Defect analysis in GaN films of HEMT structure by cross-sectional cathodoluminescence

Science.gov (United States)

Isobe, Yasuhiro; Hung, Hung; Oasa, Kohei; Ono, Tasuku; Onizawa, Takashi; Yoshioka, Akira; Takada, Yoshiharu; Saito, Yasunobu; Sugiyama, Naoharu; Tsuda, Kunio; Sugiyama, Toru; Mizushima, Ichiro

2017-06-01

Defect analysis of GaN films in high electron mobility transistor (HEMT) structures by cross-sectional cathodoluminescence (X-CL) is demonstrated as a useful technique for improving the current collapse of GaN-HEMT devices, and the relationship between crystal quality and device characteristics is also investigated. The crystal quality of intrinsic-GaN (i-GaN) and carbon-doped GaN produced clearly different peak intensities of blue luminescence (BL), yellow luminescence (YL), and band-edge emission (BE), which is independently detected by X-CL. Current collapse in GaN-HEMT devices is found to be determined by the BL/BE and YL/BE ratios at the top of the i-GaN layer, which is close to the channel. Moreover, the i-GaN thickness required in order to minimize the BL/BE and YL/BE ratios and the thickness dependency of GaN for minimizing the BL/BE and YL/BE ratios depending on the growth conditions can be evaluated by X-CL. However, there is no correlation between current collapse in GaN-HEMT devices and the YL/BE ratio by conventional photoluminescence because HEMT devices consist of multiple GaN layers and the YL signal is detected from the carbon-doped GaN layer. Thus, the X-CL analysis method is a useful technique for device design in order to suppress current collapse.

Development and characteristic analysis of a field-plated Al2O3/AlInN/GaN MOS—HEMT

International Nuclear Information System (INIS)

Mao Wei; Hao Yao; Zhang Jin-Cheng; Liu Hong-Xia; Bi Zhi-Wei; Xu Sheng-Rui; Xue Jun-Shuai; Ma Xiao-Hua; Wang Chong; Yang Lin-An; Zhang Jin-Feng; Kuang Xian-Wei; Yang Cui

2011-01-01

We present an AlInN/AlN/GaN MOS—HEMT with a 3 nm ultra-thin atomic layer deposition (ALD) Al 2 O 3 dielectric layer and a 0.3 μm field-plate (FP)-MOS—HEMT. Compared with a conventional AlInN/AlN/GaN HEMT (HEMT) with the same dimensions, a FP-MOS—HEMT with a 0.6 μm gate length exhibits an improved maximum drain current of 1141 mA/mm, an improved peak extrinsic transconductance of 325 mS/mm and effective suppression of gate leakage in both the reverse direction (by about one order of magnitude) and the forward direction (by more than two orders of magnitude). Moreover, the peak extrinsic transconductance of the FP-MOS—HEMT is slightly larger than that of the HEMT, indicating an exciting improvement of transconductance performance. The sharp transition from depletion to accumulation in the capacitance—voltage (C—V) curve of the FP-MOS—HEMT demonstrates a high-quality interface of Al 2 O 3 /AlInN. In addition, a large off-state breakdown voltage of 133 V, a high field-plate efficiency of 170 V/μm and a negligible double-pulse current collapse is achieved in the FP-MOS—HEMT. This is attributed to the adoption of an ultra-thin Al 2 O 3 gate dielectric and also of a field-plate on the dielectric of an appropriate thickness. The results show a great potential application of the ultra-thin ALD-Al 2 O 3 FP-MOS—HEMT to deliver high currents and power densities in high power microwave technologies. (rapid communication)

Effect of Passivation on Microwave Power Performances of AlGaN/GaN/Si HEMTs

Directory of Open Access Journals (Sweden)

H. MOSBAHI

2014-05-01

Full Text Available This paper reports on the use of plasma assisted molecular beam epitaxy of AlGaN/GaN high electron mobility transistors (HEMTs grown on silicon substrate. Surface passivation effects on AlGaN/GaN HEMTs were studied using SiO2/SiN dielectric layers grown by plasma enhanced chemical vapor deposition. The direct current measurement, pulsed characteristics and microwave small-signal characteristics were studied before and after passivation. An improvement of drain-source current density and the extrinsic transconductance was observed on the passivated HEMTs when compared with the unpassivated HEMTs. An enhancement of cut-off frequency (ft and maximum power gain (fmax was also observed for the devices with full SiO2/SiN passivation. A good correlation is found between pulsed and power measurements.

Reverse blocking characteristics and mechanisms in Schottky-drain AlGaN/GaN HEMT with a drain field plate and floating field plates

International Nuclear Information System (INIS)

Mao Wei; She Wei-Bo; Zhang Jin-Feng; Zheng Xue-Feng; Wang Chong; Hao Yue; Yang Cui

2016-01-01

In this paper, a novel AlGaN/GaN HEMT with a Schottky drain and a compound field plate (SD-CFP HEMT) is presented for the purpose of better reverse blocking capability. The compound field plate (CFP) consists of a drain field plate (DFP) and several floating field plates (FFPs). The physical mechanisms of the CFP to improve the reverse breakdown voltage and to modulate the distributions of channel electric field and potential are investigated by two-dimensional numerical simulations with Silvaco-ATLAS. Compared with the HEMT with a Schottky drain (SD HEMT) and the HEMT with a Schottky drain and a DFP (SD-FP HEMT), the superiorities of SD-CFP HEMT lie in the continuous improvement of the reverse breakdown voltage by increasing the number of FFPs and in the same fabrication procedure as the SD-FP HEMT. Two useful optimization laws for the SD-CFP HEMTs are found and extracted from simulation results. The relationship between the number of the FFPs and the reverse breakdown voltage as well as the FP efficiency in SD-CFP HEMTs are discussed. The results in this paper demonstrate a great potential of CFP for enhancing the reverse blocking ability in AlGaN/GaN HEMT and may be of great value and significance in the design and actual manufacture of SD-CFP HEMTs. (paper)

Novel attributes of AlGaN/AlN/GaN/SiC HEMTs with the multiple indented channel

Science.gov (United States)

Orouji, Ali A.; Ghaffari, Majid

2015-11-01

In this paper, a high performance AlGaN/AlN/GaN/SiC High Electron Mobility Transistor (HEMT) with the multiple indented channel (MIC-HEMT) is proposed. The main focus of the proposed structure is based on reduction of the space around the gate, stop of the spread of the depletion region around the source-drain, and decrement of the thickness of the channel between the gate and drain. Therefore, the breakdown voltage increases, meanwhile the elimination of the gate depletion layer extension to source/drain decreases the gate-source and gate-drain capacitances. The optimized results reveal that the breakdown voltage and the drain saturation current increase about 178% and 46% compared with a conventional HEMT (C-HEMT), respectively. Therefore, the maximum output power density is improved by factor 4.1 in comparison with conventional one. Also, the cut-off frequency of 25.2 GHz and the maximum oscillation frequency of 92.1 GHz for the MIC-HEMT are obtained compared to 13 GHz and 43 GHz for that of the C-HEMT and the minimum figure noise decreased consequently of reducing the gate-drain and gate-source capacitances by about 42% and 40%, respectively. The proposed MIC-HEMT shows a maximum stable gain (MSG) exceeding 24.1 dB at 3.1 GHz which the greatest gain is yet reported for HEMTs, showing the potential of this device for high power RF applications.

Design of Low Inductance Switching Power Cell for GaN HEMT Based Inverter

Energy Technology Data Exchange (ETDEWEB)

Gurpinar, Emre [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Power Electronics and Electric Machinery Research Group; Iannuzzo, Francesco [Aalborg Univ., Aalborg (Denmark). Dept. of Energy Technology; Yang, Yongheng [Aalborg Univ., Aalborg (Denmark). Dept. of Energy Technology; Castellazzi, Alberto [Univ. of Nottingham (United Kingdom). Power Electronics, Machines and Control (PEMC); Blaabjerg, Frede [Aalborg Univ., Aalborg (Denmark). Dept. of Energy Technology

2017-11-23

Here in this paper, an ultra-low inductance power cell is designed for a three-Level Active Neutral Point Clamped (3LANPC) based on 650 V gallium nitride (GaN) HEMT devices. The 3L-ANPC topology with GaN HEMT devices and the selected modulation scheme suitable for wide-bandgap (WBG) devices are presented. The commutation loops, which mainly contribute to voltage overshoots and increase of switching losses, are discussed. The ultra-low inductance power cell design based on a fourlayer Printed Circuit Board (PCB) with the aim to maximize the switching performance of GaN HEMTs is explained. The design of gate drivers for the GaN HEMT devices is presented. Parasitic inductance and resistance of the proposed design are extracted with finite element analysis and discussed. Common mode behaviours based on the SPICE model of the converter are analyzed. Experimental results on the designed 3L-ANPC with the output power of up to 1 kW are presented, which verifies the performance of the proposed design in terms of ultra-low inductance.

Design of Low Inductance Switching Power Cell for GaN HEMT Based Inverter

International Nuclear Information System (INIS)

Gurpinar, Emre; Iannuzzo, Francesco; Yang, Yongheng; Castellazzi, Alberto; Blaabjerg, Frede

2017-01-01

Here in this paper, an ultra-low inductance power cell is designed for a three-Level Active Neutral Point Clamped (3LANPC) based on 650 V gallium nitride (GaN) HEMT devices. The 3L-ANPC topology with GaN HEMT devices and the selected modulation scheme suitable for wide-bandgap (WBG) devices are presented. The commutation loops, which mainly contribute to voltage overshoots and increase of switching losses, are discussed. The ultra-low inductance power cell design based on a fourlayer Printed Circuit Board (PCB) with the aim to maximize the switching performance of GaN HEMTs is explained. The design of gate drivers for the GaN HEMT devices is presented. Parasitic inductance and resistance of the proposed design are extracted with finite element analysis and discussed. Common mode behaviours based on the SPICE model of the converter are analyzed. Experimental results on the designed 3L-ANPC with the output power of up to 1 kW are presented, which verifies the performance of the proposed design in terms of ultra-low inductance.

C-V characterization of Schottky- and MIS-gate SiGe/Si HEMT structures

International Nuclear Information System (INIS)

Onojima, Norio; Kasamatsu, Akihumi; Hirose, Nobumitsu; Mimura, Takashi; Matsui, Toshiaki

2008-01-01

Electrical properties of Schottky- and metal-insulator-semiconductor (MIS)-gate SiGe/Si high electron mobility transistors (HEMTs) were investigated with capacitance-voltage (C-V) measurements. The MIS-gate HEMT structure was fabricated using a SiN gate insulator formed by catalytic chemical vapor deposition (Cat-CVD). The Cat-CVD SiN thin film (5 nm) was found to be an effective gate insulator with good gate controllability and dielectric properties. We previously investigated device characteristics of sub-100-nm-gate-length Schottky- and MIS-gate HEMTs, and reported that the MIS-gate device had larger maximum drain current density and transconductance (g m ) than the Schottky-gate device. The radio frequency (RF) measurement of the MIS-gate device, however, showed a relatively lower current gain cutoff frequency f T compared with that of the Schottky-gate device. In this study, C-V characterization of the MIS-gate HEMT structure demonstrated that two electron transport channels existed, one at the SiGe/Si buried channel and the other at the SiN/Si surface channel

C-V characterization of Schottky- and MIS-gate SiGe/Si HEMT structures

Energy Technology Data Exchange (ETDEWEB)

Onojima, Norio [National Institute of Information and Communications Technology (NICT), Koganei, Tokyo 184-8795 (Japan)], E-mail: nonojima@nict.go.jp; Kasamatsu, Akihumi; Hirose, Nobumitsu [National Institute of Information and Communications Technology (NICT), Koganei, Tokyo 184-8795 (Japan); Mimura, Takashi [National Institute of Information and Communications Technology (NICT), Koganei, Tokyo 184-8795 (Japan); Fujitsu Laboratories Ltd., Atsugi, Kanagawa 243-0197 (Japan); Matsui, Toshiaki [National Institute of Information and Communications Technology (NICT), Koganei, Tokyo 184-8795 (Japan)

2008-07-30

Electrical properties of Schottky- and metal-insulator-semiconductor (MIS)-gate SiGe/Si high electron mobility transistors (HEMTs) were investigated with capacitance-voltage (C-V) measurements. The MIS-gate HEMT structure was fabricated using a SiN gate insulator formed by catalytic chemical vapor deposition (Cat-CVD). The Cat-CVD SiN thin film (5 nm) was found to be an effective gate insulator with good gate controllability and dielectric properties. We previously investigated device characteristics of sub-100-nm-gate-length Schottky- and MIS-gate HEMTs, and reported that the MIS-gate device had larger maximum drain current density and transconductance (g{sub m}) than the Schottky-gate device. The radio frequency (RF) measurement of the MIS-gate device, however, showed a relatively lower current gain cutoff frequency f{sub T} compared with that of the Schottky-gate device. In this study, C-V characterization of the MIS-gate HEMT structure demonstrated that two electron transport channels existed, one at the SiGe/Si buried channel and the other at the SiN/Si surface channel.

A Novel Application of Fourier Transform Spectroscopy with HEMT Amplifiers at Microwave Frequencies

Science.gov (United States)

Wilkinson, David T.; Page, Lyman

1995-01-01

The goal was to develop cryogenic high-electron-mobility transistor (HEMT) based radiometers and use them to measure the anisotropy in the cosmic microwave background (CMB). In particular, a novel Fourier transform spectrometer (FTS) built entirely of waveguide components would be developed. A dual-polarization Ka-band HEMT radiometer and a similar Q-band radiometer were built. In a series of measurements spanning three years made from a ground-based site in Saskatoon, SK, the amplitude, frequency spectrum, and spatial frequency spectrum of the anisotropy were measured. A prototype Ka-band FTS was built and tested, and a simplified version is proposed for the MAP satellite mission. The 1/f characteristics of HEMT amplifiers were quantified using correlation techniques.

Triple tooth AlGaN/GaN HEMT on SiC substrate: A novel structure for high-power applications

Science.gov (United States)

Ghaffari, Majid; Orouji, Ali A.; Valinataj, Mojtaba

2017-12-01

In this paper, a AlGaN/AlN/GaN/SiC High Electron Mobility Transistor (HEMT) to reduce the electric field is suggested. The main idea of this work is to improve the Direct Current (DC) and Radio Frequency (RF) properties of device by modifying the depletion region in the channel. The proposed structure consists of a floating metal like a comb with triple tooth which is located in the space between the gate and drain and inside the buffer layer. We called the proposed structure as triple tooth HEMT (TT-HEMT). The RF and DC characteristics of the proposed structure are studied using numerical simulations. The breakdown voltage ( V BR ) increases to 169.5 V for the proposed structure in comparison with 103 V for the conventional HEMT (C-HEMT) due to the modified electric field distribution in the channel of the TT-HEMT structure. The maximum output power density ( P max ) of the TT-HEMT structure is 60.4% greater than that of the C-HEMT. The optimized results show that the maximum oscillation frequency ( f max ) and cut-off frequency (fT) of the proposed structure improve 111% and 26.5%, respectively compared to the C-HEMT structure. In addition, the maximum available gain (MAG) of the TT-HEMT structure is obtained 8.5 dB higher than that of the C-HEMT structure at the frequency of 40 GHz. The optimal results show that whatever the number of teeth on metal increases, the depletion region in the channel is modified more and the breakdown voltage increases, as well. Besides, the output power density ( P max ) is improved with the increasing number of teeth on metal (N). This characteristic is also true, for the cut-off frequency ( f T ), the maximum oscillation frequency ( f max ) and the maximum available gain (MAG) of the proposed structure. However, the drain current ( I D ) of the proposed structure is reduced.

Reverse blocking characteristics and mechanisms in Schottky-drain AlGaN/GaN HEMT with a drain field plate and floating field plates

Science.gov (United States)

Wei, Mao; Wei-Bo, She; Cui, Yang; Jin-Feng, Zhang; Xue-Feng, Zheng; Chong, Wang; Yue, Hao

2016-01-01

In this paper, a novel AlGaN/GaN HEMT with a Schottky drain and a compound field plate (SD-CFP HEMT) is presented for the purpose of better reverse blocking capability. The compound field plate (CFP) consists of a drain field plate (DFP) and several floating field plates (FFPs). The physical mechanisms of the CFP to improve the reverse breakdown voltage and to modulate the distributions of channel electric field and potential are investigated by two-dimensional numerical simulations with Silvaco-ATLAS. Compared with the HEMT with a Schottky drain (SD HEMT) and the HEMT with a Schottky drain and a DFP (SD-FP HEMT), the superiorities of SD-CFP HEMT lie in the continuous improvement of the reverse breakdown voltage by increasing the number of FFPs and in the same fabrication procedure as the SD-FP HEMT. Two useful optimization laws for the SD-CFP HEMTs are found and extracted from simulation results. The relationship between the number of the FFPs and the reverse breakdown voltage as well as the FP efficiency in SD-CFP HEMTs are discussed. The results in this paper demonstrate a great potential of CFP for enhancing the reverse blocking ability in AlGaN/GaN HEMT and may be of great value and significance in the design and actual manufacture of SD-CFP HEMTs. Project supported by the National Natural Science Foundation of China (Grant Nos. 61204085, 61334002, 61306017, 61474091, 61574112, and 61574110).

Field plated 0.15 μm GaN HEMTs for millimeter-wave application

International Nuclear Information System (INIS)

Ren Chunjiang; Li Zhonghui; Yu Xuming; Wang Quanhui; Wang Wen; Chen Tangsheng; Zhang Bin

2013-01-01

SiN dielectrically-defined 0.15 μm field plated GaN HEMTs for millimeter-wave application have been presented. The AlGaN/GaN hetero-structure epitaxial material for HEMTs fabrication was grown on a 3-inch SiC substrate with an Fe doped GaN buffer layer by metal-organic chemical deposition. Electron beam lithography was used to define both the gate footprint and the cap of the gate with an integrated field plate. Gate recessing was performed to control the threshold voltage of the devices. The fabricated GaN HEMTs exhibited a unit current gain cut-off frequency of 39 GHz and a maximum frequency of oscillation of 63 GHz. Load-pull measurements carried out at 35 GHz showed a power density of 4 W/mm with associated power gain and power added efficiency of 5.3 dB and 35%, respectively, for a 0.15 mm gate width device operated at a 24 V drain bias. The developed 0.15 μm gate length GaN HEMT technology is suitable for Ka band applications and is ready for millimeter-wave power MMICs development. (semiconductor devices)

A gate current 1/f noise model for GaN/AlGaN HEMTs

International Nuclear Information System (INIS)

Liu Yu'an; Zhuang Yiqi

2014-01-01

This work presents a theoretical and experimental study on the gate current 1/f noise in AlGaN/GaN HEMTs. Based on the carrier number fluctuation in the two-dimensional electron gas channel of AlGaN/GaN HEMTs, a gate current 1/f noise model containing a trap-assisted tunneling current and a space charge limited current is built. The simulation results are in good agreement with the experiment. Experiments show that, if V g < V x (critical gate voltage of dielectric relaxation), gate current 1/f noise comes from the superimposition of trap-assisted tunneling RTS (random telegraph noise), while V g > V x , gate current 1/f noise comes from not only the trap-assisted tunneling RTS, but also the space charge limited current RTS. This indicates that the gate current 1/f noise of the GaN-based HEMTs device is sensitive to the interaction of defects and the piezoelectric relaxation. It provides a useful characterization tool for deeper information about the defects and their evolution in AlGaN/GaN HEMTs. (semiconductor devices)

New AlGaN/GaN HEMTs employing both a floating gate and a field plate

International Nuclear Information System (INIS)

Lim, Jiyong; Choi, Young-Hwan; Kim, Young-Shil; Han, Min-Koo

2010-01-01

We designed and fabricated AlGaN/GaN high-electron-mobility transistors (HEMTs) employing both a floating gate (FG) and a field plate (FP), which increase the breakdown voltage of AlGaN/GaN HEMTs significantly without sacrificing forward electric characteristics. The electric field strength at the gate-drain region of the proposed AlGaN/GaN HEMT was reduced successfully due to an increase in the number of depletion region edges. The breakdown voltage of the proposed AlGaN/GaN HEMT was 1106 V, while those of the conventional devices with only an FP or FG were 688 and 828 V, respectively. The leakage current of the proposed AlGaN/GaN HEMTs was 1.68 μA under a reverse bias of -100 V while those of the conventional devices with only an FP or FG were 3.21 and 1.91 μA, respectively, under the same condition. The forward electric characteristics of the proposed and conventional AlGaN/GaN HEMTs are similar. The maximum drain current of the proposed AlGaN/GaN HEMTs was 344 mA mm -1 while those of the conventional devices with only an FP or FG were 350 and 357 mA mm -1 , respectively. The maximum transconductance of the proposed device was 102.9 mS mm -1 , while those of the conventional devices were 97.8 and 101.9 mS mm -1 . The breakdown voltage and the leakage current of the proposed device were improved considerably without sacrificing the forward electric characteristics. It should be noted that there were no additional processing steps and mask levels compared to the conventional FP process.

Effects of combined gate and ohmic recess on GaN HEMTs

Directory of Open Access Journals (Sweden)

Sunil Kumar

2016-09-01

Full Text Available AlGaN/GaN, because of their superior material properties, are most suitable semiconductor material for High Electron Mobility Transistors (HEMTs. In this work we investigated the hidden physics behind these materials and studied the effect of recess technology in AlGaN/GaN HEMTs. The device under investigation is simulated for different recess depth using Silvaco-Atlas TCAD. Recess technology improves the performance of AlGaN/GaN HEMTs. We considered three kinds of recess technology gate, ohmic and combination of gate and ohmic. Gate recess improves transconductance gm but it reduces the drain current Id of the device under investigation. Ohmic recess improves the transconductance gm but it introduces leakage current Ig in the device. In order to use AlGaN/GaN for high voltage operation, both the transconductance and the drain current should be reasonably high which is obtained by combining both gate and ohmic recess technologies. A good balance in transconductance and drain current is achieved by combining both gate and ohmic recess technologies without any leakage current.

New GaN based HEMT with Si3N4 or un-doped region in the barrier for high power applications

Science.gov (United States)

Razavi, S. M.; Tahmasb Pour, S.; Najari, P.

2018-06-01

New AlGaN/GaN high electron mobility transistors (HEMTs) that their barrier layers under the gate are divided into two regions horizontally are presented in this work. Upper region is Si3N4 (SI-HEMT) or un-doped AlGaN (UN-HEMT) and lower region is AlGaN with heavier doping compared to barrier layer. Upper region in SI-HEMT and UN-HEMT reduces peak electric field in the channel and then improves breakdown voltage considerably. Lower region increases electron density in the two dimensional electron gas (2-DEG) and enhances drain current significantly. For instance, saturated drain current in SI-HEMT is about 100% larger than that in the conventional one. Moreover, the maximum breakdown voltage in the proposed structures is 65 V. This value is about 30% larger than that in the conventional transistor (50 V). Also, suggested structure reduces short channel effect such as DIBL. The maximum gm is obtained in UN-HEMT and conventional devices. Proposed structures improve breakdown voltage and saturated drain current and then enhance maximum output power density. Maximum output power density in the new structures is about 150% higher than that in the conventional.

Breaking Through the Multi-Mesa-Channel Width Limited of Normally Off GaN HEMTs Through Modulation of the Via-Hole-Length

Science.gov (United States)

Chien, Cheng-Yen; Wu, Wen-Hsin; You, Yao-Hong; Lin, Jun-Huei; Lee, Chia-Yu; Hsu, Wen-Ching; Kuan, Chieh-Hsiung; Lin, Ray-Ming

2017-06-01

We present new normally off GaN high-electron-mobility transistors (HEMTs) that overcome the typical limitations in multi-mesa-channel (MMC) width through modulation of the via-hole-length to regulate the charge neutrality screen effect. We have prepared enhancement-mode (E-mode) GaN HEMTs having widths of up to 300 nm, based on an enhanced surface pinning effect. E-mode GaN HEMTs having MMC structures and widths as well as via-hole-lengths of 100 nm/2 μm and 300 nm/6 μm, respectively, exhibited positive threshold voltages ( V th) of 0.79 and 0.46 V, respectively. The on-resistances of the MMC and via-hole-length structures were lower than those of typical tri-gate nanoribbon GaN HEMTs. In addition, the devices not only achieved the E-mode but also improved the power performance of the GaN HEMTs and effectively mitigated the device thermal effect. We controlled the via-hole-length sidewall surface pinning effect to obtain the E-mode GaN HEMTs. Our findings suggest that via-hole-length normally off GaN HEMTs have great potential for use in next-generation power electronics.

Annealing, temperature, and bias-induced threshold voltage instabilities in integrated E/D-mode InAlN/GaN MOS HEMTs

Science.gov (United States)

Blaho, M.; Gregušová, D.; Haščík, Š.; Ťapajna, M.; Fröhlich, K.; Šatka, A.; Kuzmík, J.

2017-07-01

Threshold voltage instabilities are examined in self-aligned E/D-mode n++ GaN/InAlN/GaN MOS HEMTs with a gate length of 2 μm and a source-drain spacing of 10 μm integrated in a logic invertor. The E-mode MOS HEMT technology is based on selective dry etching of the cap layer which is combined with Al2O3 grown by atomic-layer deposition at 380 K. In the D-mode MOS HEMT, the gate recessing is skipped. The nominal threshold voltage (VT) of E/D-mode MOS HEMTs was 0.6 and -3.4 V, respectively; the technology invariant maximal drain current was about 0.45 A/mm. Analysis after 580 K/15 min annealing step and at an elevated temperature up to 430 K reveals opposite device behavior depending on the HEMT operational mode. It was found that the annealing step decreases VT of the D-mode HEMT due to a reduced electron injection into the modified oxide. On the other hand, VT of the E-mode HEMT increases with reduced density of surface donors at the oxide/InAlN interface. Operation at the elevated temperature produces reversible changes: increase/decrease in the VT of the respective D-/E-mode HEMTs. Additional bias-induced experiments exhibit complex trapping phenomena in the devices: Coaction of shallow (˜0.1 eV below EC) traps in the GaN buffer and deep levels at the oxide/InAlN interface was identified for the E-mode device, while trapping in the D-mode HEMTs was found to be consistent with a thermo-ionic injection of electrons into bulk oxide traps (˜0.14 eV above EF) and trapping at the oxide/GaN cap interface states.

Projecting Pyongyang: The Future of North Korea's Kim Jong IL Regime

National Research Council Canada - National Science Library

Scobell, Andrew

2008-01-01

.... In this monograph, the focus is on the fate of the regime dominated by the Kim Dynasty, initially ruled by Kim Il Sung and then led by his son, Kim Jong Il, following the former's death in 1994...

DC Characteristics of AlGaN/GaN HEMTs Using a Dual-Gate Structure.

Science.gov (United States)

Hong, Sejun; Rana, Abu ul Hassan Sarwar; Heo, Jun-Woo; Kim, Hyun-Seok

2015-10-01

Multiple techniques such as fluoride-based plasma treatment, a p-GaN or p-AlGaN gate contact, and a recessed gate structure have been employed to modulate the threshold voltage of AlGaN/GaN-based high-electron-mobility transistors (HEMTs). In this study, we present dual-gate AlGaN/GaN HEMTs grown on a Si substrate, which effectively shift the threshold voltage in the positive direction. Experimental data show that the threshold voltage is shifted from -4.2 V in a conventional single-gate HEMT to -2.8 V in dual-gate HEMTs. It is evident that a second gate helps improve the threshold voltage by reducing the two-dimensional electron gas density in the channel. Furthermore, the maximum drain current, maximum transconductance, and breakdown voltage values of a single-gate device are not significantly different from those of a dual-gate device. For the fabricated single- and dual-gate devices, the values of the maximum drain current are 430 mA/mm and 428 mA/mm, respectively, whereas the values of the maximum transconductance are 83 mS/mm and 75 mS/mm, respectively.

Breaking Through the Multi-Mesa-Channel Width Limited of Normally Off GaN HEMTs Through Modulation of the Via-Hole-Length.

Science.gov (United States)

Chien, Cheng-Yen; Wu, Wen-Hsin; You, Yao-Hong; Lin, Jun-Huei; Lee, Chia-Yu; Hsu, Wen-Ching; Kuan, Chieh-Hsiung; Lin, Ray-Ming

2017-12-01

We present new normally off GaN high-electron-mobility transistors (HEMTs) that overcome the typical limitations in multi-mesa-channel (MMC) width through modulation of the via-hole-length to regulate the charge neutrality screen effect. We have prepared enhancement-mode (E-mode) GaN HEMTs having widths of up to 300 nm, based on an enhanced surface pinning effect. E-mode GaN HEMTs having MMC structures and widths as well as via-hole-lengths of 100 nm/2 μm and 300 nm/6 μm, respectively, exhibited positive threshold voltages (V th ) of 0.79 and 0.46 V, respectively. The on-resistances of the MMC and via-hole-length structures were lower than those of typical tri-gate nanoribbon GaN HEMTs. In addition, the devices not only achieved the E-mode but also improved the power performance of the GaN HEMTs and effectively mitigated the device thermal effect. We controlled the via-hole-length sidewall surface pinning effect to obtain the E-mode GaN HEMTs. Our findings suggest that via-hole-length normally off GaN HEMTs have great potential for use in next-generation power electronics.

Enhanced lateral heat dissipation packaging structure for GaN HEMTs on Si substrate

International Nuclear Information System (INIS)

Cheng, Stone; Chou, Po-Chien; Chieng, Wei-Hua; Chang, E.Y.

2013-01-01

This work presents a technology for packaging AlGaN/GaN high electron mobility transistors (HEMTs) on a Si substrate. The GaN HEMTs are attached to a V-groove copper base and mounted on a TO-3P leadframe. The various thermal paths from the GaN gate junction to the case are carried out for heat dissipation by spreading to protective coating; transferring through the bond wires; spreading in the lateral device structure through the adhesive layer, and vertical heat spreading of silicon chip bottom. Thermal characterization showed a thermal resistance of 13.72 °C/W from the device to the TO-3P package. Experimental tests of a 30 mm gate-periphery single chip packaged in a 5 × 3 mm V-groove Cu base with a 100 V drain bias showed power dissipation of 22 W. -- Highlights: ► An enhanced packaging structure designed for AlGaN/GaN HEMTs on an Si substrate. ► The V-groove copper base is designed on the device periphery surface heat conduction for enhancing Si substrate thermal dissipation. ► The proposed device shows a lower thermal resistance and upgrade in thermal conductivity capability. ► This work provides useful thermal IR imagery information to aid in designing high efficiency package for GaN HEMTs on Si

The ten thousand Kims

Science.gov (United States)

Baek, Seung Ki; Minnhagen, Petter; Kim, Beom Jun

2011-07-01

In Korean culture, the names of family members are recorded in special family books. This makes it possible to follow the distribution of Korean family names far back in history. It is shown here that these name distributions are well described by a simple null model, the random group formation (RGF) model. This model makes it possible to predict how the name distributions change and these predictions are shown to be borne out. In particular, the RGF model predicts that for married women entering a collection of family books in a certain year, the occurrence of the most common family name 'Kim' should be directly proportional to the total number of married women with the same proportionality constant for all the years. This prediction is also borne out to a high degree. We speculate that it reflects some inherent social stability in the Korean culture. In addition, we obtain an estimate of the total population of the Korean culture down to the year 500 AD, based on the RGF model, and find about ten thousand Kims.

The ten thousand Kims

International Nuclear Information System (INIS)

Baek, Seung Ki; Minnhagen, Petter; Kim, Beom Jun

2011-01-01

In Korean culture, the names of family members are recorded in special family books. This makes it possible to follow the distribution of Korean family names far back in history. It is shown here that these name distributions are well described by a simple null model, the random group formation (RGF) model. This model makes it possible to predict how the name distributions change and these predictions are shown to be borne out. In particular, the RGF model predicts that for married women entering a collection of family books in a certain year, the occurrence of the most common family name 'Kim' should be directly proportional to the total number of married women with the same proportionality constant for all the years. This prediction is also borne out to a high degree. We speculate that it reflects some inherent social stability in the Korean culture. In addition, we obtain an estimate of the total population of the Korean culture down to the year 500 AD, based on the RGF model, and find about ten thousand Kims.

60Co gamma radiation effect on AlGaN//AlN/GaN HEMT devices

International Nuclear Information System (INIS)

Wang Yanping; Luo Yinhong; Wang Wei; Zhang Keying; Guo Hongxia; Guo Xiaoqiang; Wang Yuanming

2013-01-01

The testing techniques and experimental methods of the 60 Co gamma irradiation effect on AlGaN/AlN/GaN high electron mobility transistors (HEMTs) are established. The degradation of the electrical properties of the device under the actual radiation environment are analyzed theoretically, and studies of the total dose effects of gamma radiation on AlGaN/AlN/GaN HEMTs at three different radiation bias conditions are carried out. The degradation patterns of the main parameters of the AlGaN/AlN/GaN HEMTs at different doses are then investigated, and the device parameters that were sensitive to the gamma radiation induced damage and the total dose level induced device damage are obtained. (authors)

Monolithically integrated enhancement/depletion-mode AlGaN/GaN HEMT D flip-flop using fluorine plasma treatment

International Nuclear Information System (INIS)

Xie Yuanbin; Quan Si; Ma Xiaohua; Zhang Jincheng; Li Qingmin; Hao Yue

2011-01-01

Depletion-mode and enhancement-mode AlGaN/GaN HEMTs using fluorine plasma treatment were integrated on one wafer. Direct-coupled FET logic circuits, such as an E/D HEMT inverter, NAND gate and D flip-flop, were fabricated on an AlGaN/GaN heterostructure. The D flip-flop and NAND gate are demonstrated in a GaN system for the first time. The dual-gate AlGaN/GaN E-HEMT substitutes two single-gate E-HEMTs for simplifying the NAND gate and shrinking the area, integrating with a conventional AlGaN/GaN D-HEMT and demonstrating a NAND gate. E/D-mode D flip-flop was fabricated by integrating the inverters and the NAND gate on the AlGaN/GaN heterostructure. At a supply voltage of 2 V, the E/D inverter shows an output logic swing of 1.7 V, a logic-low noise margin of 0.49 V and a logic-high noise margin of 0.83 V. The NAND gate and D flip-flop showed correct logic function demonstrating promising potential for GaN-based digital ICs. (semiconductor integrated circuits)

Demonstration of a Submillimeter-Wave HEMT Oscillator Module at 330 GHz

Science.gov (United States)

Radisic, Vesna; Deal, W. R.; Mei, X. B.; Yoshida, Wayne; Liu, P. H.; Uyeda, Jansen; Lai, Richard; Samoska, Lorene; Fung, King Man; Gaier, Todd;

Effects of structural modification on reliability of nanoscale nitride HEMTs

Science.gov (United States)

Gaddipati, Vamsi Mohan

AlGaN based nanoscale high-electron-mobility transistors (HEMTs) are the next generation of transistor technology that features the unique combination of higher power, wider bandwidth, low noise, higher efficiency, and temperature/radiation hardness than conventional AlGaAs and Si based technologies. However, as evidenced by recent stress tests, reliability of these devices (characterized by a gradual decrease in the output current/power leading to failure of the device in just tens of hours of operation) remains a major concern. Although, in these tests, physical damages were clearly visible in the device, the root cause and nature of these damages have not yet been fully assessed experimentally. Therefore, a comprehensive theoretical study of the physical mechanisms responsible for degradation of AlGaN HEMTs is essential before these devices are deployed in targeted applications. The main objective of the proposed research is to computationally investigate how degradation of state-of-the-art nanoscale AlGaN HEMTs is governed by an intricate and dynamical coupling of thermo-electromechanical processes at different length (atoms-to-transistor) and time (femtosecondto- hours) scales while operating in high voltage, large mechanical, and high temperature/radiation stresses. This work centers around a novel hypotheses as follows: High voltage applied to AlGaN HEMT causes excessive internal heat dissipation, which triggers gate metal diffusion into the semiconducting barrier layer and structural modifications (defect ii formation) leading to diminished polarization induced charge density and output current. Since the dynamical system to be studied is complex, chaotic (where the evolution rule is guided by atomicity of the underlying material), and involve coupled physical processes, an in-house multiscale simulator (QuADS 3-D) has been employed and augmented, where material parameters are obtained atomistically using firstprinciples, structural relaxation and defect

Gate metal dependent electrical characteristics of AlGaN/GaN HEMTs

International Nuclear Information System (INIS)

Koo, Sang-Mo; Kang, Min-Seok

2014-01-01

Highlights: • We investigated transfer characteristics of AlGaN/GaN high electron mobility transistors. • We demonstrate the effect of the barrier height of Schottky gate metals. • The conduction mechanisms examine by comparing the experimental results with numerical simulations. • 2-DEG concentration depends on the barrier height of Schottky gate metals. - Abstract: We investigated transfer characteristics of AlGaN/GaN high electron mobility transistors (HEMTs) and the effect of the barrier height of Schottky gate metals. It is found that the threshold voltage of the HEMT structures with the Ni Schottky contact shows a positive shift compared to that of the Ti Schottky contacts (ΔV th = 2.9 V). The maximum saturation current of the HEMT structures with the Ti Schottky contact (∼1.4 × 10 7 A/cm 2 ) is found to be ∼2.5 times higher than that of the Ni Schottky contact (2.9 × 10 7 A/cm 2 ). The conduction mechanisms have been examined by comparing the experimental results with numerical simulations, which confirm that the increased barrier height is mainly attributed to the reduction of 2-DEG concentration

Gate metal dependent electrical characteristics of AlGaN/GaN HEMTs

Energy Technology Data Exchange (ETDEWEB)

Koo, Sang-Mo, E-mail: smkoo@kw.ac.kr; Kang, Min-Seok, E-mail: hyde0220@gmail.com

2014-10-15

Highlights: • We investigated transfer characteristics of AlGaN/GaN high electron mobility transistors. • We demonstrate the effect of the barrier height of Schottky gate metals. • The conduction mechanisms examine by comparing the experimental results with numerical simulations. • 2-DEG concentration depends on the barrier height of Schottky gate metals. - Abstract: We investigated transfer characteristics of AlGaN/GaN high electron mobility transistors (HEMTs) and the effect of the barrier height of Schottky gate metals. It is found that the threshold voltage of the HEMT structures with the Ni Schottky contact shows a positive shift compared to that of the Ti Schottky contacts (ΔV{sub th} = 2.9 V). The maximum saturation current of the HEMT structures with the Ti Schottky contact (∼1.4 × 10{sup 7} A/cm{sup 2}) is found to be ∼2.5 times higher than that of the Ni Schottky contact (2.9 × 10{sup 7} A/cm{sup 2}). The conduction mechanisms have been examined by comparing the experimental results with numerical simulations, which confirm that the increased barrier height is mainly attributed to the reduction of 2-DEG concentration.

Characteristics of enhanced-mode AlGaN/GaN MIS HEMTs for millimeter wave applications

Science.gov (United States)

Lee, Jong-Min; Ahn, Ho-Kyun; Jung, Hyun-Wook; Shin, Min Jeong; Lim, Jong-Won

2017-09-01

In this paper, an enhanced-mode (E-mode) AlGaN/GaN high electron mobility transistor (HEMT) was developed by using 4-inch GaN HEMT process. We designed and fabricated Emode HEMTs and characterized device performance. To estimate the possibility of application for millimeter wave applications, we focused on the high frequency performance and power characteristics. To shift the threshold voltage of HEMTs we applied the Al2O3 insulator to the gate structure and adopted the gate recess technique. To increase the frequency performance the e-beam lithography technique was used to define the 0.15 um gate length. To evaluate the dc and high frequency performance, electrical characterization was performed. The threshold voltage was measured to be positive value by linear extrapolation from the transfer curve. The device leakage current is comparable to that of the depletion mode device. The current gain cut-off frequency and the maximum oscillation frequency of the E-mode device with a total gate width of 150 um were 55 GHz and 168 GHz, respectively. To confirm the power performance for mm-wave applications the load-pull test was performed. The measured power density of 2.32 W/mm was achieved at frequencies of 28 and 30 GHz.

An accurate and simple large signal model of HEMT

DEFF Research Database (Denmark)

Liu, Qing

1989-01-01

A large-signal model of discrete HEMTs (high-electron-mobility transistors) has been developed. It is simple and suitable for SPICE simulation of hybrid digital ICs. The model parameters are extracted by using computer programs and data provided by the manufacturer. Based on this model, a hybrid...

11.9 W Output Power at S-band from 1 mm AlGaN/GaN HEMTs

NARCIS (Netherlands)

Krämer, M.C.J.C.M.; Karouta, F.; Kwaspen, J.J.M.; Rudzinski, M.; Larsen, P.K.; Suijker, E.M.; Hek, P.A. de; Rödle, T.; Volokhine, I.; Kaufmann, L.M.F.

2008-01-01

We present radio-frequency (RF) power results of GaN-based high electron mobility transistors (HEMTs) with total gate widths (Wg) up to 1 mm. The AlGaN/GaN epi-structures are MOVPE-grown on 2-inches semi-insulating (s.i.) 4H-silicon carbide substrates. The HEMTs have been fabricated using an

Characteristics of AlGaN/GaN/AlGaN double heterojunction HEMTs with an improved breakdown voltage

International Nuclear Information System (INIS)

Ma Juncai; Zhang Jincheng; Xue Junshuai; Lin Zhiyu; Liu Ziyang; Xue Xiaoyong; Ma Xiaohua; Hao Yue

2012-01-01

We studied the performance of AlGaN/GaN double heterojunction high electron mobility transistors (DH-HEMTs) with an AlGaN buffer layer, which leads to a higher potential barrier at the backside of the two-dimensional electron gas channel and better carrier confinement. This, remarkably, reduces the drain leakage current and improves the device breakdown voltage. The breakdown voltage of AlGaN/GaN double heterojunction HEMTs (∼100 V) was significantly improved compared to that of conventional AlGaN/GaN HEMTs (∼50 V) for the device with gate dimensions of 0.5 × 100 μm and a gate—drain distance of 1 μm. The DH-HEMTs also demonstrated a maximum output power of 7.78 W/mm, a maximum power-added efficiency of 62.3% and a linear gain of 23 dB at the drain supply voltage of 35 V at 4 GHz. (semiconductor devices)

Fluorine-plasma surface treatment for gate forward leakage current reduction in AlGaN/GaN HEMTs

International Nuclear Information System (INIS)

Chen Wanjun; Zhang Jing; Zhang Bo; Chen, Kevin Jing

2013-01-01

The gate forward leakage current in AlGaN/GaN high electron mobility transistors (HEMTs) is investigated. It is shown that the current which originated from the forward biased Schottky-gate contributed to the gate forward leakage current. Therefore, a fluorine-plasma surface treatment is presented to induce the negative ions into the AlGaN layer which results in a higher metal—semiconductor barrier. Consequently, the gate forward leakage current shrinks. Experimental results confirm that the gate forward leakage current is decreased by one order magnitude lower than that of HEMT device without plasma treatment. In addition, the DC characteristics of the HEMT device with plasma treatment have been studied. (semiconductor devices)

Current collapse modeling in AlGaN/GaN HEMT using small signal equivalent circuit for high power application

Science.gov (United States)

Nirmal, D.; Arivazhagan, L.; Fletcher, A. S. Augustine; Ajayan, J.; Prajoon, P.

2018-01-01

In this paper, the drain current collapse in AlGaN/GaN High Electron Mobility Transistor (HEMT) with field plate engineering is investigated. A small signal equivalent circuit of AlGaN/GaN HEMT is developed and a new drain current model is derived. This model is useful to correlate the impact of intrinsic capacitance and conductance on drain current collapse. The proposed device suppressed the current collapse phenomena by 10% compared with the conventional AlGaN/GaN HEMT. Moreover, the DC characteristics of the simulated device shows a drain current of 900 mA/mm, breakdown voltage of 291 V and transconductance of 175 mS/mm. Besides, the intrinsic capacitance and conductance parameters are extracted and its impact on drain current is analysed. Finally, the simulation results obtained were in compliance with the derived mathematical model of AlGaN/GaN HEMT.

Anmeldelse af Kim Wind Andersen: Overblik over selskabers underskudsfremførsel

DEFF Research Database (Denmark)

Werlauff, Erik

2011-01-01

Artiklen anmelder Kim Wind Andersen: Overblik over selskabers underskudsfremførsel (Thomson Reuters Professional, 2010)......Artiklen anmelder Kim Wind Andersen: Overblik over selskabers underskudsfremførsel (Thomson Reuters Professional, 2010)...

Simplified 2DEG carrier concentration model for composite barrier AlGaN/GaN HEMT

International Nuclear Information System (INIS)

Das, Palash; Biswas, Dhrubes

2014-01-01

The self consistent solution of Schrodinger and Poisson equations is used along with the total charge depletion model and applied with a novel approach of composite AlGaN barrier based HEMT heterostructure. The solution leaded to a completely new analytical model for Fermi energy level vs. 2DEG carrier concentration. This was eventually used to demonstrate a new analytical model for the temperature dependent 2DEG carrier concentration in AlGaN/GaN HEMT

Analysis of the modulation mechanisms of the electric field and breakdown performance in AlGaN/GaN HEMT with a T-shaped field-plate

International Nuclear Information System (INIS)

Mao Wei; Fan Ju-Sheng; Du Ming; Zhang Jin-Feng; Zheng Xue-Feng; Wang Chong; Ma Xiao-Hua; Zhang Jin-Cheng; Hao Yue

2016-01-01

A novel AlGaN/GaN high electron mobility transistor (HEMT) with a source-connected T-shaped field-plate (ST-FP HEMT) is proposed for the first time in this paper. The source-connected T-shaped field-plate (ST-FP) is composed of a source-connected field-plate (S-FP) and a trench metal. The physical intrinsic mechanisms of the ST-FP to improve the breakdown voltage and the FP efficiency and to modulate the distributions of channel electric field and potential are studied in detail by means of two-dimensional numerical simulations with Silvaco-ATLAS. A comparison to the HEMT and the HEMT with an S-FP (S-FP HEMT) shows that the ST-FP HEMT could achieve a broader and more uniform channel electric field distribution with the help of a trench metal, which could increase the breakdown voltage and the FP efficiency remarkably. In addition, the relationship between the structure of the ST-FP, the channel electric field, the breakdown voltage as well as the FP efficiency in ST-FP HEMT is analyzed. These results could open up a new effective method to fabricate high voltage power devices for the power electronic applications. (paper)

High-frequency detection of cell activity of Physarum polycephalum by a planar open gate AlGaN/GaN HEMT

International Nuclear Information System (INIS)

Witte, Hartmut; Lippelt, Thomas; Warnke, Christian; Dadgar, Armin; Krost, Alois; Hauser, Marcus J B

2014-01-01

The dynamics of cells of the slime mould Physarum polycephalum are investigated with a planar AlGaN/GaN high electron mobility transistor (HEMT) without any gate metallization. The source–drain contacts are used in a two-electrode arrangement whereas the free gate surface area is occupied by the Physarum cell. In order to understand the measured signals, basic properties of the interface between the cell and the HEMT surface were analysed by impedance spectroscopy. At high frequencies the interface impedance is governed by the conductance of the cell due to a direct current through the HEMT/cell interface. The locomotive dynamics of Physarum were recorded by the source–drain impedance at 10 kHz in combination with simultaneous video imaging that monitored the degree of occupancy of the HEMT surface by the cell. A precise correlation was found between the impedance and the coverage of the HEMT surface by the cell. It is observed that the entire region between the contacts is sensitive to the cell activity. Well-resolved cellular oscillations were observed for all measured parameters. Their periods corresponded to the typical periods of the intracellular shuttle streaming of protoplasma in Physarum. This demonstrates that high-frequency impedance measurements with AlGaN/GaN HEMT structures are well suited for the analysis of both the static parts of single Physarum cells as well as of their dynamic behaviour, such as their expansion and motility. (paper)

REPRESENTATION OF KIM JONG-UN’S SUCCESSION IN BBC NEWS: A CRITICAL DISCOURSE ANALYSIS

Directory of Open Access Journals (Sweden)

Hendra Nugraha

2016-04-01

Full Text Available This research attempts to reveal representation of Kim Jong-Un’s succession in BBC News through textual and discursive practice analysis. The data of this thesis are taken from BBC News website on 29 and 31 December 2011. The theory applied to seek the objective of the research is Critical Discourse Analysis developed by Fairclough. Through textual and discursive practice analysis, the writer finds pthat BBC employs more passive material clauses than active material clauses in depicting Kim Jong-Un’s succession. BBC also represents Kim Jong-Un’s succession as premature process where Kim Jong-Un is portrayed as a young and inexperienced leader. Besides the prematurity of the succession, the present writer finds that BBC represents Kim Jong-Un’s succession as continuity of Kim’s family dynasty. Thus, the succession is based on his resemblance to Kim Il-Sung, the founder of Democratic People’s Republic of Korea, rather than Kim Jong-Un ability and competency.

