by removing the AlGaN barrier layer. Negative threshold voltages were commonly observed in all devices. To investigate the reasons of the negative threshold voltages, different oxide thickness, etching gas and bias power of inductively-coupled plasma (ICP) system were utilized in the fabrication process of the GaN MOSFETs. It is found that positive charges of around 1 × 1012 q/cm2 exist near the interface at the just threshold condition in both silane- and tetraethylorthosilicate (TEOS)-based devices. It is also found that the threshold voltages do not obviously change with the different etching gas (SiCl4, BCl3 and two-step etching of SiCl4/Cl2) at the same ICP bias power level (20-25 W) and will become deeper when higher bias power is used in the dry recess process which may be related to the much serious ion bombardment damage. Furthermore, X-ray photoelectron spectroscopy (XPS) experiments were done to investigate the surface conditions. It is found that N 1s peaks become lower with higher bias power of the dry etching process. Also, silicon contamination was found and could be removed by HNO3/HF solution. It indicates that the nitrogen vacancies are mainly responsible for the negative threshold voltages rather than the silicon contamination. It demonstrates that optimization of the ICP recess conditions and improvement of the surface condition are still necessary to realize enhancement-mode GaN MOSFETs on AlGaN/GaN heterostructure.

  18. Bearing and Range Estimation Algorithm for Buried Object in Underwater Acoustics

    Directory of Open Access Journals (Sweden)

    Dong Han

    2009-01-01

    (DOA of objects and objects-sensors distances, is used in MUSIC algorithm instead of classical model. The influence of the depth of buried objects is discussed. Finally, the numerical results are given in the case of buried cylindrical shells.

  19. Three-dimensional mesoscale heterostructures of ZnO nanowire arrays epitaxially grown on CuGaO2 nanoplates as individual diodes.

    Science.gov (United States)

    Forticaux, Audrey; Hacialioglu, Salih; DeGrave, John P; Dziedzic, Rafal; Jin, Song

    2013-09-24

    We report a three-dimensional (3D) mesoscale heterostructure composed of one-dimensional (1D) nanowire (NW) arrays epitaxially grown on two-dimensional (2D) nanoplates. Specifically, three facile syntheses are developed to assemble vertical ZnO NWs on CuGaO2 (CGO) nanoplates in mild aqueous solution conditions. The key to the successful 3D mesoscale integration is the preferential nucleation and heteroepitaxial growth of ZnO NWs on the CGO nanoplates. Using transmission electron microscopy, heteroepitaxy was found between the basal planes of CGO nanoplates and ZnO NWs, which are their respective (001) crystallographic planes, by the observation of a hexagonal Moiré fringes pattern resulting from the slight mismatch between the c planes of ZnO and CGO. Careful analysis shows that this pattern can be described by a hexagonal supercell with a lattice parameter of almost exactly 11 and 12 times the a lattice constants for ZnO and CGO, respectively. The electrical properties of the individual CGO-ZnO mesoscale heterostructures were measured using a current-sensing atomic force microscopy setup to confirm the rectifying p-n diode behavior expected from the band alignment of p-type CGO and n-type ZnO wide band gap semiconductors. These 3D mesoscale heterostructures represent a new motif in nanoassembly for the integration of nanomaterials into functional devices with potential applications in electronics, photonics, and energy.

  20. The relationship between the dislocations and microstructure in In0.82Ga0.18As/InP heterostructures

    Science.gov (United States)

    Zhao, Liang; Guo, Zuoxing; Wei, Qiulin; Miao, Guoqing; Zhao, Lei

    2016-10-01

    In this work, we propose a formation mechanism to explain the relationship between the surface morphology (and microstructure) and dislocations in the In0.82Ga0.18As/InP heterostructure. The In0.82Ga0.18As epitaxial layers were grown on the InP (100) substrate at various temperatures (430 °C, 410 °C and 390 °C) using low pressure metalorganic chemical vapor deposition (LP-MOCVD). Obvious protrusions and depressions were obseved on the surface of the In0.82Ga0.18As/InP heterostructure because of the movement of dislocations from the core to the surface. The surface morphologies of the In0.82Ga0.18As/InP (100) system became uneven with increasing temperature, which was associated with the formation of dislocations. Such research investigating the dislocation of large lattice mismatch heterostructures may play an important role in the future-design of semiconductor films.