The New North Korean Problem: History and Responsibilities in the Age of Kim Jong Un

Science.gov (United States)

2012-03-29

Kim Jong Un is the youngest of Kim Jong Il’s three male children. The oldest, Kim Jong Nam was once favored to...passport.49 In a series of interviews with Japanese reporter Yogi Gomi, Kim Jong Nam related his concerns about the future of North Korea and the...4. TITLE AND SUBTITLE THE NEW NORTH KOREAN PROBLEM: HISTORY AND RESPONSIBILITIES IN THE AGE OF KIM JONG UN 5. FUNDING NUMBERS

The effect of a HfO2 insulator on the improvement of breakdown voltage in field-plated GaN-based HEMT

International Nuclear Information System (INIS)

Mao Wei; Hao Yue; Ma Xiao-Hua; Wang Chong; Zhang Jin-Cheng; Liu Hong-Xia; Bi Zhi-Wei; Xu Sheng-Rui; Yang Lin-An; Yang Ling; Zhang Kai; Zhang Nai-Qian; Pei Yi; Yang Cui

2011-01-01

A GaN/Al 0.3 Ga 0.7 N/AlN/GaN high-electron mobility transistor utilizing a field plate (with a 0.3 μm overhang towards the drain and a 0.2 μm overhang towards the source) over a 165-nm sputtered HfO 2 insulator (HfO 2 -FP-HEMT) is fabricated on a sapphire substrate. Compared with the conventional field-plated HEMT, which has the same geometric structure but uses a 60-nm SiN insulator beneath the field plate (SiN-FP-HEMT), the HfO 2 -FP-HEMT exhibits a significant improvement of the breakdown voltage (up to 181 V) as well as a record field-plate efficiency (up to 276 V/μm). This is because the HfO 2 insulator can further improve the modulation of the field plate on the electric field distribution in the device channel, which is proved by the numerical simulation results. Based on the simulation results, a novel approach named the proportional design is proposed to predict the optimal dielectric thickness beneath the field plate. It can simplify the field-plated HEMT design significantly. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Analysis of the modulation mechanisms of the electric field and breakdown performance in AlGaN/GaN HEMT with a T-shaped field-plate

Science.gov (United States)

Mao, Wei; Fan, Ju-Sheng; Du, Ming; Zhang, Jin-Feng; Zheng, Xue-Feng; Wang, Chong; Ma, Xiao-Hua; Zhang, Jin-Cheng; Hao, Yue

2016-12-01

A novel AlGaN/GaN high electron mobility transistor (HEMT) with a source-connected T-shaped field-plate (ST-FP HEMT) is proposed for the first time in this paper. The source-connected T-shaped field-plate (ST-FP) is composed of a source-connected field-plate (S-FP) and a trench metal. The physical intrinsic mechanisms of the ST-FP to improve the breakdown voltage and the FP efficiency and to modulate the distributions of channel electric field and potential are studied in detail by means of two-dimensional numerical simulations with Silvaco-ATLAS. A comparison to the HEMT and the HEMT with an S-FP (S-FP HEMT) shows that the ST-FP HEMT could achieve a broader and more uniform channel electric field distribution with the help of a trench metal, which could increase the breakdown voltage and the FP efficiency remarkably. In addition, the relationship between the structure of the ST-FP, the channel electric field, the breakdown voltage as well as the FP efficiency in ST-FP HEMT is analyzed. These results could open up a new effective method to fabricate high voltage power devices for the power electronic applications. Project supported by the National Natural Science Foundation of China (Grant Nos. 61574112, 61334002, 61306017, 61474091, and 61574110) and the Natural Science Basic Research Plan in Shaanxi Province, China (Grant No. 605119425012).

Optical pumping of deep traps in AlGaN/GaN-on-Si HEMTs using an on-chip Schottky-on-heterojunction light-emitting diode

International Nuclear Information System (INIS)

Li, Baikui; Tang, Xi; Chen, Kevin J.

2015-01-01

In this work, by using an on-chip integrated Schottky-on-heterojunction light-emitting diode (SoH-LED) which is seamlessly integrated with the AlGaN/GaN high electron mobility transistor (HEMT), we studied the effect of on-chip light illumination on the de-trapping processes of electrons from both surface and bulk traps. Surface trapping was generated by applying OFF-state drain bias stress, while bulk trapping was generated by applying positive substrate bias stress. The de-trapping processes of surface and/or bulk traps were monitored by measuring the recovery of dynamic on-resistance R on and/or threshold voltage V th of the HEMT. The results show that the recovery processes of both dynamic R on and threshold voltage V th of the HEMT can be accelerated by the on-chip SoH-LED light illumination, demonstrating the potentiality of on-chip hybrid opto-HEMTs to minimize the influences of traps during dynamic operation of AlGaN/GaN power HEMTs

Investigation of the Performance of HEMT-Based NO, NO₂ and NH₃ Exhaust Gas Sensors for Automotive Antipollution Systems.

Science.gov (United States)

Halfaya, Yacine; Bishop, Chris; Soltani, Ali; Sundaram, Suresh; Aubry, Vincent; Voss, Paul L; Salvestrini, Jean-Paul; Ougazzaden, Abdallah

2016-02-23

We report improved sensitivity to NO, NO₂ and NH₃ gas with specially-designed AlGaN/GaN high electron mobility transistors (HEMT) that are suitable for operation in the harsh environment of diesel exhaust systems. The gate of the HEMT device is functionalized using a Pt catalyst for gas detection. We found that the performance of the sensors is enhanced at a temperature of 600 °C, and the measured sensitivity to 900 ppm-NO, 900 ppm-NO₂ and 15 ppm-NH₃ is 24%, 38.5% and 33%, respectively, at 600 °C. We also report dynamic response times as fast as 1 s for these three gases. Together, these results indicate that HEMT sensors could be used in a harsh environment with the ability to control an anti-pollution system in real time.

The sensitivity research of multiparameter biosensors based on HEMT by the mathematic modeling method

Science.gov (United States)

Tikhomirov, V. G.; Gudkov, A. G.; Agasieva, S. V.; Gorlacheva, E. N.; Shashurin, V. D.; Zybin, A. A.; Evseenkov, A. S.; Parnes, Y. M.

2017-11-01

The numerical impact modeling of some external effects on the CVC of biosensors based on AlGaN/GaN heterostructures (HEMT) was carried out. The mathematical model was created that allowed to predict the behavior of the drain current depending on condition changes on the heterostructure surface in the gate region and to start the process of directed construction optimization of the biosensors based on AlGaN/GaN HEMT with the aim of improving their performance. The calculation of the drain current of the biosensor construction was carried out to confirm the reliability of the developed mathematical model and obtained results.

A Novel Extraction Approach of Extrinsic and Intrinsic Parameters of InGaAs/GaN pHEMTs

Science.gov (United States)

2015-07-01

A Novel Extraction Approach of Extrinsic and Intrinsic Parameters of InGaAs/GaN pHEMTs Andong Huang1, 2, ZhengZhong2, 3, and Yongxin Guo2, 3...Suzhou Research Institute, Suzhou, China Abstract — A novel extraction approach of extrinsic and intrinsic parameters of InGaAs/GaN pHEMTs is...parameter error function. The extrinsic elements are optimized at multi-bias points and the intrinsic ones at specific bias points. Only broad ranges

High performance AlGaN/GaN HEMTs with 2.4 μm source-drain spacing

International Nuclear Information System (INIS)

Wang Dongfang; Wei Ke; Yuan Tingting; Liu Xinyu

2010-01-01

This paper describes the performance of AlGaN/GaN HEMTs with 2.4 μm source-drain spacing. So far these are the smallest source-drain spacing AlGaN/GaN HEMTs which have been implemented with a domestic wafer and domestic process. This paper also compares their performance with that of 4 μm source-drain spacing devices. The former exhibit higher drain current, higher gain, and higher efficiency. It is especially significant that the maximum frequency of oscillation noticeably increased. (semiconductor integrated circuits)

Impact of gate engineering in enhancement mode n++GaN/InAlN/AlN/GaN HEMTs

Science.gov (United States)

Adak, Sarosij; Swain, Sanjit Kumar; Rahaman, Hafizur; Sarkar, Chandan Kumar

2016-12-01

This paper illustrate the effect of gate material engineering on the performance of enhancement mode n++GaN/InAlN/AlN/GaN high electron mobility transistors (HEMTs). A comparative analysis of key device parameters is discussed for the Triple Material Gate (TMG), Dual Material Gate (DMG) and the Single Material Gate (SMG) structure HEMTs by considering the same device dimensions. The simulation results shows that an significant improvement is noticed in the key analysis parameters such as drain current (Id), transconductance (gm), cut off frequency (fT), RF current gain, maximum cut off frequency (fmax) and RF power gain of the gate material engineered devices with respect to SMG normally off n++GaN/InAlN/AlN/GaN HEMTs. This improvement is due to the existence of the perceivable step in the surface potential along the channel which successfully screens the drain potential variation in the source side of the channel for the gate engineering devices. The analysis suggested that the proposed TMG and DMG engineered structure enhancement mode n++GaN/InAlN/AlN/GaN HEMTs can be considered as a potential device for future high speed, microwave and digital application.

Optical pumping of deep traps in AlGaN/GaN-on-Si HEMTs using an on-chip Schottky-on-heterojunction light-emitting diode

Energy Technology Data Exchange (ETDEWEB)

Li, Baikui; Tang, Xi; Chen, Kevin J., E-mail: eekjchen@ust.hk [Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)

2015-03-02

In this work, by using an on-chip integrated Schottky-on-heterojunction light-emitting diode (SoH-LED) which is seamlessly integrated with the AlGaN/GaN high electron mobility transistor (HEMT), we studied the effect of on-chip light illumination on the de-trapping processes of electrons from both surface and bulk traps. Surface trapping was generated by applying OFF-state drain bias stress, while bulk trapping was generated by applying positive substrate bias stress. The de-trapping processes of surface and/or bulk traps were monitored by measuring the recovery of dynamic on-resistance R{sub on} and/or threshold voltage V{sub th} of the HEMT. The results show that the recovery processes of both dynamic R{sub on} and threshold voltage V{sub th} of the HEMT can be accelerated by the on-chip SoH-LED light illumination, demonstrating the potentiality of on-chip hybrid opto-HEMTs to minimize the influences of traps during dynamic operation of AlGaN/GaN power HEMTs.

Conversion Matrix Analysis of GaAs HEMT Active Gilbert Cell Mixers

DEFF Research Database (Denmark)

Jiang, Chenhui; Johansen, Tom Keinicke; Krozer, Viktor

2006-01-01

In this paper, the nonlinear model of the GaAs HEMT active Gilbert cell mixer is investigated. Based on the model, the conversion gain expression of active Gilbert cell mixers is derived theoretically by using conversion matrix analysis method. The expression is verified by harmonic balance simul...

GaN growth on sapphire by MOCVD - Material for HEMT structures

NARCIS (Netherlands)

Grzegorczyk, A.P.

2006-01-01

This thesis focuses on growth and basic characterization of AlGaN/GaN based high electron mobility structures. In order to provide theoretical background for the presented research, the basic physical properties of III-V nitrides and the characteristics of the HEMT structures are discussed.

Proton-Induced Conductivity Enhancement in AlGaN/GaN HEMT Devices

Science.gov (United States)

Lee, In Hak; Lee, Chul; Choi, Byoung Ki; Yun, Yeseul; Chang, Young Jun; Jang, Seung Yup

2018-04-01

We investigated the influence of proton irradiation on the AlGaN/GaN high-electron-mobility transistor (HEMT) devices. Unlike previous studies on the degradation behavior upon proton irradiation, we observed improvements in their electrical conductivity and carrier concentration of up to 25% for the optimal condition. As we increased the proton dose, the carrier concentration and the mobility showed a gradual increase and decrease, respectively. From the photoluminescence measurements, we observed a reduction in the near-band-edge peak of GaN ( 366 nm), which correlate on the observed electrical properties. However, neither the Raman nor the X-ray diffraction analysis showed any changes, implying a negligible influence of protons on the crystal structures. We demonstrated that high-energy proton irradiation could be utilized to modify the transport properties of HEMT devices without damaging their crystal structures.

AlGaN/GaN-HEMT power amplifiers with optimized power-added efficiency for X-band applications

OpenAIRE

Kühn, J.

2011-01-01

This work has arisen out of the strong demand for a superior power-added efficiency (PAE) of AlGaN/GaN high electron mobility transistor (HEMT) high-power amplifiers (HPAs) that are part of any advanced wireless multifunctional RF-system with limited prime energy. Different concepts and approaches on device and design level for PAE improvements are analyzed, e.g. structural and layout changes of the GaN transistor and advanced circuit design techniques for PAE improvements of GaN HEMT HPAs.

Parallel Planar-Processed and Ion-Induced Electrically Isolated Future Generation AlGaN/GaN HEMT for Gas Sensing and Opto-Telecommunication Applications

International Nuclear Information System (INIS)

Ahmed, S; Bokhari, S H; Amin, F; Khan, L A; Hussain, Z

2013-01-01

Ion-implanted AlGaN/GaN High Electron Mobility Transistors (HEMT) devices were studied thoroughly to look into the possibilities of enhancing efficiency for high-power and high-frequency electronic and gas sensing applications. A dedicated experimental design was created in order to study the influence of the physical parameters in response to high energy (by virtue of in-situ beam heating due to highly energetic implantation) ion implantation to the active device regions in nitride HEMT structures. Disorder or damage created in the HEMT structure was then studied carefully with electrical characterization techniques such as Hall, I-V and G-V measurements. The evolution of the electrical characteristics affecting the high-power, high-frequency and ultra-high efficiency gas sensing operations were also analyzed by subjecting the HEMT active device regions to progressive time-temperature annealing cycles. Our suggested model can also provide a functional process engineering window to control the extent of 2D Electron mobility in AlGaN/GaN HEMT devices undergoing a full cycle of thermal impact (i.e. from a desirable conductive region to a highly compensated one)

Noise characterization of enhancement-mode AlGaN graded barrier MIS-HEMT devices

Science.gov (United States)

Mohanbabu, A.; Saravana Kumar, R.; Mohankumar, N.

2017-12-01

This paper reports a systematic theoretical study on the microwave noise performance of graded AlGaN/GaN metal-insulator semiconductor high-electron mobility transistors (MIS-HEMTs) built on an Al2O3 substrate. The HfAlOx/AlGaN/GaN MIS-HEMT devices designed for this study show an outstanding small signal analog/RF and noise performance. The results on 1 μm gate length device show an enhancement mode operation with threshold voltage, VT = + 5.3 V, low drain leakage current, Ids,LL in the order of 1 × 10-9 A/mm along with high current gain cut-off frequency, fT of 17 GHz and maximum oscillation frequency fmax of 47 GHz at Vds = 10 V. The device Isbnd V and low-frequency noise estimation of the gate and drain noise spectral density and their correlation are evaluated using a Green's function method under different biasing conditions. The devices show a minimum noise figure (NFmin) of 1.053 dB in combination with equivalent noise resistance (Rn) of 23 Ω at 17 GHz, at Vgs = 6 V and Vds = 5 V which is relatively low and is suitable for broad-band low-noise amplifiers. This study shows that the graded AlGaN MIS-HEMT with HfAlOX gate insulator is appropriate for application requiring high-power and low-noise.

I2 basal stacking fault as a degradation mechanism in reverse gate-biased AlGaN/GaN HEMTs

Science.gov (United States)

Lang, A. C.; Hart, J. L.; Wen, J. G.; Miller, D. J.; Meyer, D. J.; Taheri, M. L.

2016-09-01

Here, we present the observation of a bias-induced, degradation-enhancing defect process in plasma-assisted molecular beam epitaxy grown reverse gate-biased AlGaN/GaN high electron mobility transistors (HEMTs), which is compatible with the current theoretical framework of HEMT degradation. Specifically, we utilize both conventional transmission electron microscopy and aberration-corrected transmission electron microscopy to analyze microstructural changes in not only high strained regions in degraded AlGaN/GaN HEMTs but also the extended gate-drain access region. We find a complex defect structure containing an I2 basal stacking fault and offer a potential mechanism for device degradation based on this defect structure. This work supports the reality of multiple failure mechanisms during device operation and identifies a defect potentially involved with device degradation.

Strain Balanced AlGaN/GaN/AlGaN nanomembrane HEMTs.

Science.gov (United States)

Chang, Tzu-Hsuan; Xiong, Kanglin; Park, Sung Hyun; Yuan, Ge; Ma, Zhenqiang; Han, Jung

2017-07-25

Single crystal semiconductor nanomembranes (NM) are important in various applications such as heterogeneous integration and flexible devices. This paper reports the fabrication of AlGaN/GaN NMs and NM high electron mobility transistors (HEMT). Electrochemical etching is used to slice off single-crystalline AlGaN/GaN layers while preserving their microstructural quality. A double heterostructure design with a symmetric strain profile is employed to ensure minimal residual strain in freestanding NMs after release. The mobility of the two-dimensional electron gas (2DEG), formed by the AlGaN/GaN heterostructure, is noticeably superior to previously reported values of many other NMs. AlGaN/GaN nanomembrane HEMTs are fabricated on SiO 2 and flexible polymeric substrates. Excellent electrical characteristics, including a high ON/OFF ratio and transconductance, suggest that III-Nitrides nanomembranes are capable of supporting high performance applications.

SEMICONDUCTOR DEVICES: Structural and electrical characteristics of lanthanum oxide gate dielectric film on GaAs pHEMT technology

Science.gov (United States)

Chia-Song, Wu; Hsing-Chung, Liu

2009-11-01

This paper investigates the feasibility of using a lanthanum oxide thin film (La2O3) with a high dielectric constant as a gate dielectric on GaAs pHEMTs to reduce gate leakage current and improve the gate to drain breakdown voltage relative to the conventional GaAs pHEMT. An E/D mode pHEMT in a single chip was realized by selecting the appropriate La2O3 thickness. The thin La2O3 film was characterized: its chemical composition and crystalline structure were determined by X-ray photoelectron spectroscopy and X-ray diffraction, respectively. La2O3 exhibited good thermal stability after post-deposition annealing at 200, 400 and 600 °C because of its high binding-energy (835.6 eV). Experimental results clearly demonstrated that the La2O3 thin film was thermally stable. The DC and RF characteristics of Pt/La2O3/Ti/Au gate and conventional Pt/Ti/Au gate pHEMTs were examined. The measurements indicated that the transistor with the Pt/La2O3/Ti/Au gate had a higher breakdown voltage and lower gate leakage current. Accordingly, the La2O3 thin film is a potential high-k material for use as a gate dielectric to improve electrical performance and the thermal effect in high-power applications.

High-temperature carrier density and mobility enhancements in AlGaN/GaN HEMT using AlN spacer layer

Science.gov (United States)

Ko, Tsung-Shine; Lin, Der-Yuh; Lin, Chia-Feng; Chang, Che-Wei; Zhang, Jin-Cheng; Tu, Shang-Ju

2017-04-01

In this paper, we experimentally studied the effect of AlN spacer layer on optical and electrical properties of AlGaN/GaN high electric mobility transistors (HEMTs) grown by metal organic chemical vapor deposition method. For AlGaN layer in HEMT structure, the Al composition of the sample was determined using x-ray diffraction and photoluminescence. Electrolyte electro-reflectance (EER) measurement not only confirmed the aluminum composition of AlGaN layer, but also determined the electric field strength on the AlGaN layer through the Franz-Keldysh oscillation phenomenon. This result indicated that the electric field on the AlGaN layer could be improved from 430 to 621 kV/cm when AlN spacer layer was inserted in HEMT structure, which increased the concentration of two dimensional electron gas (2DEG) and improve the mobility. The temperature dependent Hall results show that both the mobility and the carrier concentration of 2DEG would decrease abruptly causing HEMT loss of function due to phonon scattering and carrier thermal escape when temperature increases above a specific value. Meanwhile, our study also demonstrates using AlN spacer layer could be beneficial to allow the mobility and carrier density of 2DEG sustaining at high temperature region.

A dual-mode driver IC with monolithic negative drive-voltage capability and digital current-mode controller for depletion-mode GaN HEMT

NARCIS (Netherlands)

Wen, Y.; Rose, M.; Fernandes, R.; van Otten, R.; Bergveld, H.J.; Trescases, O.

2017-01-01

This work presents a driver and controller integrated circuit (IC) for depletion-mode gallium nitride (GaN) high-electron-mobility transistors (HEMTs). The dual-mode driver can be configured for cascode-drive (CD) or HEMT-drive (HD) mode. In the CD mode, a cascode low-voltage DMOS is driven to

A Very Robust AlGaN/GaN HEMT Technology to High Forward Gate Bias and Current

Directory of Open Access Journals (Sweden)

Bradley D. Christiansen

2012-01-01

Full Text Available Reports to date of GaN HEMTs subjected to forward gate bias stress include varied extents of degradation. We report an extremely robust GaN HEMT technology that survived—contrary to conventional wisdom—high forward gate bias (+6 V and current (>1.8 A/mm for >17.5 hours exhibiting only a slight change in gate diode characteristic, little decrease in maximum drain current, with only a 0.1 V positive threshold voltage shift, and, remarkably, a persisting breakdown voltage exceeding 200 V.

Improvement of breakdown characteristics of an AlGaN/GaN HEMT with a U-type gate foot for millimeter-wave power application

International Nuclear Information System (INIS)

Kong Xin; Wei Ke; Liu Guo-Guo; Liu Xin-Yu

2012-01-01

In this study, the physics-based device simulation tool Silvaco ATLAS is used to characterize the electrical properties of an AlGaN/GaN high electron mobility transistor (HEMT) with a U-type gate foot. The U-gate AlGaN/GaN HEMT mainly features a gradually changed sidewall angle, which effectively mitigates the electric field in the channel, thus obtaining enhanced off-state breakdown characteristics. At the same time, only a small additional gate capacitance and decreased gate resistance ensure excellent RF characteristics for the U-gate device. U-gate AlGaN/GaN HEMTs are feasible through adjusting the etching conditions of an inductively coupled plasma system, without introducing any extra process steps. The simulation results are confirmed by experimental measurements. These features indicate that U-gate AlGaN/GaN HEMTs might be promising candidates for use in millimeter-wave power applications. (interdisciplinary physics and related areas of science and technology)

Group-III nitride based high electron mobility transistor (HEMT) with barrier/spacer layer

Science.gov (United States)

Chavarkar, Prashant; Smorchkova, Ioulia P.; Keller, Stacia; Mishra, Umesh; Walukiewicz, Wladyslaw; Wu, Yifeng

2005-02-01

A Group III nitride based high electron mobility transistors (HEMT) is disclosed that provides improved high frequency performance. One embodiment of the HEMT comprises a GaN buffer layer, with an Al.sub.y Ga.sub.1-y N (y=1 or y 1) layer on the GaN buffer layer. An Al.sub.x Ga.sub.1-x N (0.ltoreq.x.ltoreq.0.5) barrier layer on to the Al.sub.y Ga.sub.1-y N layer, opposite the GaN buffer layer, Al.sub.y Ga.sub.1-y N layer having a higher Al concentration than that of the Al.sub.x Ga.sub.1-x N barrier layer. A preferred Al.sub.y Ga.sub.1-y N layer has y=1 or y.about.1 and a preferred Al.sub.x Ga.sub.1-x N barrier layer has 0.ltoreq.x.ltoreq.0.5. A 2DEG forms at the interface between the GaN buffer layer and the Al.sub.y Ga.sub.1-y N layer. Respective source, drain and gate contacts are formed on the Al.sub.x Ga.sub.1-x N barrier layer. The HEMT can also comprising a substrate adjacent to the buffer layer, opposite the Al.sub.y Ga.sub.1-y N layer and a nucleation layer between the Al.sub.x Ga.sub.1-x N buffer layer and the substrate.

Compact modelling of InAlN/GaN HEMT for low noise applications

International Nuclear Information System (INIS)

Sakalas, P; Šimukovič, A; Matulionis, A; Piotrowicz, S; Jardel, O; Delage, S L; Mukherjee, A

2014-01-01

This paper presents results of high-frequency noise modelling of InAlN/GaN high electron mobility transistors (HEMTs) with different formulations of the minimum noise figure NF min . Current–voltage characteristics and s-parameters of 0.15 μm gate length and 2 × 75 μm gate width InAlN/GaN HEMTs were measured at room temperature in a wide frequency range (300 MHz to 50 GHz) and bias range (V GS from −4.8 to 1 V and V DS from 0 to 21 V). Both the EEHEMT1 and Angelov GaN compact models yielded excellent agreement for transfer and output characteristics, transconductance g m , and f T , f max. High-frequency noise parameters NF min , R n , Γ OPT of InAlN/GaN HEMT were measured in 8–50 GHz frequency band. Noise formulation within the EEHEMT1 model underestimates the measured NF min and R n . The well known three-parameter PRC noise model is in a better agreement with the measured data but neglects the shot noise resulting from the gate leakage. The inductive degenerated source matching method and EEHEMT1 were used to design a single stage LNA operated at 8 GHz frequency. A 10 dB gain with an input reflection of −12 dB with a 2.5 dB of noise factor were obtained at 8 GHz. (paper)

AlGaN/GaN HEMT structures on ammono bulk GaN substrate

International Nuclear Information System (INIS)

Kruszewski, P; Prystawko, P; Krysko, M; Smalc-Koziorowska, J; Leszczynski, M; Kasalynas, I; Nowakowska-Siwinska, A; Plesiewicz, J; Dwilinski, R; Zajac, M; Kucharski, R

2014-01-01

The work shows a successful fabrication of AlGaN/GaN high electron mobility transistor (HEMT) structures on the bulk GaN substrate grown by ammonothermal method providing an ultralow dislocation density of 10 4  cm −2  and wafers of size up to 2 inches in diameter. The AlGaN layers grown by metalorganic chemical vapor phase epitaxy method demonstrate atomically smooth surface, flat interfaces with reproduced low dislocation density as in the substrate. The test electronic devices—Schottky diodes and transistors—were designed without surface passivation and were successfully fabricated using mask-less laser-based photolithography procedures. The Schottky barrier devices demonstrate exceptionally low reverse currents smaller by a few orders of magnitude in comparison to the Schottky diodes made of AlGaN/GaN HEMT on sapphire substrate. (paper)

Characteristics study of 2DEG transport properties of AlGaN/GaN and AlGaAs/GaAs-based HEMT

International Nuclear Information System (INIS)

Lenka, T. R.; Panda, A. K.

2011-01-01

Growth of wide bandgap material over narrow bandgap material, results into a two dimensional electron gas (2DEG) at the heterointerface due to the conduction band discontinuity. In this paper the 2DEG transport properties of AlGaN/GaN-based high electron mobility transistor (HEMT) is discussed and its effect on various characteristics such as 2DEG density, C-V characteristics and Sheet resistances for different mole fractions are presented. The obtained results are also compared with AlGaAs/GaAs-based HEMT for the same structural parameter as like AlGaN/GaN-based HEMT. The calculated results of electron sheet concentration as a function of the Al mole fraction are in excellent agreement with some experimental data available in the literature.

Design of a GaAs X-ray imaging sensor with integrated HEMT readout circuitry

Energy Technology Data Exchange (ETDEWEB)

Boardman, D

2002-01-01

A new monolithic semi-insulating (SI) GaAs sensor design for X-ray imaging applications between 10-100keV has been proposed. Monolithic pixel detectors offer a number of advantages over hybrid bump-bonded detectors, such as high device yield, low costs and are easier to produce large scale arrays. In this thesis, an investigation is made of the use of a SI GaAs wafer as both a detector element and substrate for the epitaxially grown High Electron Mobility Transistors (HEMTs). The design of the HEMT transistors, optimised for this application, were produced with the aid of the Silvaco 'Virtual Wafer Fab' simulation package. It was determined that the device characteristics would consist of a small positive threshold voltage, a low off-state drain current and high transconductance. The final HEMT transistor design, that would be integrated to a pixel detector, had a threshold voltage of 0.17V, an off-state leakage current of {approx}1nA and a transconductance of 7.4mS. A number of test detectors were characterised using an ion beam induced charge technique. Charge collection efficiency maps of the test detectors were produced to determine their quality as a X-ray detection material. From the results, the inhomogeneity of SI GaAs, homogeneity of epitaxial GaAs and granular nature of polycrystalline GaAs, were observed. The best of these detectors was used in conjunction with a commercial field effect transistor to produce a hybrid device. The charge switching nature of the hybrid device was shown and a sensitivity of 0.44pC/{mu}Gy mm{sup 2}, for a detector bias of 60V, was found. The functionality of the hybrid sensor was the same to that proposed for the monolithic sensor. The fabrication of the monolithic sensor, with an integrated HEMT transistor and external capacitor, was achieved. To reach the next stage of producing a monolithic sensor that integrates charge, requires further work in the design and the fabrication process. (author)

Design of a GaAs X-ray imaging sensor with integrated HEMT readout circuitry

International Nuclear Information System (INIS)

Boardman, D.

2002-01-01

A new monolithic semi-insulating (SI) GaAs sensor design for X-ray imaging applications between 10-100keV has been proposed. Monolithic pixel detectors offer a number of advantages over hybrid bump-bonded detectors, such as high device yield, low costs and are easier to produce large scale arrays. In this thesis, an investigation is made of the use of a SI GaAs wafer as both a detector element and substrate for the epitaxially grown High Electron Mobility Transistors (HEMTs). The design of the HEMT transistors, optimised for this application, were produced with the aid of the Silvaco 'Virtual Wafer Fab' simulation package. It was determined that the device characteristics would consist of a small positive threshold voltage, a low off-state drain current and high transconductance. The final HEMT transistor design, that would be integrated to a pixel detector, had a threshold voltage of 0.17V, an off-state leakage current of ∼1nA and a transconductance of 7.4mS. A number of test detectors were characterised using an ion beam induced charge technique. Charge collection efficiency maps of the test detectors were produced to determine their quality as a X-ray detection material. From the results, the inhomogeneity of SI GaAs, homogeneity of epitaxial GaAs and granular nature of polycrystalline GaAs, were observed. The best of these detectors was used in conjunction with a commercial field effect transistor to produce a hybrid device. The charge switching nature of the hybrid device was shown and a sensitivity of 0.44pC/μGy mm 2 , for a detector bias of 60V, was found. The functionality of the hybrid sensor was the same to that proposed for the monolithic sensor. The fabrication of the monolithic sensor, with an integrated HEMT transistor and external capacitor, was achieved. To reach the next stage of producing a monolithic sensor that integrates charge, requires further work in the design and the fabrication process. (author)

A nonlinear model for frequency dispersion and DC intrinsic parameter extraction for GaN-based HEMT

Science.gov (United States)

Nguyen, Tung The-Lam; Kim, Sam-Dong

2017-11-01

We propose in this study a practical nonlinear model for the AlGaN/GaN high electron mobility transistors (HEMTs) to extract DC intrinsic transconductance (gmDC), output conductance (gdsDC), and electron mobility from the intrinsic parameter set measured at high frequencies. An excellent agreement in I-V characteristics of the model with a fitting error of 0.11% enables us successfully extract the gmDC, gdsDC, and the total transconductance dispersion. For this model, we also present a reliable analysis scheme wherein the frequency dispersion effect due regional surface states in AlGaN/GaN HEMTs is taken into account under various bias conditions.

Thin-barrier enhancement-mode AlGaN/GaN MIS-HEMT using ALD Al2O3 as gate insulator

International Nuclear Information System (INIS)

Wang Zheli; Zhou Jianjun; Kong Yuechan; Kong Cen; Dong Xun; Yang Yang; Chen Tangsheng

2015-01-01

A high-performance enhancement-mode (E-mode) gallium nitride (GaN)-based metal–insulator–semiconductor high electron mobility transistor (MIS-HEMT) that employs a 5-nm-thick aluminum gallium nitride (Al 0.3 Ga 0.7 N) as a barrier layer and relies on silicon nitride (SiN) passivation to control the 2DEG density is presented. Unlike the SiN passivation, aluminum oxide (Al 2 O 3 ) by atomic layer deposition (ALD) on AlGaN surface would not increase the 2DEG density in the heterointerface. ALD Al 2 O 3 was used as gate insulator after the depletion by etching of the SiN in the gate region. The E-mode MIS-HEMT with gate length (L G ) of 1 μm showed a maximum drain current density (I DS ) of 657 mA/mm, a maximum extrinsic transconductance (g m ) of 187 mS/mm and a threshold voltage (V th ) of 1 V. Comparing with the corresponding E-mode HEMT, the device performances had been greatly improved due to the insertion of Al 2 O 3 gate insulator. This provided an excellent way to realize E-mode AlGaN/GaN MIS-HEMTs with both high V th and I DS . (paper)

Investigation of the Performance of HEMT-Based NO, NO2 and NH3 Exhaust Gas Sensors for Automotive Antipollution Systems

Science.gov (United States)

Halfaya, Yacine; Bishop, Chris; Soltani, Ali; Sundaram, Suresh; Aubry, Vincent; Voss, Paul L.; Salvestrini, Jean-Paul; Ougazzaden, Abdallah

2016-01-01

We report improved sensitivity to NO, NO2 and NH3 gas with specially-designed AlGaN/GaN high electron mobility transistors (HEMT) that are suitable for operation in the harsh environment of diesel exhaust systems. The gate of the HEMT device is functionalized using a Pt catalyst for gas detection. We found that the performance of the sensors is enhanced at a temperature of 600 °C, and the measured sensitivity to 900 ppm-NO, 900 ppm-NO2 and 15 ppm-NH3 is 24%, 38.5% and 33%, respectively, at 600 °C. We also report dynamic response times as fast as 1 s for these three gases. Together, these results indicate that HEMT sensors could be used in a harsh environment with the ability to control an anti-pollution system in real time. PMID:26907298

Investigation of the Performance of HEMT-Based NO, NO2 and NH3 Exhaust Gas Sensors for Automotive Antipollution Systems

Directory of Open Access Journals (Sweden)

Yacine Halfaya

2016-02-01

Full Text Available We report improved sensitivity to NO, NO2 and NH3 gas with specially-designed AlGaN/GaN high electron mobility transistors (HEMT that are suitable for operation in the harsh environment of diesel exhaust systems. The gate of the HEMT device is functionalized using a Pt catalyst for gas detection. We found that the performance of the sensors is enhanced at a temperature of 600 °C, and the measured sensitivity to 900 ppm-NO, 900 ppm-NO 2 and 15 ppm-NH 3 is 24%, 38.5% and 33%, respectively, at 600 °C. We also report dynamic response times as fast as 1 s for these three gases. Together, these results indicate that HEMT sensors could be used in a harsh environment with the ability to control an anti-pollution system in real time.

Suppression of the self-heating effect in GaN HEMT by few-layer graphene heat spreading elements

Science.gov (United States)

Volcheck, V. S.; Stempitsky, V. R.

2017-11-01

Self-heating has an adverse effect on characteristics of gallium nitride (GaN) high electron mobility transistors (HEMTs). Various solutions to the problem have been proposed, however, a temperature rise due to dissipated electrical power still hinders the production of high power and high speed GaN devices. In this paper, thermal management of GaN HEMT via few-layer graphene (FLG) heat spreading elements is investigated. It is shown that integration of the FLG elements on top of the device structure considerably reduces the maximum temperature and improves the DC and small signal AC performance.

Noise performance in AlGaN/GaN HEMTs under high drain bias

International Nuclear Information System (INIS)

Pang Lei; Pu Yan; Lin Xinyu; Wang Liang; Liu Jian

2009-01-01

The advent of fully integrated GaN PA-LNA circuits makes it meaningful to investigate the noise performance under high drain bias. However, noise performance of AlGaN/GaN HEMTs under high bias has not received worldwide attention in theoretical studies due to its complicated mechanisms. The noise value is moderately higher and its rate of increase is fast with increasing high voltage. In this paper, several possible mechanisms are proposed to be responsible for it. Impact ionization under high electric field incurs great fluctuation of carrier density, which increases the drain diffusion noise. Besides, higher gate leakage current related shot noise and a more severe self-heating effect are also contributors to the noise increase at high bias. Analysis from macroscopic and microscopic perspectives can help us to design new device structures to improve noise performance of AlGaN/GaN HEMTs under high bias. (semiconductor devices)

Performance analysis of 20 nm gate-length In0.2Al0.8N/GaN HEMT with Cu-gate having a remarkable high ION/IOFF ratio

International Nuclear Information System (INIS)

Bhattacharjee, A.; Lenka, T. R.

2014-01-01

We propose a new structure of In x Al 1−x N/GaN high electron mobility transistor (HEMT) with gate length of 20 nm. The threshold voltage of this HEMT is achieved as −0.472 V. In this device the InAlN barrier layer is intentionally n-doped to boost the I ON /I OFF ratio. The InAlN layer acts as donor barrier layer for this HEMT which exhibits an I ON = 10 −4.3 A and a very low I OFF = 10 −14.4 A resulting in an I ON /I OFF ratio of 10 10.1 . We compared our obtained results with the conventional InAlN/GaN HEMT device having undoped barrier and found that the proposed device has almost 10 5 times better I ON /I OFF ratio. Further, the mobility analysis in GaN channel of this proposed HEMT structure along with DC analysis, C–V and conductance characteristics by using small-signal analysis are also presented in this paper. Moreover, the shifts in threshold voltage by DIBL effect and gate leakage current in the proposed HEMT are also discussed. InAlN was chosen as the most preferred barrier layer as a replacement of AlGaN for its excellent thermal conductivity and very good scalability. (semiconductor devices)

Mechanism of improving forward and reverse blocking voltages in AlGaN/GaN HEMTs by using Schottky drain

International Nuclear Information System (INIS)

Zhao Sheng-Lei; Mi Min-Han; Luo Jun; Wang Yi; Dai Yang; Zhang Jin-Cheng; Ma Xiao-Hua; Hao Yue; Hou Bin

2014-01-01

In this paper, we demonstrate that a Schottky drain can improve the forward and reverse blocking voltages (BVs) simultaneously in AlGaN/GaN high-electron mobility transistors (HEMTs). The mechanism of improving the two BVs is investigated by analysing the leakage current components and by software simulation. The forward BV increases from 72 V to 149 V due to the good Schottky contact morphology. During the reverse bias, the buffer leakage in the Ohmicdrain HEMT increases significantly with the increase of the negative drain bias. For the Schottky-drain HEMT, the buffer leakage is suppressed effectively by the formation of the depletion region at the drain terminal. As a result, the reverse BV is enhanced from −5 V to −49 V by using a Schottky drain. Experiments and the simulation indicate that a Schottky drain is desirable for power electronic applications. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

The influence of gate length on the electron injection of velocity in an AlGaN/AlN/GaN HEMT channel

Science.gov (United States)

Mikhailovich, S. V.; Galiev, R. R.; Zuev, A. V.; Pavlov, A. Yu.; Ponomarev, D. S.; Khabibullin, R. A.

2017-08-01

Field-effect high-electron-mobility transistors (HEMTs) based on AlGaN/AlN/GaN heterostructures with various gate lengths L g have been studied. The maximum values of current and power gaincutoff frequencies ( f T and f max, respectively) amounted to 88 and 155 GHz for HEMTs with L g = 125 nm, while those for the transistors with L g = 360 nm were 26 and 82 GHz, respectively. Based on the measured S-parameters, the values of elements in small-signal equivalent schemes of AlGaN/AlN/GaN HEMTs were extracted and the dependence of electron-injection velocity vinj on the gate-drain voltage was determined. The influence of L g and the drain-source voltage on vinj has been studied.

Design and characterization of a 200 V, 45 A all-GaN HEMT-based power module

International Nuclear Information System (INIS)

Chou, Po-Chien; Cheng, Stone

2013-01-01

Emerging gallium nitride (GaN)-based high electron mobility transistor (HEMT) technology has the potential to make lower loss and higher power switching characteristics than those made using traditional silicon (Si) components. This work designed, developed, and tested an all-GaN-based power module. In a 200 V, 45 A module, each switching element comprises three GaN chips in parallel, each of which includes six 2.1 A AlGaN/GaN-on-Si HEMT cells. The cells are wire-bonded in parallel to scale up the power rating. Static I D -V DS characteristics of the module are experimentally obtained over widely varying base plate temperatures, and a low on-state resistance is obtained at an elevated temperature of 125 °C. The fabricated module has a blocking voltage exceeding 200 V at a reverse-leakage current density below 1 mA/mm. Two standard temperature measurements are made to provide a simple means of determining mean cell temperature in the module. Self-heating in AlGaN/GaN HEMTs is studied by electrical analysis and infrared thermography. Electrical analysis provides fast temperature overviews while infrared thermography reveals temperature behavior in selected active regions. The current distribution among cells was acceptable over the measured operating temperature range. The characterization of electrical performance and mechanical performance confirm the potential use of the packaged module for high-power applications. -- Highlights: • This work proposes the design, development, and testing of all-GaN power module. • We develop module package and determine their thermal and electrical properties. • ID-VDS characteristics are obtained over a wide range of base plate temperatures. • Self-heating in GaN HEMTs is studied by electrical analysis and IR thermography

Gate less-FET pH Sensor Fabricated on Undoped AlGaN/ GaN HEMT Structure

International Nuclear Information System (INIS)

Maneea Eizadi Sharifabad; Mastura Shafinaz Zainal Abidin; Shaharin Fadzli Abd Rahman; Abdul Manaf Hashim; Abdul Rahim Abdul Rahman

2011-01-01

Gallium nitride with wurtzite crystal structure is a chemically stable semiconductor with high internal spontaneous and piezoelectric polarization, which make it highly suitable materials to create very sensitive and robust sensors for the detection of ions, gases and liquids. Sensing characteristics of an open-gate liquid-phase sensor fabricated on undoped-AlGaN/ GaN high-electron-mobility-transistor (HEMT) structure in aqueous solution was investigated. In ambient atmosphere, the open-gate undoped AlGaN/ GaN HEMT clearly showed only the presence of linear region of currents while Si-doped AlGaN/ GaN showed the linear and saturation regions of currents, very similar to those of gated devices. This seems to show that very low Fermi level pinning by surface states exists in undoped AlGaN/ GaN sample. In aqueous solution, the typical current-voltage (I-V) characteristics of HEMTs with good gate controllability were observed. The potential of the AlGaN surface at the open-gate area is effectively controlled via aqueous solution by Ag/ AgCl reference gate electrode. The open-gate undoped AlGaN/ GaN HEMT structure is capable of stable operation in aqueous electrolytes and exhibit linear sensitivity, and high sensitivity of 1.9 mA/ pH or 3.88 mA/ mm/ pH at drain-source voltage, VDS = 5 V was obtained. Due to large leakage current where it increases with the negative reference gate voltage, the Nernstians like sensitivity cannot be determined. Suppression of current leakage is likely to improve the device performance. The open-gate undoped-AlGaN/ GaN structure is expected to be suitable for pH sensing application. (author)

Effect of self-heating on electrical characteristics of AlGaN/ GaN HEMT on Si (111) substrate

Science.gov (United States)

Nigam, Adarsh; Bhat, Thirumaleshwara N.; Rajamani, Saravanan; Dolmanan, Surani Bin; Tripathy, Sudhiranjan; Kumar, Mahesh

2017-08-01

In order to study the effect of self-heating of AlGaN/ GaN high electron mobility transistors (HEMTs) characteristics fabricated on Si(111) substrate, simulations of 2DEG temperature on different drain voltages have been carried out by Sentaurus TCAD simulator tool. Prior to the electrical direct-current (DC) characteristics studies, structural properties of the HEMT structures were examined by scanning transmission electron microscopy. The comparative analysis of simulation and experimental data provided sheet carrier concentration, mobility, surface traps, electron density at 2DEG by considering factors such as high field saturation, tunneling and recombination models. Mobility, surface trap concentration and contact resistance were obtained by TCAD simulation and found out to be ˜1270cm2/Vs, ˜2×1013 cm-2 and ˜0.2 Ω.mm, respectively, which are in agreement with the experimental results. Consequently, simulated current-voltage characteristics of HEMTs are in good agreement with experimental results. The present simulator tool can be used to design new device structures for III-nitride technology.

Effect of self-heating on electrical characteristics of AlGaN/ GaN HEMT on Si (111 substrate

Directory of Open Access Journals (Sweden)

Adarsh Nigam

2017-08-01

Full Text Available In order to study the effect of self-heating of AlGaN/ GaN high electron mobility transistors (HEMTs characteristics fabricated on Si(111 substrate, simulations of 2DEG temperature on different drain voltages have been carried out by Sentaurus TCAD simulator tool. Prior to the electrical direct-current (DC characteristics studies, structural properties of the HEMT structures were examined by scanning transmission electron microscopy. The comparative analysis of simulation and experimental data provided sheet carrier concentration, mobility, surface traps, electron density at 2DEG by considering factors such as high field saturation, tunneling and recombination models. Mobility, surface trap concentration and contact resistance were obtained by TCAD simulation and found out to be ∼1270cm2/Vs, ∼2×1013 cm-2 and ∼0.2 Ω.mm, respectively, which are in agreement with the experimental results. Consequently, simulated current-voltage characteristics of HEMTs are in good agreement with experimental results. The present simulator tool can be used to design new device structures for III-nitride technology.

Temperature dependent DC characterization of InAlN/(AlN)/GaN HEMT for improved reliability

Science.gov (United States)

Takhar, K.; Gomes, U. P.; Ranjan, K.; Rathi, S.; Biswas, D.

2015-02-01

InxAl1-xN/AlN/GaN HEMT device performance is analysed at various temperatures with the help of physics based 2-D simulation using commercially available BLAZE and GIGA modules from SILVACO. Various material parameters viz. band-gap, low field mobility, density of states, velocity saturation, and substrate thermal conductivity are considered as critical parameters for predicting temperature effect in InxAl1-xN/AlN/GaN HEMT. Reduction in drain current and transconductance has been observed due to the decrease of 2-DEG mobility and effective electron velocity with the increase in temperature. Degradation in cut-off frequency follows the transconductance profile as variation in gate-source/gate-drain capacitances observed very small.

Investigations of AlGaN/GaN MOS-HEMT with Al2O3 deposition by ultrasonic spray pyrolysis method

International Nuclear Information System (INIS)

Chou, Bo-Yi; Hsu, Wei-Chou; Liu, Han-Yin; Wu, Yu-Sheng; Lee, Ching-Sung; Sun, Wen-Ching; Wei, Sung-Yen; Yu, Sheng-Min; Chiang, Meng-Hsueh

2015-01-01

This work investigates Al 2 O 3 /AlGaN/GaN metal-oxide-semiconductor high electron mobility transistors (MOS-HEMTs) grown on SiC substrate by using the non-vacuum ultrasonic spray pyrolysis deposition (USPD) method. The Al 2 O 3 was deposited as gate dielectric and surface passivation simultaneously to effectively suppress gate leakage current, enhance output current density, reduce RF drain current collapse, and improve temperature-dependent stabilities performance. The present MOS-HEMT design has shown improved device performances with respect to a Schottky-gate HEMT, including drain-source saturation current density at zero gate bias (I DSS : 337.6 mA mm −1  → 462.9 mA mm −1 ), gate-voltage swing (GVS: 1.55 V → 2.92 V), two-terminal gate-drain breakdown voltage (BV GD : −103.8 V → −183.5 V), unity-gain cut-off frequency (f T : 11.3 GHz → 17.7 GHz), maximum oscillation frequency (f max : 14.2 GHz → 19.1 GHz), and power added effective (P.A.E.: 25.1% → 43.6%). The bias conditions for measuring f T and f max of the studied MOS-HEMT (Schottky-gate HEMT) are V GS  = −2.5 (−2) V and V DS  = 7 V. The corresponding V GS and V DS biases are −2.5 (−2) V and 15 V for measuring the P.A.E. characteristic. Moreover, small capacitance-voltage (C–V) hysteresis is obtained in the Al 2 O 3 -MOS structure by using USPD. Temperature-dependent characteristics of the present designs at 300–480 K are also studied. (paper)

Extended behavioural modelling of FET and lattice-mismatched HEMT devices

Science.gov (United States)

Khawam, Yahya; Albasha, Lutfi

2017-07-01

This study presents an improved large signal model that can be used for high electron mobility transistors (HEMTs) and field effect transistors using measurement-based behavioural modelling techniques. The steps for accurate large and small signal modelling for transistor are also discussed. The proposed DC model is based on the Fager model since it compensates between the number of model's parameters and accuracy. The objective is to increase the accuracy of the drain-source current model with respect to any change in gate or drain voltages. Also, the objective is to extend the improved DC model to account for soft breakdown and kink effect found in some variants of HEMT devices. A hybrid Newton's-Genetic algorithm is used in order to determine the unknown parameters in the developed model. In addition to accurate modelling of a transistor's DC characteristics, the complete large signal model is modelled using multi-bias s-parameter measurements. The way that the complete model is performed is by using a hybrid multi-objective optimisation technique (Non-dominated Sorting Genetic Algorithm II) and local minimum search (multivariable Newton's method) for parasitic elements extraction. Finally, the results of DC modelling and multi-bias s-parameters modelling are presented, and three-device modelling recommendations are discussed.

An analytical turn-on power loss model for 650-V GaN eHEMTs

DEFF Research Database (Denmark)

Shen, Yanfeng; Wang, Huai; Shen, Zhan

2018-01-01

This paper proposes an improved analytical turn-on power loss model for 650-V GaN eHEMTs. The static characteristics, i.e., the parasitic capacitances and transconductance, are firstly modeled. Then the turn-on process is divided into multiple stages and analyzed in detail; as results, the time-d......-domain solutions to the drain-source voltage and drain current are obtained. Finally, double-pulse tests are conducted to verify the proposed power loss model. This analytical model enables an accurate and fast switching behavior characterization and power loss prediction.......This paper proposes an improved analytical turn-on power loss model for 650-V GaN eHEMTs. The static characteristics, i.e., the parasitic capacitances and transconductance, are firstly modeled. Then the turn-on process is divided into multiple stages and analyzed in detail; as results, the time...

Analysis of the device characteristics of AlGaN/GaN HEMTs over a wide temperature range

International Nuclear Information System (INIS)

Zhao, M.; Liu, X.Y.; Zheng, Y.K.; Li, Yankui; Ouyang, Sihua

2013-01-01

Highlights: ► We report the behavior of the current–voltage characteristics of AlGaN/GaN HEMT in the temperature range of 223–398 K. ► The origin of the leakage current and the current transport behaviors are reported. ► There is a linear relationship between the barrier height and the ideality factor, which is attributed to barrier height in homogeneities. -- Abstract: In this study, we investigate the behavior of the current–voltage (I–V) characteristics of AlGaN/GaN HEMT in the temperature range of 223–398 K. Temperature dependent device characteristics and the current transport mechanism are reported. It is observed that the Schottky barrier height Φ increases and the ideality factor n decreases with temperature. There is a linear relationship between the barrier height and the ideality factor, which is attributed to barrier height inhomogeneities of AlGaN/GaN HEMT. The estimated values of the series resistances (R s ) are in the range of 144.2 Ω at 223 K to 74.3 Ω at 398 K. The Φ, n, R s , G m and Schottky leakage current values are seen to be strongly temperature dependent

Evaluation and Reliability Assessment of GaN-on-Si MIS-HEMT for Power Switching Applications

Directory of Open Access Journals (Sweden)

Po-Chien Chou

2017-02-01

Full Text Available This paper reports an extensive analysis of the physical mechanisms responsible for the failure of GaN-based metal–insulator–semiconductor (MIS high electron mobility transistors (HEMTs. When stressed under high applied electric fields, the traps at the dielectric/III-N barrier interface and inside the III-N barrier cause an increase in dynamic on-resistance and a shift of threshold voltage, which might affect the long term stability of these devices. More detailed investigations are needed to identify epitaxy- or process-related degradation mechanisms and to understand their impact on electrical properties. The present paper proposes a suitable methodology to characterize the degradation and failure mechanisms of GaN MIS-HEMTs subjected to stress under various off-state conditions. There are three major stress conditions that include: VDS = 0 V, off, and off (cascode-connection states. Changes of direct current (DC figures of merit in voltage step-stress experiments are measured, statistics are studied, and correlations are investigated. Hot electron stress produces permanent change which can be attributed to charge trapping phenomena and the generation of deep levels or interface states. The simultaneous generation of interface (and/or bulk and buffer traps can account for the observed degradation modes and mechanisms. These findings provide several critical characteristics to evaluate the electrical reliability of GaN MIS-HEMTs which are borne out by step-stress experiments.

Low temperature (100 °C) atomic layer deposited-ZrO2 for recessed gate GaN HEMTs on Si

Science.gov (United States)

Byun, Young-Chul; Lee, Jae-Gil; Meng, Xin; Lee, Joy S.; Lucero, Antonio T.; Kim, Si Joon; Young, Chadwin D.; Kim, Moon J.; Kim, Jiyoung

2017-08-01

In this paper, the effect of atomic layer deposited ZrO2 gate dielectrics, deposited at low temperature (100 °C), on the characteristics of recessed-gate High Electron Mobility Transistors (HEMTs) on Al0.25Ga0.75N/GaN/Si is investigated and compared with the characteristics of those with ZrO2 films deposited at typical atomic layer deposited (ALD) process temperatures (250 °C). Negligible hysteresis (ΔVth 4 V), and low interfacial state density (Dit = 3.69 × 1011 eV-1 cm-2) were observed on recessed gate HEMTs with ˜5 nm ALD-ZrO2 films grown at 100 °C. The excellent properties of recessed gate HEMTs are due to the absence of an interfacial layer and an amorphous phase of the film. An interfacial layer between 250 °C-ZrO2 and GaN is observed via high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. However, 100 °C-ZrO2 and GaN shows no significant interfacial layer formation. Moreover, while 100 °C-ZrO2 films maintain an amorphous phase on either substrate (GaN and Si), 250 °C-ZrO2 films exhibit a polycrystalline-phase when deposited on GaN and an amorphous phase when deposited on Si. Contrary to popular belief, the low-temperature ALD process for ZrO2 results in excellent HEMT performance.

Optimization of the parameters of HEMT GaN/AlN/AlGaN heterostructures for microwave transistors using numerical simulation

Energy Technology Data Exchange (ETDEWEB)

Tikhomirov, V. G., E-mail: VV11111@yandex.ru [Saint Petersburg Electrotechnical University “LETI” (Russian Federation); Zemlyakov, V. E.; Volkov, V. V.; Parnes, Ya. M.; Vyuginov, V. N. [Joint Stock Company “Svetlana-Electronpribor” (Russian Federation); Lundin, W. V.; Sakharov, A. V.; Zavarin, E. E.; Tsatsulnikov, A. F. [Russian Academy of Sciences, Submicron Heterostructures for Microelectronics Research and Engineering Center (Russian Federation); Cherkashin, N. A. [CEMES-CNRS-Université de Toulouse (France); Mizerov, M. N. [Russian Academy of Sciences, Submicron Heterostructures for Microelectronics Research and Engineering Center (Russian Federation); Ustinov, V. M. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation)

2016-02-15

The numerical simulation, and theoretical and experimental optimization of field-effect microwave high-electron-mobility transistors (HEMTs) based on GaN/AlN/AlGaN heterostructures are performed. The results of the study showed that the optimal thicknesses and compositions of the heterostructure layers, allowing high microwave power implementation, are in relatively narrow ranges. It is shown that numerical simulation can be efficiently applied to the development of microwave HEMTs, taking into account basic physical phenomena and features of actual device structures.

InP HEMT Integrated Circuits for Submillimeter Wave Radiometers in Earth Remote Sensing

Science.gov (United States)

Deal, William R.; Chattopadhyay, Goutam

2012-01-01

The operating frequency of InP integrated circuits has pushed well into the Submillimeter Wave frequency band, with amplification reported as high as 670 GHz. This paper provides an overview of current performance and potential application of InP HEMT to Submillimeter Wave radiometers for earth remote sensing.

Wideband Monolithic Microwave Integrated Circuit Frequency Converters with GaAs mHEMT Technology

DEFF Research Database (Denmark)

Krozer, Viktor; Johansen, Tom Keinicke; Djurhuus, Torsten

2005-01-01

We present monolithic microwave integrated circuit (MMIC) frequency converter, which can be used for up and down conversion, due to the large RF and IF port bandwidth. The MMIC converters are based on commercially available GaAs mHEMT technology and are comprised of a Gilbert mixer cell core...

Indium antimonide based HEMT for RF applications

International Nuclear Information System (INIS)

Subash, T. D.; Gnanasekaran, T.

2014-01-01

We report on an indium antimonide high electron mobility transistor with record cut-off frequency characteristics. For high frequency response it is important to minimize parasitic resistance and capacitance to improve short-channel effects. For analog applications adequate pinch-off behavior is demonstrated. For proper device scaling we need high electron mobility and high electron density. Toward this end, the device design features and simulation are carried out by the Synopsys TCAD tool. A 30 nm InSb HEMT exhibits an excellent cut-off frequency of 586 GHz. To the knowledge of the authors, the obtained cut-off frequency is the highest ever reported in any FET on any material system. (semiconductor materials)

Thermal characterization of polycrystalline diamond thin film heat spreaders grown on GaN HEMTs

Science.gov (United States)

Zhou, Yan; Ramaneti, Rajesh; Anaya, Julian; Korneychuk, Svetlana; Derluyn, Joff; Sun, Huarui; Pomeroy, James; Verbeeck, Johan; Haenen, Ken; Kuball, Martin

2017-07-01

Polycrystalline diamond (PCD) was grown onto high-k dielectric passivated AlGaN/GaN-on-Si high electron mobility transistor (HEMT) structures, with film thicknesses ranging from 155 to 1000 nm. Transient thermoreflectance results were combined with device thermal simulations to investigate the heat spreading benefit of the diamond layer. The observed thermal conductivity (κDia) of PCD films is one-to-two orders of magnitude lower than that of bulk PCD and exhibits a strong layer thickness dependence, which is attributed to the grain size evolution. The films exhibit a weak temperature dependence of κDia in the measured 25-225 °C range. Device simulation using the experimental κDia and thermal boundary resistance values predicts at best a 15% reduction in peak temperature when the source-drain opening of a passivated AlGaN/GaN-on-Si HEMT is overgrown with PCD.

Impacts of recessed gate and fluoride-based plasma treatment approaches toward normally-off AlGaN/GaN HEMT.

Science.gov (United States)

Heo, Jun-Woo; Kim, Young-Jin; Kim, Hyun-Seok

2014-12-01

We report two approaches to fabricating high performance normally-off AIGaN/GaN high-electron mobility transistors (HEMTs). The fabrication techniques employed were based on recessed-metal-insulator-semiconductor (MIS) gate and recessed fluoride-based plasma treatment. They were selectively applied to the area under the gate electrode to deplete the two-dimensional electron gas (2-DEG) density. We found that the recessed gate structure was effective in shifting the threshold voltage by controlling the etching depth of gate region to reduce the AIGaN layer thickness to less than 8 nm. Likewise, the CF4 plasma treatment effectively incorporated negatively charged fluorine ions into the thin AIGaN barrier so that the threshold voltage shifted to higher positive values. In addition to the increased threshold voltage, experimental results showed a maximum drain current and a maximum transconductance of 315 mA/mm and 100 mS/mm, respectively, for the recessed-MIS gate HEMT, and 340 mA/mm and 330 mS/mm, respectively, for the fluoride-based plasma treated HEMT.

North Korean Leadership Dynamics and Decision-making under Kim Jong-un: A First Year Assessment

Science.gov (United States)

2013-09-01

Kim Jong-un’s ’Sick’ Aunt Resurfaces,” Chosun Ilbo Online, 27 July 2013. Kim has a reported history of alcoholism and depression , which was...exacer- bated in the mid-2000s with her marital problems and the death of her daughter, Jang Kum-song, who committed suicide in 2006. Some reports claim...the Party and state apparatus. She was born in 1974, and, when in her teens , began work in Kim Il-sung’s Presidential Office. She moved over to the

Urinary KIM-1 and AQP-1 in patients with clear renal cell carcinoma: Potential noninvasive biomarkers

Directory of Open Access Journals (Sweden)

Mijušković Mirjana

2016-01-01

Full Text Available Background/Aim. Kidney injury molecule-1 (KIM-1 and aquaporin-1 (AQP-1 are potential early urinary biomarkers of clear renal cell carcinoma (cRCC. The aim of this study was to ascertain relationship between the urine concentrations KIM-1 and AQP-1 with tumor size, grade, pT stage and type of operation (radical or partial nephrectomy in patients with cRCC. Methods. Urinary concentrations of urinary KIM-1 (uKIM-1 and urinary AQP-1 (uAQP-1 were determined by commercially available ELISA kits. The analysis included 40 patients undergoing partial or radical nephrectomy for cRCC and 40 age- and sex-matched healthy adult volunteers. Results. The median preoperative concentrations of KIM-1 in the cRCC group [0.724 ± 1.120 ng/mg urinary creatinine (Ucr] were significantly greater compared with controls (healthy volunteers (0.210 ± 0.082 ng/mgUcr (p = 0.0227. Postoperatively, uKIM-1 concentration decreased significantly to control values (0.177 ± 0.099 ng/mgUcr vs 0.210 ± 0.082 ng/mgUcr, respectively. The size, grade and stage of tumor were correlated positively with preoperative uKIM-1 concentrations. Contrary to these results, concentrations of uAQP-1 in the cRCC group were significantly lower (0.111 ± 0.092 ng/mgUcr compared with the control group (0.202 ± 0.078 ng/mgUcr (p = 0.0014. Postoperatively, the concentrations of uAQP-1 increased progressively up to control values, approximately. We find no significant correlation between preoperative uAQP-1 concentrations and tumor size, grade and stage. Conclusion. uKIM-1 was found to be a reliable diagnostic marker of cRCC, based on its significantly increased values before and decreased values after the nephrectomy. [Projekat Ministarstva nauke Republike Srbije, br. III41018

Simultaneous measurement of temperature, stress, and electric field in GaN HEMTs with micro-Raman spectroscopy.

Science.gov (United States)

Bagnall, Kevin R; Moore, Elizabeth A; Badescu, Stefan C; Zhang, Lenan; Wang, Evelyn N

2017-11-01

As semiconductor devices based on silicon reach their intrinsic material limits, compound semiconductors, such as gallium nitride (GaN), are gaining increasing interest for high performance, solid-state transistor applications. Unfortunately, higher voltage, current, and/or power levels in GaN high electron mobility transistors (HEMTs) often result in elevated device temperatures, degraded performance, and shorter lifetimes. Although micro-Raman spectroscopy has become one of the most popular techniques for measuring localized temperature rise in GaN HEMTs for reliability assessment, decoupling the effects of temperature, mechanical stress, and electric field on the optical phonon frequencies measured by micro-Raman spectroscopy is challenging. In this work, we demonstrate the simultaneous measurement of temperature rise, inverse piezoelectric stress, thermoelastic stress, and vertical electric field via micro-Raman spectroscopy from the shifts of the E 2 (high), A 1 longitudinal optical (LO), and E 2 (low) optical phonon frequencies in wurtzite GaN. We also validate experimentally that the pinched OFF state as the unpowered reference accurately measures the temperature rise by removing the effect of the vertical electric field on the Raman spectrum and that the vertical electric field is approximately the same whether the channel is open or closed. Our experimental results are in good quantitative agreement with a 3D electro-thermo-mechanical model of the HEMT we tested and indicate that the GaN buffer acts as a semi-insulating, p-type material due to the presence of deep acceptors in the lower half of the bandgap. This implementation of micro-Raman spectroscopy offers an exciting opportunity to simultaneously probe thermal, mechanical, and electrical phenomena in semiconductor devices under bias, providing unique insight into the complex physics that describes device behavior and reliability. Although GaN HEMTs have been specifically used in this study to

Simultaneous measurement of temperature, stress, and electric field in GaN HEMTs with micro-Raman spectroscopy

Science.gov (United States)

Bagnall, Kevin R.; Moore, Elizabeth A.; Badescu, Stefan C.; Zhang, Lenan; Wang, Evelyn N.

2017-11-01

As semiconductor devices based on silicon reach their intrinsic material limits, compound semiconductors, such as gallium nitride (GaN), are gaining increasing interest for high performance, solid-state transistor applications. Unfortunately, higher voltage, current, and/or power levels in GaN high electron mobility transistors (HEMTs) often result in elevated device temperatures, degraded performance, and shorter lifetimes. Although micro-Raman spectroscopy has become one of the most popular techniques for measuring localized temperature rise in GaN HEMTs for reliability assessment, decoupling the effects of temperature, mechanical stress, and electric field on the optical phonon frequencies measured by micro-Raman spectroscopy is challenging. In this work, we demonstrate the simultaneous measurement of temperature rise, inverse piezoelectric stress, thermoelastic stress, and vertical electric field via micro-Raman spectroscopy from the shifts of the E2 (high), A1 longitudinal optical (LO), and E2 (low) optical phonon frequencies in wurtzite GaN. We also validate experimentally that the pinched OFF state as the unpowered reference accurately measures the temperature rise by removing the effect of the vertical electric field on the Raman spectrum and that the vertical electric field is approximately the same whether the channel is open or closed. Our experimental results are in good quantitative agreement with a 3D electro-thermo-mechanical model of the HEMT we tested and indicate that the GaN buffer acts as a semi-insulating, p-type material due to the presence of deep acceptors in the lower half of the bandgap. This implementation of micro-Raman spectroscopy offers an exciting opportunity to simultaneously probe thermal, mechanical, and electrical phenomena in semiconductor devices under bias, providing unique insight into the complex physics that describes device behavior and reliability. Although GaN HEMTs have been specifically used in this study to

Coenite seiklused ja Kim Ki-duki huumor / Merit Kask

Index Scriptorium Estoniae

Kask, Merit

2007-01-01

60-nda Cannes'i filmifestivali filme : Ethan ja Joel Coen'i "Pole maad vanadele meestele" ("No Country for Old Men" ; Ameerika Ühendriigid), Kim Ki-duki "Hingetõmme" ("Soom"/"Breath" ; Lõuna-Korea) ja Raphael Nadjari "Tehilim" (Prantsusmaa - Iisrael - Ameerika Ühendriigid)

Prikljutshenija Koenov i jumor Kim Ki-duka / Merit Kask

Index Scriptorium Estoniae

Kask, Merit

2007-01-01

60-nda Cannes'i filmifestivali filme : Ethan ja Joel Coen'i "Pole maad vanadele meestele" ("No Country for Old Men" ; Ameerika Ühendriigid), Kim Ki-duki "Hingetõmme" ("Soom"/"Breath" ; Lõuna-Korea) ja Raphael Nadjari "Tehilim" (Prantsusmaa - Iisrael - Ameerika Ühendriigid)

Chang Sei Kim's Activities on Public Health in Colonial Korea

Directory of Open Access Journals (Sweden)

Park Yunjae

2006-12-01

Full Text Available After graduating from Severance Medical College in 1916, Chang Sei Kim went to Shanghai to work as a missionary in a adventist hospital. The establishment of the Korean Provisional Government led him to participate in the independence movement. Educating nurses to assist the forthcoming war for independence, he seemed to realize the fact that the health of Koreans would be a key factor for achieving independence. He left for the U.S. to conduct comprehensive research on medicine. Chang Sei Kim was the first Korean to receive a Ph. D. degree of Public Health, graduating from the Johns Hopkins School of Hygiene and Public Health in 1925. He then gained an opportunity to work for Korea as a professor at Severance Medical College. His objective was the 'Reconstruction of the Korean People In Terms of Physical Constitution.' He pointed out that Koreans' weak state of health was a major reason for Korea's colonization. To gain independence, he emphasized that the Korean people should receive education on public health in order to improve the primitive conditions of sanitation. There is little doubt that Chang Sei Kim's ideas developed Heungsadan's views on medicine in terms of its stress on cultivation of ability, especially considering the fact that he was a member of the organization. As a member of the colonized who could not participate in the developing official policy, Chang Sei Kim was not able to implement his ideas fully, because an individual or a private organization could not carry out policy on public health as large a scale as the government did. Never giving up his hopes for Korean independence, he rejected requests to assume official posts in the Government-General. That was why he was particularly interested in the Self-Governing Movement in 1920s Korea. If the movement had attained its goal, he might have worked for the enhancement of sanitary environment as a director of Sanitary Department. His application for funding to establish

Bridging communication between public and government: a case study on kim surabaya

Science.gov (United States)

Aji, G. G.; Tsuroyya; Dewi, P. A. R.

2018-01-01

In democratic era, the public communication paradigm has shifted from a one-way socialization to more interactive one. As a consequence of freedom of speech, the public can Actively communicate with the government and vice versa. The problem is government is almost impossible to reach all public groups. Therefore, they has created the concept of social institutions as a communication hub between the government and its public, named the Kelompok Informasi Masyarakat (KIM). This research examines the activity of KIM in Surabaya on bridging public between government and the public. Using a case study approach, this research utilized various techniques of data collection such as: interviews, observation, and documentation. The results Showed that KIM plays a role in the two-way flow of information; to diseminate program and submit complaints and suggestions from the public about the policy. This study confirm the urgency of utilization on various channels in communicating with the public.

Performance characterization of gallium nitride HEMT cascode switch for power conditioning applications

International Nuclear Information System (INIS)

Chou, Po-Chien; Cheng, Stone

2015-01-01

Highlights: • We develop TO-257 cascoded GaN switch configuration in power conversion applications. • The normally-off cascode circuit provides 14.6 A/600 V characteristics. • Analysis of resistive and inductive switching performances shown in loaded circuits. • A 48-to-96 V boost converter is used to evaluate the benefit of GaN cascode switches. - Abstract: A hybrid cascoded GaN switch configuration is demonstrated in power conversion applications. A novel metal package is proposed for the packaging of a D-mode GaN MIS-HEMT cascoded with an integrated power MOSFET and a SBD. The normally-off cascode circuit provides a maximum drain current of 14.6 A and a blocking capability of 600 V. Analysis of 200 V/1 A power conversion characteristics are discussed and show the excellent switching performance in load circuits. Switching characteristics of the integral SiC SBD are also demonstrated. Finally, a 48-to-96 V boost converter is used to evaluate the benefit of GaN cascode switches. These results show that high-voltage GaN-HEMTs can be switching devices for an ultralow-loss converter circuit

Analysis of the thermal behavior of AlGaN/GaN HEMTs

International Nuclear Information System (INIS)

Russo, Salvatore; D’Alessandro, Vincenzo; Costagliola, Maurizio; Sasso, Grazia; Rinaldi, Niccolò

2012-01-01

Highlights: ► The thermal behavior of advanced multifinger AlGaN/GaN HEMTs grown on SiC is analyzed. ► The study is performed through accurate FEM simulations and DC/dynamic measurements. ► The FEM analysis is supported by an in-house tool devised for a smart mesh generation. ► Illustrative technology/layout guidelines to minimize the thermal issues are provided. - Abstract: The thermal behavior of state-of-the-art multifinger AlGaN/GaN HEMTs grown on SiC is thoroughly analyzed under steady-state and dynamic conditions. Accurate 3-D FEM simulations – based on a novel in-house tool devised to automatically build the device mesh – are performed using a commercial software to explore the influence of various layout and technological solutions on the temperature field. An in-house routine is employed to determine the Foster/Cauer networks suited to describe the dynamic heat propagation through the device structure. To conclude, various experimental techniques are employed to assess the thermal resistance and to allow the monitoring of the thermal impedance versus time of the transistors under test.

Performance characterization of gallium nitride HEMT cascode switch for power conditioning applications

Energy Technology Data Exchange (ETDEWEB)

Chou, Po-Chien; Cheng, Stone, E-mail: stonecheng@mail.nctu.edu.tw

2015-08-15

Highlights: • We develop TO-257 cascoded GaN switch configuration in power conversion applications. • The normally-off cascode circuit provides 14.6 A/600 V characteristics. • Analysis of resistive and inductive switching performances shown in loaded circuits. • A 48-to-96 V boost converter is used to evaluate the benefit of GaN cascode switches. - Abstract: A hybrid cascoded GaN switch configuration is demonstrated in power conversion applications. A novel metal package is proposed for the packaging of a D-mode GaN MIS-HEMT cascoded with an integrated power MOSFET and a SBD. The normally-off cascode circuit provides a maximum drain current of 14.6 A and a blocking capability of 600 V. Analysis of 200 V/1 A power conversion characteristics are discussed and show the excellent switching performance in load circuits. Switching characteristics of the integral SiC SBD are also demonstrated. Finally, a 48-to-96 V boost converter is used to evaluate the benefit of GaN cascode switches. These results show that high-voltage GaN-HEMTs can be switching devices for an ultralow-loss converter circuit.

Characterization of 0.18- μm gate length AlGaN/GaN HEMTs on SiC fabricated using two-step gate recessing

Science.gov (United States)

Yoon, Hyung Sup; Min, Byoung-Gue; Lee, Jong Min; Kang, Dong Min; Ahn, Ho Kyun; Cho, Kyu-Jun; Do, Jae-Won; Shin, Min Jeong; Jung, Hyun-Wook; Kim, Sung Il; Kim, Hae Cheon; Lim, Jong Won

2017-09-01

We fabricated a 0.18- μm gate-length AlGaN/GaN high electron mobility transistor (HEMT) on SiC substrate fabricated by using two-step gate recessing which was composed of inductively coupled plasma (ICP) dry etching with a gas mixture of BCl3/Cl2 and wet chemical etching using the oxygen plasma treatment and HCl-based cleaning. The two-step gate recessing process exhibited an etch depth of 4.5 nm for the AlGaN layer and the clean surface of AlGaN layer at the AlGaN/gate metal contact region for the AlGaN/GaN HEMT structure. The recessed 0.18 μm × 200 μm AlGaN/GaN HEMT devices showed good DC characteristics, having a good Schottky diode ideality factor of 1.25, an extrinsic transconductance ( g m ) of 345 mS/mm, and a threshold voltage ( V th ) of -2.03 V. The recessed HEMT devices exhibited high RF performance, having a cut-off frequency ( f T ) of 48 GHz and a maximum oscillation frequency ( f max ) of 130 GHz. These devices also showed minimum noise figure of 0.83 dB and associated gain of 12.2 dB at 10 GHz.

[KIM-1 and NGAL as potential biomarkers for the diagnosis and cancer progression].

Science.gov (United States)

Marchewka, Zofia; Tacik, Aneta; Piwowar, Agnieszka

2016-04-18

On the basis of scientific literature, there is growing evidence that KIM-1 and NGAL are interesting and promising biomarkers not only in acute and chronic inflammatory processes but also in oncogenesis. There are a number of studies which investigate their possible use in diagnosis, treatment and monitoring of therapy effectiveness. The results of recent research suggests that they may play an important role in standard oncology practice. Simultaneous measurement of KIM-1 and NGAL in urine can play a crucial role in carcinogenesis assessment and cancer progression. In the future, they can become rapid diagnostic indicators, which allow one to determine cancer subtype leading to biopsy replacement and therapy improvement. In the present work, beside biochemical characteristics of KIM-1 and NGAL, we will also discuss their role in the diagnosis and assessment of development of cancer.

KIM-1 and NGAL as potential biomarkers for the diagnosis and cancer progression

Directory of Open Access Journals (Sweden)

Zofia Marchewka

2016-04-01

Full Text Available On the basis of scientific literature, there is growing evidence that KIM-1 and NGAL are interesting and promising biomarkers not only in acute and chronic inflammatory processes but also in oncogenesis. There are a number of studies which investigate their possible use in diagnosis, treatment and monitoring of therapy effectiveness. The results of recent research suggests that they may play an important role in standard oncology practice. Simultaneous measurement of KIM-1 and NGAL in urine can play a crucial role in carcinogenesis assessment and cancer progression. In the future, they can become rapid diagnostic indicators, which allow one to determine cancer subtype leading to biopsy replacement and therapy improvement. In the present work, beside biochemical characteristics of KIM-1 and NGAL, we will also discuss their role in the diagnosis and assessment of development of cancer.

An analytical turn-on power loss model for 650-V GaN eHEMTs

DEFF Research Database (Denmark)

Shen, Yanfeng; Wang, Huai; Shen, Zhan

2018-01-01

This paper proposes an improved analytical turn-on power loss model for 650-V GaN eHEMTs. The static characteristics, i.e., the parasitic capacitances and transconductance, are firstly modeled. Then the turn-on process is divided into multiple stages and analyzed in detail; as results, the time-d...

Design and analysis of 30 nm T-gate InAlN/GaN HEMT with AlGaN back-barrier for high power microwave applications

Science.gov (United States)

Murugapandiyan, P.; Ravimaran, S.; William, J.; Meenakshi Sundaram, K.

2017-11-01

In this article, we present the DC and microwave characteristics of a novel 30 nm T-gate InAlN/AlN/GaN HEMT with AlGaN back-barrier. The device structure is simulated by using Synopsys Sentaurus TCAD Drift-Diffusion transport model at room temperature. The device features are heavily doped (n++ GaN) source/drain regions with Si3N4 passivated device surface for reducing the contact resistances and gate capacitances of the device, which uplift the microwave characteristics of the HEMTs. 30 nm gate length D-mode (E-mode) HEMT exhibited a peak drain current density Idmax of 2.3 (2.42) A/mm, transconductance gm of 1.24(1.65) S/mm, current gain cut-off frequency ft of 262 (246) GHz, power gain cut-off frequency fmax of 246(290) GHz and the three terminal off-state breakdown voltage VBR of 40(38) V. The preeminent microwave characteristics with the higher breakdown voltage of the proposed GaN-based HEMT are the expected to be the most optimistic applicant for future high power millimeter wave applications.

Electron beam irradiation effect on GaN HEMT

International Nuclear Information System (INIS)

Lou Yinhong; Guo Hongxia; Zhang Keying; Wang Yuanming; Zhang Fengqi

2011-01-01

In this work, GaN HEMTs (High Electron Mobility Transistor) were irradiated by 0.8 and 1.2 MeV electron beams, and the irradiation effects were investigated. The results show that the device damage caused by 0.8 MeV electrons is more serious than that by 1.2 MeV electrons. Saturation drain current increase and threshold voltage negative shift are due to trapped positive charge from ionization in the AlGaN layer and N, Ga vacancy from non-ionizing energy loss in the GaN layer. Electron traps and trapped positive charges from non-ionizing in the AlGaN layer act as trap-assisted-tunneling centers that increase the gate leakage current.(authors)

Impact of the lateral width of the gate recess on the DC and RF characteristics of InAlAs/InGaAs HEMTs

International Nuclear Information System (INIS)

Zhong Yinghui; Zhang Yuming; Wang Xiantai; Su Yongbo; Cao Yuxiong; Jin Zhi; Liu Xinyu

2012-01-01

We fabricated 88 nm gate-length InP-based InAlAs/InGaAs high electron mobility transistors (HEMTs) with a current gain cutoff frequency of 100 GHz and a maximum oscillation frequency of 185 GHz. The characteristics of HEMTs with side-etched region lengths (L side ) of 300, 412 and 1070 nm were analyzed. With the increase in L side , the kink effect became notable in the DC characteristics, which resulted from the surface state and the effect of impact ionization. The kink effect was qualitatively explained through energy band diagrams, and then eased off by reducing the L side . Meanwhile, the L side dependence of the radio frequency characteristics, which were influenced by the parasitic capacitance, as well as the parasitic resistance of the source and drain, was studied. This work will be of great importance in fabricating high-performance InP HEMTs. (semiconductor devices)

Arhitektuurimuuseum vaatab Aasiasse / Kim Sung Hong ; intervjueerinud Karin Hallas-Murula

Index Scriptorium Estoniae

Kim Sung Hong

2009-01-01

Näituse kuraatori Kim Sung Hongiga 21. aprillini Eesti Arhitektuurimuuseumis avatud Lõuna-Korea kaasaegse arhitektuuri näitusest "Megacity network" ("Megalinna võrgustik"), Korea arhitektuurist, arhitektidest, muinsuskaitsest ja avalikust ruumist. Näituse kujundas Hwang Doo Jin

Degradation mechanisms of 2 MeV proton irradiated AlGaN/GaN HEMTs

International Nuclear Information System (INIS)

Greenlee, Jordan D.; Anderson, Travis J.; Koehler, Andrew D.; Weaver, Bradley D.; Kub, Francis J.; Hobart, Karl D.; Specht, Petra; Dubon, Oscar D.; Luysberg, Martina; Weatherford, Todd R.

2015-01-01

Proton-induced damage in AlGaN/GaN HEMTs was investigated using energy-dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM), and simulated using a Monte Carlo technique. The results were correlated to electrical degradation using Hall measurements. It was determined by EDS that the interface between GaN and AlGaN in the irradiated HEMT was broadened by 2.2 nm, as estimated by the width of the Al EDS signal compared to the as-grown interface. The simulation results show a similar Al broadening effect. The extent of interfacial roughening was examined using high resolution TEM. At a 2 MeV proton fluence of 6 × 10 14 H + /cm 2 , the electrical effects associated with the Al broadening and surface roughening include a degradation of the ON-resistance and a decrease in the electron mobility and 2DEG sheet carrier density by 28.9% and 12.1%, respectively

Degradation mechanisms of 2 MeV proton irradiated AlGaN/GaN HEMTs

Energy Technology Data Exchange (ETDEWEB)

Greenlee, Jordan D., E-mail: jordan.greenlee.ctr@nrl.navy.mil; Anderson, Travis J.; Koehler, Andrew D.; Weaver, Bradley D.; Kub, Francis J.; Hobart, Karl D. [U.S. Naval Research Laboratory, 4555 Overlook Ave. SW, Washington, DC 20375 (United States); Specht, Petra; Dubon, Oscar D. [University of California at Berkeley, Berkeley, California 94720 (United States); Luysberg, Martina [ERC, Research Center Juelich GmbH, 52425 Juelich (Germany); Weatherford, Todd R. [Naval Postgraduate School, Monterey, California 93943 (United States)

2015-08-24

Proton-induced damage in AlGaN/GaN HEMTs was investigated using energy-dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM), and simulated using a Monte Carlo technique. The results were correlated to electrical degradation using Hall measurements. It was determined by EDS that the interface between GaN and AlGaN in the irradiated HEMT was broadened by 2.2 nm, as estimated by the width of the Al EDS signal compared to the as-grown interface. The simulation results show a similar Al broadening effect. The extent of interfacial roughening was examined using high resolution TEM. At a 2 MeV proton fluence of 6 × 10{sup 14} H{sup +}/cm{sup 2}, the electrical effects associated with the Al broadening and surface roughening include a degradation of the ON-resistance and a decrease in the electron mobility and 2DEG sheet carrier density by 28.9% and 12.1%, respectively.

Basic Equations for the Modeling of Gallium Nitride (gan) High Electron Mobility Transistors (hemts)

Science.gov (United States)

Freeman, Jon C.

2003-01-01

Gallium nitride (GaN) is a most promising wide band-gap semiconductor for use in high-power microwave devices. It has functioned at 320 C, and higher values are well within theoretical limits. By combining four devices, 20 W has been developed at X-band. GaN High Electron Mobility Transistors (HEMTs) are unique in that the two-dimensional electron gas (2DEG) is supported not by intentional doping, but instead by polarization charge developed at the interface between the bulk GaN region and the AlGaN epitaxial layer. The polarization charge is composed of two parts: spontaneous and piezoelectric. This behavior is unlike other semiconductors, and for that reason, no commercially available modeling software exists. The theme of this document is to develop a self-consistent approach to developing the pertinent equations to be solved. A Space Act Agreement, "Effects in AlGaN/GaN HEMT Semiconductors" with Silvaco Data Systems to implement this approach into their existing software for III-V semiconductors, is in place (summer of 2002).

North Korean Leadership Dynamics and Decision-making under Kim Jong-un: A Second Year Assessment

Science.gov (United States)

2014-03-01

Kim Kyong-hui was critically ill. Kim has a reported history of alcoholism and depression , which was exacerbated in the mid-2000s with her mari- tal...problems and the death of her daughter, Jang Kum-song, who com- mitted suicide in 2006. Some reports claim that she is also suffering from... teens , were

Bi-layer SixNy passivation on AlGaN/GaN HEMTs to suppress current collapse and improve breakdown

International Nuclear Information System (INIS)

Lee, K B; Green, R T; Houston, P A; Tan, W S; Uren, M J; Wallis, D J; Martin, T

2010-01-01

Si x N y deposited at low temperature was found to improve the breakdown voltage of AlGaN/GaN HEMTs at the expense of current collapse due to the presence of a high density of charge trapping states. On the other hand, stoichiometric Si 3 N 4 film deposited at high temperature was effective in mitigating current slump but no improvement in the breakdown voltage was observed. Combining the benefit of both films, a bi-layer stacked passivation has been employed on the HEMTs. Gate lag measurements revealed that the current collapse was mitigated and the breakdown voltage of the devices was found to increase from 120 V to 238 V upon passivation

Groove-type channel enhancement-mode AlGaN/GaN MIS HEMT with combined polar and nonpolar AlGaN/GaN heterostructures

International Nuclear Information System (INIS)

Duan Xiao-Ling; Zhang Jin-Cheng; Xiao Ming; Zhao Yi; Ning Jing; Hao Yue

2016-01-01

A novel groove-type channel enhancement-mode AlGaN/GaN MIS high electron mobility transistor (GTCE-HEMT) with a combined polar and nonpolar AlGaN/GaN heterostucture is presented. The device simulation shows a threshold voltage of 1.24 V, peak transconductance of 182 mS/mm, and subthreshold slope of 85 mV/dec, which are obtained by adjusting the device parameters. Interestingly, it is possible to control the threshold voltage accurately without precisely controlling the etching depth in fabrication by adopting this structure. Besides, the breakdown voltage ( V B ) is significantly increased by 78% in comparison with the value of the conventional MIS-HEMT. Moreover, the fabrication process of the novel device is entirely compatible with that of the conventional depletion-mode (D-mode) polar AlGaN/GaN HEMT. It presents a promising way to realize the switch application and the E/D-mode logic circuits. (paper)

AlGaN/GaN HEMTs with very thin buffer on Si (111) for nanosystems applications

International Nuclear Information System (INIS)

Leclaire, P; Chenot, S; Cordier, Y; Buchaillot, L; Théron, D; Faucher, M

2014-01-01

In the present work, AlGaN/GaN high electron mobility transistors (HEMTs) have been grown with very thin buffer layers on silicon substrates in view of developing nano electromechanical systems (NEMS) for sensors applications. To ensure transducer operation in the MHz range together with low mechanical stiffness, epitaxial structures with thickness below 1 μm have to be developed. We report on the evolution of the material and electrical properties of AlGaN/GaN HEMTs with thicknesses varying from 2 μm to 0.5 μm. The set of parameters obtained includes in-plane Young modulus of 250 GPa in association with carrier density of 6 × 10 12 cm −2 and mobility above 1000 cm 2  V −1  s −1 . The resulting behavior of demonstration transistors validates these epilayers for electromechanical resonators operation. (paper)

A Decade-Bandwidth Distributed Power Amplifier MMIC Using 0.25 μm GaN HEMT Technology

Directory of Open Access Journals (Sweden)

Dong-Hwan Shin

2017-10-01

Full Text Available This study presents a 2–20 GHz monolithic distributed power amplifier (DPA using a 0.25 μm AlGaN/GaN on SiC high electron mobility transistor (HEMT technology. The gate width of the HEMT was selected after considering the input capacitance of the unit cell that guarantees decade bandwidth. To achieve high output power using small transistors, a 12-stage DPA was designed with a nonuniform drain line impedance to provide optimal output power matching. The maximum operating frequency of the proposed DPA is above 20 GHz, which is higher than those of other DPAs manufactured with the same gate-length process. The measured output power and power-added efficiency of the DPA monolithic microwave integrated circuit (MMIC are 35.3–38.6 dBm and 11.4%–31%, respectively, for 2–20 GHz.

Ka-Band AlGaN/GaN HEMT high power and driver amplifier MMICs

NARCIS (Netherlands)

Heijningen, M. van; Vliet, F.E. van; Quay, R.; Raay, F. van; Kiefer, R.; Mueller, S.; Krausse, D.; Seelmann-Eggebert, M.; Mikulla, M.; Schlechtweg, M.

2005-01-01

In this paper the MMIC technology, design and characterization of a high power amplifier and driver amplifier MMIC at 30 GHz in AlGaN/GaN HEMT technology are presented. The MMICs are designed using CPW technology on a 390 μm thick SiC substrate. The measured small-signal gain of the driver is 14 dB

Lõuna-Korea teatel võib Kim peagi surra / Evelyn Kaldoja

Index Scriptorium Estoniae

Kaldoja, Evelyn, 1980-

2009-01-01

Viidates Lõuna-Korea ja Hiina luureandmetele, väidab Lõuna-Korea meedia, et Põhja-Korea liidril Kim Jong-ilil on kõhunäärmevähk ja talle pole antud elada rohkem kui 5 aastat. Põhja-Korea valitsejadünastia

Optical Sensitivity of a Monolithic Integrated InP PIN-HEMT-HBT Transimpedance Amplifier

OpenAIRE

Matiss, A.; Janssen, G.; Bertenburg, R. M.; Brockerhoff, W.; Tegude, F.J.

2004-01-01

To improve sensitivity of optical receivers, a special integration concept is chosen that includes a pinphotodiode, high-electron mobility transistors (HEMT) and heterostructure bipolar transistors (HBT) on a single substrate. This work focuses on the optimization of the amplifier design to achieve lowest input noise currents of a transimpedance amplifier, and thus highest receiver sensitivity. The respective advantages of the components used are investigated with respect...

Low-leakage-current AlGaN/GaN HEMTs on Si substrates with partially Mg-doped GaN buffer layer by metal organic chemical vapor deposition

International Nuclear Information System (INIS)

Li Ming; Wang Yong; Wong Kai-Ming; Lau Kei-May

2014-01-01

High-performance low-leakage-current AlGaN/GaN high electron mobility transistors (HEMTs) on silicon (111) substrates grown by metal organic chemical vapor deposition (MOCVD) with a novel partially Magnesium (Mg)-doped GaN buffer scheme have been fabricated successfully. The growth and DC results were compared between Mg-doped GaN buffer layer and a unintentionally one. A 1-μm gate-length transistor with Mg-doped buffer layer exhibited an OFF-state drain leakage current of 8.3 × 10 −8 A/mm, to our best knowledge, which is the lowest value reported for MOCVD-grown AlGaN/GaN HEMTs on Si featuring the same dimension and structure. The RF characteristics of 0.25-μm gate length T-shaped gate HEMTs were also investigated

Effects of doping concentration ratio on electrical characterization in pseudomorphic HEMT-based MMIC switches for ICT system

Science.gov (United States)

Mun, Jae-Kyoung; Oh, Jung-Hun; Sung, Ho-Kun; Wang, Cong

2015-12-01

The effects of the doping concentration ratios between upper and lower silicon planar-doping layers on the DC and RF characteristics of the double planar doped pseudomorphic high electron mobility transistors (pHEMTs) are investigated. From the device simulation, an increase of maximum extrinsic transconductance and a decrease of total on- and off-state capacitances are observed, as well as an increase of the upper to lower planar-doping concentration ratios (UTLPDR), which give rise to an enhancement of the switching speed and isolation characteristics. On the basis of simulation results, two types of pHEMTs are fabricated with two different UTLPDRs of 4:1 and 1:2. After applying these two types' pHEMTs, single-pole-double-throw (SPDT) transmitter/receiver monolithic microwave integrated circuit (MMIC) switches are also designed and fabricated. The SPDT MMIC switch with a 4:1 UTLPDR shows an insertion loss of 0.58 dB, isolation of 40.2 dB, and switching speed of 100 ns, respectively, which correspondingly indicate a 0.23 dB lower insertion loss, 2.90 dB higher isolation and 2.5 times faster switching speed than those of 1:2 UTLPDR at frequency range of 2-6 GHz. From the simulation results and comparative studies, we propose that the UTLPDR must be greater than 4:1 for the best switching performance. With the abovementioned excellent performances, the proposed switch would be quite promising in the application of information and communications technology system.

Monte Carlo lattice program KIM

International Nuclear Information System (INIS)

Cupini, E.; De Matteis, A.; Simonini, R.

1980-01-01

The Monte Carlo program KIM solves the steady-state linear neutron transport equation for a fixed-source problem or, by successive fixed-source runs, for the eigenvalue problem, in a two-dimensional thermal reactor lattice. Fluxes and reaction rates are the main quantities computed by the program, from which power distribution and few-group averaged cross sections are derived. The simulation ranges from 10 MeV to zero and includes anisotropic and inelastic scattering in the fast energy region, the epithermal Doppler broadening of the resonances of some nuclides, and the thermalization phenomenon by taking into account the thermal velocity distribution of some molecules. Besides the well known combinatorial geometry, the program allows complex configurations to be represented by a discrete set of points, an approach greatly improving calculation speed

Investigation of the fabrication processes of AlGaN/AlN/GaN HEMTs with in situ Si3N4 passivation

International Nuclear Information System (INIS)

Tomosh, K. N.; Pavlov, A. Yu.; Pavlov, V. Yu.; Khabibullin, R. A.; Arutyunyan, S. S.; Maltsev, P. P.

2016-01-01

The optimum mode of the in situ plasma-chemical etching of a Si 3 N 4 passivating layer in C 3 F 8 /O 2 medium is chosen for the case of fabricating AlGaN/AlN/GaN HEMTs. It is found that a bias of 40–50 V at a high-frequency electrode provides anisotropic etching of the insulator through a resist mask and introduces no appreciable radiation-induced defects upon overetching of the insulator films in the region of gate-metallization formation. To estimate the effect of in situ Si 3 N 4 growth together with the heterostructure in one process on the AlGaN/AlN/GaN HEMT characteristics, transistors with gates without the insulator and with gates through Si 3 N 4 slits are fabricated. The highest drain current of the AlGaN/AlN/GaN HEMT at 0 V at the gate is shown to be 1.5 times higher in the presence of Si 3 N 4 than without it.

Enhanced terahertz detection using multiple GaAs HEMTs connected in series

KAUST Repository

Elkhatib, Tamer A.; Veksler, Dmitry B.; Salama, Khaled N.; Zhang, Xi-C.; Shur, Michael S.

2012-01-01

We report here, for the first time, on enhanced nonresonant detection of terahertz radiation using multiple InGaAs/GaAs high-electron-mobility transistors (HEMTs) connected in series and biased by a direct drain current. A 1.63 THz (184 mum) response is proportional to the number of detecting transistors operating in saturation region at the same gate-source bias voltage. The experimental data are in agreement with the detection mechanism based on the rectification of overdamped plasma waves excited by radiation in channels of devices.

Enhanced terahertz detection using multiple GaAs HEMTs connected in series

KAUST Repository

Elkhatib, Tamer A.

2012-07-28

We report here, for the first time, on enhanced nonresonant detection of terahertz radiation using multiple InGaAs/GaAs high-electron-mobility transistors (HEMTs) connected in series and biased by a direct drain current. A 1.63 THz (184 mum) response is proportional to the number of detecting transistors operating in saturation region at the same gate-source bias voltage. The experimental data are in agreement with the detection mechanism based on the rectification of overdamped plasma waves excited by radiation in channels of devices.

Electron Mobilities and Effective Masses in InGaAs/InAlAs HEMT Structures with High In Content

Science.gov (United States)

Yuzeeva, N. A.; Sorokoumova, A. V.; Lunin, R. A.; Oveshnikov, L. N.; Galiev, G. B.; Klimov, E. A.; Lavruchin, D. V.; Kulbachinskii, V. A.

2016-12-01

InxGa_{1-{x}}As/InyAl_{1-{y}}As HEMT structures {δ}-doped by Si were grown by molecular beam epitaxy on InP substrate. We investigated the influence of the In content on the electron mobilities and effective masses in dimensionally quantized subbands. The electron effective masses were determined by the temperature dependence of the amplitude of the Shubnikov-de Haas effect at 1.6 and 4.2 K. We found that the more the In content in quantum well (QW), the less the electron effective masses. The mobilities are higher in HEMT structures with wider and deeper QW. The energy band diagrams were calculated by using Vegard's law for basic parameters. The calculated band diagrams are in a good agreement with the experimental data of photoluminescence spectra.

Investigations on MgO-dielectric GaN/AlGaN/GaN MOS-HEMTs by using an ultrasonic spray pyrolysis deposition technique

International Nuclear Information System (INIS)

Lee, Ching-Sung; Liu, Han-Yin; Wu, Ting-Ting; Hsu, Wei-Chou; Sun, Wen-Ching; Wei, Sung-Yen; Yu, Sheng-Min

2016-01-01

This work investigates GaN/Al 0.24 Ga 0.76 N/GaN metal-oxide-semiconductor high electron mobility transistors (MOS-HEMTs) grown on a Si substrate with MgO gate dielectric by using the non-vacuum ultrasonic spray pyrolysis deposition (USPD) technique. The oxide layer thickness is tuned to be 30 nm with the dielectric constant of 8.8. Electron spectroscopy for chemical analysis (ESCA), secondary ion mass spectrometry (SIMS), atomic force microscopy (AFM), transmission electron microscopy (TEM), C–V, low-frequency noise spectra, and pulsed I–V measurements are performed to characterize the interface and oxide quality for the MOS-gate structure. Improved device performances have been successfully achieved for the present MOS-HEMT (Schottky-gate HEMT) design, consisting of a maximum drain-source current density (I DS, max ) of 681 (500) mA/mm at V GS  = 4 (2) V, I DS at V GS  = 0 V (I DSS0 ) of 329 (289) mA/mm, gate-voltage swing (GVS) of 2.2 (1.6) V, two-terminal gate-drain breakdown voltage (BV GD ) of −123 (−104) V, turn-on voltage (V on ) of 1.7 (0.8) V, three-terminal off-state drain-source breakdown voltage (BV DS ) of 119 (96) V, and on/off current ratio (I on /I off ) of 2.5 × 10 8 (1.2 × 10 3 ) at 300 K. Improved high-frequency and power performances are also achieved in the present MOS-HEMT design. (paper)

Quantum ballistic transistor and low noise HEMT for cryo-electronics lower than 4.2 K; Transistor balistique quantique et HEMT bas-bruit pour la cryoelectronique inferieure a 4.2 K

Energy Technology Data Exchange (ETDEWEB)

Gremion, E

2008-01-15

Next generations of cryo-detectors, widely used in physics of particles and physics of universe, will need in the future high-performance cryo-electronics less noisy and closer to the detector. Within this context, this work investigates properties of two dimensional electron gas GaAlAs/GaAs by studying two components, quantum point contact (QPC) and high electron mobility transistor (HEMT). Thanks to quantized conductance steps in QPC, we have realized a quantum ballistic transistor (voltage gain higher than 1), a new component useful for cryo-electronics thanks to its operating temperature and weak power consumption (about 1 nW). Moreover, the very low capacity of this component leads to promising performances for multiplexing low temperature bolometer dedicated to millimetric astronomy. The second study focused on HEMT with very high quality 2DEG. At 4.2 K, a voltage gain higher than 20 can be obtained with a very low power dissipation of less than 100 {mu}W. Under the above experimental conditions, an equivalent input voltage noise of 1.2 nV/{radical}(Hz) at 1 kHz and 0.12 nV/{radical}(Hz) at 100 kHz has been reached. According to the Hooge formula, these noise performances are get by increasing gate capacity estimated to 60 pF. (author)

Influence of PECVD deposited SiNx passivation layer thickness on In0.18Al0.82N/GaN/Si HEMT

International Nuclear Information System (INIS)

Singh, Sarab Preet; Liu, Yi; Ngoo, Yi Jie; Kyaw, Lwin Min; Bera, Milan Kumar; Chor, Eng Fong; Dolmanan, S B; Tripathy, Sudhiranjan

2015-01-01

The influence of plasma enhanced chemical vapour deposited (PECVD) silicon nitride (SiN x ) passivation film thickness on In 0.18 Al 0.82 N/GaN/Si heterostructures and HEMTs has been investigated. The formation of Si 3 N 4 was confirmed by x-ray photoelectron spectroscopy (XPS) measurements. X-ray reflectivity (XRR) measurements reveal that both the density and roughness of the SiN x film increase with increasing film thickness. With an increase in SiN x film thickness, a significant increase in two-dimensional electron gas (2DEG) density, drain current, extrinsic transconductance and negative threshold voltage shift of the In 0.18 Al 0.82 /GaN/Si HEMTs are observed. An optimal thickness of SiN x is ∼100 nm and it yields a substantial increase in 2DEG density (∼30%) with a minimum sheet resistance for In 0.18 Al 0.82 N/GaN/Si heterostructures. Furthermore, we correlate the observed SiN x film thickness-dependent electrical characteristics of In 0.18 Al 0.82 /GaN/Si HEMTs with the density of the SiN x film. (paper)

Comparative studies of AlGaN/GaN MOS-HEMTs with stacked gate dielectrics by the mixed thin film growth method

International Nuclear Information System (INIS)

Chou, Bo-Yi; Hsu, Wei-Chou; Liu, Han-Yin; Ho, Chiu-Sheng; Lee, Ching-Sung

2013-01-01

This paper reports Al 0.27 Ga 0.73 N/GaN metal–oxide–semiconductor high electron mobility transistors (MOS-HEMTs) with stacked Al 2 O 3 /HfO 2 gate dielectrics by using hydrogen peroxideoxidation/sputtering techniques. The Al 2 O 3 employed as a gate dielectric and surface passivation layer effectively suppresses the gate leakage current, improves RF drain current collapse and exhibits good thermal stability. Moreover, by stacking the good insulating high-k HfO 2 dielectric further suppresses the gate leakage, enhances the dielectric breakdown field and power-added efficiency, and decreases the equivalent oxide thickness. The present MOS-HEMT design has demonstrated superior improvements of 10.1% (16.4%) in the maximum drain–source current (I DS,max ), 11.4% (22.5%) in the gate voltage swing and 12.5%/14.4% (21.9%/22.3%) in the two-terminal gate–drain breakdown/turn-on voltages (BV GD /V ON ), and the present design also demonstrates the lowest gate leakage current and best thermal stability characteristics as compared to two reference MOS-HEMTs with a single Al 2 O 3 /(HfO 2 ) dielectric layer of the same physical thickness. (invited paper)

Characterization of modulation doped pseudomorphic AlGaAs/InGaAs/GaAs HEMT structures by electron beam electroreflectance and photoluminescence

International Nuclear Information System (INIS)

Herman, M.A.; Ward, I.D.; Kopf, R.F.; Pearton, S.J.; Jones, E.D.

1990-01-01

The authors have investigated the optical transitions present in MBE-grown modulation doped pseudomorphic Al x Ga 1-x As/In y Ga 1-y As/GaAs HEMT structures of 120 Angstrom InGaAs thickness, y values 0 to 0.28, and x values 0.20 to 0.30. From both 300K electron beam electroreflectance (EBER) and 4K photoluminescence (PL) measurements the authors observe transitions from the InGaAs strained quantum well layer. The intensity and lineshape of the InGaAs transition in both optical spectra are affected by processing temperatures, and provides an indication of the quality of the HEMT

Comparative studies of MOS-gate/oxide-passivated AlGaAs/InGaAs pHEMTs by using ozone water oxidation technique

International Nuclear Information System (INIS)

Lee, Ching-Sung; Hung, Chun-Tse; Chou, Bo-Yi; Hsu, Wei-Chou; Liu, Han-Yin; Ho, Chiu-Sheng; Lai, Ying-Nan

2012-01-01

Al 0.22 Ga 0.78 As/In 0.24 Ga 0.76 As pseudomorphic high-electron-mobility transistors (pHEMTs) with metal-oxide-semiconductor (MOS)-gate structure or oxide passivation by using ozone water oxidation treatment have been comprehensively investigated. Annihilated surface states, enhanced gate insulating property and improved device gain have been achieved by the devised MOS-gate structure and oxide passivation. The present MOS-gated or oxide-passivated pHEMTs have demonstrated superior device performances, including superior breakdown, device gain, noise figure, high-frequency characteristics and power performance. Temperature-dependent device characteristics of the present designs at 300–450 K are also studied. (paper)

Against the Nihilism of Suffering and Death: Richard E. K. Kim and His Works

Directory of Open Access Journals (Sweden)

Jooyeon Rhee

2016-03-01

Full Text Available This article examines the life and works of Richard E. K. Kim (1932–2009, a first-generation Korean diasporic writer in the United States. It focuses on how Kim struggled to overcome the nihilism of suffering and death that derived from colonialism and the Korean War through his literary works. Kim witnessed firsthand these two major historical events, which caused irrevocable psychological and physical damage to many people of his generation. In his autobiographical fiction, he conveys painful memories of the events by reviving the voices of people in that era. What his works offer us goes beyond vivid memories of the past, however; they also present the power of forgiveness as a condition to overcome the nihilism of suffering and death. Remembrance and forgiveness are, therefore, two major thematic pillars of his works that enable us to connect to these difficult and traumatic times. These themes are portrayed in such a gripping way mainly because Kim tried to maintain a certain distance—an emotional and linguistic distance—from the familiar, in order to elucidate the reality of the human condition: an ontological position of the exile from which he produced his works. This article argues that Kim’s works provide us the possibility to transcend the nihilism of historical trauma through articulating the meaning of remembrance and forgiveness from his self-assumed position of exile.

Simulation of InGaAs subchannel DG-HEMTs for analogue/RF applications

Science.gov (United States)

Saravana Kumar, R.; Mohanbabu, A.; Mohankumar, N.; Godwin Raj, D.

2018-03-01

The paper reports on the influence of a barrier thickness and gate length on the various device parameters of double gate high electron mobility transistors (DG-HEMTs). The DC and RF performance of the device have been studied by varying the barrier thickness from 1 to 5 nm and gate length from 10 to 150 nm, respectively. As the gate length is reduced below 50 nm regime, the barrier thickness plays an important role in device performance. Scaling the gate length leads to higher transconductance and high frequency operations with the expense of poor short channel effects. The authors claim that the 30-nm gate length, mole fractions tuned In0.53Ga0.47As/In0.7Ga0.3As/In0.53Ga0.47As subchannel DG-HEMT with optimised device structure of 2 nm In0.48Al0.52As barrier layer show a peak gm of 3.09 mS/µm, VT of 0.29 V, ION/IOFF ratio of 2.24 × 105, subthreshold slope 73 mV/decade and drain induced barrier lowering 68 mV/V with fT and fmax of 776 and 905 GHz at Vds = 0.5 V is achieved. These superior performances are achieved by using double-gate architecture with reduced gate to channel distance.

Open-gated pH sensor fabricated on an undoped-AlGaN/GaN HEMT structure.

Science.gov (United States)

Abidin, Mastura Shafinaz Zainal; Hashim, Abdul Manaf; Sharifabad, Maneea Eizadi; Rahman, Shaharin Fadzli Abd; Sadoh, Taizoh

2011-01-01

The sensing responses in aqueous solution of an open-gated pH sensor fabricated on an AlGaN/GaN high-electron-mobility-transistor (HEMT) structure are investigated. Under air-exposed ambient conditions, the open-gated undoped AlGaN/GaN HEMT only shows the presence of a linear current region. This seems to show that very low Fermi level pinning by surface states exists in the undoped AlGaN/GaN sample. In aqueous solution, typical current-voltage (I-V) characteristics with reasonably good gate controllability are observed, showing that the potential of the AlGaN surface at the open-gated area is effectively controlled via aqueous solution by the Ag/AgCl gate electrode. The open-gated undoped AlGaN/GaN HEMT structure is capable of distinguishing pH level in aqueous electrolytes and exhibits linear sensitivity, where high sensitivity of 1.9 mA/pH or 3.88 mA/mm/pH at drain-source voltage, V(DS) = 5 V is obtained. Due to the large leakage current where it increases with the negative gate voltage, Nernstian like sensitivity cannot be determined as commonly reported in the literature. This large leakage current may be caused by the technical factors rather than any characteristics of the devices. Surprisingly, although there are some imperfections in the device preparation and measurement, the fabricated devices work very well in distinguishing the pH levels. Suppression of current leakage by improving the device preparation is likely needed to improve the device performance. The fabricated device is expected to be suitable for pH sensing applications.

Open-Gated pH Sensor Fabricated on an Undoped-AlGaN/GaN HEMT Structure

Directory of Open Access Journals (Sweden)

Taizoh Sadoh

2011-03-01

Full Text Available The sensing responses in aqueous solution of an open-gated pH sensor fabricated on an AlGaN/GaN high-electron-mobility-transistor (HEMT structure are investigated. Under air-exposed ambient conditions, the open-gated undoped AlGaN/GaN HEMT only shows the presence of a linear current region. This seems to show that very low Fermi level pinning by surface states exists in the undoped AlGaN/GaN sample. In aqueous solution, typical current-voltage (I-V characteristics with reasonably good gate controllability are observed, showing that the potential of the AlGaN surface at the open-gated area is effectively controlled via aqueous solution by the Ag/AgCl gate electrode. The open-gated undoped AlGaN/GaN HEMT structure is capable of distinguishing pH level in aqueous electrolytes and exhibits linear sensitivity, where high sensitivity of 1.9 mA/pH or 3.88 mA/mm/pH at drain-source voltage, VDS = 5 V is obtained. Due to the large leakage current where it increases with the negative gate voltage, Nernstian like sensitivity cannot be determined as commonly reported in the literature. This large leakage current may be caused by the technical factors rather than any characteristics of the devices. Surprisingly, although there are some imperfections in the device preparation and measurement, the fabricated devices work very well in distinguishing the pH levels. Suppression of current leakage by improving the device preparation is likely needed to improve the device performance. The fabricated device is expected to be suitable for pH sensing applications.

Negative charging effect of traps on the gate leakage current of an AlGaN/GaN HEMT

Energy Technology Data Exchange (ETDEWEB)

Kim, J. J.; Lim, J. H.; Yang, J. W. [Chonbuk National University, Jeonju (Korea, Republic of); Stanchina, W. [University of Pittsburgh, Pittsburgh, PA (United States)

2014-08-15

The negative charging effect of surface traps on the gate leakage current of AlGaN/GaN high electron mobility transistors (HEMTs) was investigated. The gate leakage current could be decreased by two orders of magnitude by using a photo-electrochemical process to treat of the source and the drain region, but current flowed into the gate even at a negative voltage in a limited region when the measurement was executed with a gate voltage sweep from negative to positive voltage. Also the electrical characteristics of the HEMT were degraded by pulsed operation of the gate. Traps newly generated on the surface were regarded as sources for the current that flowed against the applied voltage, and the number of traps was estimated. Also, a slow transient in the drain current was confirmed based on the results of delayed sweep measurements.

Global Policing and the Case of Kim Dotcom

OpenAIRE

Darren Palmer; Ian J Warren

2013-01-01

In early 2012, 76 heavily armed police conducted a raid on a house in Auckland, New Zealand. The targets were Kim Dotcom, a German national with a NZ residency visa, and several colleagues affiliated with Megaupload, an online subscription-based peer-to-peer (P2P) file sharing facility. The alleged offences involved facilitating unlawful file sharing and United States federal criminal copyright violations. Following the raid, several court cases provide valuable insights into emerging ‘global...

Ab initio and Gordon--Kim intermolecular potentials for two nitrogen molecules

International Nuclear Information System (INIS)

Ree, F.H.; Winter, N.W.

1980-01-01

Both ab initio MO--LCAO--SCF and the electron-gas (or Gordon--Kim) methods have been used to compute the intermolecular potential (Phi) of N 2 molecules for seven different N 2 --N 2 orientations. The ab initio calculations were carried out using a [4s3p] contracted Gaussian basis set with and without 3d polarization functions. The larger basis set provides adequate results for Phi>0.002 hartree or intermolecular separations less than 6.5--7 bohr. We use a convenient analytic expression to represent the ab initio data in terms of the intermolecular distance and three angles defining the orientations of the two N 2 molecules. The Gordon--Kim method with Rae's self-exchange correction yields Phi, which agrees reasonably well over a large repulsive range. However, a detailed comparison of the electron kinetic energy contributions shows a large difference between the ab initio and the Gordon--Kim calculations. Using the ab initio data we derive an atom--atom potential of the two N 2 molecules. Although this expression does not accurately fit the data at some orientations, its spherical average agrees with the corresponding average of the ab initio Phi remarkably well. The spherically averaged ab initio Phi is also compared with the corresponding quantities derived from experimental considerations. The approach of the ab initio Phi to the classical quadrupole--quadrupole interaction at large intermolecular separation is also discussed

Barrier layer engineering: Performance evaluation of E-mode InGaN/AlGaN/GaN HEMT

Science.gov (United States)

Majumdar, Shubhankar; Das, S.; Biswas, D.

2015-08-01

Impact on DC characteristics of InGaN/AlGaN/GaN HEMT due to variation in the hetero-structure parameters i.e. molar fraction of Al and thickness of AlGaN barrier layer is presented in this paper. Gate controllability over the channel is dependent on barrier layer thickness, and molar fraction has an impact on band offset and 2DEG, which further affects the current. HEMT device that is simulated in SILVACO has InGaN cap layer of 2 nm thickness with 15% In molar fraction, variation of Al percentage and thickness of the AlGaN barrier layer are taken as 15-45% and 5-20nm, respectively. A tremendous change in threshold voltage (Vth), maximum transconductance (Gmmax) and subthreshold swing is found due to variation in hetero-structure parameter of barrier layer and the values are typically 1.3-0.1 V, 0.6-0.44 S/mm and 75-135 mV/dec respectively.

Kim C. Sturgess. Shakespeare and the American Nation.

OpenAIRE

Claret, Jean‑Louis

2006-01-01

The front page of Kim C Sturgess’s recent book entitled Shakespeare and the American Nation is particularly mind‑teasing insofar as it represents the famous Droeshout engraving of the bard (it illustrated the front‑page of the 1623 edition of Shakespeare’s works) standing out against a background that superimposes the head of the Statue of Liberty on the spangled banner. The starting point of Sturgess’s 234‑page demonstration endorsed by Cambridge University Press is a paradox that the Britis...

Algan/Gan Hemt By Magnetron Sputtering System

Science.gov (United States)

Garcia Perez, Roman

In this thesis, the growth of the semiconductor materials AlGaN and GaN is achieved by magnetron sputtering for the fabrication of High Electron Mobility Transistors (HEMTs). The study of the deposited nitrides is conducted by spectroscopy, diffraction, and submicron scale microscope methods. The preparation of the materials is performed using different parameters in terms of power, pressure, temperature, gas, and time. Silicon (Si) and Sapphire (Al2O3) wafers are used as substrates. The chemical composition and surface topography of the samples are analyzed to calculate the materials atomic percentages and to observe the devices surface. The instruments used for the semiconductors characterization are X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Atomic Force Microscope (AFM). The project focused its attention on the reduction of impurities during the deposition, the controlled thicknesses of the thin-films, the atomic configuration of the alloy AlxGa1-xN, and the uniformity of the surfaces.

AlN/GaN-Based MOS-HEMT Technology: Processing and Device Results

Directory of Open Access Journals (Sweden)

S. Taking

2011-01-01

Full Text Available Process development of AlN/GaN MOS-HEMTs is presented, along with issues and problems concerning the fabrication processes. The developed technology uses thermally grown Al2O3 as a gate dielectric and surface passivation for devices. Significant improvement in device performance was observed using the following techniques: (1 Ohmic contact optimisation using Al wet etch prior to Ohmic metal deposition and (2 mesa sidewall passivation. DC and RF performance of the fabricated devices will be presented and discussed in this paper.

30 nm T-gate enhancement-mode InAlN/AlN/GaN HEMT on SiC substrates for future high power RF applications

Science.gov (United States)

Murugapandiyan, P.; Ravimaran, S.; William, J.

2017-08-01

The DC and RF performance of 30 nm gate length enhancement mode (E-mode) InAlN/AlN/GaN high electron mobility transistor (HEMT) on SiC substrate with heavily doped source and drain region have been investigated using the Synopsys TCAD tool. The proposed device has the features of a recessed T-gate structure, InGaN back barrier and Al2O3 passivated device surface. The proposed HEMT exhibits a maximum drain current density of 2.1 A/mm, transconductance {g}{{m}} of 1050 mS/mm, current gain cut-off frequency {f}{{t}} of 350 GHz and power gain cut-off frequency {f}\\max of 340 GHz. At room temperature the measured carrier mobility (μ), sheet charge carrier density ({n}{{s}}) and breakdown voltage are 1580 cm2/(V \\cdot s), 1.9× {10}13 {{cm}}-2, and 10.7 V respectively. The superlatives of the proposed HEMTs are bewitching competitor or future sub-millimeter wave high power RF VLSI circuit applications.

Urinary NGAL, KIM-1 and L-FABP concentrations in antenatal hydronephrosis.

Science.gov (United States)

Noyan, Aytul; Parmaksiz, Gonul; Dursun, Hasan; Ezer, Semire Serin; Anarat, Ruksan; Cengiz, Nurcan

2015-10-01

The clinical tests currently in use for obstructive nephropathy (such as renal ultrasonography, differential radionuclide renal scans and urinary creatinine concentration data) are not efficient predictors of the subsequent clinical course. Novel and simple biomarkers are required which, if proven, could be clinically beneficial in determining if a patient is eligible for surgery or reno-protective therapy. More recently, the interest of clinicians has focused on the potential of urinary neutrophil gelatinase-associated lipocalin (uNGAL), urinary kidney injury molecule-1 (uKIM-1) and urinary liver-type fatty acid-binding proteins (uL-FABP) as biomarkers for renal function in children with hydronephrosis (HN). The purpose of this study was to investigate possible clinical applications of uNGAL, uKIM-1 and uL-FABP as beneficial non-invasive biomarkers to determine whether or not surgical intervention is required in children with HN. Renal ultrasonography and radionuclide renal scans were used as diagnostic tools to detect HN. Patients were divided into two groups based on the antero-posterior diameter of their renal pelvis and the presence of dysfunction. Group 1 included 26 children with severe HN (with dysfunction), and group 2 consisted of 36 children with mild HN (without dysfunction). Urine samples were collected from 62 children with HN and 20 healthy children. Hydronephrosis was more common in males than in females, with a male to female ratio of 9:1 in the study sample. The incidence of left kidney involvement (32 patients) was slightly higher than right kidney involvement (28 patients). Compared with controls and group 2, the ratio of uNGAL to creatinine was significantly higher in group 1 (p hydronephrosis and dysfunction had significantly increased uNGAL, and uNGAL/Cr concentrations. However, uKIM-1, uKIM-1/Cr, uL-FABP and uL-FABP/Cr concentrations were not significantly different when compared with controls. These results support the use of u

5 Watt GaN HEMT Power Amplifier for LTE

Directory of Open Access Journals (Sweden)

K. Niotaki

2014-04-01

Full Text Available This work presents the design and implementation of a stand-alone linear power amplifier at 2.4 GHz with high output power. A GaN HEMT transistor is selected for the design and implementation of the power amplifier. The device exhibits a gain of 11.7 dB and a drain efficiency of 39% for an output power of 36.7 dBm at 2.4 GHz for an input power of 25dBm. The carrier to intermodulation ratio is better than 25 dB for a two tone input signal of 25 dBm of total power and a spacing of 5 MHz. The fabricated device is also tested with LTE input signals of different bandwidths (5MHz to 20MHz.

Optimal III-nitride HEMTs: from materials and device design to compact model of the 2DEG charge density

Science.gov (United States)

Li, Kexin; Rakheja, Shaloo

2017-02-01

In this paper, we develop a physically motivated compact model of the charge-voltage (Q-V) characteristics in various III-nitride high-electron mobility transistors (HEMTs) operating under highly non-equilibrium transport conditions, i.e. high drain-source current. By solving the coupled Schrödinger-Poisson equation and incorporating the two-dimensional electrostatics in the channel, we obtain the charge at the top-of-the-barrier for various applied terminal voltages. The Q-V model accounts for cutting off of the negative momenta states from the drain terminal under high drain-source bias and when the transmission in the channel is quasi-ballistic. We specifically focus on AlGaN and AlInN as barrier materials and InGaN and GaN as the channel material in the heterostructure. The Q-V model is verified and calibrated against numerical results using the commercial TCAD simulator Sentaurus from Synopsys for a 20-nm channel length III-nitride HEMT. With 10 fitting parameters, most of which have a physical origin and can easily be obtained from numerical or experimental calibration, the compact Q-V model allows us to study the limits and opportunities of III-nitride technology. We also identify optimal material and geometrical parameters of the device that maximize the carrier concentration in the HEMT channel in order to achieve superior RF performance. Additionally, the compact charge model can be easily integrated in a hierarchical circuit simulator, such as Keysight ADS and CADENCE, to facilitate circuit design and optimization of various technology parameters.

Kim C. Sturgess. Shakespeare and the American Nation.

Directory of Open Access Journals (Sweden)

Jean‑Louis Claret

2006-04-01

Full Text Available The front page of Kim C Sturgess’s recent book entitled Shakespeare and the American Nation is particularly mind‑teasing insofar as it represents the famous Droeshout engraving of the bard (it illustrated the front‑page of the 1623 edition of Shakespeare’s works standing out against a background that superimposes the head of the Statue of Liberty on the spangled banner. The starting point of Sturgess’s 234‑page demonstration endorsed by Cambridge University Press is a paradox that the Britis...

The first clinical treatment with kilovoltage intrafraction monitoring (KIM): A real-time image guidance method

DEFF Research Database (Denmark)

Keall, Paul J.; Aun Ng, Jin; O'Brien, Ricky

2015-01-01

on September 16, 2014. Methods: KIM uses current and prior 2D x-ray images to estimate the 3D target position during cancer radiotherapy treatment delivery. KIM software was written to process kilovoltage (kV) images streamed from a standard C-arm linear accelerator with a gantry-mounted kV x-ray imaging...... system. A 120° pretreatment kV imaging arc was acquired to build the patient-specific 2D to 3D motion correlation. The kV imager was activated during the megavoltage (MV) treatment, a dual arc VMAT prostate treatment, to estimate the 3D prostate position in real-time. All necessary ethics, legal......, and regulatory requirements were met for this clinical study. The quality assurance processes were completed and peer reviewed. Results: During treatment, a prostate position offset of nearly 3 mm in the posterior direction was observed with KIM. This position offset did not trigger a gating event. After...

Analytical high frequency GaN HEMT model for noise simulations

Science.gov (United States)

Eshetu Muhea, Wondwosen; Mulugeta Yigletu, Fetene; Lazaro, Antonio; Iñiguez, Benjamin

2017-12-01

A compact high frequency model for AlGaN/GaN HEMT device valid for noise simulations is presented in this paper. The model is developed based on active transmission line approach and linear two port noise theory that makes it applicable for quasi static as well as non-quasi static device operation. The effects of channel length modulation and velocity saturation are discussed. Moreover, the effect of the gate leakage current on the noise performance of the device is investigated. It is shown that there is an apparent increase in noise generated in the device due to the gate current related shot noise. The common noise figures of merit for HFET are calculated and verified with experimental data.

Lg = 100 nm T-shaped gate AlGaN/GaN HEMTs on Si substrates with non-planar source/drain regrowth of highly-doped n+-GaN layer by MOCVD

International Nuclear Information System (INIS)

Huang Jie; Li Ming; Tang Chak-Wah; Lau Kei-May

2014-01-01

High-performance AlGaN/GaN high electron mobility transistors (HEMTs) grown on silicon substrates by metal—organic chemical-vapor deposition (MOCVD) with a selective non-planar n-type GaN source/drain (S/D) regrowth are reported. A device exhibited a non-alloyed Ohmic contact resistance of 0.209 Ω·mm and a comprehensive transconductance (g m ) of 247 mS/mm. The current gain cutoff frequency f T and maximum oscillation frequency f MAX of 100-nm HEMT with S/D regrowth were measured to be 65 GHz and 69 GHz. Compared with those of the standard GaN HEMT on silicon substrate, the f T and f MAX is 50% and 52% higher, respectively. (interdisciplinary physics and related areas of science and technology)

Dispersion Free Doped and Undoped AlGaN/GaN HEMTs on Sapphire and SiC Substrates

NARCIS (Netherlands)

Kraemer, M.C.J.C.M.; Jacobs, B.; Kwaspen, J.J.M.; Suijker, E.M.; Hek, A.P. de; Karouta, F.; Kaufmann, L.M.F.; Hoskens, R.C.P.

2004-01-01

We present dispersion free pulsed current voltage (I-V) and radio frequency (RF) power results of undoped and doped AlGaN/GaN HEMTs on sapphire and SiC substrates. The most significant processing step leading to these results is the application of a reactive ion etching (RIE) argon (Ar) plasma

Determination of channel temperature for AlGaN/GaN HEMTs by high spectral resolution micro-Raman spectroscopy

International Nuclear Information System (INIS)

Zhang Guangchen; Feng Shiwei; Li Jingwan; Guo Chunsheng; Zhao Yan

2012-01-01

Channel temperature determinations of AlGaN/GaN high electron mobility transistors (HEMTs) by high spectral resolution micro-Raman spectroscopy are proposed. The temperature dependence of the E2 phonon frequency of GaN material is calibrated by using a JYT-64000 micro-Raman system. By using the Lorentz fitting method, the measurement uncertainty for the Raman phonon frequency of ±0.035 cm −1 is achieved, corresponding to a temperature accuracy of ±3.2 °C for GaN material, which is the highest temperature resolution in the published works. The thermal resistance of the tested AlGaN/GaN HEMT sample is 22.8 °C/W, which is in reasonably good agreement with a three dimensional heat conduction simulation. The difference among the channel temperatures obtained by micro-Raman spectroscopy, the pulsed electrical method and the infrared image method are also investigated quantificationally. (semiconductor devices)

Analytical modeling and simulation of subthreshold behavior in nanoscale dual material gate AlGaN/GaN HEMT

Science.gov (United States)

Kumar, Sona P.; Agrawal, Anju; Chaujar, Rishu; Gupta, Mridula; Gupta, R. S.

2008-07-01

A two-dimensional (2-D) analytical model for a Dual Material Gate (DMG) AlGaN/GaN High Electron Mobility Transistor (HEMT) has been developed to demonstrate the unique attributes of this device structure in suppressing short channel effects (SCEs). The model accurately predicts the channel potential, electric field variation along the channel, and sub-threshold drain current, taking into account the effect of lengths of the two gate metals, their work functions, barrier layer thicknesses, and applied drain biases. It is seen that the SCEs and hot carrier effects in DMG AlGaN/GaN HEMT are suppressed due to the work function difference of the two metal gates, thereby screening the drain potential variations by the gate near the drain. Besides, a more uniform electric field along the channel leads to improved carrier transport efficiency. The accuracy of the results obtained from our analytical model has been verified using ATLAS device simulations.

Thickness engineering of atomic layer deposited Al2O3 films to suppress interfacial reaction and diffusion of Ni/Au gate metal in AlGaN/GaN HEMTs up to 600 °C in air

Science.gov (United States)

Suria, Ateeq J.; Yalamarthy, Ananth Saran; Heuser, Thomas A.; Bruefach, Alexandra; Chapin, Caitlin A.; So, Hongyun; Senesky, Debbie G.

2017-06-01

In this paper, we describe the use of 50 nm atomic layer deposited (ALD) Al2O3 to suppress the interfacial reaction and inter-diffusion between the gate metal and semiconductor interface, to extend the operation limit up to 600 °C in air. Suppression of diffusion is verified through Auger electron spectroscopy (AES) depth profiling and X-ray diffraction (XRD) and is further supported with electrical characterization. An ALD Al2O3 thin film (10 nm and 50 nm), which functions as a dielectric layer, was inserted between the gate metal (Ni/Au) and heterostructure-based semiconductor material (AlGaN/GaN) to form a metal-insulator-semiconductor high electron mobility transistor (MIS-HEMT). This extended the 50 nm ALD Al2O3 MIS-HEMT (50-MIS) current-voltage (Ids-Vds) and gate leakage (Ig,leakage) characteristics up to 600 °C. Both, the 10 nm ALD Al2O3 MIS-HEMT (10-MIS) and HEMT, failed above 350 °C, as evidenced by a sudden increase of approximately 50 times and 5.3 × 106 times in Ig,leakage, respectively. AES on the HEMT revealed the formation of a Ni-Au alloy and Ni present in the active region. Additionally, XRD showed existence of metal gallides in the HEMT. The 50-MIS enables the operation of AlGaN/GaN based electronics in oxidizing high-temperature environments, by suppressing interfacial reaction and inter-diffusion of the gate metal with the semiconductor.

The diagnostic importance of the new marker KIM-1 in kidney damage

Directory of Open Access Journals (Sweden)

Zofia Marchewka

2013-07-01

Full Text Available In recent years, the rapid development of scientific research led to the introduction of strategies based on new markers that allow for estimation of the latent disease period before the clinical symptoms of actual kidney failure are revealed.The experimental tests carried out on animals and cell lines derived from the proximal tubule have made possible the detection of genes that are induced early after hypoxia [1].The protein products of these genes can be considered as useful markers for the diagnosis of renal failure. The induction of gene KIM-1 (called Kidney Injury Molecule-1 results in the formation of protein that can be considered as a diagnostic marker.This work describes the data on the structure, biological function and importance of determining the concentrations of KIM-1 in the diagnosis of drug-induced toxicity and kidney damage.

[The diagnostic importance of the new marker KIM-1 in kidney damage].

Science.gov (United States)

Marchewka, Zofia; Płonka, Joanna

2013-07-24

In recent years, the rapid development of scientific research led to the introduction of strategies based on new markers that allow for estimation of the latent disease period before the clinical symptoms of actual kidney failure are revealed. The experimental tests carried out on animals and cell lines derived from the proximal tubule have made possible the detection of genes that are induced early after hypoxia. The protein products of these genes can be considered as useful markers for the diagnosis of renal failure. The induction of gene KIM-1 (called Kidney Injury Molecule-1) results in the formation of protein that can be considered as a diagnostic marker. This work describes the data on the structure, biological function and importance of determining the concentrations of KIM-1 in the diagnosis of drug-induced toxicity and kidney damage.

Analysis of field-plate effects on buffer-related lag phenomena and current collapse in GaN MESFETs and AlGaN/GaN HEMTs

International Nuclear Information System (INIS)

Horio, Kazushige; Nakajima, Atsushi; Itagaki, Keiichi

2009-01-01

A two-dimensional transient analysis of field-plate GaN MESFETs and AlGaN/GaN HEMTs is performed in which a deep donor and a deep acceptor are considered in a semi-insulating buffer layer, and quasi-pulsed current–voltage curves are derived from them. How the existence of a field plate affects buffer-related drain lag, gate lag and current collapse is studied. It is shown that in both MESFET and HEMT, the drain lag is reduced by introducing a field plate because electron injection into the buffer layer is weakened by it, and the buffer-trapping effects are reduced. It is also shown that the field plate could reduce buffer-related current collapse and gate lag in the FETs. The dependence of lag phenomena and current collapse on the field-plate length and on the SiN passivation layer thickness is also studied. The work suggests that in the field-plate structures, there is an optimum thickness of the SiN layer to minimize the buffer-related current collapse and drain lag in GaN MESFETs and AlGaN/GaN HEMTs

Investigation of the fabrication processes of AlGaN/AlN/GaN HEMTs with in situ Si{sub 3}N{sub 4} passivation

Energy Technology Data Exchange (ETDEWEB)

Tomosh, K. N., E-mail: sky77781@mail.ru; Pavlov, A. Yu.; Pavlov, V. Yu.; Khabibullin, R. A.; Arutyunyan, S. S.; Maltsev, P. P. [Russian Academy of Sciences, Institute of Ultra-High-Frequency Semiconductor Electronics (Russian Federation)

2016-10-15

The optimum mode of the in situ plasma-chemical etching of a Si{sub 3}N{sub 4} passivating layer in C{sub 3}F{sub 8}/O{sub 2} medium is chosen for the case of fabricating AlGaN/AlN/GaN HEMTs. It is found that a bias of 40–50 V at a high-frequency electrode provides anisotropic etching of the insulator through a resist mask and introduces no appreciable radiation-induced defects upon overetching of the insulator films in the region of gate-metallization formation. To estimate the effect of in situ Si{sub 3}N{sub 4} growth together with the heterostructure in one process on the AlGaN/AlN/GaN HEMT characteristics, transistors with gates without the insulator and with gates through Si{sub 3}N{sub 4} slits are fabricated. The highest drain current of the AlGaN/AlN/GaN HEMT at 0 V at the gate is shown to be 1.5 times higher in the presence of Si{sub 3}N{sub 4} than without it.

Wideband Monolithic Microwave Integrated Circuit Frequency Converters with GaAs mHEMT Technology

OpenAIRE

Krozer, Viktor; Johansen, Tom Keinicke; Djurhuus, Torsten; Vidkjær, Jens

2005-01-01

We present monolithic microwave integrated circuit (MMIC) frequency converter, which can be used for up and down conversion, due to the large RF and IF port bandwidth. The MMIC converters are based on commercially available GaAs mHEMT technology and are comprised of a Gilbert mixer cell core, baluns and combiners. Single ended and balanced configurations DC and AC coupled have been investigated. The instantaneous 3 dB bandwidth at both the RF and the IF port of the frequency converters is ∼ 2...

Improved DC and RF performance of InAlAs/InGaAs InP based HEMTs using ultra-thin 15 nm ALD-Al2O3 surface passivation

Science.gov (United States)

Asif, Muhammad; Chen, Chen; Peng, Ding; Xi, Wang; Zhi, Jin

2018-04-01

Owing to the great influence of surface passivation on DC and RF performance of InP-based HEMTs, the DC and RF performance of InAlAs/InGaAs InP HEMTs were studied before and after passivation, using an ultra-thin 15 nm atomic layer deposition Al2O3 layer. Increase in Cgs and Cgd was significantly limited by scaling the thickness of the Al2O3 layer. For verification, an analytical small-signal equivalent circuit model was developed. A significant increase in maximum transconductance (gm) up to 1150 mS/mm, drain current (IDS) up to 820 mA/mm and fmax up to 369.7 GHz was observed, after passivation. Good agreement was obtained between the measured and the simulated results. This shows that the RF performance of InP-based HEMTs can be improved by using an ultra-thin ALD-Al2O3 surface passivation.

Kim Wŏn-haeng’s Intellectual Influences on Hong Tae-yong: The Case of Relations between

Directory of Open Access Journals (Sweden)

Login Lok-yin Law

2015-08-01

Full Text Available In the 18th century Chosŏn (1392-1910, some scholars, such as Hong Tae-yong (1731-1783 advocated that Chosŏn should learn the advantages of the Qing (1644-1912 society to reform the social structure and government of Chosŏn. The school of these advocates has been known as Pukhak by historians. The intellectual factors of the school of Pukhak’s formation and development have been overlooked by the academia of Chosŏn intellectual history. In fact, Pukhak was closely related to the idea of the school of Nakhak which believed that nature of things was equivalent to humans. Kim Wŏn-haeng, was one of the supporters of Nakhak and Hong Tae-yong was one of the students of Kim. Hong’s thought and writing exposed that his thought was profoundly influenced by Kim Wŏn-haeng. Hong was deemed to be the first prominent scholar of the Pukhak School during the 18th century Chosŏn. Hong and other scholars of Pukhak advocated learning the new knowledge from Qing China even though it was a barbarian society. Therefore, this paper will investigate the intellectual relationships between Hong Tae-yong and Kim Wŏn-haeng to reveal how intellectuals of Nakhak shaped the formation of Pukhak School and exposed the idea of learning from Qing China.

Interface Si donor control to improve dynamic performance of AlGaN/GaN MIS-HEMTs

Science.gov (United States)

Song, Liang; Fu, Kai; Zhang, Zhili; Sun, Shichuang; Li, Weiyi; Yu, Guohao; Hao, Ronghui; Fan, Yaming; Shi, Wenhua; Cai, Yong; Zhang, Baoshun

2017-12-01

In this letter, we have studied the performance of AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) with different interface Si donor incorporation which is tuned during the deposition process of LPCVD-SiNx which is adopted as gate dielectric and passivation layer. Current collapse of the MIS-HEMTs without field plate is suppressed more effectively by increasing the SiH2Cl2/NH3 flow ratio and the normalized dynamic on-resistance (RON) is reduced two orders magnitude after off-state VDS stress of 600 V for 10 ms. Through interface characterization, we have found that the interface deep-level traps distribution with high Si donor incorporation by increasing the SiH2Cl2/NH3 flow ratio is lowered. It's indicated that the Si donors are most likely to fill and screen the deep-level traps at the interface resulting in the suppression of slow trapping process and the virtual gate effect. Although the Si donor incorporation brings about the increase of gate leakage current (IGS), no clear degradation of breakdown voltage can be seen by choosing appropriate SiH2Cl2/NH3 flow ratio.

Quantum ballistic transistor and low noise HEMT for cryo-electronics lower than 4.2 K

International Nuclear Information System (INIS)

Gremion, E.

2008-01-01

Next generations of cryo-detectors, widely used in physics of particles and physics of universe, will need in the future high-performance cryo-electronics less noisy and closer to the detector. Within this context, this work investigates properties of two dimensional electron gas GaAlAs/GaAs by studying two components, quantum point contact (QPC) and high electron mobility transistor (HEMT). Thanks to quantized conductance steps in QPC, we have realized a quantum ballistic transistor (voltage gain higher than 1), a new component useful for cryo-electronics thanks to its operating temperature and weak power consumption (about 1 nW). Moreover, the very low capacity of this component leads to promising performances for multiplexing low temperature bolometer dedicated to millimetric astronomy. The second study focused on HEMT with very high quality 2DEG. At 4.2 K, a voltage gain higher than 20 can be obtained with a very low power dissipation of less than 100 μW. Under the above experimental conditions, an equivalent input voltage noise of 1.2 nV/√(Hz) at 1 kHz and 0.12 nV/√(Hz) at 100 kHz has been reached. According to the Hooge formula, these noise performances are get by increasing gate capacity estimated to 60 pF. (author)

Comparative study on nitridation and oxidation plasma interface treatment for AlGaN/GaN MIS-HEMTs with AlN gate dielectric

Science.gov (United States)

Zhu, Jie-Jie; Ma, Xiao-Hua; Hou, Bin; Chen, Li-Xiang; Zhu, Qing; Hao, Yue

2017-02-01

This paper demonstrated the comparative study on interface engineering of AlN/AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs) by using plasma interface pre-treatment in various ambient gases. The 15 nm AlN gate dielectric grown by plasma-enhanced atomic layer deposition significantly suppressed the gate leakage current by about two orders of magnitude and increased the peak field-effect mobility by more than 50%. NH3/N2 nitridation plasma treatment (NPT) was used to remove the 3 nm poor-quality interfacial oxide layer and N2O/N2 oxidation plasma treatment (OPT) to improve the quality of interfacial layer, both resulting in improved dielectric/barrier interface quality, positive threshold voltage (V th) shift larger than 0.9 V, and negligible dispersion. In comparison, however, NPT led to further decrease in interface charges by 3.38 × 1012 cm-2 and an extra positive V th shift of 1.3 V. Analysis with fat field-effect transistors showed that NPT resulted in better sub-threshold characteristics and transconductance linearity for MIS-HEMTs compared with OPT. The comparative study suggested that direct removing the poor interfacial oxide layer by nitridation plasma was superior to improving the quality of interfacial layer by oxidation plasma for the interface engineering of GaN-based MIS-HEMTs.

Comparison of Surface Passivation Films for Reduction of Current Collapse in AlGaN/GaN High Electron Mobility Transistors (HEMTs)

National Research Council Canada - National Science Library

Fitch, R

2002-01-01

Three different passivation layers (SiN(x), MgO, and Sc2O3) were examined for their effectiveness in mitigating surface-state-induced current collapse in AlGaN/GaN high electron mobility transistors (HEMTs...

Impact of the Gate Width of Al0.27Ga0.73N/AlN/Al0.04Ga0.96N/GaN HEMT on Its Characteristics

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Liwei Jin

2013-01-01

Full Text Available This paper presents impact of layout sizes of Al0.27Ga0.73N/AlN/Al0.04Ga0.96N/GaN HEMT heterostructure high-mobility transistors (HEMTs on SiC substrate on its characteristics that include the threshold voltage, the maximum transconductance, characteristic frequency, and the maximum oscillation frequency. The changing parameters include the gate finger number, the gate width per finger. The measurement results based on common-source devices demonstrate that the above parameters have different effects on the threshold voltage, maximum transconductance, and frequency characteristics.

Language and Family Dispersion: North Korean Linguist Kim Su-gyŏng and the Korean War

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Ryuta Itagaki

2017-03-01

Full Text Available This article analyzes the unpublished memoir of Kim Su-gyŏng (1918–2000, a linguist who was active in North Korea from the mid-1940s until the late 1960s, and situates his account of his experience of the Korean War within the context of his linguistic essays and correspondence. In doing so, the article considers the role that the personal and the social play in language, utilizing Saussure’s theoretical framework, with which Kim himself was well versed. Kim wrote his memoirs in the 1990s to his family, from whom he had become separated during the Korean War and who now lived in Toronto. In this text, he writes in “personal” language that reveals his uncertainty and his feelings for his family, but then immediately negates these feelings through the use of “social” language, which resonates with his interpretation of the linguistic thesis that Josef Stalin developed during the Korean War on language and national identity. For Kim, the relationship between language and nation was not at all self-evident, but something that he idealized in response to the dispersal of his family. By offering a reflexive reading of a memoir written by a North Korean linguist, this article makes a breakthrough in the investigation of North Korean wartime academic history, which has not risen above the level of analyzing articles in the field of linguistics that were published at the time.

Understanding internal backgrounds in NaI(Tl) crystals toward a 200 kg array for the KIMS-NaI experiment

Energy Technology Data Exchange (ETDEWEB)

Adhikari, P.; Adhikari, G.; Oh, S.Y. [Sejong University, Department of Physics, Seoul (Korea, Republic of); Choi, S.; Joo, H.W.; Kim, K.W.; Kim, S.K. [Seoul National University, Department of Physics and Astronomy, Seoul (Korea, Republic of); Ha, C.; Jeon, E.J.; Kang, W.G.; Kim, H.O.; Kim, N.Y.; Lee, H.S.; Lee, J.H.; Lee, M.H.; Leonard, D.S.; Li, J.; Olsen, S.L.; Park, H.K.; Park, K.S.; So, J.H.; Yoon, Y.S. [Institute for Basic Science, Center for Underground Physics, Daejeon (Korea, Republic of); Hahn, I.S. [Ewha Womans University, Department of Science Education, Seoul (Korea, Republic of); Kim, H.J. [Kyungpook National University, Department of Physics, Daegu (Korea, Republic of); Kim, Y.D. [Sejong University, Department of Physics, Seoul (Korea, Republic of); Institute for Basic Science, Center for Underground Physics, Daejeon (Korea, Republic of); Kim, Y.H. [Institute for Basic Science, Center for Underground Physics, Daejeon (Korea, Republic of); Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of); Park, H.S. [Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of)

2016-04-15

The Korea Invisible Mass Search (KIMS) collaboration has developed low-background NaI(Tl) crystals that are suitable for the direct detection of WIMP dark matter. Building on experience accumulated during the KIMS-CsI programs, the KIMS-NaI experiment will consist of a 200 kg NaI(Tl) crystal array surrounded by layers of shielding structures and will be operated at the Yangyang underground laboratory. The goal is to provide an unambiguous test of the DAMA/LIBRA annual modulation signature. Measurements of six prototype crystals show progress in the reduction of internal contamination from radioisotopes. Based on our understanding of these measurements, we expect to achieve a background level in the final detector configuration that is less than 1 count/day/keV/kg for recoil energies around 2 keV. The annual modulation sensitivity for the KIMS-NaI experiment shows that an unambiguous 7σ test of the DAMA/LIBRA signature would be possible with a 600 kg year exposure with this system. (orig.)

Design and simulation of a novel E-mode GaN MIS-HEMT based on a cascode connection for suppression of electric field under gate and improvement of reliability

Science.gov (United States)

Li, Weiyi; Zhang, Zhili; Fu, Kai; Yu, Guohao; Zhang, Xiaodong; Sun, Shichuang; Song, Liang; Hao, Ronghui; Fan, Yaming; Cai, Yong; Zhang, Baoshun

2017-07-01

We proposed a novel AlGaN/GaN enhancement-mode (E-mode) high electron mobility transistor (HEMT) with a dual-gate structure and carried out the detailed numerical simulation of device operation using Silvaco Atlas. The dual-gate device is based on a cascode connection of an E-mode and a D-mode gate. The simulation results show that electric field under the gate is decreased by more than 70% compared to that of the conventional E-mode MIS-HEMTs (from 2.83 MV/cm decreased to 0.83 MV/cm). Thus, with the discussion of ionized trap density, the proposed dual-gate structure can highly improve electric field-related reliability, such as, threshold voltage stability. In addition, compared with HEMT with field plate structure, the proposed structure exhibits a simplified fabrication process and a more effective suppression of high electric field. Project supported by the Key Technologies Support Program of Jiangsu Province (No. BE2013002-2) and the National Key Scientific Instrument and Equipment Development Projects of China (No. 2013YQ470767).

Interface Si donor control to improve dynamic performance of AlGaN/GaN MIS-HEMTs

Directory of Open Access Journals (Sweden)

Liang Song

2017-12-01

Full Text Available In this letter, we have studied the performance of AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs with different interface Si donor incorporation which is tuned during the deposition process of LPCVD-SiNx which is adopted as gate dielectric and passivation layer. Current collapse of the MIS-HEMTs without field plate is suppressed more effectively by increasing the SiH2Cl2/NH3 flow ratio and the normalized dynamic on-resistance (RON is reduced two orders magnitude after off-state VDS stress of 600 V for 10 ms. Through interface characterization, we have found that the interface deep-level traps distribution with high Si donor incorporation by increasing the SiH2Cl2/NH3 flow ratio is lowered. It’s indicated that the Si donors are most likely to fill and screen the deep-level traps at the interface resulting in the suppression of slow trapping process and the virtual gate effect. Although the Si donor incorporation brings about the increase of gate leakage current (IGS, no clear degradation of breakdown voltage can be seen by choosing appropriate SiH2Cl2/NH3 flow ratio.

Comparative study on stress in AlGaN/GaN HEMT structures grown on 6H-SiC, Si and on composite substrates of the 6H-SiC/poly-SiC and Si/poly-SiC

International Nuclear Information System (INIS)

Guziewicz, M; Kaminska, E; Piotrowska, A; Golaszewska, K; Domagala, J Z; Poisson, M-A; Lahreche, H; Langer, R; Bove, P

2008-01-01

The stresses in GaN-based HEMT structures grown on both single crystal 6H SiC(0001) and Si(111) have been compared to these in the HEMT structures grown on new composite substrates engendered as a thin monocrystalline film attached to polycrystalline 3C-SiC substrate. By using HRXRD technique and wafer curvature method we show that stress of monocrystalline layer in composite substrates of the type mono-Si/poly-SiC is lower than 100 MPa and residual stress of epitaxial GaN buffer grown on the composite substrate does not exceed 0.31 GPa, but in the cases of single crystal SiC or Si substrates the GaN buffer stress is compressive in the range of -0.5 to -0.75 GPa. The total stress of the HEMT structure calculated from strains is consistent with the averaged stress of the multilayers stack measured by wafer curvature method. The averaged stress of HEMT structure grown on single crystals is higher than those in structures grown on composites substrates

Environmental data qualification system

International Nuclear Information System (INIS)

Hester, O.V.; Groh, M.R.

1989-01-01

The Integrated Environmental Data Management System (IEDMS) is a PC-based system that can support environmental investigations from their design stage and throughout the duration of the study. The system integrates data originating from the Sampling and Analysis Plan, field data and analytical findings. The IEDMS automated features include sampling guidance forms, barcoded sample labels and tags, field and analytical forms reproduction, sample tracking, analytical data qualification, completeness reports, and results and QC data reporting. The IEDMS has extensive automated capabilities that support a systematic and comprehensive process for performing quality assessment of EPA-CLP chemical analyses data. One product of this process is a unique and extremely useful tabular presentation of the data. One table contains the complete set of results and QC data included on the CLP data forms while presenting the information consistent with the chronology in which the analysis was performed. 3 refs., 1 fig

Reliability improvement in GaN HEMT power device using a field plate approach

Science.gov (United States)

Wu, Wen-Hao; Lin, Yueh-Chin; Chin, Ping-Chieh; Hsu, Chia-Chieh; Lee, Jin-Hwa; Liu, Shih-Chien; Maa, Jer-shen; Iwai, Hiroshi; Chang, Edward Yi; Hsu, Heng-Tung

2017-07-01

This study investigates the effect of implementing a field plate on a GaN high-electron-mobility transistor (HEMT) to improve power device reliability. The results indicate that the field plate structure reduces the peak electrical field and interface traps in the device, resulting in higher breakdown voltage, lower leakage current, smaller current collapse, and better threshold voltage control. Furthermore, after high voltage stress, steady dynamic on-resistance and gate capacitance degradation improvement were observed for the device with the field plate. This demonstrates that GaN device reliability can be improved by using the field plate approach.

Inverse temperature dependence of reverse gate leakage current in AlGaN/GaN HEMT

International Nuclear Information System (INIS)

Kaushik, J K; Balakrishnan, V R; Muralidharan, R; Panwar, B S

2013-01-01

The experimentally observed inverse temperature dependence of the reverse gate leakage current in AlGaN/GaN HEMT is explained using a virtual gate trap-assisted tunneling model. The virtual gate is formed due to the capture of electrons by surface states in the vicinity of actual gate. The increase and decrease in the length of the virtual gate with temperature due to trap kinetics are used to explain this unusual effect. The simulation results have been validated experimentally. (paper)

Analysis of reverse gate leakage mechanism of AlGaN/GaN HEMTs with N2 plasma surface treatment

Science.gov (United States)

Liu, Hui; Zhang, Zongjing; Luo, Weijun

2018-06-01

The mechanism of reverse gate leakage current of AlGaN/GaN HEMTs with two different surface treatment methods are studied by using C-V, temperature dependent I-V and theoretical analysis. At the lower reverse bias region (VR >- 3.5 V), the dominant leakage current mechanism of the device with N2 plasma surface treatment is the Poole-Frenkel emission current (PF), and Trap-Assisted Tunneling current (TAT) is the principal leakage current of the device which treated by HCl:H2O solution. At the higher reverse bias region (VR current of the device with N2 plasma surface treatment is one order of magnitude smaller than the device which treated by HCl:H2O solution. This is due to the recovery of Ga-N bond in N2 plasma surface treatment together with the reduction of the shallow traps in post-gate annealing (PGA) process. The measured results agree well with the theoretical calculations and demonstrate N2 plasma surface treatment can reduce the reverse leakage current of the AlGaN/GaN HEMTs.

Static and dynamic characteristics of Lg 50 nm InAlN/AlN/GaN HEMT with AlGaN back-barrier for high power millimeter wave applications

Directory of Open Access Journals (Sweden)

P. Murugapandiyan

2017-12-01

Full Text Available A novel 50 nm recessed T-gate AlN spacer based InAlN/GaN HEMT with AlGaN back-barrier is designed. The static and dynamic characteristics of the proposed device structure are investigated using Synopsys TCAD tool. The remarkable potential device features such as heavily doped source/drain region, Al2O3 passivated device surface helped the device to suppress the parasitic resistances and capacitances of the transistor for enhancing the microwave characteristics. The designed InAlN/GaN HEMT exhibits the sheet carrier density (ns of 1.9 × 1013 cm−2, the drain current density (Ids of 2.1 A/mm, the transconductance (gm of 800 mS/mm, the breakdown voltage (VBR of 40 V, the current gain cut-off frequency (ft of 221 GHz and the power gain cut-off frequency (fmax of 290 GHz. The superior static and dynamic characteristics of obtained InAlN/GaN HEMTs undoubtedly placed the device at the forefront for high power millimeter wave applications.

Non-integrability of the Armbruster-Guckenheimer-Kim quartic Hamiltonian through Morales-Ramis theory

OpenAIRE

Acosta-Humánez, P.; Alvarez-Ramírez, M.; Stuchi, T.

2017-01-01

We show the non-integrability of the three-parameter Armburster-Guckenheimer-Kim quartic Hamiltonian using Morales-Ramis theory, with the exception of the three already known integrable cases. We use Poincar\\'e sections to illustrate the breakdown of regular motion for some parameter values.

Validation Study of Kim's Sham Needle by Measuring Facial Temperature: An N-of-1 Randomized Double-Blind Placebo-Controlled Clinical Trial

Directory of Open Access Journals (Sweden)

Sanghun Lee

2012-01-01

Full Text Available Introduction. In 2008, Kim's sham needle was developed to improve the quality of double-blinded studies. The aim of this study is to validate Kim's sham needle by measuring facial temperature. Methods. We designed “N-of-1” trials involving 7 smokers. One session was composed of 2 stimulations separated by a 2 h washout period. Six sessions were applied daily for all subjects. Infrared thermal imaging was used to examine the effects of acupuncture (HT8, KI2 on facial temperature following smoking-induced decrease. Results. All subjects demonstrated decreased temperatures after sham needle treatment, but 5 of the 7 subjects showed increased temperatures after real needle treatment. 6 of the 7 subjects showed a significant difference (P<0.05 between treatments with real and sham needles. Thus, the physiological stimulation of Kim's sham needle is different from that of a real needle, suggesting that Kim's sham needle is a potential inactive control intervention.

Electrothermal DC characterization of GaN on Si MOS-HEMTs

Science.gov (United States)

Rodríguez, R.; González, B.; García, J.; Núñez, A.

2017-11-01

DC characteristics of AlGaN/GaN on Si single finger MOS-HEMTs, for different gate geometries, have been measured and numerically simulated with substrate temperatures up to 150 °C. Defect density, depending on gate width, and thermal resistance, depending additionally on temperature, are extracted from transfer characteristics displacement and the AC output conductance method, respectively, and modeled for numerical simulations with Atlas. The thermal conductivity degradation in thin films is also included for accurate simulation of the heating response. With an appropriate methodology, the internal model parameters for temperature dependencies have been established. The numerical simulations show a relative error lower than 4.6% overall, for drain current and channel temperature behavior, and account for the measured device temperature decrease with the channel length increase as well as with the channel width reduction, for a set bias.

Effect of Surface Passivation on the Electrical Characteristics of Nanoscale AlGaN/GaN HEMT

Science.gov (United States)

Gupta, Akriti; Chatterjee, Neel; Kumar, Pradeep; Pandey, Sujata

2017-08-01

In this paper, we present the effect of passivation layer on the electrical characteristics of AlGaN/GaN HEMT. The energy band diagram, drain current voltage characteristics, transconductance and cut off frequency was calculated for both long channel and short channel devices. It was found that the electrical characteristics of the device improve with the introduction of high K dielectric in the passivation layer. The results obtained agree well with the data available in literature.

Improved power simulation of AlGaN/GaN HEMT at class-AB operation via an RF drain—source current correction method

International Nuclear Information System (INIS)

Pongthavornkamol Tiwat; Pang Lei; Yuan Ting-Ting; Liu Xin-Yu

2014-01-01

A new modified Angelov current—voltage characteristic model equation is proposed to improve the drain—source current (I ds ) simulation of an AlGaN/GaN-based (gallium nitride) high electron mobility transistor (AlGaN/GaN-based HEMT) at high power operation. Since an accurate radio frequency (RF) current simulation is critical for a correct power simulation of the device, in this paper we propose a method of AlGaN/GaN high electron mobility transistor (HEMT) nonlinear large-signal model extraction with a supplemental modeling of RF drain—source current as a function of RF input power. The improved results of simulated output power, gain, and power added efficiency (PAE) at class-AB quiescent bias of V gs = −3.5 V, V ds = 30 V with a frequency of 9.6 GHz are presented. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Electrical degradation on DC and RF characteristics of short channel AlGaN/GaN-on-Si hemt with highly doped carbon buffer

Science.gov (United States)

Kim, Dong-Hwan; Jeong, Jun-Seok; Eom, Su-Keun; Lee, Jae-Gil; Seo, Kwang-Seok; Cha, Ho-Young

2017-11-01

In this study, we investigated the effects of highly doped carbon (C) buffer on the microwave performance of AlGaN/GaN-on-Si high electron mobility transistor (HEMT).We fabricated AlGaN/GaN-on-Si HEMTs with two different buffer structures. One structure had an un-doped buffer layer and the other structure had C-doped buffer layer with the doping concentration of 1 × 1019 cm -3 with GaN channel thickness of 350 nm. Despite higher leakage current, the device fabricated on the un-doped buffer structure exhibited better transfer and current collapse characteristics which, in turn, resulted in superior small-signal characteristics and radio frequency (RF) output power. Photoluminescence and secondary ion mass spectrometry measurements were carried out to investigate the effects of the highly-doped C buffer on microwave characteristics.

Plasma diagnostics and device properties of AlGaN/GaN HEMT passivated with SiN deposited by plasma-enhanced chemical vapour deposition

Energy Technology Data Exchange (ETDEWEB)

Romero, M F; Sanz, M M; Munoz, E [ISOM-Universidad Politecnica de Madrid (UPM). ETSIT, Madrid (Spain); Tanarro, I [Instituto de Estructura de la Materia, CSIC, Madrid (Spain); Jimenez, A, E-mail: itanarro@iem.cfmac.csic.e [Departamento Electronica, Escuela Politecnica Superior, Universidad de Alcala, Alcala de Henares, Madrid (Spain)

2010-12-15

In this work, silicon nitride thin films have been deposited by plasma enhanced chemical vapour deposition on both silicon samples and AlGaN/GaN high electron mobility transistors (HEMT) grown on sapphire substrates. Commercial parallel-plate RF plasma equipment has been used. During depositions, the dissociation rates of SiH{sub 4} and NH{sub 3} precursors and the formation of H{sub 2} and N{sub 2} have been analysed by mass spectrometry as a function of the NH{sub 3}/SiH{sub 4} flow ratio and the RF power applied to the plasma reactor. Afterwards, the properties of the films and the HEMT electrical characteristics have been studied. Plasma composition has been correlated with the SiN deposition rate, refractive index, H content and the final electric characteristics of the passivated transistors.

Influence of the structural and compositional properties of PECVD silicon nitride layers on the passivation of AIGaN/GaN HEMTs

NARCIS (Netherlands)

Karouta, F.; Krämer, M.C.J.C.M.; Kwaspen, J.J.M.; Grzegorczyk, A.; Hageman, P.R.; Hoex, B.; Kessels, W.M.M.; Klootwijk, J.H.; Timmering, E.C.; Smit, M.K.; Wang, J.; Shiojima, K.

2008-01-01

We have investigated the influence of the structural and compositional properties of silicon nitride layers on the passivation of AlGaN/GaN HEMTs grown on sapphire substrates by assessing their continuous wave (CW) and pulsed current-voltage (I-V) characteristics. We have looked at the effect of

Clinical significance of NGAL and KIM-1 for acute kidney injury in patients with scrub typhus.

Directory of Open Access Journals (Sweden)

In O Sun

Full Text Available The aim of this study is to investigate the clinical significance of neutrophil gelatinase-associated lipocalin (NGAL and kidney injury molecule-1 (KIM-1 for acute kidney injury (AKI in patients with scrub typhus.From 2014 to 2015, 145 patients were diagnosed with scrub typhus. Of these, we enrolled 138 patients who were followed up until renal recovery or for at least 3 months. We measured serum and urine NGAL and KIM-1 levels and evaluated prognostic factors affecting scrub typhus-associated AKI.Of the 138 patients, 25 had scrub typhus-associated AKI. The incidence of AKI was 18.1%; of which 11.6%, 4.3%, and 2.2% were classified as risk, injury, and failure, respectively, according to RIFLE criteria. Compared with patients in the non-AKI group, patients in the AKI group were older and showed higher total leukocyte counts and hypoalbuminemia or one or more comorbidities such as hypertension (72% vs 33%, p<0.01, diabetes (40% vs 14%, p<0.01, or chronic kidney disease (32% vs 1%, p<0.01. In addition, serum NGAL values (404± 269 vs 116± 78 ng/mL, P<0.001, KIM-1 values (0.80± 0.52 vs 0.33± 0.68 ng/mL, P<0.001, urine NGAL/creatinine values (371± 672 vs 27± 39 ng/mg, P<0.001 and urine KIM-1/creatinine values (4.04± 2.43 vs 2.38± 1.89 ng/mg, P<0.001 were higher in the AKI group than in the non-AKI group. By multivariate logistic regression, serum NGAL and the presence of chronic kidney disease were significant predictors of AKI.Serum NGAL might be an additive predictor for scrub typhus-associated AKI.

Channel Temperature Model for Microwave AlGaN/GaN HEMTs on SiC and Sapphire MMICs in High Power, High Efficiency SSPAs

Science.gov (United States)

Freeman, Jon C.

2004-01-01

A key parameter in the design trade-offs made during AlGaN/GaN HEMTs development for microwave power amplifiers is the channel temperature. An accurate determination can, in general, only be found using detailed software; however, a quick estimate is always helpful, as it speeds up the design cycle. This paper gives a simple technique to estimate the channel temperature of a generic microwave AlGaN/GaN HEMT on SiC or Sapphire, while incorporating the temperature dependence of the thermal conductivity. The procedure is validated by comparing its predictions with the experimentally measured temperatures in microwave devices presented in three recently published articles. The model predicts the temperature to within 5 to 10 percent of the true average channel temperature. The calculation strategy is extended to determine device temperature in power combining MMICs for solid-state power amplifiers (SSPAs).

Social influence of a religious hero: the late Cardinal Stephen Kim Sou-hwan's effect on cornea donation and volunteerism.

Science.gov (United States)

Bae, Hyuhn-Suhck; Brown, William J; Kang, Seok

2011-01-01

This study examined the mediated influence of a celebrated religious hero in South Korea, Cardinal Stephen Kim, through two forms of involvement--parasocial interaction and identification--on intention toward cornea donation and volunteerism, and it investigated how the news media diffused of his death. A structural equation modeling analysis with a Web-based voluntary survey of more than 1,200 people in South Korea revealed a multistep social influence process, beginning with parasocial interaction with Cardinal Kim, leading to identification with him, which predicted intention toward cornea donation and volunteerism. Additional investigations found that news of Cardinal Kim's death diffused rapidly through media and interpersonal communication. Results of this study demonstrate that religious leaders who achieve a celebrity hero status can prompt public discussion of important issues rather quickly through extensive media coverage, enabling them to promote prosocial behavior and positively affect public health.

X-band 5-bit MMIC phase shifter with GaN HEMT technology

Science.gov (United States)

Sun, Pengpeng; Liu, Hui; Zhang, Zongjing; Geng, Miao; Zhang, Rong; Luo, Weijun

2017-10-01

The design approach and performance of a 5-bit digital phase shifter implemented with 0.25 μm GaN HEMT technology for X-band phased arrays are described. The switched filter and high-pass/low-pass networks are proposed in this article. For all 32 states of the 5-bit phase shifter, the RMS phase error less than 5.5°, RMS amplitude error less than 0.8 dB, insertion loss less than 12 dB and input/output return loss less than 8.5 dB are obtained overall 8-12 GHz. The continuous wave power capability is also measured, and a typical input RF P1dB data of 32 dBm is achieved at 8 GHz.

Global Policing and the Case of Kim Dotcom

Directory of Open Access Journals (Sweden)

Darren Palmer

2013-11-01

Full Text Available In early 2012, 76 heavily armed police conducted a raid on a house in Auckland, New Zealand. The targets were Kim Dotcom, a German national with a NZ residency visa, and several colleagues affiliated with Megaupload, an online subscription-based peer-to-peer (P2P file sharing facility. The alleged offences involved facilitating unlawful file sharing and United States federal criminal copyright violations. Following the raid, several court cases provide valuable insights into emerging ‘global policing’ practices (Bowling and Sheptycki 2012 based on communications between sovereign enforcement agencies.  This article uses these cases to explore the growth of ‘extraterritorial’ police powers that operate ‘across borders’ (Nadelmann 1993 as part of several broader transformations of global policing in the digital age.

North Korea after Kim Chong-il: Leadership Dynamics and Potential Crisis Scenarios

Science.gov (United States)

2011-11-01

legal responsibility, and with specified procedures , the actual process is different.3 To date, regime dynamics in the Kim Chong-il era have been... procedures and regulations provide the outlines of formal rule, the 3 For a detailed examination of how...was also made an alternate member. It is also worth noting that 10 of the 12 members of the NDC were represented in the new Politburo lineup , thus

Design and Characterization of a 6 W GaN HEMT Microwave Power Amplifier with Digital Predistortion Linearization

OpenAIRE

Mitrevski, Dragan

2011-01-01

In this thesis, characterization of a 6W GaN HEMT power amplifier for optimal operating conditions through load pull simulations and measurements is investigated.The purpose is to find source and load impedances to achieve for instance maximum efficiency and maximum output power, and investigate whether thesimulated results can be replicated in a measurement setup. Simulations show that when matching for maximum output power, a peak output power of 13W is achieved, while in 1 dB compression, ...

Urinary KIM-1, NGAL and L-FABP for the diagnosis of AKI in patients with acute coronary syndrome or heart failure undergoing coronary angiography.

Science.gov (United States)

Torregrosa, Isidro; Montoliu, Carmina; Urios, Amparo; Andrés-Costa, María Jesús; Giménez-Garzó, Carla; Juan, Isabel; Puchades, María Jesús; Blasco, María Luisa; Carratalá, Arturo; Sanjuán, Rafael; Miguel, Alfonso

2015-11-01

Acute kidney injury (AKI) is a common complication after coronary angiography. Early biomarkers of this disease are needed since increase in serum creatinine levels is a late marker. To assess the usefulness of urinary kidney injury molecule-1 (uKIM-1), neutrophil gelatinase-associated lipocalin (uNGAL) and liver-type fatty acid-binding protein (uL-FABP) for early detection of AKI in these patients, comparing their performance with another group of cardiac surgery patients. Biomarkers were measured in 193 patients, 12 h after intervention. In the ROC analysis, AUC for KIM-1, NGAL and L-FABP was 0.713, 0.958 and 0.642, respectively, in the coronary angiography group, and 0.716, 0.916 and 0.743 in the cardiac surgery group. Urinary KIM-1 12 h after intervention is predictive of AKI in adult patients undergoing coronary angiography, but NGAL shows higher sensitivity and specificity. L-FABP provides inferior discrimination for AKI than KIM-1 or NGAL in contrast to its performance after cardiac surgery. This is the first study showing the predictive capacity of KIM-1 for AKI after coronary angiography. Further studies are still needed to answer relevant questions about the clinical utility of biomarkers for AKI in different clinical settings.

Wafer-level MOCVD growth of AlGaN/GaN-on-Si HEMT structures with ultra-high room temperature 2DEG mobility

Directory of Open Access Journals (Sweden)

Xiaoqing Xu

2016-11-01

Full Text Available In this work, we investigate the influence of growth temperature, impurity concentration, and metal contact structure on the uniformity and two-dimensional electron gas (2DEG properties of AlGaN/GaN high electron mobility transistor (HEMT structure grown by metal-organic chemical vapor deposition (MOCVD on 4-inch Si substrate. High uniformity of 2DEG mobility (standard deviation down to 0.72% across the radius of the 4-inch wafer has been achieved, and 2DEG mobility up to 1740.3 cm2/V⋅s at room temperature has been realized at low C and O impurity concentrations due to reduced ionized impurity scattering. The 2DEG mobility is further enhanced to 2161.4 cm2/V⋅s which is comparable to the highest value reported to date when the contact structure is switched from a square to a cross pattern due to reduced piezoelectric scattering at lower residual strain. This work provides constructive insights and promising results to the field of wafer-scale fabrication of AlGaN/GaN HEMT on Si.

Analyses of 2-DEG characteristics in GaN HEMT with AlN/GaN super-lattice as barrier layer grown by MOCVD.

Science.gov (United States)

Xu, Peiqiang; Jiang, Yang; Chen, Yao; Ma, Ziguang; Wang, Xiaoli; Deng, Zhen; Li, Yan; Jia, Haiqiang; Wang, Wenxin; Chen, Hong

2012-02-20

GaN-based high-electron mobility transistors (HEMTs) with AlN/GaN super-lattices (SLs) (4 to 10 periods) as barriers were prepared on (0001) sapphire substrates. An innovative method of calculating the concentration of two-dimensional electron gas (2-DEG) was brought up when AlN/GaN SLs were used as barriers. With this method, the energy band structure of AlN/GaN SLs was analyzed, and it was found that the concentration of 2-DEG is related to the thickness of AlN barrier and the thickness of the period; however, it is independent of the total thickness of the AlN/GaN SLs. In addition, we consider that the sheet carrier concentration in every SL period is equivalent and the 2-DEG concentration measured by Hall effect is the average value in one SL period. The calculation result fitted well with the experimental data. So, we proposed that our method can be conveniently applied to calculate the 2-DEG concentration of HEMT with the AlN/GaN SL barrier.

Benefits of Considering More than Temperature Acceleration for GaN HEMT Life Testing

Directory of Open Access Journals (Sweden)

Ronald A. Coutu

2016-06-01

Full Text Available The purpose of this work was to investigate the validity of Arrhenius accelerated-life testing when applied to gallium nitride (GaN high electron mobility transistors (HEMT lifetime assessments, where the standard assumption is that only critical stressor is temperature, which is derived from operating power, device channel-case, thermal resistance, and baseplate temperature. We found that power or temperature alone could not explain difference in observed degradation, and that accelerated life tests employed by industry can benefit by considering the impact of accelerating factors besides temperature. Specifically, we found that the voltage used to reach a desired power dissipation is important, and also that temperature acceleration alone or voltage alone (without much power dissipation is insufficient to assess lifetime at operating conditions.

Dynamic Monte Carlo study of isolated-gate InAs/AlSb HEMTs

International Nuclear Information System (INIS)

Rodilla, H; González, T; Mateos, J; Moschetti, G; Grahn, J

2011-01-01

In this work, by means of Monte Carlo simulations, the static and dynamic behavior of isolated-gate InAs/AlSb high electron mobility transistors (Sb-HEMTs) has been studied and compared with experimental results. The influence of the existence of a native oxide under the gate, the value of the surface charges in the gate recess and the possible variation of electron sheet carrier density, n s , have been studied. A decrease in the gate-source capacitance, transconductance and intrinsic cutoff frequency is observed because of the presence of the native oxide, while changes in the value of the surface charges in the recess only introduce a threshold voltage shift. The increase of n s shifts the maximum of the transconductance and intrinsic cutoff frequency to higher values of drain current and improves the agreement with the experimental results

Sexualidad violenta en el cine de Kim Ki-duk

Directory of Open Access Journals (Sweden)

Daniel Muñoz Ruiz

2011-07-01

Full Text Available En sus más de 110 años de vida el cine ha representado la sexualidad humana en todas sus modalidades y desde los más variados puntos de vista. El cine de Kim Ki-duk ha sorprendido y escandalizado al público por su crudeza y, a veces, excesiva violencia. El director surcoreano ha explorado a lo largo de su filmografía el tema del sexo siempre desde puntos de vista dramáticos y hasta truculentos. En sus películas la mayoría de las relaciones sexuales carecen de amor y afecto. Nunca son placenteras. La violación, la prostitución, la violencia de género y las frustraciones sexuales son temas recurrentes en su cine.

Millimeter-wave pseudomorphic HEMT MMIC phased array components for space communications

Science.gov (United States)

Lan, G. L.; Pao, C. K.; Wu, C. S.; Mandolia, G.; Hu, M.; Yuan, S.; Leonard, Regis

1991-01-01

Recent advances in pseudomorphic HEMT MMIC (PMHEMT/MMIC) technology have made it the preferred candidate for high performance millimeter-wave components for phased array applications. This paper describes the development of PMHEMT/MMIC components at Ka-band and V-band. Specifically, the following PMHEMT/MMIC components will be described: power amplifiers at Ka-band; power amplifiers at V-band; and four-bit phase shifters at V-band. For the Ka-band amplifier, 125 mW output power with 5.5 dB gain and 21 percent power added efficiency at 2 dB compression point has been achieved. For the V-band amplifier, 112 mW output power with 6 dB gain and 26 percent power added efficiency has been achieved. And, for the V-band phase shifter, four-bit (45 deg steps) phase shifters with less than 8 dB insertion loss from 61 GHz to 63 GHz will be described.

Children on Social Media, Twiter and Facebook (profile of Beyonce and Kim Kardashian

Directory of Open Access Journals (Sweden)

Anamarija Bilan

2017-09-01

Full Text Available Publishing children’s photos in the media violates their privacy right, which is protected, guaranteed and regulated by numerous international and Croatian laws and regulations. Likewise, publishing photos of children on social network profiles, such as Facebook or Twitter, violates the right to privacy. In this paper it will be researched the extent to which children’s photos are being disclosed and their privacy is being undermined in case of two Facebook and two Twitter profiles - Beyonce Knowles and Kim Kardashian. It will also research whether children are used for business purposes, whether they are advertising some of their products or shows, and so on, with the photographs of children. The content analysis methodology analyzed the Facebook and Twitter profiles of two respondents in the period from January 1 to February 22, 2016, during which they published a total of 459 posts on profiles of both networks. The analysis found that the total number of “posts” shows a small number of photographs of children but also that those published by Kim Kardashian are often used to promote or promote some of the products or programs, which violates the privacy of children and increases the number “like”.

Differential InP HEMT MMIC Amplifiers Embedded in Waveguides

Science.gov (United States)

Kangaslahti, Pekka; Schlecht, Erich; Samoska, Lorene

2009-01-01

Monolithic microwave integrated-circuit (MMIC) amplifiers of a type now being developed for operation at frequencies of hundreds of gigahertz contain InP high-electron-mobility transistors (HEMTs) in a differential configuration. The differential configuration makes it possible to obtain gains greater than those of amplifiers having the single-ended configuration. To reduce losses associated with packaging, the MMIC chips are designed integrally with, and embedded in, waveguide packages, with the additional benefit that the packages are compact enough to fit into phased transmitting and/or receiving antenna arrays. Differential configurations (which are inherently balanced) have been used to extend the upper limits of operating frequencies of complementary metal oxide/semiconductor (CMOS) amplifiers to the microwave range but, until now, have not been applied in millimeter- wave amplifier circuits. Baluns have traditionally been used to transform from single-ended to balanced configurations, but baluns tend to be lossy. Instead of baluns, finlines are used to effect this transformation in the present line of development. Finlines have been used extensively to drive millimeter- wave mixers in balanced configurations. In the present extension of the finline balancing concept, finline transitions are integrated onto the affected MMICs (see figure). The differential configuration creates a virtual ground within each pair of InP HEMT gate fingers, eliminating the need for inductive vias to ground. Elimination of these vias greatly reduces parasitic components of current and the associated losses within an amplifier, thereby enabling more nearly complete utilization of the full performance of each transistor. The differential configuration offers the additional benefit of multiplying (relative to the single-ended configuration) the input and output impedances of each transistor by a factor of four, so that it is possible to use large transistors that would otherwise have

Degradation mechanism of enhancement-mode AlGaN/GaN HEMTs using fluorine ion implantation under the on-state gate overdrive stress

International Nuclear Information System (INIS)

Sun Wei-Wei; Zheng Xue-Feng; Fan Shuang; Wang Chong; Du Ming; Zhang Kai; Mao Wei; Zhang Jin-Cheng; Hao Yue; Chen Wei-Wei; Cao Yan-Rong; Ma Xiao-Hua

2015-01-01

The degradation mechanism of enhancement-mode AlGaN/GaN high electron mobility transistors (HEMTs) fabricated by fluorine plasma ion implantation technology is one major concern of HEMT’s reliability. It is observed that the threshold voltage shows a significant negative shift during the typical long-term on-state gate overdrive stress. The degradation does not originate from the presence of as-grown traps in the AlGaN barrier layer or the generated traps during fluorine ion implantation process. By comparing the relationships between the shift of threshold voltage and the cumulative injected electrons under different stress conditions, a good agreement is observed. It provides direct experimental evidence to support the impact ionization physical model, in which the degradation of E-mode HEMTs under gate overdrive stress can be explained by the ionization of fluorine ions in the AlGaN barrier layer by electrons injected from 2DEG channel. Furthermore, our results show that there are few new traps generated in the AlGaN barrier layer during the gate overdrive stress, and the ionized fluorine ions cannot recapture the electrons. (paper)

Non-destructive determination of ultra-thin GaN cap layer thickness in AlGaN/GaN HEMT structure by angle resolved x-ray photoelectron spectroscopy (ARXPS)

Science.gov (United States)

Goyal, Anshu; Yadav, Brajesh S.; Raman, R.; Kapoor, Ashok K.

2018-02-01

Angle resolved X-ray photoelectron spectroscopy (ARXPS) and secondary ion mass spectrometry (SIMS) investigations have been carried out to characterize the GaN cap layer in AlGaN/GaN HEMT structure. The paper discusses the qualitative (presence or absence of a cap layer) and quantitative (cap layer thickness) characterization of cap layer in HEMT structure non-destructively using ARXPS measurements in conjunction with the theoretical modeling. Further the relative sensitive factor (RSF=σ/Ga σAl ) for Ga to Al ratio was estimated to be 0.963 and was used in the quantification of GaN cap layer thickness. Our results show that Al/Ga intensity ratio varies with the emission angle in the presence of GaN cap layer and otherwise remains constant. Also, the modeling of this intensity ratio gives its thickness. The finding of ARXPS was also substantiated by SIMS depth profiling studies.

Non-destructive determination of ultra-thin GaN cap layer thickness in AlGaN/GaN HEMT structure by angle resolved x-ray photoelectron spectroscopy (ARXPS

Directory of Open Access Journals (Sweden)

Anshu Goyal

2018-02-01

Full Text Available Angle resolved X-ray photoelectron spectroscopy (ARXPS and secondary ion mass spectrometry (SIMS investigations have been carried out to characterize the GaN cap layer in AlGaN/GaN HEMT structure. The paper discusses the qualitative (presence or absence of a cap layer and quantitative (cap layer thickness characterization of cap layer in HEMT structure non-destructively using ARXPS measurements in conjunction with the theoretical modeling. Further the relative sensitive factor (RSF=σGaσAl for Ga to Al ratio was estimated to be 0.963 and was used in the quantification of GaN cap layer thickness. Our results show that Al/Ga intensity ratio varies with the emission angle in the presence of GaN cap layer and otherwise remains constant. Also, the modeling of this intensity ratio gives its thickness. The finding of ARXPS was also substantiated by SIMS depth profiling studies.

The effect of ammonia flow in the AlN spacer on the electrical properties of InAlN/AlN/GaN HEMT structures

International Nuclear Information System (INIS)

Gamarra, Piero; Lacam, Cedric; Magis, Michelle; Tordjman, Maurice; Di Forte Poisson, Marie-Antoinette

2012-01-01

During the past few years it has been reported that a thin AlN spacer of few nanometers needs to be inserted in InAlN/GaN high electron mobility transistors (HEMTs) to obtain high 2DEG carrier mobility. This work presents a systematic study of the effects of varying the ammonia flow in the AlN spacer of InAlN/AlN/GaN HEMTs grown by low pressure metalorganic vapour phase epitaxy (LP-MOVPE). The strain state, the surface roughness and the growth rate of AlN were found to be dependent on the V/III ratio. In addition the ammonia flow in the interlayer has a strong impact on the structural properties of the subsequent InAlN barrier layer and on the electrical properties of the structure. A sheet resistance as low as 327 Ω/□ with a sheet carrier density of 1.5 x 10 13 cm -2 has been obtained at room temperature. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

The effect of ammonia flow in the AlN spacer on the electrical properties of InAlN/AlN/GaN HEMT structures

Energy Technology Data Exchange (ETDEWEB)

Gamarra, Piero; Lacam, Cedric; Magis, Michelle; Tordjman, Maurice; Di Forte Poisson, Marie-Antoinette [III-V Lab., Marcussis (France)

2012-01-15

During the past few years it has been reported that a thin AlN spacer of few nanometers needs to be inserted in InAlN/GaN high electron mobility transistors (HEMTs) to obtain high 2DEG carrier mobility. This work presents a systematic study of the effects of varying the ammonia flow in the AlN spacer of InAlN/AlN/GaN HEMTs grown by low pressure metalorganic vapour phase epitaxy (LP-MOVPE). The strain state, the surface roughness and the growth rate of AlN were found to be dependent on the V/III ratio. In addition the ammonia flow in the interlayer has a strong impact on the structural properties of the subsequent InAlN barrier layer and on the electrical properties of the structure.istance as low as 327 {omega}/{open_square} with a sheet carrier density of 1.5 x 10{sup 13} cm{sup -2} has been obtained at room temperature. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

A low-noise X-band microstrip VCO with 2.5 GHz tuning range using a GaN-on-SiC p-HEMT

NARCIS (Netherlands)

Maas, A.M.P.; Vliet, F.E. van

2005-01-01

A low-noise X-band microstrip hybrid VCO has been designed and realised using a 2 × 50 μm GaN-on-SiC pseudo-morphic HEMT as the active device. The transistor has been manufactured by TIGER and features a gate-length of 0.15 μm, an fT of 22 GHz, a break-down voltage of 42 Volts and an Idss, close to

Clinical significance of NGAL and KIM-1 for acute kidney injury in patients with scrub typhus.

Science.gov (United States)

Sun, In O; Shin, Sung Hye; Cho, A Young; Yoon, Hyun Ju; Chang, Mi Yok; Lee, Kwang Young

2017-01-01

The aim of this study is to investigate the clinical significance of neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1) for acute kidney injury (AKI) in patients with scrub typhus. From 2014 to 2015, 145 patients were diagnosed with scrub typhus. Of these, we enrolled 138 patients who were followed up until renal recovery or for at least 3 months. We measured serum and urine NGAL and KIM-1 levels and evaluated prognostic factors affecting scrub typhus-associated AKI. Of the 138 patients, 25 had scrub typhus-associated AKI. The incidence of AKI was 18.1%; of which 11.6%, 4.3%, and 2.2% were classified as risk, injury, and failure, respectively, according to RIFLE criteria. Compared with patients in the non-AKI group, patients in the AKI group were older and showed higher total leukocyte counts and hypoalbuminemia or one or more comorbidities such as hypertension (72% vs 33%, pscrub typhus-associated AKI.

Electrical characterization and nanoscale surface morphology of optimized Ti/Al/Ta/Au ohmic contact for AlGaN/GaN HEMT.

Science.gov (United States)

Wang, Cong; Kim, Nam-Young

2012-02-07

Good ohmic contacts with low contact resistance, smooth surface morphology, and a well-defined edge profile are essential to ensure optimal device performances for the AlGaN/GaN high electron mobility transistors [HEMTs]. A tantalum [Ta] metal layer and an SiNx thin film were used for the first time as an effective diffusion barrier and encapsulation layer in the standard Ti/Al/metal/Au ohmic metallization scheme in order to obtain high quality ohmic contacts with a focus on the thickness of Ta and SiNx. It is found that the Ta thickness is the dominant factor affecting the contact resistance, while the SiNx thickness affects the surface morphology significantly. An optimized Ti/Al/Ta/Au ohmic contact including a 40-nm thick Ta barrier layer and a 50-nm thick SiNx encapsulation layer is preferred when compared with the other conventional ohmic contact stacks as it produces a low contact resistance of around 7.27 × 10-7 Ω·cm2 and an ultra-low nanoscale surface morphology with a root mean square deviation of around 10 nm. Results from the proposed study play an important role in obtaining excellent ohmic contact formation in the fabrication of AlGaN/GaN HEMTs.

High sensitivity cardiac troponin I detection in physiological environment using AlGaN/GaN High Electron Mobility Transistor (HEMT) Biosensors.

Science.gov (United States)

Sarangadharan, Indu; Regmi, Abiral; Chen, Yen-Wen; Hsu, Chen-Pin; Chen, Pei-Chi; Chang, Wen-Hsin; Lee, Geng-Yen; Chyi, Jen-Inn; Shiesh, Shu-Chu; Lee, Gwo-Bin; Wang, Yu-Lin

2018-02-15

In this study, we report the development of a high sensitivity assay for the detection of cardiac troponin I using electrical double layer gated high field AlGaN/GaN HEMT biosensor. The unique gating mechanism overcomes the drawback of charge screening seen in traditional FET based biosensors, allowing detection of target proteins in physiological solutions without sample processing steps. Troponin I specific antibody and aptamer are used as receptors. The tests carried out using purified protein solution and clinical serum samples depict high sensitivity, specificity and wide dynamic range (0.006-148ng/mL). No additional wash or sample pre-treatment steps are required, which greatly simplifies the biosensor system. The miniaturized HEMT chip is packaged in a polymer substrate and easily integrated with a portable measurement unit, to carry out quantitative troponin I detection in serum samples with < 2µl sample volume in 5min. The integrated prototype biosensor unit demonstrates the potential of the method as a rapid, inexpensive, high sensitivity CVD biomarker assay. The highly simplified protocols and enhanced sensor performance make our biosensor an ideal choice for point of care diagnostics and personal healthcare systems. Copyright © 2017 Elsevier B.V. All rights reserved.

A Misleading Review of Response Bias: Comment on McGrath, Mitchell, Kim, and Hough (2010)

Science.gov (United States)

Rohling, Martin L.; Larrabee, Glenn J.; Greiffenstein, Manfred F.; Ben-Porath, Yossef S.; Lees-Haley, Paul; Green, Paul; Greve, Kevin W.

2011-01-01

In the May 2010 issue of "Psychological Bulletin," R. E. McGrath, M. Mitchell, B. H. Kim, and L. Hough published an article entitled "Evidence for Response Bias as a Source of Error Variance in Applied Assessment" (pp. 450-470). They argued that response bias indicators used in a variety of settings typically have insufficient data to support such…

New Nordic Exceptionalism: Jeuno JE Kim and Ewa Einhorn's The United Nations of Norden and other realist utopias

Directory of Open Access Journals (Sweden)

Mathias Danbolt

2016-11-01

Full Text Available At the 2009 Nordic Culture Forum summit in Berlin that centered on the profiling and branding of the Nordic region in a globalized world, one presenter stood out from the crowd. The lobbyist Annika Sigurdardottir delivered a speech that called for the establishment of “The United Nations of Norden”: A Nordic union that would gather the nations and restore Norden's role as the “moral superpower of the world.” Sigurdardottir's presentation generated such a heated debate that the organizers had to intervene and reveal that the speech was a performance made by the artists Jeuno JE Kim and Ewa Einhorn. This article takes Kim and Einhorn's intervention as a starting point for a critical discussion of the history and politics of Nordic image-building. The article suggests that the reason Kim and Einhorn's speech passed as a serious proposal was due to its meticulous mimicking of two discursive formations that have been central to the debates on the branding of Nordicity over the last decades: on the one hand, the discourse of “Nordic exceptionalism,” that since the 1960s has been central to the promotion of a Nordic political, socio-economic, and internationalist “third way” model, and, on the other hand, the discourse on the “New Nordic,” that emerged out of the New Nordic Food-movement in the early 2000s, and which has given art and culture a privileged role in the international re-fashioning of the Nordic brand. Through an analysis of Kim and Einhorn's United Nations of Norden (UNN-performance, the article examines the historical development and ideological underpinnings of the image of Nordic unity at play in the discourses of Nordic exceptionalism and the New Nordic. By focusing on how the UNN-project puts pressure on the role of utopian imaginaries in the construction of Nordic self-images, the article describes the emergence of a discursive framework of New Nordic Exceptionalism.

Validation of a triangular quantum well model for GaN-based HEMTs used in pH and dipole moment sensing

International Nuclear Information System (INIS)

Rabbaa, S; Stiens, J

2012-01-01

Gallium nitride (GaN) is a relatively new semiconductor material that has the potential of replacing gallium arsenide (GaAs) in some of the more recent technological applications, for example chemical sensor applications. In this paper, we introduce a triangular quantum well model for an undoped AlGaN/GaN high electron mobility transistor (HEMT) structure used as a chemical and biological sensor for pH and dipole moment measurements of polar liquids. We have performed theoretical calculations related to the HEMT characteristics and we have compared them with experimental measurements carried out in many previous papers. These calculations include the current-voltage (I-V) characteristics of the device, the surface potential, the change in the drain current with the dipole moment and the drain current as a function of pH. The results exhibit good agreement with experimental measurements for different polar liquids and electrolyte solutions. It is also found that the drain current of the device exhibits a large linear variation with the dipole moment, and that the surface potential and the drain current depend strongly on the pH. Therefore, it can distinguish molecules with slightly different dipole moments and solutions with small variations in pH. The ability of the device to sense biomolecules (such as proteins) with very large dipole moments is investigated.

Design and simulation of a novel 1400 V–4000 V enhancement mode buried gate GaN HEMT for power applications

International Nuclear Information System (INIS)

Faramehr, Soroush; Kalna, Karol; Igić, Petar

2014-01-01

A novel enhancement mode structure, a buried gate gallium nitride (GaN) high electron mobility transistor (HEMT) with a breakdown voltage (BV) of 1400 V–4000 V for a source-to-drain spacing (L SD ) of 6 μm–32 μm, is investigated using simulations by Silvaco Atlas. The simulations are based on meticulous calibration of a conventional lateral 1 μm gate length GaN HEMT with a source-to-drain spacing of 6 μm against its experimental transfer characteristics and BV. The specific on-resistance R S for the new power transistor with the source-to-drain spacing of 6 μm showing BV = 1400 V and the source-to-drain spacing of 8 μm showing BV = 1800 V is found to be 2.3 mΩ · cm 2 and 3.5 mΩ · cm 2 , respectively. Further improvement up to BV  = 4000 V can be achieved by increasing the source-to-drain spacing to 32 μm with the specific on-resistance of R S = 35.5 mΩ · cm 2 . The leakage current in the proposed devices stays in the range of ∼5 × 10 −9 mA mm −1 . (paper)

Procjena citomorfologije, HPV statusa i HPV 16 genotipa u predikciji ishoda bolesti kod pacijentica s citološkim nalazom ASCUS i LSIL

OpenAIRE

Vrdoljak-Mozetič, Danijela; Štemberger-Papić, Snježana; Verša Ostojić, Damjana; Rubeša-Mihaljević, Roberta; Dinter, Morana; Brnčić-Fischer, Alemka; Krašević, Maja

2016-01-01

Cilj: Istražiti međusobnu povezanost i prognostički značaj HPV statusa (humani papiloma-virus), HPV 16 genotipa i citomorfologije kod pacijentica s citološkim nalazom abnormalnih stanica pločastog epitela vrata maternice graničnog i blagog stupnja. Materijali i metode: U studiju su uključene pacijentice s inicijalnim citološkim nalazom vrata maternice atipičnih skvamoznih stanica neodređenog značenja (ASCUS, N = 160) i skvamozne intraepitelne lezije niskog stupnja (LSIL, N = 155). Analizirane...

Remote PECVD silicon nitride films with improved electrical properties for GaAs P-HEMT passivation

CERN Document Server

Sohn, M K; Kim, K H; Yang, S G; Seo, K S

1998-01-01

In order to obtain thin silicon nitride films with excellent electrical and mechanical properties, we employed RPECVD (Remote Plasma Enhanced Chemical Vapor Deposition) process which produces less plasma-induced damage than the conventional PECVD. Through the optical and electrical measurements of the deposited films, we optimized the various RPECVD process parameters. The optimized silicon nitride films showed excellent characteristics such as small etch rate (approx 33 A/min by 7:1 BHF), high breakdown field (>9 MV/cm), and low compressive stress (approx 3.3x10 sup 9 dyne/cm sup 2). We successfully applied thin RPECVD silicon nitride films to the surface passivation of GaAs pseudomorphic high electron mobility transistors (P-HEMTs) with negligible degradations in DC and RF characteristics.

Electrical characteristics and interface properties of ALD-HfO2/AlGaN/GaN MIS-HEMTs fabricated with post-deposition annealing

Science.gov (United States)

Kubo, Toshiharu; Egawa, Takashi

2017-12-01

HfO2/AlGaN/GaN metal-insulator-semiconductor (MIS)-type high electron mobility transistors (HEMTs) on Si substrates were fabricated by atomic layer deposition of HfO2 layers and post-deposition annealing (PDA). The current-voltage characteristics of the MIS-HEMTs with as-deposited HfO2 layers showed a low gate leakage current (I g) despite the relatively low band gap of HfO2, and a dynamic threshold voltage shift (ΔV th) was observed. After PDA above 500 °C, ΔV th was reduced from 2.9 to 0.7 V with an increase in I g from 2.2 × 10-7 to 4.8 × 10-2 mA mm-1. Effects of the PDA on the HfO2 layer and the HfO2/AlGaN interface were investigated by x-ray photoelectron spectroscopy (XPS) using synchrotron radiation. XPS data showed that oxygen vacancies exist in the as-deposited HfO2 layers and they disappeared with an increase in the PDA temperature. These results indicate that the deep electron traps that cause ΔV th are related to the oxygen vacancies in the HfO2 layers.

Characterization and Modeling I(V of the Gate Schottky Structures HEMTs Ni/Au/AlInN/GaN

Directory of Open Access Journals (Sweden)

N. Benyahya

2014-05-01

Full Text Available In this paper, we have studied the Schottky contact of Ni/Au/AlInN/GaN HEMTs. The current–voltage Igs (Vgs of Ni/Au/AlInN/GaN structures were investigated at room temperature. The electrical parameters such as ideality factor (2.3, barrier height (0.72 eV and series resistance (33 W were evaluated from I(V data, the threshold voltage (-2.42 V, the 2D gas density (1.35 ´ 1013 cm-2 and barrier height (0.94 eV were evaluated from C(V data.

Investigation on de-trapping mechanisms related to non-monotonic kink pattern in GaN HEMT devices

Directory of Open Access Journals (Sweden)

Chandan Sharma

2017-08-01

Full Text Available This article reports an experimental approach to analyze the kink effect phenomenon which is usually observed during the GaN high electron mobility transistor (HEMT operation. De-trapping of charge carriers is one of the prominent reasons behind the kink effect. The commonly observed non-monotonic behavior of kink pattern is analyzed under two different device operating conditions and it is found that two different de-trapping mechanisms are responsible for a particular kink behavior. These different de-trapping mechanisms are investigated through a time delay analysis which shows the presence of traps with different time constants. Further voltage sweep and temperature analysis corroborates the finding that different de-trapping mechanisms play a role in kink behavior under different device operating conditions.

Investigation on de-trapping mechanisms related to non-monotonic kink pattern in GaN HEMT devices

Science.gov (United States)

Sharma, Chandan; Laishram, Robert; Amit, Rawal, Dipendra Singh; Vinayak, Seema; Singh, Rajendra

2017-08-01

This article reports an experimental approach to analyze the kink effect phenomenon which is usually observed during the GaN high electron mobility transistor (HEMT) operation. De-trapping of charge carriers is one of the prominent reasons behind the kink effect. The commonly observed non-monotonic behavior of kink pattern is analyzed under two different device operating conditions and it is found that two different de-trapping mechanisms are responsible for a particular kink behavior. These different de-trapping mechanisms are investigated through a time delay analysis which shows the presence of traps with different time constants. Further voltage sweep and temperature analysis corroborates the finding that different de-trapping mechanisms play a role in kink behavior under different device operating conditions.

Normally-off AlGaN/GaN-based MOS-HEMT with self-terminating TMAH wet recess etching

Science.gov (United States)

Son, Dong-Hyeok; Jo, Young-Woo; Won, Chul-Ho; Lee, Jun-Hyeok; Seo, Jae Hwa; Lee, Sang-Heung; Lim, Jong-Won; Kim, Ji Heon; Kang, In Man; Cristoloveanu, Sorin; Lee, Jung-Hee

2018-03-01

Normally-off AlGaN/GaN-based MOS-HEMT has been fabricated by utilizing damage-free self-terminating tetramethyl ammonium hydroxide (TMAH) recess etching. The device exhibited a threshold voltage of +2.0 V with good uniformity, extremely small hysteresis of ∼20 mV, and maximum drain current of 210 mA/mm. The device also exhibited excellent off-state performances, such as breakdown voltage of ∼800 V with off-state leakage current as low as ∼10-12 A and high on/off current ratio (Ion/Ioff) of 1010. These excellent device performances are believed to be due to the high quality recessed surface, provided by the simple self-terminating TMAH etching.

Materialismo percettivo. Da Democrito a Lenin, da Hobbes a Kim

Directory of Open Access Journals (Sweden)

Michele Gardini

2012-05-01

Full Text Available The paper tries to outline something like a short “critique of pure materialism” in the domain of perception, a sketch showing – through a series of examples, picked out in an apparently heterogeneous fashion from the Western philosophical tradition – how this epistemological model each time, and in everyone of its forms, fails in giving account of the basic features of perceiving.  After giving a survey of authors like Democritus, Hobbes, De Sade, Lenin, the final appendix, devoted to the concept of “supervenience” and its treatment in Davidson and Kim, aims at summarizing the whole problem through the categories of the contemporary philosophy of mind. The conclusion is that a pure materialistic approach is incapable to give reason to some of the fundamental characteristics of perception, that make it one of the basic moods of “being-in-the-world”.

"The Day All of the Different Parts of Me Can Come Along": Intersectionality and U.S. Third World Feminism in the Poetry of Pat Parker and Willyce Kim.

Science.gov (United States)

Van Ausdall, Mimi Iimuro

2015-01-01

This article brings to light the poetry of Pat Parker and Willyce Kim, two key figures within the 1970s and '80s women in print movement. While Parker and Kim have been rightly placed within African-American and Asian-American histories, respectively, and working-class and lesbian-feminist literary histories, their work is most fully understood within the context of U.S. Third World Feminism. Through close readings of poetic form and content in addition to engagement with current debates about intersectionality as a methodology, the article links Kim and Parker's works to central contributions of U.S. Third World Feminism such as intersectionality and power across and within difference that continue to influence feminist theory today.

Muusikauudised : Lu : k ja Jäääär koos laval. Britney Spears tegutseb. Lenny Kravitz ja Mick Jagger. Kim Wilde

Index Scriptorium Estoniae

2001-01-01

Tartus Sõbra majas toimunud kontserdist. Videost "Britney: The video". Heliplaatidest: "Britney", "The Best of Pink Floyd", "Lenny", Mick Jagger "Goddess In The Doorway", "The Very Best Of Kim Wilde"

Thirty-five-nm T-Gate In0.52Al0.48As/In0.53Ga0.47As metamorphic HEMTs with an ultrahigh fmax of 610 GHz

International Nuclear Information System (INIS)

Choi, Do-Young; Kim, Sung-Ho; Choi, Gil-Bok; Jung, Sung-Woo; Jeong, Yoon-Ha

2010-01-01

Thirty-five-nanometer T-gate GaAs-based In 0.52 Al 0.48 As/In 0.53 Ga 0.47 As metamorphic high electron mobility transistors (mHEMTs) are successfully fabricated using a zigzag-shaped T-gate. We obtain a maximum extrinsic transconductance (g m ) of 1060 mS/mm and a maximum oscillation frequency (f max ) of 610 GHz. These superior results are obtained by reducing the T-gate's length to 35 nm without the assistance of a supporting layer and by fabricating a wide-recessed-gate structure. The stand-alone 35-nm T-gate effectively improves the device performance because it doesn't cause additional parasitic capacitances. The wide-recessed-gate structure alleviates impact ionization in the channel, which suppresses the kink effect in the output characteristic and reduces the output conductance (g ds ). In addition, the wide-recessed-gate structure reduces the gate-to-drain capacitance (C gd ); consequently realizing a state-of-the-art f max . The f max of 610 GHz, to our knowledge, is the highest value reported to date for GaAs-based HEMTs.

"Sundiata, Lion King of Mali." Adapted by Kim Hines, Featuring Griot Alhaji Papa Susso, Cue Sheet for Students.

Science.gov (United States)

Freeman, Aakhu TuahNera

This performance guide is designed for teachers to use with students before and after a performance of "Sundiata: Lion King of Mali," adapted by Kim Hines and featuring Griot Alhaji Papa Susso. The guide, called a "Cuesheet," contains seven activity sheets for use in class, addressing: (1) Sundiata: Man & Myth (discusses…

Simulation study of HEMT structures with HfO{sub 2} cap layer for mitigating inverse piezoelectric effect related device failures

Energy Technology Data Exchange (ETDEWEB)

Nagulapally, Deepthi; Joshi, Ravi P., E-mail: rjoshi@odu.edu [Department of Electrical and Computer Engineering, Old Dominion University, Norfolk, VA 23529-0246 (United States); Pradhan, Aswini [Department of Engineering and Center for Materials Research, Norfolk State University, 700 Park Avenue, Norfolk, VA 23504 (United States)

2015-01-15

The Inverse Piezoelectric Effect (IPE) is thought to contribute to possible device failure of GaN High Electron Mobility Transistors (HEMTs). Here we focus on a simulation study to probe the possible mitigation of the IPE by reducing the internal electric fields and related elastic energy through the use of high-k materials. Inclusion of a HfO{sub 2} “cap layer” above the AlGaN barrier particularly with a partial mesa structure is shown to have potential advantages. Simulations reveal even greater reductions in the internal electric fields by using “field plates” in concert with high-k oxides.

Simulation study of HEMT structures with HfO2 cap layer for mitigating inverse piezoelectric effect related device failures

Directory of Open Access Journals (Sweden)

Deepthi Nagulapally

2015-01-01

Full Text Available The Inverse Piezoelectric Effect (IPE is thought to contribute to possible device failure of GaN High Electron Mobility Transistors (HEMTs. Here we focus on a simulation study to probe the possible mitigation of the IPE by reducing the internal electric fields and related elastic energy through the use of high-k materials. Inclusion of a HfO2 “cap layer” above the AlGaN barrier particularly with a partial mesa structure is shown to have potential advantages. Simulations reveal even greater reductions in the internal electric fields by using “field plates” in concert with high-k oxides.

Differences in immunolocalization of Kim-1, RPA-1, and RPA-2 in kidneys of gentamicin-, cisplatin-, and valproic acid-treated rats: potential role of iNOS and nitrotyrosine.

Science.gov (United States)

Zhang, Jun; Goering, Peter L; Espandiari, Parvaneh; Shaw, Martin; Bonventre, Joseph V; Vaidya, Vishal S; Brown, Ronald P; Keenan, Joe; Kilty, Cormac G; Sadrieh, Nakissa; Hanig, Joseph P

2009-08-01

The present study compared the immunolocalization of Kim-1, renal papillary antigen (RPA)-1, and RPA-2 with that of inducible nitric oxide synthase (iNOS) and nitrotyrosine in kidneys of gentamicin sulfate (Gen)- and cisplatin (Cis)-treated rats. The specificity of acute kidney injury (AKI) biomarkers, iNOS, and nitrotyrosine was evaluated by dosing rats with valproic acid (VPA). Sprague-Dawley (SD) rats were injected subcutaneously (sc) with 100 mg/kg/day of Gen for six or fourteen days; a single intraperitoneal (ip) dose of 1, 3, or 6 mg/kg of Cis; or 650 mg/kg/day of VPA (ip) for four days. In Gen-treated rats, Kim-1 was expressed in the epithelial cells, mainly in the S1/S2 segments but less so in the S3 segment, and RPA-1 was increased in the epithelial cells of collecting ducts (CD) in the cortex. Spatial expression of iNOS or nitrotyrosine with Kim-1 or RPA-1 was detected. In Cis-treated rats, Kim-1 was expressed only in the S3 segment cells, and RPA-1 and RPA-2 were increased in the epithelial cells of medullary CD or medullary loop of Henle (LH), respectively. Spatial expression of iNOS or nitrotyrosine with RPA-1 or RPA-2 was also identified. These findings suggest that peroxynitrite formation may be involved in the pathogenesis of Gen and Cis nephrotoxicity and that Kim-1, RPA-1, and RPA-2 have the potential to serve as site-specific biomarkers for Gen or Cis AKI.

Growth of quaternary InAlGaN barrier with ultrathin thickness for HEMT application

Science.gov (United States)

Li, Zhonghui; Li, Chuanhao; Peng, Daqing; Zhang, Dongguo; Dong, Xun; Pan, Lei; Luo, Weike; Li, Liang; Yang, Qiankun

2018-06-01

Quaternary InAlGaN barriers with thickness of 7 nm for HEMT application were grown on 3-inch semi-insulating 4H-SiC substrates by metal organic chemical vapor deposition (MOCVD). Focused on growth mechanism of the InAlGaN barrier, the surface morphology and characteristics of InAlGaN/AlN/GaN heterostructures were studied with different growth parameters, including the temperature, Al/Ga ratio and chamber pressure. Among the as-grown samples, high electron mobility is consistent with smooth surface morphology, while high crystalline quality of the quaternary barrier is confirmed by measurements of Photoluminescence (PL) and Mercury-probe Capacity-Voltage (C-V). The recommended heterostructures without SiN passivation is characterized by mobility of 1720 cm2/(V·s), 2DEG density of 1.71*1013 cm-2, sheet resistance of about 210 Ω/□ with a smooth surface morphology and moderate tensile state, specially applied for microwave devices.

Demonstration of an RF front-end based on GaN HEMT technology

Science.gov (United States)

Ture, Erdin; Musser, Markus; Hülsmann, Axel; Quay, Rüdiger; Ambacher, Oliver

2017-05-01

The effectiveness of the developed front-end on blocking the communication link of a commercial drone vehicle has been demonstrated in this work. A jamming approach has been taken in a broadband fashion by using GaN HEMT technology. Equipped with a modulated-signal generator, a broadband power amplifier, and an omni-directional antenna, the proposed system is capable of producing jamming signals in a very wide frequency range between 0.1 - 3 GHz. The maximum RF output power of the amplifier module has been software-limited to 27 dBm (500 mW), complying to the legal spectral regulations of the 2.4 GHz ISM band. In order to test the proof of concept, a real-world scenario has been prepared in which a commercially-available quadcopter UAV is flown in a controlled environment while the jammer system has been placed in a distance of about 10 m from the drone. It has been proven that the drone of interest can be neutralized as soon as it falls within the range of coverage (˜3 m) which endorses the promising potential of the broadband jamming approach.

Fe doping for making resistive GaN layers with low dislocation density; consequence on HEMTs

Energy Technology Data Exchange (ETDEWEB)

Bougrioua, Z.; Lorenzini, P. [CRHEA-CNRS, rue Bernard Gregory, 06560 Valbonne (France); Azize, M. [CRHEA-CNRS, rue Bernard Gregory, 06560 Valbonne (France); LUMILOG, 2720 Chemin St Bernard, 06220 Vallauris (France); Jimenez, A. [E. Politecnica. Universidad de Alcala, 28871 Alcala de Henares (Spain); Brana, A.F.; Munoz, E. [ETSI Telecomunicacion, UPM, 28040 Madrid (Spain); Beaumont, B.; Gibart, P. [LUMILOG, 2720 Chemin St Bernard, 06220 Vallauris (France)

2005-05-01

Highly resistive GaN (>10{sup 8} {omega}{sub {upsilon}}) is grown by MOVPE on sapphire with dislocation density in the range 10{sup 8} to 8 x 10{sup 8} cm{sup -2}, using Fe modulation doping. High mobility 2DEGs are created at AlGaN/GaN:Fe interface for moderate Al composition: 2200 cm{sup 2}/V/s at n{sub s}{proportional_to}7.6 x 10{sup 12} cm{sup -2}. Good DC and RF small signal behaviour could be obtained in HEMTs processed on structures with less dislocated GaN:Fe template: I{sub DS}{sup max}=1.28 A/mm, g{sub m}{sup max} {proportional_to}290 mS/mm and f{sub T} {proportional_to}23 GHz were measured for 0.2 {mu}m transistors. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Urinary Biomarkers KIM-1 and NGAL for Detection of Chronic Kidney Disease of Uncertain Etiology (CKDu) among Agricultural Communities in Sri Lanka

Science.gov (United States)

Mohammed Abdul, Khaja Shameem; Eakanayake, Eakanayake M. D. V.; Jayasinghe, Sudheera Sammanthi; Jayasumana, Channa; Asanthi, Hewa Bandulage; Perera, Hettiarachigae S. D.; Chaminda, Gamage G. Tushara; Chandana, Ediriweera P. S.; Siribaddana, Sisira H.

2016-01-01

Chronic Kidney Disease of uncertain etiology (CKDu) is an emerging epidemic among farming communities in rural Sri Lanka. Victims do not exhibit common causative factors, however, histopathological studies revealed that CKDu is a tubulointerstitial disease. Urine albumin or albumin-creatinine ratio is still being used as a traditional diagnostic tool to identify CKDu, but accuracy and prevalence data generated are questionable. Urinary biomarkers have been used in similar nephropathy and are widely recognised for their sensitivity, specificity and accuracy in determining CKDu and early renal injury. However, these biomarkers have never been used in diagnosing CKDu in Sri Lanka. Male farmers (n = 1734) were recruited from 4 regions in Sri Lanka i.e. Matara and Nuwara Eliya (farming locations with no CKDu prevalence) and two CKDu emerging locations from Hambantota District in Southern Sri Lanka; Angunakolapelessa (EL1) and Bandagiriya (EL2). Albuminuria (ACR ≥ 30mg/g); serum creatinine based estimation of glomerular filtration rate (eGFR); creatinine normalized urinary kidney injury molecule (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) were measured. Fourteen new CKDu cases (18%) from EL1 and nine CKDu cases (9%) from EL2 were recognized for the first time from EL1, EL2 locations, which were previously considered as non-endemic of the disease and associated with persistent albuminuria (ACR ≥ 30mg/g Cr). No CKDu cases were identified in non-endemic study locations in Matara (CM) and Nuwara Eliya (CN). Analysis of urinary biomarkers showed urinary KIM-1 and NGAL were significantly higher in new CKDu cases in EL1 and EL2. However, we also reported significantly higher KIM-1 and NGAL in apparently healthy farmers in EL 1 and EL 2 with comparison to both control groups. These observations may indicate possible early renal damage in absence of persistent albuminuria and potential capabilities of urinary KIM-1 and NGAL in early detection of renal injury

Urinary Biomarkers KIM-1 and NGAL for Detection of Chronic Kidney Disease of Uncertain Etiology (CKDu among Agricultural Communities in Sri Lanka.

Directory of Open Access Journals (Sweden)

Pallagae Mangala C S De Silva

2016-09-01

Full Text Available Chronic Kidney Disease of uncertain etiology (CKDu is an emerging epidemic among farming communities in rural Sri Lanka. Victims do not exhibit common causative factors, however, histopathological studies revealed that CKDu is a tubulointerstitial disease. Urine albumin or albumin-creatinine ratio is still being used as a traditional diagnostic tool to identify CKDu, but accuracy and prevalence data generated are questionable. Urinary biomarkers have been used in similar nephropathy and are widely recognised for their sensitivity, specificity and accuracy in determining CKDu and early renal injury. However, these biomarkers have never been used in diagnosing CKDu in Sri Lanka. Male farmers (n = 1734 were recruited from 4 regions in Sri Lanka i.e. Matara and Nuwara Eliya (farming locations with no CKDu prevalence and two CKDu emerging locations from Hambantota District in Southern Sri Lanka; Angunakolapelessa (EL1 and Bandagiriya (EL2. Albuminuria (ACR ≥ 30mg/g; serum creatinine based estimation of glomerular filtration rate (eGFR; creatinine normalized urinary kidney injury molecule (KIM-1 and neutrophil gelatinase-associated lipocalin (NGAL were measured. Fourteen new CKDu cases (18% from EL1 and nine CKDu cases (9% from EL2 were recognized for the first time from EL1, EL2 locations, which were previously considered as non-endemic of the disease and associated with persistent albuminuria (ACR ≥ 30mg/g Cr. No CKDu cases were identified in non-endemic study locations in Matara (CM and Nuwara Eliya (CN. Analysis of urinary biomarkers showed urinary KIM-1 and NGAL were significantly higher in new CKDu cases in EL1 and EL2. However, we also reported significantly higher KIM-1 and NGAL in apparently healthy farmers in EL 1 and EL 2 with comparison to both control groups. These observations may indicate possible early renal damage in absence of persistent albuminuria and potential capabilities of urinary KIM-1 and NGAL in early detection of renal

Urinary Biomarkers KIM-1 and NGAL for Detection of Chronic Kidney Disease of Uncertain Etiology (CKDu) among Agricultural Communities in Sri Lanka.

Science.gov (United States)

De Silva, Pallagae Mangala C S; Mohammed Abdul, Khaja Shameem; Eakanayake, Eakanayake M D V; Jayasinghe, Sudheera Sammanthi; Jayasumana, Channa; Asanthi, Hewa Bandulage; Perera, Hettiarachigae S D; Chaminda, Gamage G Tushara; Chandana, Ediriweera P S; Siribaddana, Sisira H

2016-09-01

Chronic Kidney Disease of uncertain etiology (CKDu) is an emerging epidemic among farming communities in rural Sri Lanka. Victims do not exhibit common causative factors, however, histopathological studies revealed that CKDu is a tubulointerstitial disease. Urine albumin or albumin-creatinine ratio is still being used as a traditional diagnostic tool to identify CKDu, but accuracy and prevalence data generated are questionable. Urinary biomarkers have been used in similar nephropathy and are widely recognised for their sensitivity, specificity and accuracy in determining CKDu and early renal injury. However, these biomarkers have never been used in diagnosing CKDu in Sri Lanka. Male farmers (n = 1734) were recruited from 4 regions in Sri Lanka i.e. Matara and Nuwara Eliya (farming locations with no CKDu prevalence) and two CKDu emerging locations from Hambantota District in Southern Sri Lanka; Angunakolapelessa (EL1) and Bandagiriya (EL2). Albuminuria (ACR ≥ 30mg/g); serum creatinine based estimation of glomerular filtration rate (eGFR); creatinine normalized urinary kidney injury molecule (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) were measured. Fourteen new CKDu cases (18%) from EL1 and nine CKDu cases (9%) from EL2 were recognized for the first time from EL1, EL2 locations, which were previously considered as non-endemic of the disease and associated with persistent albuminuria (ACR ≥ 30mg/g Cr). No CKDu cases were identified in non-endemic study locations in Matara (CM) and Nuwara Eliya (CN). Analysis of urinary biomarkers showed urinary KIM-1 and NGAL were significantly higher in new CKDu cases in EL1 and EL2. However, we also reported significantly higher KIM-1 and NGAL in apparently healthy farmers in EL 1 and EL 2 with comparison to both control groups. These observations may indicate possible early renal damage in absence of persistent albuminuria and potential capabilities of urinary KIM-1 and NGAL in early detection of renal injury

Improvements to the extraction of an AlGaN/GaN HEMT small-signal model

International Nuclear Information System (INIS)

Pu Yan; Pang Lei; Wang Liang; Chen Xiaojuan; Li Chengzhan; Liu Xinyu

2009-01-01

The accurate extraction of AlGaN/GaN HEMT small-signal models, which is an important step in large-signal modeling, can exactly reflect the microwave performance of the physical structure of the device. A new method of extracting the parasitic elements is presented, and an open dummy structure is introduced to obtain the parasitic capacitances. With a Schottky resistor in the gate, a new method is developed to extract R g . In order to characterize the changes of the depletion region under various drain voltages, the drain delay factor is involved in the output conductance of the device. Compared to the traditional method, the fitting of S 11 and S 22 is improved, and f T and f max can be better predicted. The validity of the proposed method is verified with excellent correlation between the measured and simulated S-parameters in the range of 0.1 to 26.1 GHz. (semiconductor devices)

Magnetic flux creep in HTSC and Anderson-Kim theory

International Nuclear Information System (INIS)

Lykov, A.N.

2014-01-01

The theoretical and experimental data on flux creep in high-temperature superconductors (HTSC) were analyzed in the review paper. On the one hand, the main attention is paid to the most striking experimental results which have had a significant influence on the investigations of flux creep in HTSC. On the other hand, the analysis of theoretical studies is concentrated on the works, which explain the features of flux creep on the basis of the Anderson-Kim (AK) theory modifications, and received previously unsufficient attention. However, it turned out that the modified AK theory could explain a lot of features of flux creep in HTSC: the scaling behaviour of current-voltage curves of HTSC, the finite rate of flux creep at ultra low temperatures, the logarithmic dependence of effective pinning potential as a function of transport current and its decrease with temperature. The harmonic potential field which is used in this approach makes it possible to solve accurately the both problems: viscous vortex motion and flux creep in this field. Moreover the distribution of pinning potential and the interaction of vortices with each other are taken into account in the approach. Thus, the modification of the AK theory consists, essentially, in its detailed elaboration and approaching to real situations in superconductors

Investigation of In0.7Ga0.3As/In0.7Al0.3As metamorphic HEMT- heterostructures by photoluminescence spectroscopy

International Nuclear Information System (INIS)

LETT', Prof. Popova 5, St. Petersburg 197376 (Russian Federation))" data-affiliation=" (Saint-Petersburg Electrotechnical University LETT', Prof. Popova 5, St. Petersburg 197376 (Russian Federation))" >Romanovskiy, D S; LETT', Prof. Popova 5, St. Petersburg 197376 (Russian Federation))" data-affiliation=" (Saint-Petersburg Electrotechnical University LETT', Prof. Popova 5, St. Petersburg 197376 (Russian Federation))" >Tarasov, S A; Galiev, G B; Pushkarev, S S

2014-01-01

Low-temperature photoluminescence and photoreflectance have been studied in several metamorphic HEMT- (MHEMT-) heterostructures with the same active regions and different buffer layer designs grown by solid-source molecular beam epitaxy. The indium mole fraction in InAlAs/InGaAs/InAlAs single quantum well (QW) is 0.7. It was found that structures with step-graded metamorphic buffer have better quality. Also it was shown that mismatched superlattices in metamorphic buffer can influence on the half-width of photoluminescence spectra. The possible attribution of photoluminescence and photoreflectance spectral lines and their thermal behaviour are critically discussed

Reduction of proteinuria in adriamycin-induced nephropathy is associated with reduction of renal kidney injury molecule (Kim-1) over time

NARCIS (Netherlands)

Kramer, Andrea B.; van Timmeren, Mirjan M.; Schuurs, Theo A.; Vaidya, Vishal S.; Bonventre, Joseph V.; van Goor, Harry; Navis, Gerjan

Kramer AB, van Timmeren MM, Schuurs TA, Vaidya VS, Bonventre JV, van Goor H, Navis G. Reduction of proteinuria in adriamycin-induced nephropathy is associated with reduction of renal kidney injury molecule (Kim-1) over time. Am J Physiol Renal Physiol 296: F1136-F1145, 2009. First published February

On recoverable behavior of PBTI in AlGaN/GaN MOS-HEMT

Science.gov (United States)

Acurio, E.; Crupi, F.; Magnone, P.; Trojman, L.; Meneghesso, G.; Iucolano, F.

2017-06-01

This experimental study focuses on the positive bias temperature instability (PBTI) in a fully recessed-gate AlGaN/GaN MOS-HEMT. A positive stress voltage to the gate results in positive threshold voltage shift (ΔVth), which is attributed to the trapping of electrons from the GaN layer into the pre-existing oxide traps. The trapping rate exhibits a universal decreasing behavior as a function of the number of filled traps, independently of stress time, stress voltage, stress temperature, and device-to-device variability. The stress-induced ΔVth can be fully recovered by applying a small negative voltage, which causes the electron de-trapping. In the explored time window (between 1 s and thousands of s), the recovery dynamics is well described by the superimposition of two exponential functions associated with two different traps. Both trap time constants are independent of the stress voltage, decrease with temperature and increase with the recovery voltage. The activation energy of the slower trap is 0.93 eV, while the faster trap exhibits an activation energy with a large spread in the range between 0.45 eV and 0.82 eV.

Theoretical and experimental studies of the current–voltage and capacitance–voltage of HEMT structures and field-effect transistors

Energy Technology Data Exchange (ETDEWEB)

Tarasova, E. A.; Obolenskaya, E. S., E-mail: obolensk@rf.unn.ru; Hananova, A. V.; Obolensky, S. V. [Lobachevsky State University of Nizhny Novgorod (NNSU) (Russian Federation); Zemliakov, V. E.; Egorkin, V. I. [National Research University of Electronic Technology (MIET) (Russian Federation); Nezhenzev, A. V. [Lobachevsky State University of Nizhny Novgorod (NNSU) (Russian Federation); Saharov, A. V.; Zazul’nokov, A. F.; Lundin, V. V.; Zavarin, E. E. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation); Medvedev, G. V. [JSC RPE Salut (Russian Federation)

2016-12-15

The sensitivity of classical n{sup +}/n{sup –} GaAs and AlGaN/GaN structures with a 2D electron gas (HEMT) and field-effect transistors based on these structures to γ-neutron exposure is studied. The levels of their radiation hardness were determined. A method for experimental study of the structures on the basis of a differential analysis of their current–voltage characteristics is developed. This method makes it possible to determine the structure of the layers in which radiation-induced defects accumulate. A procedure taking into account changes in the plate area of the experimentally measured barrier-contact capacitance associated with the emergence of clusters of radiation-induced defects that form dielectric inclusions in the 2D-electron-gas layer is presented for the first time.

Improved performance of AlGaN/GaN HEMT by N2O plasma pre-treatment

International Nuclear Information System (INIS)

Mi Min-Han; Zhang Kai; Zhao Sheng-Lei; Wang Chong; Zhang Jin-Cheng; Ma Xiao-Hua; Hao Yue

2015-01-01

The influence of an N 2 O plasma pre-treatment technique on characteristics of AlGaN/GaN high electron mobility transistor (HEMT) prepared by using a plasma-enhanced chemical vapor deposition (PECVD) system is presented. After the plasma treatment, the peak transconductance (g m ) increases from 209 mS/mm to 293 mS/mm. Moreover, it is observed that the reverse gate leakage current is lowered by one order of magnitude and the drain current dispersion is improved in the plasma-treated device. From the analysis of frequency-dependent conductance, it can be seen that the trap state density (D T ) and time constant (τ T ) of the N 2 O-treated device are smaller than those of a non-treated device. The results indicate that the N 2 O plasma pre-pretreatment before the gate metal deposition could be a promising approach to enhancing the performance of the device. (paper)

Teasing out the compressed education debates in contemporary South Korea: Media portrayal of figure skater Yuna Kim

OpenAIRE

Kim, Hye Jin

2013-01-01

In this thesis, I argue that the heated debates about South Korea’s education policy consist of problems that arise from different genres of discourses that in turn belong to different historical moments and education values. I engage in a media discourse analysis of the reportage on South Korean international sport celebrity Yuna Kim that highlight the key education debates currently taking place in South Korea. First, I deal with the neologism umchinttal (my mom’s friend’s daughter) as an i...

Improved AlGaN/GaN HEMTs Grown on Si Substrates Using Stacked AlGaN/AlN Interlayer by MOCVD

International Nuclear Information System (INIS)

Wang Yong; Yu Nai-Sen; Li Ming; Lau Kei-May

2011-01-01

AlGaN/GaN high electron mobility transistors (HEMTs) are grown on 2-inch Si (111) substrates by MOCVD. The stacked AlGaN/AlN interlayer with different AlGaN thickness and indium surfactant doped is designed and optimized to relieve the tensile stress during GaN epitaxial growth. The top 1.0μm GaN buffer layer grown on the optimized AlGaN/AlN interlayer shows a crack-free and shining surface. The XRD results show that GaN(002) FWHM is 480 arcsec and GaN(102) FWHM is 900 arcsec. The AGaN/GaN HEMTs with optimized and non-optimized AlGaN/AlN interlayer are grown and processed for comparison and the dc and rf characteristics are characterized. For the dc characteristics of the device with optimized AlGaN/AlN interlayer, maximum drain current density I dss of 737mA/mm, peak transconductance G m of 185mS/mm, drain leakage current density I ds of 1.7μA/mm, gate leakage current density I gs of 24.8 μA/mm and off-state breakdown voltage V BR of 67 V are achieved with L g /W g /L gs /L gd = 1/10/1/1 μm. For the small signal rf characteristics of the device with optimized AlGaN/AlN interlayer, current gain cutoff frequency f T of 8.3 GHz and power gain cutoff frequency f max of 19.9 GHz are achieved with L g /W g /L gs /L gd = 1/100/1/1 μm. Furthermore, the best rf performance with f T of 14.5 GHz and f max of 37.3 GHz is achieved with a reduced gate length of 0.7μm. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

The physical mechanism on the threshold voltage temperature stability improvement for GaN HEMTs with pre-fluorination argon treatment

Energy Technology Data Exchange (ETDEWEB)

Wang, Yun-Hsiang [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 119260 (Singapore); A*STAR Institute of Microelectronics, Singapore 117685 (Singapore); Liang, Yung C., E-mail: chii@nus.edu.sg [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 119260 (Singapore); National University of Singapore (Suzhou) Research Institute, Suzhou 215123 (China); Samudra, Ganesh S. [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 119260 (Singapore); Huang, Chih-Fang [Department of Electrical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Kuo, Wei-Hung [Industrial Technology Research Institute, Chutung 31040, Taiwan (China); Lo, Guo-Qiang [A*STAR Institute of Microelectronics, Singapore 117685 (Singapore)

2016-06-06

In this paper, a normally-off AlGaN/GaN MIS-HEMT with improved threshold voltage (V{sub TH}) thermal stability is reported with investigations on its physical mechanism. The normally-off operation of the device is achieved from novel short argon plasma treatment (APT) prior to the fluorine plasma treatment (FPT) on Al{sub 2}O{sub 3} gate dielectrics. For the MIS-HEMT with FPT only, its V{sub TH} drops from 4.2 V at room temperature to 0.5 V at 200 °C. Alternatively, for the device with APT-then-FPT process, its V{sub TH} can retain at 2.5 V at 200 °C due to the increased amount of deep-level traps that do not emit electrons at 200 °C. This thermally stable V{sub TH} makes this device suitable for high power applications. The depth profile of the F atoms in Al{sub 2}O{sub 3}, measured by the secondary ion mass spectroscopy, reveals a significant increase in the F concentration when APT is conducted prior to FPT. The X-ray photoelectron spectroscopy (XPS) analysis on the plasma-treated Al{sub 2}O{sub 3} surfaces observes higher composition of Al-F bonds if APT was applied before FPT. The enhanced breaking of Al-O bonds due to Ar bombardment assisted in the increased incorporation of F radicals at the surface during the subsequent FPT process. The Schrödinger equation of Al{sub 2}O{sub x}F{sub y} cells, with the same Al-F compositions as obtained from XPS, was solved by Gaussian 09 molecular simulations to extract electron state distribution as a function of energy. The simulation results show creation of the deeper trap states in the Al{sub 2}O{sub 3} bandgap when APT is used before FPT. Finally, the trap distribution extracted from the simulations is verified by the gate-stress experimental characterization to confirm the physical mechanism described.

On a two-layer Si_3N_4/SiO_2 dielectric mask for low-resistance ohmic contacts to AlGaN/GaN HEMTs

International Nuclear Information System (INIS)

Arutyunyan, S. S.; Pavlov, A. Yu.; Pavlov, B. Yu.; Tomosh, K. N.; Fedorov, Yu. V.

2016-01-01

The fabrication of a two-layer Si_3N_4/SiO_2 dielectric mask and features of its application in the technology of non-fired epitaxially grown ohmic contacts for high-power HEMTs on AlGaN/GaN heterostructures are described. The proposed Si_3N_4/SiO_2 mask allows the selective epitaxial growth of heavily doped ohmic contacts by nitride molecular-beam epitaxy and the fabrication of non-fired ohmic contacts with a resistance of 0.15–0.2 Ω mm and a smooth surface and edge morphology.

Channel Temperature Determination for AlGaN/GaN HEMTs on SiC and Sapphire

Science.gov (United States)

Freeman, Jon C.; Mueller, Wolfgang

2008-01-01

Numerical simulation results (with emphasis on channel temperature) for a single gate AlGaN/GaN High Electron Mobility Transistor (HEMT) with either a sapphire or SiC substrate are presented. The static I-V characteristics, with concomitant channel temperatures (T(sub ch)) are calculated using the software package ATLAS, from Silvaco, Inc. An in-depth study of analytical (and previous numerical) methods for the determination of T(sub ch) in both single and multiple gate devices is also included. We develop a method for calculating T(sub ch) for the single gate device with the temperature dependence of the thermal conductivity of all material layers included. We also present a new method for determining the temperature on each gate in a multi-gate array. These models are compared with experimental results, and show good agreement. We demonstrate that one may obtain the channel temperature within an accuracy of +/-10 C in some cases. Comparisons between different approaches are given to show the limits, sensitivities, and needed approximations, for reasonable agreement with measurements.

Enhancement mode operation in AlInN/GaN (MIS)HEMTs on Si substrates using a fluorine implant

International Nuclear Information System (INIS)

Zaidi, Z H; Lee, K B; Qian, H; Jiang, S; Houston, P A; Guiney, I; Wallis, D J; Humphreys, C J

2015-01-01

We have demonstrated enhancement mode operation of AlInN/GaN (MIS)HEMTs on Si substrates using the fluorine treatment technique. The plasma RF power and treatment time was optimized to prevent the penetration of the fluorine into the channel region to maintain high channel conductivity and transconductance. An analysis of the threshold voltage was carried out which defined the requirement for the fluorine sheet concentration to exceed the charge at the dielectric/AlInN interface to achieve an increase in the positive threshold voltage after deposition of the dielectric. This illustrates the importance of control of both the plasma conditions and the interfacial charge for a reproducible threshold voltage. A positive threshold voltage of +3 V was achieved with a maximum drain current of 367 mA mm −1 at a forward gate bias of 10 V. (paper)

Electrical properties of AlGaN/GaN HEMTs in stretchable geometries

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Tompkins, R. P.; Mahaboob, I.; Shahedipour-Sandvik, F.; Lazarus, N.

2017-10-01

Many biological materials are naturally soft and stretchable, far more so than crystalline semiconductors. Creating systems that can be placed directly on a surface such as human skin has required new approaches in electronic device design and materials, a field known as stretchable electronics. One common method for fabricating a highly brittle semiconductor device able to survive tens of percent strain is to incorporate stress relief structures ('waves'). Although the mechanical advantages of this approach are well known, the effects on the electrical behavior of a device such as a transistor compared to a more traditional geometry have not been studied. Here, AlGaN/GaN high electron mobility transistors (HEMTs) grown on rigid sapphire substrates were fabricated in a common wavy geometry, a sinusoid, with dimensions similar to those used in stretchable electronics. The study analyzes control parameters available to the designer including gate location along the sinusoid, angle the source-drain contacts make with the gate, as well as variation of the gate length at the peak of the sinusoid. Common electrical parameters such as saturation current density, threshold voltage, and transconductance were compared between the sinusoidal and conventional straight geometries and results found to fall to within experimental uncertainty, suggesting shifting to a stretchable geometry is possible without appreciably degrading semiconductor device performance.

Endogenous Tim-1 (Kim-1) promotes T-cell responses and cell-mediated injury in experimental crescentic glomerulonephritis.

Science.gov (United States)

Nozaki, Yuji; Nikolic-Paterson, David J; Snelgrove, Sarah L; Akiba, Hisaya; Yagita, Hideo; Holdsworth, Stephen R; Kitching, A Richard

2012-05-01

The T-cell immunoglobulin mucin 1 (Tim-1) modulates CD4(+) T-cell responses and is also expressed by damaged proximal tubules in the kidney where it is known as kidney injury molecule-1 (Kim-1). We sought to define the role of endogenous Tim-1 in experimental T-cell-mediated glomerulonephritis induced by sheep anti-mouse glomerular basement membrane globulin acting as a planted foreign antigen. Tim-1 is expressed by infiltrating activated CD4(+) cells in this model, and we studied the effects of an inhibitory anti-Tim-1 antibody (RMT1-10) on immune responses and glomerular disease. Crescentic glomerulonephritis, proliferative injury, and leukocyte accumulation were attenuated following treatment with anti-Tim-1 antibodies, but interstitial foxp3(+) cell accumulation and interleukin-10 mRNA were increased. T-cell proliferation and apoptosis decreased in the immune system along with a selective reduction in Th1 and Th17 cellular responses both in the immune system and within the kidney. The urinary excretion and renal expression of Kim-1 was reduced by anti-Tim-1 antibodies reflecting diminished interstitial injury. The effects of anti-Tim-1 antibodies were not apparent in the early phase of renal injury, when the immune response to sheep globulin was developing. Thus, endogenous Tim-1 promotes Th1 and Th17 nephritogenic immune responses and its neutralization reduces renal injury while limiting inflammation in cell-mediated glomerulonephritis.

Viscous flux flow velocity and stress distribution in the Kim model of a long rectangular slab superconductor

Science.gov (United States)

Yang, Yong; Chai, Xueguang

2018-05-01

When a bulk superconductor endures the magnetization process, enormous mechanical stresses are imposed on the bulk, which often leads to cracking. In the present work, we aim to resolve the viscous flux flow velocity υ 0/w, i.e. υ 0 (because w is a constant) and the stress distribution in a long rectangular slab superconductor for the decreasing external magnetic field (B a ) after zero-field cooling (ZFC) and field cooling (FC) using the Kim model and viscous flux flow equation simultaneously. The viscous flux flow velocity υ 0/w and the magnetic field B* at which the body forces point away in all of the slab volumes during B a reduction, are determined by both B a and the decreasing rate (db a /dt) of the external magnetic field normalized by the full penetration field B p . In previous studies, υ 0/w obtained by the Bean model with viscous flux flow is only determined by db a /dt, and the field B* that is derived only from the Kim model is a positive constant when the maximum external magnetic field is chosen. This means that the findings in this paper have more physical contents than the previous results. The field B* stress changing with decreasing field B a after ZFC if B* ≤ 0. The effect of db a /dt on the stress is significant in the cases of both ZFC and FC.

Helen Kim as New Woman and Collaborator: A Comprehensive Assessment of Korean Collaboration under Japanese Colonial Rule

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AhRan Ellie Bae

2017-02-01

Full Text Available Although almost seventy years has passed since Korea's liberation from Japanese rule, the issue of collaboration still haunts Korea today. Attempts to resolve this issue have tended to focus attention on the traitorous actions of "collaborators" without considering the gray areas that surround their actions such as the circumstances that influenced the accused to commit their alleged traitorous acts and the intentions that drove their decisions. Helen Kim, as a "new woman" and an educator, valued the necessity of providing education for women. Yet, her efforts to realize this goal, to the contrary, forced her into actions that would later be used to construct a reputation as a Japanese collaborator. Korea's nationalist historiography has a tendency to polarize this issue by categorizing a "collaborator" as either a traitor or a patriot. However, when we take a closer look at these collaborators' lives, we discover that most collaboration happened in gray areas where it is often difficult to clearly draw a line between treason and collaboration. Helen Kim's case suggests that the issue of collaboration cannot be fully explained by nationalist historiography's framework and we must give attention to these gray areas. Through her story I hope to complicate the issue of collaboration by raising questions that address the gray areas that surround the actions of "collaborators." In doing so, I hope to challenge the nationalist historiography's propensity to oversimplify this issue and present a more nuanced understanding of it.

High breakdown voltage in AlGaN/GaN HEMTs using AlGaN/GaN/AlGaN quantum-well electron-blocking layers.

Science.gov (United States)

Lee, Ya-Ju; Yao, Yung-Chi; Huang, Chun-Ying; Lin, Tai-Yuan; Cheng, Li-Lien; Liu, Ching-Yun; Wang, Mei-Tan; Hwang, Jung-Min

2014-01-01

In this paper, we numerically study an enhancement of breakdown voltage in AlGaN/GaN high-electron-mobility transistors (HEMTs) by using the AlGaN/GaN/AlGaN quantum-well (QW) electron-blocking layer (EBL) structure. This concept is based on the superior confinement of two-dimensional electron gases (2-DEGs) provided by the QW EBL, resulting in a significant improvement of breakdown voltage and a remarkable suppression of spilling electrons. The electron mobility of 2-DEG is hence enhanced as well. The dependence of thickness and composition of QW EBL on the device breakdown is also evaluated and discussed.

Multiscale Modelling of Electronic and Thermal Transport : Thermoelectrics, Turbostratic 2D Materials and Diamond/c-BN HEMT

Science.gov (United States)

Narendra, Namita

Multiscale modelling has become necessary with the advent of low dimensional devices as well as use of heterostructures which necessitates atomistic treatment of the interfaces. Multiscale methodology is able to capture the quantum mechanical atomistic details while enabling the simulation of micro-scale structures at the same time. In this thesis, multiscale modelling has been applied to study transport in thermoelectrics, turbostratic 2D MoS2/WS 2 heterostructure and diamond/c-BN high mobility electron transistor (HEMT). The possibility of enhanced thermoelectric properties through nanostructuring is investigated theoretically in a p-type Bi2Te3/Sb 2Te3 heterostructure. A multi-scale modeling approach is adopted to account for the atomistic characteristics of the interface as well as the carrier/phonon transport properties in the larger scales. The calculations clearly illustrate the desired impact of carrier energy filtering at the potential barrier by locally boosting the power factor over a sizable distance in the well region. Further, the phonon transport analysis illustrates a considerable reduction in the thermal conductivity at the heterointerface. Both effects are expected to provide an effective means to engineer higher zT in this material system. Next, power factor enhancement through resonant doping is explored in Bi2Te3 based on a detailed first-principles study. Of the dopant atoms investigated, it is found that the formation of resonant states may be achieved with In, Po and Na, leading potentially to significant increase in the thermoelectric efficiency at room temperature. While doping with Po forms twin resonant state peaks in the valence and conduction bands, the incorporation of Na or In results in the resonant states close to the valence band edge. Further analysis reveals the origin of these resonant states. Transport calculations are also carried out to estimate the anticipated level of enhancement. Next, in-plane and cross-plane transport

An Inquiry of Intentions in Kim Hye-yong's 'First Meeting': A North Korean Short Story in Korea Today (2007).

OpenAIRE

Alzo David-West

2013-01-01

This paper examines the problem of the intentional fallacy in the North Korean short story 'First Meeting' by Kim Hye-yong. Serially published in Korea Today in 2007, the nationalist allegory centres on Shin Ch'ong-mi, a young female journalist in Pyongyang, who falls in love with her penfriend Song-u, a soldier in the Korean People's Army, and struggles to remain devoted to him when he suddenly stops writing. With the literary-critical method of counterintuitive reading, the inquiry analyses...

Influence of the gate edge on the reverse leakage current of AlGaN/GaN HEMTs

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YongHe Chen

2015-09-01

Full Text Available By comparing the Schottky diodes of different area and perimeter, reverse gate leakage current of AlGaN/GaN high mobility transistors (HEMT at gate bias beyond threshold voltage is studied. It is revealed that reverse current consists of area-related and perimeter-related current. An analytical model of electric field calculation is proposed to obtain the average electric field around the gate edge at high revers bias and estimate the effective range of edge leakage current. When the reverse bias increases, the increment of electric field is around the gate edge of a distance of ΔL, and perimeter-related gate edge current keeps increasing. By using the calculated electric field and the temperature-dependent current-voltage measurements, the edge gate leakage current mechanism is found to be Fowler-Nordheim tunneling at gate bias bellows -15V caused by the lateral extended depletion region induced barrier thinning. Effective range of edge current of Schottky diodes is about hundred to several hundred nano-meters, and is different in different shapes of Schottky diodes.

The trouble with halos: invited commentary on Kim, S., & Harris, P. L. (2014). Children prefer to learn from mind-readers. British Journal of Developmental Psychology.

Science.gov (United States)

Richert, Rebekah A

2014-11-01

This commentary on Kim and Harris (2014) addresses the authors' interpretation of the halo effect, in which 5- to 6-year-old children preferentially agreed with an informant who could read other people's minds, regardless of domain of knowledge. © 2014 The British Psychological Society.

Can You Anchor a Shimmering Nation State via Regional Indigenous Roots? Kim Scott talks to Anne Brewster about That Deadman Dance

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Anne Brewster

2011-10-01

Full Text Available This interview focuses mainly on Kim Scott’s new novel That Deadman Dance which won the regional Commonwealth Writers Prize (Southeast Asian and Pacific region and the Miles Franklin Award. The topics of conversation include Scott’s involvement in the Noongar language project (and the relationship of this project to the novel, the novel itself, the challenges of writing in English, the resistance paradigm and indigenous sovereignty and nationalism.

Modeling and simulation of enhancement mode p-GaN Gate AlGaN/GaN HEMT for RF circuit switch applications

Science.gov (United States)

Panda, D. K.; Lenka, T. R.

2017-06-01

An enhancement mode p-GaN gate AlGaN/GaN HEMT is proposed and a physics based virtual source charge model with Landauer approach for electron transport has been developed using Verilog-A and simulated using Cadence Spectre, in order to predict device characteristics such as threshold voltage, drain current and gate capacitance. The drain current model incorporates important physical effects such as velocity saturation, short channel effects like DIBL (drain induced barrier lowering), channel length modulation (CLM), and mobility degradation due to self-heating. The predicted I d-V ds, I d-V gs, and C-V characteristics show an excellent agreement with the experimental data for both drain current and capacitance which validate the model. The developed model was then utilized to design and simulate a single-pole single-throw (SPST) RF switch.

Role of AlGaN/GaN interface traps on negative threshold voltage shift in AlGaN/GaN HEMT

Science.gov (United States)

Malik, Amit; Sharma, Chandan; Laishram, Robert; Bag, Rajesh Kumar; Rawal, Dipendra Singh; Vinayak, Seema; Sharma, Rajesh Kumar

2018-04-01

This article reports negative shift in the threshold-voltage in AlGaN/GaN high electron mobility transistor (HEMT) with application of reverse gate bias stress. The device is biased in strong pinch-off and low drain to source voltage condition for a fixed time duration (reverse gate bias stress), followed by measurement of transfer characteristics. Negative threshold voltage shift after application of reverse gate bias stress indicates the presence of more carriers in channel as compared to the unstressed condition. We propose the presence of AlGaN/GaN interface states to be the reason of negative threshold voltage shift, and developed a process to electrically characterize AlGaN/GaN interface states. We verified the results with Technology Computer Aided Design (TCAD) ATLAS simulation and got a good match with experimental measurements.

Proceedings of the International Conference on Educational Data Mining (EDM) (5th, Chania, Greece, June 19-21, 2012)

Science.gov (United States)

International Educational Data Mining Society, 2012

2012-01-01

The 5th International Conference on Educational Data Mining (EDM 2012) is held in picturesque Chania on the beautiful Crete island in Greece, under the auspices of the International Educational Data Mining Society (IEDMS). The EDM 2012 conference is a leading international forum for high quality research that mines large data sets of educational…

A STUDY OF MICROBES IN FRUIT JUICES, KIMS-AMALAPURAM

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Nagaraja

2015-12-01

Full Text Available INTRODUCTION Fruit and sugarcane juices are nutritious drinks with great taste and health benefits. Food borne illnesses associated with consumption of Fruit and sugarcane juices at several places in India and elsewhere. Fruit juices were served with added ice pieces. Hygienic standards are not maintained while transporting from the field to the place of extraction and preparation. Hence a rapid review of the fruit juices from street vendors has been undertaken along with sugarcane juice. Raw sugarcane juice is a refreshing juice in many parts of Andhra Pradesh. The present study is to assess the prevalence of different organisms from different fruit juices collected from street vendors. METHODS Fruit juices are collected namely sugarcane, sweet lemon, orange, grape apple, pineapple pomegranate. A total 100 samples of fruit juices were collected from road side from different vendors. 150 ml of each variety of fruit juices were collected from different vendors in screw capped bottles and subjected to microbial analysis, processed with in 30mts in the department of microbiology at KIMS by standard methods. RESULTS The analysed samples of fruit juices are found to be contaminated with different bacteria, Escherichia coli 30% Klebsiella pneumoniae 10% Staphylococcus aureus 20% Enterococcus faecalis 04% Pseudomonas aeruginosa 10% ASB 04% (aerobic spore bearers Micrococci 02% Proteus 20% Salmonella. Shigella and Vibrios were not isolated. CONCLUSION It is high time that street vendors should have health education by volunteers, health workers from PHC (primary health centers and people well versed with community medicine practice for implementation of standard hygienic protocols may reduce contamination of fruit and sugarcane juices The concerned health authorities need to ensure and insist to follow the protocols by the vendors and license holders to the vendors.

On a two-layer Si{sub 3}N{sub 4}/SiO{sub 2} dielectric mask for low-resistance ohmic contacts to AlGaN/GaN HEMTs

Energy Technology Data Exchange (ETDEWEB)

Arutyunyan, S. S., E-mail: spartakmain@gmail.com; Pavlov, A. Yu.; Pavlov, B. Yu.; Tomosh, K. N.; Fedorov, Yu. V. [Russian Academy of Sciences, Institute of Ultrahigh Frequency Semiconductor Electronics (Russian Federation)

2016-08-15

The fabrication of a two-layer Si{sub 3}N{sub 4}/SiO{sub 2} dielectric mask and features of its application in the technology of non-fired epitaxially grown ohmic contacts for high-power HEMTs on AlGaN/GaN heterostructures are described. The proposed Si{sub 3}N{sub 4}/SiO{sub 2} mask allows the selective epitaxial growth of heavily doped ohmic contacts by nitride molecular-beam epitaxy and the fabrication of non-fired ohmic contacts with a resistance of 0.15–0.2 Ω mm and a smooth surface and edge morphology.

Evaluation of a commercially available ELISA kit for quantifying imidacloprid residues in Erthrina sandwicensis leaves for management of the Erythrina gall wasp, Quadrastichus erythrinae Kim.

Science.gov (United States)

Joseph Fischer; Brian Strom; Sheri Smith

2009-01-01

The erythrina gall wasp (EGW), Quadrastichus erythrinae Kim 2004, was first detected in Hawaii in 2005 and has been infesting and killing Erythrina trees throughout the island chain since. It is believed EGW originated from Africa (Messing et al. 2009). Its host range appears to be limited to Erythrina; its...

Interface traps at Al2O3/InAlN/GaN MOS-HEMT -on- 200 mm Si

Science.gov (United States)

Kumar, Sandeep; Remesh, Nayana; Dolmanan, S. B.; Tripathy, S.; Raghavan, S.; Muralidharan, R.; Nath, Digbijoy N.

2017-11-01

We report on the characterization of the interfaces of Al2O3/InAlN/GaN HEMT structure grown on 200 mm diameter silicon using conductance dispersion technique. Irreversible threshold voltage (VTH) shift of up to +∼2.5 V was observed due to the gate stress induced activation of acceptor states. Further, frequency dependent VTH shift during capacitance voltage measurements were also recorded due to the presence of slow traps at InAlN/GaN interface. The conductance dispersion indicated the presence of acceptor traps of the order of ∼4 × 1012 to 7 × 1013 cm-2 eV-1 with a time constant of ∼10 to 350 μs at the InAlN/GaN interface. Trap density at the Al2O3/InAlN was found to be in similar range but with a time constant of ∼2 μs. The presence of high density of traps at InAlN/GaN interface is attributed to the unavoidable growth interruption before the start of InAlN growth.

Report on visit from Prof. Kim Lutzen: Friday, 6 November 1998, Korolinska Institute (dept of nursing Stockholm, Sweden

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Kim Lutzen

1999-10-01

Full Text Available Prof. Kim Lutzen contacted the Department of Advanced Nursing Sciences, Unisa, via the Department's Web Page. Prof. Lutzen is the Chair of the Department of Nursing, which offers undergraduate, master and doctoral programmes. This Department of Nursing is situated within the Karolinska Institute, which comprises 29 Departments of Health Sciences, including a number of Medical Departments, Dentistry, Occupational Therapy, Physiotherapy, and Nursing. Prof. Lutzen emphasised that there is no Swedish phrase similar to "nursing science", consequently this t e n seems to be somewhat unfamiliar to the Swedish nurses. *Please note: This is a reduced version of the abstract. Please refer to PDF for full text.

Prospects for 6-party talks: Nuclear weapons are a means of survival for Kim Jong Un

International Nuclear Information System (INIS)

Miyake, Kunihiko

2012-04-01

The author considers the impact of leader Kim Jong Il's death on 6-party talks surrounding the nuclear issue. Firstly, the history of these 6-party talks has to be reexamined to ensure an accurate understanding of their 'objectives and limitations' because the author believes that there are 3 'unpleasant truths' behind these talks, held 6 times since the summer of 2003, that no one wants to talk about. 1. North Korea has no interest in abandoning nuclear weapons; 2. Japan, the U.S., China, and South Korea do not want war; 3. The nuclear issue will not be resolved by 6-party talks. In fact, there is little potential that 6-party talks which aim to resolve the North Korean nuclear issue will move towards a new substantive agreement

The complete larval development of Eurypanopeus canalensis Abele and Kim, 1989 (Crustacea: Brachyura: Panopeidae described from laboratory reared material

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Marcelo U. García-Guerrero

2005-09-01

Full Text Available The estuarine panopeid crab Eurypanopeus canalensis Abele and Kim, 1989, is an eastern tropical Pacific species with a known distribution from the southeastern Gulf of California, Mexico, to Panama. Its complete larval development is fully described and illustrated from laboratory-reared material. The four zoeal stages and the megalopa are compared with two congeneric species from the West Atlantic, E. abbreviatus (Stimpson, 1860 and E. depressus (Smith, 1869. The main differences between larvae of E. canalensis and those of these two species include telson setation and the presence/absence of a stout hook-like spine in the megalopae cheliped ischium.

The Expression of the Femininity and Imperialism : Through comparison study of works of Toshiko Tamura and Myung-soon Kim

OpenAIRE

金, 玟妵

2005-01-01

Toshiko Tamura and Myung-soon Kim flourished in 1910-20 in Japan and Korea. In those days it was an act of a man to write. The feminine was demanded above all to the thing which a woman wrote by the literary world and the society, so that woman does not invade a domain of a man. A lot of studies about that the motherhood is one of a model of feminine, it was used to mobilize a woman for war, while militarism advances. Then is what kind of position was there the femininity at socially and cult...

Electronic and optical properties of HEMT heterostructures with δ-Si doped GaAs/AlGaAs quantum rings — quantum well system

Science.gov (United States)

Sibirmovsky, Y. D.; Vasil'evskii, I. S.; Vinichenko, A. N.; Zhigunov, D. M.; Eremin, I. S.; Kolentsova, O. S.; Safonov, D. A.; Kargin, N. I.

2017-11-01

Samples of δ-Si doped AlGaAs/GaAs/AlGaAs HEMT heterostructures with GaAs quantum rings (QRs) on top of the quantum well (QW) were grown by molecular beam epitaxy and their properties were compared to the reference samples without QRs. The thickness of the QW was 6 - 10 nm for the samples with QRs and 20 nm for the reference samples. Photoluminescence measurements at low temperatures for all samples show at least two distinct lines in addition to the bulk GaAs line. The Hall effect and low temperature magnetotransport measurements at 4 - 320 K show that conductivity with and without illumination decreases significantly with QRs introduction, however the relative photoconductivity increases. Samples with 6 nm QW are insulating, which could be caused by the strong localization of the charge carriers in the QRs.

Specific features of NH3 and plasma-assisted MBE in the fabrication of III-N HEMT heterostructures

International Nuclear Information System (INIS)

Alexeev, A. N.; Krasovitsky, D. M.; Petrov, S. I.; Chaly, V. P.; Mamaev, V. V.; Sidorov, V. G.

2015-01-01

The specific features of how nitride HEMT heterostructures are produced by NH 3 and plasma-assisted (PA) molecular-beam epitaxy (MBE) are considered. It is shown that the use of high-temperature AlN/AlGaN buffer layers grown with ammonia at extremely high temperatures (up to 1150°C) can drastically improve the structural perfection of the active GaN layers and reduce the dislocation density in these layers to values of 9 × 10 8 −1 × 10 9 cm −2 . The use of buffer layers of this kind makes it possible to obtain high-quality GaN/AlGaN heterostructures by both methods. At the same time, in contrast to ammonia MBE which is difficult to apply at T < 500°C (because of the low efficiency of ammonia decomposition), PA MBE is rather effective at low temperatures, e.g., for the growth of InAlN layers lattice-matched with GaN. The results obtained in the MBE growth of AlN/AlGaN/GaN/InAlN heterostructures by both PA-MBE and NH 3 -MBE with an extremely high ammonia flux are demonstrated

Growth and characterization of AlGaN/GaN/AlGaN double-heterojunction high-electron-mobility transistors on 100-mm Si(111) using ammonia-molecular beam epitaxy

Energy Technology Data Exchange (ETDEWEB)

Ravikiran, L.; Radhakrishnan, K., E-mail: ERADHA@ntu.edu.sg; Yiding, Lin; Ng, G. I. [NOVITAS-Nanoelectronics Centre of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Dharmarasu, N.; Agrawal, M.; Arulkumaran, S.; Vicknesh, S. [Temasek Laboratories@NTU, Nanyang Technological University, Singapore 637553 (Singapore)

2015-01-14

To improve the confinement of two-dimensional electron gas (2DEG) in AlGaN/GaN high electron mobility transistor (HEMT) heterostructures, AlGaN/GaN/AlGaN double heterojunction HEMT (DH-HEMT) heterostructures were grown using ammonia-MBE on 100-mm Si substrate. Prior to the growth, single heterojunction HEMT (SH-HEMT) and DH-HEMT heterostructures were simulated using Poisson-Schrödinger equations. From simulations, an AlGaN buffer with “Al” mole fraction of 10% in the DH-HEMT was identified to result in both higher 2DEG concentration (∼10{sup 13 }cm{sup −2}) and improved 2DEG confinement in the channel. Hence, this composition was considered for the growth of the buffer in the DH-HEMT heterostructure. Hall measurements showed a room temperature 2DEG mobility of 1510 cm{sup 2}/V.s and a sheet carrier concentration (n{sub s}) of 0.97 × 10{sup 13 }cm{sup −2} for the DH-HEMT structure, while they are 1310 cm{sup 2}/V.s and 1.09 × 10{sup 13 }cm{sup −2}, respectively, for the SH-HEMT. Capacitance-voltage measurements confirmed the improvement in the confinement of 2DEG in the DH-HEMT heterostructure, which helped in the enhancement of its room temperature mobility. DH-HEMT showed 3 times higher buffer break-down voltage compared to SH-HEMT, while both devices showed almost similar drain current density. Small signal RF measurements on the DH-HEMT showed a unity current-gain cut-off frequency (f{sub T}) and maximum oscillation frequency (f{sub max}) of 22 and 25 GHz, respectively. Thus, overall, DH-HEMT heterostructure was found to be advantageous due to its higher buffer break-down voltages compared to SH-HEMT heterostructure.

Growth and characterization of AlGaN/GaN/AlGaN double-heterojunction high-electron-mobility transistors on 100-mm Si(111) using ammonia-molecular beam epitaxy

International Nuclear Information System (INIS)

Ravikiran, L.; Radhakrishnan, K.; Yiding, Lin; Ng, G. I.; Dharmarasu, N.; Agrawal, M.; Arulkumaran, S.; Vicknesh, S.

2015-01-01

To improve the confinement of two-dimensional electron gas (2DEG) in AlGaN/GaN high electron mobility transistor (HEMT) heterostructures, AlGaN/GaN/AlGaN double heterojunction HEMT (DH-HEMT) heterostructures were grown using ammonia-MBE on 100-mm Si substrate. Prior to the growth, single heterojunction HEMT (SH-HEMT) and DH-HEMT heterostructures were simulated using Poisson-Schrödinger equations. From simulations, an AlGaN buffer with “Al” mole fraction of 10% in the DH-HEMT was identified to result in both higher 2DEG concentration (∼10 13  cm −2 ) and improved 2DEG confinement in the channel. Hence, this composition was considered for the growth of the buffer in the DH-HEMT heterostructure. Hall measurements showed a room temperature 2DEG mobility of 1510 cm 2 /V.s and a sheet carrier concentration (n s ) of 0.97 × 10 13  cm −2 for the DH-HEMT structure, while they are 1310 cm 2 /V.s and 1.09 × 10 13  cm −2 , respectively, for the SH-HEMT. Capacitance-voltage measurements confirmed the improvement in the confinement of 2DEG in the DH-HEMT heterostructure, which helped in the enhancement of its room temperature mobility. DH-HEMT showed 3 times higher buffer break-down voltage compared to SH-HEMT, while both devices showed almost similar drain current density. Small signal RF measurements on the DH-HEMT showed a unity current-gain cut-off frequency (f T ) and maximum oscillation frequency (f max ) of 22 and 25 GHz, respectively. Thus, overall, DH-HEMT heterostructure was found to be advantageous due to its higher buffer break-down voltages compared to SH-HEMT heterostructure

A C-band 55% PAE high gain two-stage power amplifier based on AlGaN/GaN HEMT

International Nuclear Information System (INIS)

Zheng Jia-Xin; Ma Xiao-Hua; Zhang Hong-He; Zhang Meng; Hao Yue; Lu Yang; Zhao Bo-Chao; Cao Meng-Yi

2015-01-01

A C-band high efficiency and high gain two-stage power amplifier based on AlGaN/GaN high electron mobility transistor (HEMT) is designed and measured in this paper. The input and output impedances for the optimum power-added efficiency (PAE) are determined at the fundamental and 2nd harmonic frequency (f 0 and 2f 0 ). The harmonic manipulation networks are designed both in the driver stage and the power stage which manipulate the second harmonic to a very low level within the operating frequency band. Then the inter-stage matching network and the output power combining network are calculated to achieve a low insertion loss. So the PAE and the power gain is greatly improved. In an operation frequency range of 5.4 GHz–5.8 GHz in CW mode, the amplifier delivers a maximum output power of 18.62 W, with a PAE of 55.15% and an associated power gain of 28.7 dB, which is an outstanding performance. (paper)

Association of urinary KIM-1, L-FABP, NAG and NGAL with incident end-stage renal disease and mortality in American Indians with type 2 diabetes mellitus.

Science.gov (United States)

Fufaa, Gudeta D; Weil, E Jennifer; Nelson, Robert G; Hanson, Robert L; Bonventre, Joseph V; Sabbisetti, Venkata; Waikar, Sushrut S; Mifflin, Theodore E; Zhang, Xiaoming; Xie, Dawei; Hsu, Chi-Yuan; Feldman, Harold I; Coresh, Josef; Vasan, Ramachandran S; Kimmel, Paul L; Liu, Kathleen D

2015-01-01

Kidney injury molecule 1 (KIM-1), liver fatty acid-binding protein (L-FABP), N-acetyl-β-D-glucosaminidase (NAG) and neutrophil gelatinase-associated lipocalin (NGAL) are urinary biomarkers of renal tubular injury. We examined their association with incident end-stage renal disease (ESRD) and all-cause mortality in American Indians with type 2 diabetes. Biomarker concentrations were measured in baseline urine samples in 260 Pima Indians who were followed for a median of 14 years. HRs were reported per SD of creatinine (Cr)-normalised log-transformed KIM-1, NAG and NGAL, and for three categories of L-FABP. During follow-up, 74 participants developed ESRD and 101 died. Median concentrations of KIM-1/Cr, NAG/Cr and NGAL/Cr and the proportion of detectable L-FABP were highest in those with macroalbuminuria (p associated with ESRD (HR 1.59, 95% CI 1.20, 2.11) and mortality (HR 1.39, 95% CI 1.06, 1.82); L-FABP/Cr was inversely associated with ESRD (HR [for highest vs lowest tertile] 0.40, 95% CI 0.19, 0.83). Addition of NGAL/Cr to models that included albuminuria and glomerular filtration rate increased the c-statistic for predicting ESRD from 0.828 to 0.833 (p = 0.001) and for death from 0.710 to 0.722 (p = 0.018). Addition of L-FABP/Cr increased the c-statistic for ESRD from 0.828 to 0.832 (p = 0.042). In Pima Indians with type 2 diabetes, urinary concentrations of NGAL and L-FABP are associated with important health outcomes, but they are unlikely to add to risk prediction with standard markers in a clinically meaningful way given the small increase in the c-statistic.

KIM, Steady-State Transport for Fixed Source in 2-D Thermal Reactor by Monte-Carlo

International Nuclear Information System (INIS)

Cupini, E.; De Matteis, A.; Simonini, R.

1980-01-01

1 - Description of problem or function: KIM (K-infinite Monte Carlo) is a program which solves the steady-state linear transport equation for a fixed-source problem (or, by successive fixed-source runs, for the eigenvalue problem) in a two-dimensional infinite thermal reactor lattice. The main quantities computed in some broad energy groups are the following: - Fluxes and cross sections averaged over the region (i.e. a space portion that can be unconnected but contains everywhere the same homogeneous material), grouping of regions, the whole element. - Average absorption and fission rates per nuclide. - Average flux, absorption and production distributions versus energy. 2 - Method of solution: Monte Carlo simulation is used by tracing particle histories from fission birth down through the resonance region until absorption in the thermal range. The program is organised in three sections for fast, epithermal and thermal simulation, respectively; each section implements a particular model for both numerical techniques and cross section representation (energy groups in the fast section, groups or resonance parameters in the epithermal section, points in the thermal section). During slowing down (energy above 1 eV) nuclei are considered as stationary, with the exception of some resonance nuclei whose spacing between resonances is much greater than the resonance width. The Doppler broadening of s-wave resonances of these nuclides is taken into account by computing cross sections at the current neutron energy and at the temperature of the nucleus hit. During thermalization (energy below 1 eV) the thermal motion of some nuclides is also considered, by exploiting scattering kernels provided by the library for light water, heavy water and oxygen at several temperatures. KIM includes splitting and Russian roulette. A characteristic feature of the program is its approach to the lattice geometry. In fact, besides the usual continuous treatment of the geometry using the well

Epitaxial growth of GaN/AlN/InAlN heterostructures for HEMTs in horizontal MOCVD reactors with different designs

Energy Technology Data Exchange (ETDEWEB)

Tsatsulnikov, A. F., E-mail: andrew@beam.ioffe.ru; Lundin, W. V.; Sakharov, A. V.; Zavarin, E. E.; Usov, S. O.; Nikolaev, A. E.; Yagovkina, M. A.; Ustinov, V. M. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation); Cherkashin, N. A. [CEMES–CNRS—Université de Toulouse (France)

2016-09-15

The epitaxial growth of InAlN layers and GaN/AlN/InAlN heterostructures for HEMTs in growth systems with horizontal reactors of the sizes 1 × 2', 3 × 2', and 6 × 2' is investigated. Studies of the structural properties of the grown InAlN layers and electrophysical parameters of the GaN/AlN/InAlN heterostructures show that the optimal quality of epitaxial growth is attained upon a compromise between the growth conditions for InGaN and AlGaN. A comparison of the epitaxial growth in different reactors shows that optimal conditions are realized in small-scale reactors which make possible the suppression of parasitic reactions in the gas phase. In addition, the size of the reactor should be sufficient to provide highly homogeneous heterostructure parameters over area for the subsequent fabrication of devices. The optimal compositions and thicknesses of the InAlN layer for attaining the highest conductance in GaN/AlN/InAlN transistor heterostructures.

The prevalence of musculoskeletal disorders and occupational risk factors in Kashan SAIPA automobile industry workers by key indicator method (KIM, 1390

Directory of Open Access Journals (Sweden)

2012-05-01

Full Text Available Introduction: work related musculoskeletal disorders are the most wide spread type of occupational diseases among workers. Awkward body postures during work and manual material handling are among the most important risk factors of musculoskeletal disorders in different jobs. Due to importance of recognizing these factors prevalence and risk factor of work related musculoskeletal disorders, this research was aimed to study the among employees of Kashan City’s Saipa automobile industry in 2011. .Material and Method: This study is a descriptive-cross sectional study conducted among workers with manual material handling 37 activities and 84 work duties. To recognize musculoskeletal disorders, body map questionnaire was applied and occupational risk factors were evaluated using Key Index Method (KIM. Data was analyzed using SPSS and Excel software. .Result: Highest prevalence of musculoskeletal disorders was in low and upper back region (%92. Based on the results from KIM, workers in the installing the tire, shuttle-aided fitting of seat, and engine work station had higher risk level with the scores of 66, 52 and 52, respectively. Risk level among three individuals (%3.6 was at 1, 40 (%47.6 at 2, 38 (%45.2 risk level 3, and 3 (%3.6 at 4. .Conclusion: Awkward body posture, improper twisting and flexion of low back were major risk factor among worker doing manual material handling tasks. Regarding the high prevalence of musculoskeletal disorders, appropriate ergonomic interventions such as engineering and organization interactions can reduce this risk factors (posture, heavy load, duration, workplace conditions as much as the risk level reach to an acceptable level.

Effects of trap density on drain current LFN and its model development for E-mode GaN MOS-HEMT

Science.gov (United States)

Panda, D. K.; Lenka, T. R.

2017-12-01

In this paper the drain current low-frequency noise (LFN) of E-mode GaN MOS-HEMT is investigated for different gate insulators such as SiO2, Al2O3/Ga2O3/GdO3, HfO2/SiO2, La2O3/SiO2 and HfO2 with different trap densities by IFM based TCAD simulation. In order to analyze this an analytical model of drain current low frequency noise is developed. The model is developed by considering 2DEG carrier fluctuations, mobility fluctuations and the effects of 2DEG charge carrier fluctuations on the mobility. In the study of different gate insulators it is observed that carrier fluctuation is the dominant low frequency noise source and the non-uniform exponential distribution is critical to explain LFN behavior, so the analytical model is developed by considering uniform distribution of trap density. The model is validated with available experimental data from literature. The effect of total number of traps and gate length scaling on this low frequency noise due to different gate dielectrics is also investigated.

Determination of Temperature-Dependent Stress State in Thin AlGaN Layer of AlGaN/GaN HEMT Heterostructures by Near-Resonant Raman Scattering

Directory of Open Access Journals (Sweden)

Yanli Liu

2015-01-01

Full Text Available The temperature-dependent stress state in the AlGaN barrier layer of AlGaN/GaN heterostructure grown on sapphire substrate was investigated by ultraviolet (UV near-resonant Raman scattering. Strong scattering peak resulting from the A1(LO phonon mode of AlGaN is observed under near-resonance condition, which allows for the accurate measurement of Raman shifts with temperature. The temperature-dependent stress in the AlGaN layer determined by the resonance Raman spectra is consistent with the theoretical calculation result, taking lattice mismatch and thermal mismatch into account together. This good agreement indicates that the UV near-resonant Raman scattering can be a direct and effective method to characterize the stress state in thin AlGaN barrier layer of AlGaN/GaN HEMT heterostructures.

Effects of NH3 Flow Rate During AlGaN Barrier Layer Growth on the Material Properties of AlGaN/GaN HEMT Heterostructure

Science.gov (United States)

Lumbantoruan, Franky J.; Wong, Yuen-Yee; Huang, Wei-Ching; Yu, Hung-Wei; Chang, Edward-Yi

2017-10-01

NH3 flow rate during AlGaN barrier layer growth not only affects the growth efficiency and surface morphology as a result of parasitic reactions but also influences the concentration of carbon impurity in the AlGaN barrier. Carbon, which decomposes from metal precursors, plays a role in electron compensation for AlGaN/GaN HEMT. No 2-dimensional electron gas (2-DEG) was detected in the AlGaN/GaN structure if grown with 0.5 slm of NH3 due to the presence of higher carbon impurity (2.6 × 1019 cm-2). When the NH3 flow rate increased to 6.0 slm, the carbon impurity reduced to 2.10 × 1018 atom cm-3 and the 2 DEG electron density recovered to 9.57 × 1012 cm-2.

Mechanisms of thermally induced threshold voltage instability in GaN-based heterojunction transistors

International Nuclear Information System (INIS)

Yang, Shu; Liu, Shenghou; Liu, Cheng; Lu, Yunyou; Chen, Kevin J.

2014-01-01

In this work, we attempt to reveal the underlying mechanisms of divergent V TH -thermal-stabilities in III-nitride metal-insulator-semiconductor high-electron-mobility transistor (MIS-HEMT) and MOS-Channel-HEMT (MOSC-HEMT). In marked contrast to MOSC-HEMT featuring temperature-independent V TH , MIS-HEMT with the same high-quality gate-dielectric/III-nitride interface and similar interface trap distribution exhibits manifest thermally induced V TH shift. The temperature-dependent V TH of MIS-HEMT is attributed to the polarized III-nitride barrier layer, which spatially separates the critical gate-dielectric/III-nitride interface from the channel and allows “deeper” interface trap levels emerging above the Fermi level at pinch-off. This model is further experimentally validated by distinct V G -driven Fermi level movements at the critical interfaces in MIS-HEMT and MOSC-HEMT. The mechanisms of polarized III-nitride barrier layer in influencing V TH -thermal-stability provide guidelines for the optimization of insulated-gate III-nitride power switching devices

Specific features of NH{sub 3} and plasma-assisted MBE in the fabrication of III-N HEMT heterostructures

Energy Technology Data Exchange (ETDEWEB)

Alexeev, A. N. [NTO ZAO (Russian Federation); Krasovitsky, D. M. [Svetlana-Rost ZAO (Russian Federation); Petrov, S. I., E-mail: petrov@semiteq.ru [NTO ZAO (Russian Federation); Chaly, V. P.; Mamaev, V. V. [Svetlana-Rost ZAO (Russian Federation); Sidorov, V. G. [St. Petersburg State Polytechnic University (Russian Federation)

2015-01-15

The specific features of how nitride HEMT heterostructures are produced by NH{sub 3} and plasma-assisted (PA) molecular-beam epitaxy (MBE) are considered. It is shown that the use of high-temperature AlN/AlGaN buffer layers grown with ammonia at extremely high temperatures (up to 1150°C) can drastically improve the structural perfection of the active GaN layers and reduce the dislocation density in these layers to values of 9 × 10{sup 8}−1 × 10{sup 9} cm{sup −2}. The use of buffer layers of this kind makes it possible to obtain high-quality GaN/AlGaN heterostructures by both methods. At the same time, in contrast to ammonia MBE which is difficult to apply at T < 500°C (because of the low efficiency of ammonia decomposition), PA MBE is rather effective at low temperatures, e.g., for the growth of InAlN layers lattice-matched with GaN. The results obtained in the MBE growth of AlN/AlGaN/GaN/InAlN heterostructures by both PA-MBE and NH{sub 3}-MBE with an extremely high ammonia flux are demonstrated.

Moral is political Notions of ideal citizenship in Lie Kim Hok’s Hikajat Khonghoetjoe

Directory of Open Access Journals (Sweden)

Evi Sutrisno

2017-04-01

Full Text Available This paper argues that the Hikajat Khonghoetjoe (The life story of Confucius, written by Lie Kim Hok in 1897, is a medium to propose modern ideas of flexible subjectivity, cosmopolitanism, active citizenship and the concepts of good governance to the Chinese Peranakans who experienced political and racial discrimination under Dutch colonization. Using the figure of Confucius, Lie aimed to cultivate virtuous subjects who apply their faith and morality in political sphere. He intended to raise political awareness and rights among the Chinese as colonial subjects and to valorize their bargaining power with the Dutch colonial government. By introducing Confucianism, Lie proposed that the Chinese reconnect themselves with China as an alternative patronage which could subvert White supremacy. Instead of using sources in Chinese, Lie translated the biography of Confucius from the European texts. In crafting his story, Lie applied conglomerate authorship, a technique commonly practised by Malay authors. It allowed him to select, combine and appropriate the source texts. To justify that Confucius' virtue and his teaching were superb and are applicable to contemporary life, Lie borrowed and emphasized European writers’ high appraisal of Confucianism, instead of using his own arguments and opinions. I call this writing technique “indirect agency”.

A NIM (Nuclear Instrumentation Module) system conjugated with optional input for pHEMT amplifier for beta and gamma spectroscopy; Um sistema de modulos NIM conjugados com entrada opcional por amplificador pHEMT para espectroscopia beta e gama

Energy Technology Data Exchange (ETDEWEB)

Konrad, Barbara; Lüdke, Everton, E-mail: barbarakonradmev@gmail.com, E-mail: eludke@smail.ufsm.br [Universidade Federal de Santa Maria (LAE/UFSM), RS (Brazil). Lab. de Astrofisica e Eletronica

2014-07-01

This work presents a high speed NIM module (Nuclear Instrumentation Module) to detect radiation, gamma and muons, as part of a system for natural radiation monitoring and of extraterrestrial origin. The subsystem developed consists of a preamplifier and an integrated SCA (Single Channel Analyzer), including power supplies of ± 12 and ± 24V with derivations of +3.6 and ± 5V. The single channel analyzer board, consisting of discrete logic components, operating in window modes, normal and integral. The pulse shaping block is made up of two voltage comparators working at 120 MHz with a response time > 60 ns and a logic anticoincidence system. The preamplifier promotes a noise reduction and introduces the impedance matching between the output of anode / diode photomultiplier tubes (PMTs) and subsequent equipment, providing an input impedance of 1MΩ and output impedance of 40 to 140Ω. The shaper amplifier is non-inverting and has variable input capacitance of 1000 pF. The upper and lower thresholds of the SCA are adjustable from 0 to ± 10V, and the equipment is compatible with various types of detectors, like PMTs coupled to sodium iodide crystals. For use with liquid scintillators and photodiodes with crystals (CsI: Tl) is proposed to include a preamplifier circuit pHEMT (pseudomorphic High Electron Mobility Transistor) integrated. Yet, the system presents the possibility of applications for various purposes of gamma spectroscopy and automatic detection of events producing of beta particles.

Mechanisms of thermally induced threshold voltage instability in GaN-based heterojunction transistors

Energy Technology Data Exchange (ETDEWEB)

Yang, Shu; Liu, Shenghou; Liu, Cheng; Lu, Yunyou; Chen, Kevin J., E-mail: eekjchen@ust.hk [Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)

2014-12-01

In this work, we attempt to reveal the underlying mechanisms of divergent V{sub TH}-thermal-stabilities in III-nitride metal-insulator-semiconductor high-electron-mobility transistor (MIS-HEMT) and MOS-Channel-HEMT (MOSC-HEMT). In marked contrast to MOSC-HEMT featuring temperature-independent V{sub TH}, MIS-HEMT with the same high-quality gate-dielectric/III-nitride interface and similar interface trap distribution exhibits manifest thermally induced V{sub TH} shift. The temperature-dependent V{sub TH} of MIS-HEMT is attributed to the polarized III-nitride barrier layer, which spatially separates the critical gate-dielectric/III-nitride interface from the channel and allows “deeper” interface trap levels emerging above the Fermi level at pinch-off. This model is further experimentally validated by distinct V{sub G}-driven Fermi level movements at the critical interfaces in MIS-HEMT and MOSC-HEMT. The mechanisms of polarized III-nitride barrier layer in influencing V{sub TH}-thermal-stability provide guidelines for the optimization of insulated-gate III-nitride power switching devices.

Determination of the in-plane effective mass and quantum lifetime of 2D electrons in AlGaN/GaN based HEMTs

Energy Technology Data Exchange (ETDEWEB)

Celik, Ozlem; Tiras, Engin; Ardali, Sukru [Department of Physics, Faculty of Science, Anadolu University, Yunus Emre Campus, 26470 Eskisehir (Turkey); Lisesivdin, Sefer Bora [Department of Physics, Faculty of Science and Arts, Gazi University, Teknikokullar, 06500 Ankara (Turkey); Ozbay, Ekmel [Nanotechnology Research Center, Department of Physics, and Department of Electrical and Electronics Engineering, Bilkent University, Ankara (Turkey)

2011-05-15

Magnetoresistance and Hall resistance measurements have been used to investigate the electronic transport properties of AlGaN/GaN based HEMTs. The Shubnikov-de Haas (SdH) oscillations from magnetoresistance, is obtained by fitting the nonoscillatory component to a polynomial of second degree, and then subtracting it from the raw experimental data. It is shown that only first subband is occupied with electrons. The two-dimensional (2D) carrier density and the Fermi energy with respect to subband energy (E{sub F}-E{sub 1}) have been determined from the periods of the SdH oscillations. The in-plane effective mass (m*) and the quantum lifetime ({tau}{sub q}) of electrons have been obtained from the temperature and magnetic field dependencies of the SdH amplitude, respectively. The in-plane effective mass of 2D electrons is in the range between 0.19 m{sub 0} and 0.22 m{sub 0}. Our results for in-plane effective mass are in good agreement with those reported in the literature (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

AlGaN/GaN high-electron-mobility transistors with transparent gates by Al-doped ZnO

International Nuclear Information System (INIS)

Wang Chong; He Yun-Long; Zheng Xue-Feng; Ma Xiao-Hua; Zhang Jin-Cheng; Hao Yue

2013-01-01

AlGaN/GaN high-electron-mobility transistors (HEMTs) with Al-doped ZnO (AZO) transparent gate electrodes are fabricated, and Ni/Au/Ni-gated HEMTs are produced in comparison. The AZO-gated HEMTs show good DC characteristics and Schottky rectifying characteristics, and the gate electrodes achieve excellent transparencies. Compared with Ni/Au/Ni-gated HEMTs, AZO-gated HEMTs show a low saturation current, high threshold voltage, high Schottky barrier height, and low gate reverse leakage current. Due to the higher gate resistivity, AZO-gated HEMTs exhibit a current—gain cutoff frequency (f T ) of 10 GHz and a power gain cutoff frequency (f max ) of 5 GHz, and lower maximum oscillation frequency than Ni/Au/Ni-gated HEMTs. Moreover, the C—V characteristics are measured and the gate interface characteristics of the AZO-gated devices are investigated by a C—V dual sweep

Recessed insulator and barrier AlGaN/GaN HEMT: A novel structure for improving DC and RF characteristics

Science.gov (United States)

Razavi, S. M.; Zahiri, S. H.; Hosseini, S. E.

2017-04-01

In this study, a gallium nitride (GaN) high electron mobility transistor (HEMT) with recessed insulator and barrier is reported. In the proposed structure, insulator is recessed into the barrier at the drain side and barrier is recessed into the buffer layer at the source side. We study important device characteristics such as electric field, breakdown voltage, drain current, maximum output power density, gate-drain capacitance, short channel effects and DC transconductance using two-dimensional and two-carrier device simulator. Recessed insulator in the drain side of the proposed structure reduces maximum electric field in the channel and therefore increases the breakdown voltage and maximum output power density compared to the conventional counterpart. Also, gate-drain capacitance value in the proposed structure is less than that of the conventional structure. Overall, the proposed structure reduces short channel effects. Because of the recessed regions at both the source and the drain sides, the average barrier thickness of the proposed structure is not changed. Thus, the drain current of the proposed structure is almost equivalent to that of the conventional transistor. In this work, length ( L r) and thickness ( T r) of the recessed region of the barrier at the source side are the same as those of the insulator at the drain side.

Supporting NATO C2-Simulation Experimentation with Scripted Web Services

Science.gov (United States)

2011-06-01

SBMLServices services must parse the input scripts. • Semaphores are created to insure serial access to the remaining global resources: − Since there can only...be one connection to the JC3IEDM RI, that connection now must be shared among all instances; this requires a semaphore to control access...Initialization of SBMLServer is also now protected by a semaphore . • Setting and using object identifiers (OIDs) for pushing to the RI requires

Improved DC performance of AlGaN/GaN high electron mobility transistors using hafnium oxide for surface passivation

International Nuclear Information System (INIS)

Liu, Chang; Chor, Eng Fong; Tan, Leng Seow

2007-01-01

Improved DC performance of AlGaN/GaN high electron mobility transistors (HEMTs) have been demonstrated using reactive-sputtered hafnium oxide (HfO 2 ) thin film as the surface passivation layer. Hall data indicate a significant increase in the product of sheet carrier concentration (n s ) and electron mobility (μ n ) in the HfO 2 -passivated HEMTs, compared to the unpassivated HEMTs. This improvement in electron carrier characteristics gives rise to a 22% higher I Dmax and an 18% higher g mmax in HEMTs with HfO 2 passivation relative to the unpassivated devices. On the other hand, I gleak of the HEMTs decreases by nearly one order of magnitude when HfO 2 passivation is applied. In addition, drain current is measured in the subthreshold regime. Compared to the unpassivated HEMTs, HfO 2 -passivated HEMTs exhibit a much smaller off-state I D , indicating better turn-off characteristics

Analytical models for the 2DEG concentration and gate leakage current in AlGaN/GaN HEMTs

Science.gov (United States)

Ahmed, Nadim; Dutta, Aloke K.

2017-06-01

In this paper, we present a completely analytical model for the 2DEG concentration in AlGaN/GaN HEMTs as a function of gate bias, considering the donor-like trap states present at the metal/AlGaN interface to be the primary source of 2DEG carriers. To the best of our knowledge, this is a completely new contribution of this work. The electric field in the AlGaN layer is calculated using this model, which is further used to model the gate leakage current under reverse bias. We have modified the existing TTT (Thermionic Trap-Assisted Tunneling) current model, taking into account the effect of both metal/AlGaN interface traps as well as AlGaN bulk traps. The gate current under forward bias is also modeled using the existing thermionic emission model, approximating it by its Taylor series expansion. To take into account the effect of non-zero drain-source bias (VDS), an empirical fitting parameter is introduced in order to model the channel voltage in terms of VDS. The results of our models have been compared with the experimental data reported in the literature for three different devices, and the match is found to be excellent for both forward and reverse bias as well as for zero and non-zero VDS.

An Inquiry of Intentions in Kim Hye-yong's 'First Meeting': A North Korean Short Story in Korea Today (2007.

Directory of Open Access Journals (Sweden)

Alzo David-West

2013-11-01

Full Text Available This paper examines the problem of the intentional fallacy in the North Korean short story 'First Meeting' by Kim Hye-yong. Serially published in Korea Today in 2007, the nationalist allegory centres on Shin Ch'ong-mi, a young female journalist in Pyongyang, who falls in love with her penfriend Song-u, a soldier in the Korean People's Army, and struggles to remain devoted to him when he suddenly stops writing. With the literary-critical method of counterintuitive reading, the inquiry analyses the structural relations of the narrative, its discourse on desire, its apparent intentions, and its contravening elements, revealing an incidental unstable narrative that is symbolically protesting of the moral of the story to affectionately embrace the political authority of the North Korean party-army regime in the military-first (songun era.

Cooling Simulation and Thermal Abuse Modeling of Lithium-Ion Batteries Using the Newman, Tiedemann, Gu, and Kim (NTGK) Model

DEFF Research Database (Denmark)

Saeed Madani, Seyed; Swierczynski, Maciej Jozef; Kær, Søren Knudsen

2017-01-01

This paper gives insight into the cooling simulation and thermal abuse modeling of lithium-ion batteries by ANSYS FLUENT. Cooling strategies are important issues in the thermal management of lithium-ion battery systems, and it is essential to investigate them attentively in order to maintain...... the functioning temperature of batteries within an optimum range. The high temperature is able not only to decrease the efficiency of batteries but also may lead to the thermal runaway. To comprehend further, the thermal abuse behavior of lithium-ion batteries based on The Newman, Tiedemann, Gu, and Kim (NTGK......) model has been implemented in ANSYS FLUENT software. The results show that to achieve an optimum energy consumption for battery cooling, a minimum value of average heat transfer coefficient can be selected in order to keep the functioning temperature of batteries within an optimum range....

Atomic Layer Deposition of Gallium Oxide Films as Gate Dielectrics in AlGaN/GaN Metal-Oxide-Semiconductor High-Electron-Mobility Transistors.

Science.gov (United States)

Shih, Huan-Yu; Chu, Fu-Chuan; Das, Atanu; Lee, Chia-Yu; Chen, Ming-Jang; Lin, Ray-Ming

2016-12-01

In this study, films of gallium oxide (Ga2O3) were prepared through remote plasma atomic layer deposition (RP-ALD) using triethylgallium and oxygen plasma. The chemical composition and optical properties of the Ga2O3 thin films were investigated; the saturation growth displayed a linear dependence with respect to the number of ALD cycles. These uniform ALD films exhibited excellent uniformity and smooth Ga2O3-GaN interfaces. An ALD Ga2O3 film was then used as the gate dielectric and surface passivation layer in a metal-oxide-semiconductor high-electron-mobility transistor (MOS-HEMT), which exhibited device performance superior to that of a corresponding conventional Schottky gate HEMT. Under similar bias conditions, the gate leakage currents of the MOS-HEMT were two orders of magnitude lower than those of the conventional HEMT, with the power-added efficiency enhanced by up to 9 %. The subthreshold swing and effective interfacial state density of the MOS-HEMT were 78 mV decade(-1) and 3.62 × 10(11) eV(-1) cm(-2), respectively. The direct-current and radio-frequency performances of the MOS-HEMT device were greater than those of the conventional HEMT. In addition, the flicker noise of the MOS-HEMT was lower than that of the conventional HEMT.

Fabrication and characterization of V-gate AlGaN/GaN high-electron-mobility transistors

International Nuclear Information System (INIS)

Zhang Kai; Cao Meng-Yi; Chen Yong-He; Yang Li-Yuan; Wang Chong; Ma Xiao-Hua; Hao Yue

2013-01-01

V-gate GaN high-electron-mobility transistors (HEMTs) are fabricated and investigated systematically. A V-shaped recess geometry is obtained using an improved Si 3 N 4 recess etching technology. Compared with standard HEMTs, the fabricated V-gate HEMTs exhibit a 17% higher peak extrinsic transconductance due to a narrowed gate foot. Moreover, both the gate leakage and current dispersion are dramatically suppressed simultaneously, although a slight degradation of frequency response is observed. Based on a two-dimensional electric field simulation using Silvaco “ATLAS” for both standard HEMTs and V-gate HEMTs, the relaxation in peak electric field at the gate edge is identified as the predominant factor leading to the superior performance of V-gate HEMTs. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Electrothermal evaluation of thick GaN epitaxial layers and AlGaN/GaN high-electron-mobility transistors on large-area engineered substrates

Science.gov (United States)

Anderson, Travis J.; Koehler, Andrew D.; Tadjer, Marko J.; Hite, Jennifer K.; Nath, Anindya; Mahadik, Nadeemullah A.; Aktas, Ozgur; Odnoblyudov, Vladimir; Basceri, Cem; Hobart, Karl D.; Kub, Francis J.

2017-12-01

AlGaN/GaN high-electron-mobility transistor (HEMT) device layers were grown by metal organic chemical vapor deposition (MOCVD) on commercial engineered QST™ substrates to demonstrate a path to scalable, cost-effective foundry processing while supporting the thick epitaxial layers required for power HEMT structures. HEMT structures on 150 mm Si substrates were also evaluated. The HEMTs on engineered substrates exhibited material quality, DC performance, and forward blocking performance superior to those of the HEMT on Si. GaN device layers up to 15 µm were demonstrated with a wafer bow of 1 µm, representing the thickest films grown on 150-mm-diameter substrates with low bow to date.

A Ka-band low-noise amplifier with a coplanar waveguide (CPW) structure with 0.15-μm GaAs pHEMT technology

International Nuclear Information System (INIS)

Wu Chia-Song; Chang Chien-Huang; Liu Hsing-Chung; Lin Tah-Yeong; Wu Hsien-Ming

2010-01-01

This investigation explores a low-noise amplifier (LNA) with a coplanar waveguide (CPW) structure, in which a two-stage amplifier is associated with a cascade schematic circuit, implemented in 0.15-μm GaAs pseudomorphic high electron mobility transistor (pHEMT) technology in a Ka-band (26.5-40.0 GHz) microwave monolithic integrated circuit (MMIC). The experimental results demonstrate that the proposed LNA has a peak gain of 12.53 dB at 30 GHz and a minimum noise figure of 3.3 dB at 29.5 GHz, when biased at a V ds of 2 V and a V gs of -0.6 V with a drain current of 16 mA in the circuit. The results show that the millimeter-wave LNA with coplanar waveguide structure has a higher gain and wider bandwidth than a conventional circuit. Finally, the overall LNA characterization exhibits high gain and low noise, indicating that the LNA has a compact circuit and favorable RF characteristics. The strong RF character exhibited by the LNA circuit can be used in millimeter-wave circuit applications. (semiconductor integrated circuits)

Metal-interconnection-free integration of InGaN/GaN light emitting diodes with AlGaN/GaN high electron mobility transistors

Energy Technology Data Exchange (ETDEWEB)

Liu, Chao; Cai, Yuefei; Liu, Zhaojun; Ma, Jun; Lau, Kei May, E-mail: eekmlau@ust.hk [Photonics Technology Center, Department of Electronic and Computer Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)

2015-05-04

We report a metal-interconnection-free integration scheme for InGaN/GaN light emitting diodes (LEDs) and AlGaN/GaN high electron mobility transistors (HEMTs) by combining selective epi removal (SER) and selective epitaxial growth (SEG) techniques. SER of HEMT epi was carried out first to expose the bottom unintentionally doped GaN buffer and the sidewall GaN channel. A LED structure was regrown in the SER region with the bottom n-type GaN layer (n-electrode of the LED) connected to the HEMTs laterally, enabling monolithic integration of the HEMTs and LEDs (HEMT-LED) without metal-interconnection. In addition to saving substrate real estate, minimal interface resistance between the regrown n-type GaN and the HEMT channel is a significant improvement over metal-interconnection. Furthermore, excellent off-state leakage characteristics of the driving transistor can also be guaranteed in such an integration scheme.

Investigation of trap states in high Al content AlGaN/GaN high electron mobility transistors by frequency dependent capacitance and conductance analysis

International Nuclear Information System (INIS)

Zhu, Jie-Jie; Ma, Xiao-Hua; Hou, Bin; Chen, Wei-Wei; Hao, Yue

2014-01-01

Trap states in Al 0.55 Ga 0.45 N/GaN Schottky-gate high-electron-mobility transistors (S-HEMTs) and Al 2 O 3 /Al 0.55 Ga 0.45 N/GaN metal-oxide-semiconductor HEMTs (MOS-HEMTs) were investigated with conductance method in this paper. Surface states with time constant of (0.09–0.12) μs were found in S-HEMTs, and electron tunneling rather than emission was deemed to be the dominant de-trapping mechanism due to the high electric field in high Al content barrier. The density of surface states evaluated in S-HEMTs was (1.02–4.67)×10 13 eV −1 ·cm −2 . Al 2 O 3 gate insulator slightly reduced the surface states, but introduced low density of new traps with time constant of (0.65–1.29) μs into MOS-HEMTs

Metal-interconnection-free integration of InGaN/GaN light emitting diodes with AlGaN/GaN high electron mobility transistors

International Nuclear Information System (INIS)

Liu, Chao; Cai, Yuefei; Liu, Zhaojun; Ma, Jun; Lau, Kei May

2015-01-01

We report a metal-interconnection-free integration scheme for InGaN/GaN light emitting diodes (LEDs) and AlGaN/GaN high electron mobility transistors (HEMTs) by combining selective epi removal (SER) and selective epitaxial growth (SEG) techniques. SER of HEMT epi was carried out first to expose the bottom unintentionally doped GaN buffer and the sidewall GaN channel. A LED structure was regrown in the SER region with the bottom n-type GaN layer (n-electrode of the LED) connected to the HEMTs laterally, enabling monolithic integration of the HEMTs and LEDs (HEMT-LED) without metal-interconnection. In addition to saving substrate real estate, minimal interface resistance between the regrown n-type GaN and the HEMT channel is a significant improvement over metal-interconnection. Furthermore, excellent off-state leakage characteristics of the driving transistor can also be guaranteed in such an integration scheme

Investigation of high sensitivity radio-frequency readout circuit based on AlGaN/GaN high electron mobility transistor

International Nuclear Information System (INIS)

Zhang Xiao-Yu; Sun Jian-Dong; Li Xin-Xing; Zhou Yu; Lü Li; Qin Hua; Tan Ren-Bing

2015-01-01

An AlGaN/GaN high electron mobility transistor (HEMT) device is prepared by using a semiconductor nanofabrication process. A reflective radio-frequency (RF) readout circuit is designed and the HEMT device is assembled in an RF circuit through a coplanar waveguide transmission line. A gate capacitor of the HEMT and a surface-mounted inductor on the transmission line are formed to generate LC resonance. By tuning the gate voltage V g , the variations of gate capacitance and conductance of the HEMT are reflected sensitively from the resonance frequency and the magnitude of the RF reflection signal. The aim of the designed RF readout setup is to develop a highly sensitive HEMT-based detector. (paper)

„Ritualno” i „struktuirano” odbacivanje u arheološkim interpretacijama: primer sistema za vodosnabdevanje na lokalitetu „Kale” u Krševici

Directory of Open Access Journals (Sweden)

Ivan Vranić

2016-11-01

Full Text Available Pitanja vezana za rituale, kultove, religiju ili magiju predstavljaju važne ali u značajnoj meri zanemarene i teorijski nedovoljno precizno utemeljene teme u savremenim arheološkim interpretacijama. Cilj rada jeste da na konkretnim primerima potencijalno ritualnih aktivnosti vezanih za izgradnju i moguće „ritualno ubijanje” sistema za vodosnabdevanje na lokalitetu „Kale” u Krševici pokaže kako ovo zanemarivanje nije samo posledica aktuelnosti i trendova o odabiru istraživačkih tema, već se radi o ozbiljnijem problemu koji pokazuje određene nedostatke savremenih pristupa vezanih za arheologiju identiteta i koncepte struktuiranog ili simboličkog odbacivanja.

Polar semiconductor heterojunction structure energy band diagram considerations

International Nuclear Information System (INIS)

Lin, Shuxun; Wen, Cheng P.; Wang, Maojun; Hao, Yilong

2016-01-01

The unique nature of built-in electric field induced positive/negative charge pairs of polar semiconductor heterojunction structure has led to a more realistic device model for hexagonal III-nitride HEMT. In this modeling approach, the distribution of charge carriers is dictated by the electrostatic potential profile instead of Femi statistics. The proposed device model is found suitable to explain peculiar properties of GaN HEMT structures, including: (1) Discrepancy in measured conventional linear transmission line model (LTLM) sheet resistance and contactless sheet resistance of GaN HEMT with thin barrier layer. (2) Below bandgap radiation from forward biased Nickel Schottky barrier diode on GaN HEMT structure. (3) GaN HEMT barrier layer doping has negligible effect on transistor channel sheet charge density.

Polar semiconductor heterojunction structure energy band diagram considerations

Energy Technology Data Exchange (ETDEWEB)

Lin, Shuxun; Wen, Cheng P., E-mail: cpwen@ieee.org; Wang, Maojun; Hao, Yilong [Institute of Microelectronics, Peking University, Beijing (China)

2016-03-28

The unique nature of built-in electric field induced positive/negative charge pairs of polar semiconductor heterojunction structure has led to a more realistic device model for hexagonal III-nitride HEMT. In this modeling approach, the distribution of charge carriers is dictated by the electrostatic potential profile instead of Femi statistics. The proposed device model is found suitable to explain peculiar properties of GaN HEMT structures, including: (1) Discrepancy in measured conventional linear transmission line model (LTLM) sheet resistance and contactless sheet resistance of GaN HEMT with thin barrier layer. (2) Below bandgap radiation from forward biased Nickel Schottky barrier diode on GaN HEMT structure. (3) GaN HEMT barrier layer doping has negligible effect on transistor channel sheet charge density.

Urinary Vitamin D Binding Protein and KIM-1 Are Potent New Biomarkers of Major Adverse Renal Events in Patients Undergoing Coronary Angiography.

Directory of Open Access Journals (Sweden)

Lyubov Chaykovska

Full Text Available Vitamin-D-binding protein (VDBP is a low molecular weight protein that is filtered through the glomerulus as a 25-(OH vitamin D 3/VDBP complex. In the normal kidney VDBP is reabsorbed and catabolized by proximal tubule epithelial cells reducing the urinary excretion to trace amounts. Acute tubular injury is expected to result in urinary VDBP loss. The purpose of our study was to explore the potential role of urinary VDBP as a biomarker of an acute renal damage.We included 314 patients with diabetes mellitus or mild renal impairment undergoing coronary angiography and collected blood and urine before and 24 hours after the CM application. Patients were followed for 90 days for the composite endpoint major adverse renal events (MARE: need for dialysis, doubling of serum creatinine after 90 days, unplanned emergency rehospitalization or death.Increased urine VDBP concentration 24 hours after contrast media exposure was predictive for dialysis need (no dialysis: 113.06 ± 299.61 ng/ml, n = 303; need for dialysis: 613.07 ± 700.45 ng/ml, n = 11, Mean ± SD, p<0.001, death (no death during follow-up: 121.41 ± 324.45 ng/ml, n = 306; death during follow-up: 522.01 ± 521.86 ng/ml, n = 8; Mean ± SD, p<0.003 and MARE (no MARE: 112.08 ± 302.00 ng/ml, n = 298; MARE: 506.16 ± 624.61 ng/ml, n = 16, Mean ± SD, p<0.001 during the follow-up of 90 days after contrast media exposure. Correction of urine VDBP concentrations for creatinine excretion confirmed its predictive value and was consistent with increased levels of urinary Kidney Injury Molecule-1 (KIM-1 and baseline plasma creatinine in patients with above mentioned complications. The impact of urinary VDBP and KIM-1 on MARE was independent of known CIN risk factors such as anemia, preexisting renal failure, preexisting heart failure, and diabetes.Urinary VDBP is a promising novel biomarker of major contrast induced nephropathy-associated events 90 days after contrast media exposure.

A NIM (Nuclear Instrumentation Module) system conjugated with optional input for pHEMT amplifier for beta and gamma spectroscopy

International Nuclear Information System (INIS)

Konrad, Barbara; Lüdke, Everton

2014-01-01

This work presents a high speed NIM module (Nuclear Instrumentation Module) to detect radiation, gamma and muons, as part of a system for natural radiation monitoring and of extraterrestrial origin. The subsystem developed consists of a preamplifier and an integrated SCA (Single Channel Analyzer), including power supplies of ± 12 and ± 24V with derivations of +3.6 and ± 5V. The single channel analyzer board, consisting of discrete logic components, operating in window modes, normal and integral. The pulse shaping block is made up of two voltage comparators working at 120 MHz with a response time > 60 ns and a logic anticoincidence system. The preamplifier promotes a noise reduction and introduces the impedance matching between the output of anode / diode photomultiplier tubes (PMTs) and subsequent equipment, providing an input impedance of 1MΩ and output impedance of 40 to 140Ω. The shaper amplifier is non-inverting and has variable input capacitance of 1000 pF. The upper and lower thresholds of the SCA are adjustable from 0 to ± 10V, and the equipment is compatible with various types of detectors, like PMTs coupled to sodium iodide crystals. For use with liquid scintillators and photodiodes with crystals (CsI: Tl) is proposed to include a preamplifier circuit pHEMT (pseudomorphic High Electron Mobility Transistor) integrated. Yet, the system presents the possibility of applications for various purposes of gamma spectroscopy and automatic detection of events producing of beta particles

Enhanced two dimensional electron gas transport characteristics in Al2O3/AlInN/GaN metal-oxide-semiconductor high-electron-mobility transistors on Si substrate

International Nuclear Information System (INIS)

Freedsman, J. J.; Watanabe, A.; Urayama, Y.; Egawa, T.

2015-01-01

The authors report on Al 2 O 3 /Al 0.85 In 0.15 N/GaN Metal-Oxide-Semiconductor High-Electron-Mobility Transistor (MOS-HEMT) on Si fabricated by using atomic layer deposited Al 2 O 3 as gate insulator and passivation layer. The MOS-HEMT with the gate length of 2 μm exhibits excellent direct-current (dc) characteristics with a drain current maximum of 1270 mA/mm at a gate bias of 3 V and an off-state breakdown voltage of 180 V for a gate-drain spacing of 4 μm. Also, the 1 μm-gate MOS-HEMT shows good radio-frequency (rf) response such as current gain and maximum oscillation cut-off frequencies of 10 and 34 GHz, respectively. The capacitance-voltage characteristics at 1 MHz revealed significant increase in two-dimensional electron gas (2DEG) density for the MOS-HEMT compared to conventional Schottky barrier HEMTs. Analyses using drain-source conductivity measurements showed improvements in 2DEG transport characteristics for the MOS-HEMT. The enhancements in dc and rf performances of the Al 2 O 3 /Al 0.85 In 0.15 N/GaN MOS-HEMT are attributed to the improvements in 2DEG characteristics

Physical and electrical characteristics of AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors with rare earth Er2O3 as a gate dielectric

International Nuclear Information System (INIS)

Lin, Ray-Ming; Chu, Fu-Chuan; Das, Atanu; Liao, Sheng-Yu; Chou, Shu-Tsun; Chang, Liann-Be

2013-01-01

In this study, the rare earth erbium oxide (Er 2 O 3 ) was deposited using an electron beam onto an AlGaN/GaN heterostructure to fabricate metal-oxide-semiconductor high-electron-mobility transistors (MOS–HEMTs) that exhibited device performance superior to that of a conventional HEMT. Under similar bias conditions, the gate leakage currents of these MOS–HEMT devices were four orders of magnitude lower than those of conventional Schottky gate HEMTs. The measured sub-threshold swing (SS) and the effective trap state density (N t ) of the MOS–HEMT were 125 mV/decade and 4.3 × 10 12 cm −2 , respectively. The dielectric constant of the Er 2 O 3 layer in this study was 14, as determined through capacitance–voltage measurements. In addition, the gate–source reverse breakdown voltage increased from –166 V for the conventional HEMT to –196 V for the Er 2 O 3 MOS–HEMT. - Highlights: ► GaN/AlGaN/Er 2 O 3 metal-oxide semiconductor high electron mobility transistor ► Physical and electrical characteristics are presented. ► Electron beam evaporated Er 2 O 3 with excellent surface roughness ► Device exhibits reduced gate leakage current and improved I ON /I OFF ratio

Viscosity-dependent drain current noise of AlGaN/GaN high electron mobility transistor in polar liquids

International Nuclear Information System (INIS)

Fang, J. Y.; Hsu, C. P.; Kang, Y. W.; Fang, K. C.; Kao, W. L.; Yao, D. J.; Chen, C. C.; Li, S. S.; Yeh, J. A.; Wang, Y. L.; Lee, G. Y.; Chyi, J. I.; Hsu, C. H.; Huang, Y. F.; Ren, F.

2013-01-01

The drain current fluctuation of ungated AlGaN/GaN high electron mobility transistors (HEMTs) measured in different fluids at a drain-source voltage of 0.5 V was investigated. The HEMTs with metal on the gate region showed good current stability in deionized water, while a large fluctuation in drain current was observed for HEMTs without gate metal. The fluctuation in drain current for the HEMTs without gate metal was observed and calculated as standard deviation from a real-time measurement in air, deionized water, ethanol, dimethyl sulfoxide, ethylene glycol, 1,2-butanediol, and glycerol. At room temperature, the fluctuation in drain current for the HEMTs without gate metal was found to be relevant to the dipole moment and the viscosity of the liquids. A liquid with a larger viscosity showed a smaller fluctuation in drain current. The viscosity-dependent fluctuation of the drain current was ascribed to the Brownian motions of the liquid molecules, which induced a variation in the surface dipole of the gate region. This study uncovers the causes of the fluctuation in drain current of HEMTs in fluids. The results show that the AlGaN/GaN HEMTs may be used as sensors to measure the viscosity of liquids within a certain range of viscosity

Off state breakdown behavior of AlGaAs / InGaAs field plate pHEMTs

International Nuclear Information System (INIS)

Palma, John; Mil'shtein, Samson

2014-01-01

Off-state breakdown voltage, V br , is an important parameter determining the maximum power output of microwave Field Effect Transistors (FETs). In recent years, the use of field plates has been widely adopted to significantly increase V br . This important technological development has extended FET technologies into new areas requiring these higher voltages and power levels. Keeping with this goal, field plates were added to an existing AlGaAs / InGaAs pseudomorphic High Electron Mobility Transistor (pHEMT) process with the aim of determining the off-state breakdown mechanism and the dependency of V br on the field plate design. To find the mechanism responsible for breakdown, temperature dependent off-state breakdown measurements were conducted. It was found that at low current levels, the temperature dependence indicates thermionic field emission at the Schottky gate and at higher current levels, impact ionization is indicated. The combined results imply that impact ionization is ultimately the mechanism that is responsible for the breakdown in the tested transistors, but that it is preceded by thermionic field emission from the gate. To test the dependence of V br upon the field plate design, the field plate length and the etch depth through the highly-doped cap layer under the field plate were varied. Also, non-field plate devices were tested along side field plate transistors. It was found that the length of the etched region under the field plate is the dominant factor in determining the off-state breakdown of the more deeply etched devices. For less deeply etched devices, the length of the field plate is more influential. The influence of surface states between the highly doped cap layer and the passivation layer along the recess are believed to have a significant influence in the case of the more deeply etched examples. It is believed that these traps spread the electric field, thus raising the breakdown voltage. Three terminal breakdown voltages

Enhanced two dimensional electron gas transport characteristics in Al{sub 2}O{sub 3}/AlInN/GaN metal-oxide-semiconductor high-electron-mobility transistors on Si substrate

Energy Technology Data Exchange (ETDEWEB)

Freedsman, J. J., E-mail: freedy54@gmail.com; Watanabe, A.; Urayama, Y. [Research Center for Nano-Devices and Advanced Materials, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466 8555 (Japan); Egawa, T., E-mail: egawa.takashi@nitech.ac.jp [Research Center for Nano-Devices and Advanced Materials, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466 8555 (Japan); Innovation Center for Multi-Business of Nitride Semiconductors, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466 8555 (Japan)

2015-09-07

The authors report on Al{sub 2}O{sub 3}/Al{sub 0.85}In{sub 0.15}N/GaN Metal-Oxide-Semiconductor High-Electron-Mobility Transistor (MOS-HEMT) on Si fabricated by using atomic layer deposited Al{sub 2}O{sub 3} as gate insulator and passivation layer. The MOS-HEMT with the gate length of 2 μm exhibits excellent direct-current (dc) characteristics with a drain current maximum of 1270 mA/mm at a gate bias of 3 V and an off-state breakdown voltage of 180 V for a gate-drain spacing of 4 μm. Also, the 1 μm-gate MOS-HEMT shows good radio-frequency (rf) response such as current gain and maximum oscillation cut-off frequencies of 10 and 34 GHz, respectively. The capacitance-voltage characteristics at 1 MHz revealed significant increase in two-dimensional electron gas (2DEG) density for the MOS-HEMT compared to conventional Schottky barrier HEMTs. Analyses using drain-source conductivity measurements showed improvements in 2DEG transport characteristics for the MOS-HEMT. The enhancements in dc and rf performances of the Al{sub 2}O{sub 3}/Al{sub 0.85}In{sub 0.15}N/GaN MOS-HEMT are attributed to the improvements in 2DEG characteristics.

Control of short-channel effects in InAlN/GaN high-electron mobility transistors using graded AlGaN buffer

Science.gov (United States)

Han, Tiecheng; Zhao, Hongdong; Peng, Xiaocan; Li, Yuhai

2018-04-01

A graded AlGaN buffer is designed to realize the p-type buffer by inducing polarization-doping holes. Based on the two-dimensional device simulator, the effect of the graded AlGaN buffer on the direct-current (DC) and radio-frequency (RF) performance of short-gate InAlN/GaN high-electron mobility transistors (HEMTs) are investigated, theoretically. Compared to standard HEMT, an enhancement of electron confinement and a good control of short-channel effect (SCEs) are demonstrated in the graded AlGaN buffer HEMT. Accordingly, the pinched-off behavior and the ability of gate modulation are significantly improved. And, no serious SCEs are observed in the graded AlGaN buffer HEMT with an aspect ratio (LG/tch) of about 6.7, much lower than that of the standard HEMT (LG/tch = 13). In addition, for a 70-nm gate length, a peak current gain cutoff frequency (fT) of 171 GHz and power gain cutoff frequency (fmax) of 191 GHz are obtained in the grade buffer HEMT, which are higher than those of the standard one with the same gate length.

An enzymatic biosensor based on three-dimensional ZnO nanotetrapods spatial net modified AlGaAs/GaAs high electron mobility transistors

Energy Technology Data Exchange (ETDEWEB)

Song, Yu [State Key Laboratory for Advanced Metals and Materials, School of Materials Science and Engineering, University of Science and Technology, Beijing 100083 (China); Bioengineering Program, Lehigh University, Bethlehem, Pennsylvania 18015 (United States); Zhang, Xiaohui; Yan, Xiaoqin; Liao, Qingliang; Wang, Zengze; Zhang, Yue, E-mail: yuezhang@ustb.edu.cn [State Key Laboratory for Advanced Metals and Materials, School of Materials Science and Engineering, University of Science and Technology, Beijing 100083 (China)

2014-11-24

We designed and constructed three dimensional (3D) zinc oxide Nanotetrapods (T-ZnOs) modified AlGaAs/GaAs high electron mobility transistors (HEMTs) for enzymatic uric acid (UA) detection. The chemical vapor deposition synthesized T-ZnOs was distributed on the gate areas of HEMTs in order to immobilize uricase and improve the sensitivity of the HEMTs. Combining with the high efficiency of enzyme immobilization by T-ZnOs and high sensitivity from HEMT, the as-constructed uricase/T-ZnOs/HEMTs biosensor showed fast response towards UA at ∼1 s, wide linear range from 0.2 nM to 0.2 mM and the low detect limit at 0.2 nM. The results point out an avenue to design electronic device as miniaturized lab-on-chip device for high sensitive and specific in biomedical and clinical diagnosis applications.

X-ray diffraction study of InAlAs-InGaAs on InP high electron mobility transistor structure prepared by molecular-beam epitaxy

International Nuclear Information System (INIS)

Liu, H.Y.; Kao, Y.C.; Kim, T.S.

1990-01-01

High-electron mobility transistors (HEMTs) can be prepared by growing alternating epitaxial layers of InAlAs and InGaAs on InP substrates. Lattice matched HEMTs are obtained by growing layers of IN x Al (1-x) As and In y Ga (1-y) As with x ≅ 0.5227 and y ≅ 0.5324. Varying the values of x and y by controlling the individual flux during molecular-beam epitaxial (MBE) growth, one can obtain pseudomorphic HEMTs. Pseudomorphic HEMTs may have superior electronic transport properties and larger conduction band discontinuity when compared to an unstrained one. The precise control of the composition is thus important to the properties of HEMTs. This control is however very difficult and the values of x and y may vary from run to run. The authors demonstrate in this paper the capability of a double crystal rocking curve (DCRC) on the structure characterization

Investigation of the current collapse induced in InGaN back barrier AlGaN/GaN high electron mobility transistors

International Nuclear Information System (INIS)

Wan Xiaojia; Wang Xiaoliang; Xiao Hongling; Feng Chun; Jiang Lijuan; Qu Shenqi; Wang Zhanguo; Hou Xun

2013-01-01

Current collapses were studied, which were observed in AlGaN/GaN high electron mobility transistors (HEMTs) with and without InGaN back barrier (BB) as a result of short-term bias stress. More serious drain current collapses were observed in InGaN BB AlGaN/GaN HEMTs compared with the traditional HEMTs. The results indicate that the defects and surface states induced by the InGaN BB layer may enhance the current collapse. The surface states may be the primary mechanism of the origination of current collapse in AlGaN/GaN HEMTs for short-term direct current stress. (semiconductor devices)

Oxygen and carbon dioxide sensing

Science.gov (United States)

Ren, Fan (Inventor); Pearton, Stephen John (Inventor)

2012-01-01

A high electron mobility transistor (HEMT) capable of performing as a CO.sub.2 or O.sub.2 sensor is disclosed, hi one implementation, a polymer solar cell can be connected to the HEMT for use in an infrared detection system. In a second implementation, a selective recognition layer can be provided on a gate region of the HEMT. For carbon dioxide sensing, the selective recognition layer can be, in one example, PEI/starch. For oxygen sensing, the selective recognition layer can be, in one example, indium zinc oxide (IZO). In one application, the HEMTs can be used for the detection of carbon dioxide and oxygen in exhaled breath or blood.

Physisorption of functionalized gold nanoparticles on AlGaN/GaN high electron mobility transistors for sensing applications.

Science.gov (United States)

Makowski, M S; Kim, S; Gaillard, M; Janes, D; Manfra, M J; Bryan, I; Sitar, Z; Arellano, C; Xie, J; Collazo, R; Ivanisevic, A

2013-02-18

AlGaN/GaN high electron mobility transistors (HEMTs) were used to measure electrical characteristics of physisorbed gold nanoparticles (Au NPs) functionalized with alkanethiols with a terminal methyl, amine, or carboxyl functional group. Additional alkanethiol was physisorbed onto the NP treated devices to distinguish between the effects of the Au NPs and alkanethiols on HEMT operation. Scanning Kelvin probe microscopy and electrical measurements were used to characterize the treatment effects. The HEMTs were operated near threshold voltage due to the greatest sensitivity in this region. The Au NP/HEMT system electrically detected functional group differences on adsorbed NPs which is pertinent to biosensor applications.

Investigating interoperability between JC3IEDM and HLA

CSIR Research Space (South Africa)

Uys, DC

2009-07-01

Full Text Available in table 3. The rest of the entities are de ned as data types that can be present in the attributes of the objects (see table 4). To handle the inheritance, a new data-type is de ned for every entity in the inheri- tance tree. Each child entity’s data...

Anthropocene Knowledge Practices in McKenzie Wark’s Molecular Red and Kim Stanley Robinson’s Aurora

Directory of Open Access Journals (Sweden)

Gib Prettyman

2018-02-01

Full Text Available Through a close reading of McKenzie Wark’s theoretical treatise 'Molecular Red' (2015 and Kim Stanley Robinson’s novel 'Aurora' (2015, this essay examines how Anthropocene knowledge practices challenge our conceptions of human agency in provocative and potentially productive ways. For example, our knowledge of climate science arises through global material infrastructures. As material components of Anthropocene knowledge practices, these infrastructures reveal the material labors and cyborg structures by means of which our knowledge is produced. Wark sees the heterogenous materiality of Anthropocene knowledge practices as evidence for the value of ‘low theories’ based on a ‘labor point of view.’ At the same time, Anthropocene knowledge practices reveal ‘eco-logical’ complexities and fundamental recognitions of the ‘intra-action’ of entangled matter. These complexities produce very estranged views of human agency. Robinson’s novel highlights the eco-logical implications of contemporary knowledge practices by imagining an interstellar ship that must function as a completely artificial ecosystem for a 170-year voyage to another solar system. The significance of knowledge practices and eco-logical complexity is most evident when failures or crises arise, and 'Aurora' tells the story of many such failures. However, I argue that Robinson’s novel and Wark’s ‘low theory’ ultimately function as hopeful accounts of Anthropocene knowledge practices. Among other things, these practices show the material importance of storytelling and point the way toward more complexly realist theories of human agency.

Potassium selective chemically modified field effect transistors based on AlGaN/GaN two-dimensional electron gas heterostructures.

Science.gov (United States)

Alifragis, Y; Volosirakis, A; Chaniotakis, N A; Konstantinidis, G; Adikimenakis, A; Georgakilas, A

2007-06-15

We investigate the use of the AlGaN/GaN high electron mobility transistor (HEMT) as a novel transducer for the development of ion-selective chemically modified HEMT sensors (ChemHEMTs). For this, polyvinyl chloride (PVC) membrane doped with ion-selective ionophores is deposited onto the area of the gate for the chemical recognition step, while the AlGaN/GaN HEMT is used as the transducer. In particular, the use of a valinocycin doped membrane with thickness of 50 microm generates a sensor with excellent analytical characteristics for the monitoring of K(+). The K(+)-ChemHEMT has sensitivity of 52.4 mV/pK(+)in the linear range of 10(-5) to 10(-2)M, while the detection limit is in the order of 3.1 x 10(-6)M. Also, the sensor shows selectivity similar to valinomycin-based ISEs, while the signal stability over time and the measurement to measurement reproducibility are very good.

Suppression of self-heating effect in AlGaN/GaN high electron mobility transistors by substrate-transfer technology using h-BN

International Nuclear Information System (INIS)

Hiroki, Masanobu; Kumakura, Kazuhide; Kobayashi, Yasuyuki; Akasaka, Tetsuya; Makimoto, Toshiki; Yamamoto, Hideki

2014-01-01

We fabricated AlGaN/GaN high electron mobility transistors (HEMTs) on h-BN/sapphire substrates and transferred them from the host substrates to copper plates using h-BN as a release layer. In current–voltage characteristics, the saturation drain current decreased by about 30% under a high-bias condition before release by self-heating effect. In contrast, after transfer, the current decrement was as small as 8% owing to improved heat dissipation: the device temperature increased to 50 °C in the as-prepared HEMT, but only by several degrees in the transferred HEMT. An effective way to improve AlGaN/GaN HEMT performance by a suppression of self-heating effect has been demonstrated

Suppression of self-heating effect in AlGaN/GaN high electron mobility transistors by substrate-transfer technology using h-BN

Energy Technology Data Exchange (ETDEWEB)

Hiroki, Masanobu, E-mail: hiroki.masanobu@lab.ntt.co.jp; Kumakura, Kazuhide; Kobayashi, Yasuyuki; Akasaka, Tetsuya; Makimoto, Toshiki; Yamamoto, Hideki [NTT Basic Research Laboratories, NTT Corporation 3-1 Morinosato Wakamiya, Atsugi-shi 243-0198 (Japan)

2014-11-10

We fabricated AlGaN/GaN high electron mobility transistors (HEMTs) on h-BN/sapphire substrates and transferred them from the host substrates to copper plates using h-BN as a release layer. In current–voltage characteristics, the saturation drain current decreased by about 30% under a high-bias condition before release by self-heating effect. In contrast, after transfer, the current decrement was as small as 8% owing to improved heat dissipation: the device temperature increased to 50 °C in the as-prepared HEMT, but only by several degrees in the transferred HEMT. An effective way to improve AlGaN/GaN HEMT performance by a suppression of self-heating effect has been demonstrated.

Simulation study of InAlN/GaN high-electron mobility transistor with AlInN back barrier

International Nuclear Information System (INIS)

Han Tie-Cheng; Zhao Hong-Dong; Yang Lei; Wang Yang

2017-01-01

In this work, we use a 3-nm-thick Al 0.64 In 0.36 N back-barrier layer in In 0.17 Al 0.83 N/GaN high-electron mobility transistor (HEMT) to enhance electron confinement. Based on two-dimensional device simulations, the influences of Al 0.64 In 0.36 N back-barrier on the direct-current (DC) and radio-frequency (RF) characteristics of InAlN/GaN HEMT are investigated, theoretically. It is shown that an effective conduction band discontinuity of approximately 0.5 eV is created by the 3-nm-thick Al 0.64 In 0.36 N back-barrier and no parasitic electron channel is formed. Comparing with the conventional InAlN/GaN HEMT, the electron confinement of the back-barrier HEMT is significantly improved, which allows a good immunity to short-channel effect (SCE) for gate length decreasing down to 60 nm (9-nm top barrier). For a 70-nm gate length, the peak current gain cut-off frequency ( f T ) and power gain cut-off frequency ( f max ) of the back-barrier HEMT are 172 GHz and 217 GHz, respectively, which are higher than those of the conventional HEMT with the same gate length. (paper)

Kinase detection with gallium nitride based high electron mobility transistors.

Science.gov (United States)

Makowski, Matthew S; Bryan, Isaac; Sitar, Zlatko; Arellano, Consuelo; Xie, Jinqiao; Collazo, Ramon; Ivanisevic, Albena

2013-07-01

A label-free kinase detection system was fabricated by the adsorption of gold nanoparticles functionalized with kinase inhibitor onto AlGaN/GaN high electron mobility transistors (HEMTs). The HEMTs were operated near threshold voltage due to the greatest sensitivity in this operational region. The Au NP/HEMT biosensor system electrically detected 1 pM SRC kinase in ionic solutions. These results are pertinent to drug development applications associated with kinase sensing.

Processing of nanocrystalline diamond thin films for thermal management of wide-bandgap semiconductor power electronics

International Nuclear Information System (INIS)

Govindaraju, N.; Singh, R.N.

2011-01-01

Highlights: → Studied effect of nanocrystalline diamond (NCD) deposition on device metallization. → Deposited NCD on to top of High Electron Mobility Transistors (HEMTs) and Si devices. → Temperatures below 290 deg. C for Si devices and 320 deg. C for HEMTs prevent metal damage. → Development of novel NCD-based thermal management for power electronics feasible. - Abstract: High current densities in wide-bandgap semiconductor electronics operating at high power levels results in significant self-heating of devices, which necessitates the development thermal management technologies to effectively dissipate the generated heat. This paper lays the foundation for the development of such technology by ascertaining process conditions for depositing nanocrystalline diamond (NCD) on AlGaN/GaN High Electron Mobility Transistors (HEMTs) with no visible damage to device metallization. NCD deposition is carried out on Si and GaN HEMTs with Au/Ni metallization. Raman spectroscopy, optical and scanning electron microscopy are used to evaluate the quality of the deposited NCD films. Si device metallization is used as a test bed for developing process conditions for NCD deposition on AlGaN/GaN HEMTs. Results indicate that no visible damage occurs to the device metallization for deposition conditions below 290 deg. C for Si devices and below 320 deg. C for the AlGaN/GaN HEMTs. Possible mechanisms for metallization damage above the deposition temperature are enumerated. Electrical testing of the AlGaN/GaN HEMTs indicates that it is indeed possible to deposit NCD on GaN-based devices with no significant degradation in device performance.

Aluminum gallium nitride (GaN)/GaN high electron mobility transistor-based sensors for glucose detection in exhaled breath condensate.

Science.gov (United States)

Chu, Byung Hwan; Kang, Byoung Sam; Hung, Sheng Chun; Chen, Ke Hung; Ren, Fan; Sciullo, Andrew; Gila, Brent P; Pearton, Stephen J

2010-01-01

Immobilized aluminum gallium nitride (AlGaN)/GaN high electron mobility transistors (HEMTs) have shown great potential in the areas of pH, chloride ion, and glucose detection in exhaled breath condensate (EBC). HEMT sensors can be integrated into a wireless data transmission system that allows for remote monitoring. This technology offers the possibility of using AlGaN/GaN HEMTs for extended investigations of airway pathology of detecting glucose in EBC without the need for clinical visits. HEMT structures, consisting of a 3-microm-thick undoped GaN buffer, 30-A-thick Al(0.3)Ga(0.7)N spacer, and 220-A-thick silicon-doped Al(0.3)Ga(0.7)N cap layer, were used for fabricating the HEMT sensors. The gate area of the pH, chloride ion, and glucose detection was immobilized with scandium oxide (Sc(2)O(3)), silver chloride (AgCl) thin film, and zinc oxide (ZnO) nanorods, respectively. The Sc(2)O(3)-gated sensor could detect the pH of solutions ranging from 3 to 10 with a resolution of approximately 0.1 pH. A chloride ion detection limit of 10(-8) M was achieved with a HEMT sensor immobilized with the AgCl thin film. The drain-source current of the ZnO nanorod-gated AlGaN/GaN HEMT sensor immobilized with glucose oxidase showed a rapid response of less than 5 seconds when the sensor was exposed to the target glucose in a buffer with a pH value of 7.4. The sensor could detect a wide range of concentrations from 0.5 nM to 125 microM. There is great promise for using HEMT-based sensors to enhance the detection sensitivity for glucose detection in EBC. Depending on the immobilized material, HEMT-based sensors can be used for sensing different materials. These electronic detection approaches with rapid response and good repeatability show potential for the investigation of airway pathology. The devices can also be integrated into a wireless data transmission system for remote monitoring applications. This sensor technology could use the exhaled breath condensate to measure the

Molecular beam epitaxy for high-performance Ga-face GaN electron devices

International Nuclear Information System (INIS)

Kaun, Stephen W; Speck, James S; Wong, Man Hoi; Mishra, Umesh K

2013-01-01

Molecular beam epitaxy (MBE) has emerged as a powerful technique for growing GaN-based high electron mobility transistor (HEMT) epistructures. Over the past decade, HEMT performance steadily improved, mainly through the optimization of device fabrication processes. Soon, HEMT performance will be limited by the crystalline quality of the epistructure. MBE offers heterostructure growth with highly abrupt interfaces, low point defect concentrations, and very low carbon and hydrogen impurity concentrations. Minimizing parasitic leakage pathways and resistances is essential in the growth of HEMTs for high-frequency and high-power applications. Through growth on native substrates with very low threading dislocation density, low-leakage HEMTs with very low on-resistance can be realized. Ga-rich plasma-assisted MBE (PAMBE) has been studied extensively, and it is clear that this technique has inherent limitations, including a high density of leakage pathways and a very small growth parameter space. Relatively new MBE growth techniques—high-temperature N-rich PAMBE and ammonia-based MBE—are being developed to circumvent the shortcomings of Ga-rich PAMBE. (invited review)

Fermi edge singularity evidence from photoluminescence spectroscopy of AlGaAs/InGaAs/GaAs pseudomorphic HEMTs grown on (3 1 1)A GaAs substrates

International Nuclear Information System (INIS)

Rekaya, S.; Sfaxi, L.; Bru-Chevallier, C.; Maaref, H.

2011-01-01

InGaAs/AlGaAs/GaAs pseudomorphic high electron mobility transistor (P-HEMT) structures were grown by Molecular Beam Epitaxy (MBE) on (3 1 1)A GaAs substrates with different well widths, and studied by photoluminescence (PL) spectroscopy as a function of temperature and excitation density. The PL spectra are dominated by one or two spectral bands, corresponding, respectively, to one or two populated electron sub-bands in the InGaAs quantum well. An enhancement of PL intensity at the Fermi level energy (E F ) in the high-energy tail of the PL peak is clearly observed and associated with the Fermi edge singularity (FES). This is practically detected at the same energy for all samples, in contrast with energy transitions in the InGaAs channel, which are shifted to lower energy with increasing channel thickness. PL spectra at low temperature and low excitation density are used to optically determine the density of the two-dimensional electron gas (2DEG) in the InGaAs channel for different thicknesses. The results show an enhancement of the 2DEG density when the well width increases, in good agreement with our previous theoretical study.

An analytic current-voltage model for quasi-ballistic III-nitride high electron mobility transistors

Science.gov (United States)

Li, Kexin; Rakheja, Shaloo

2018-05-01

We present an analytic model to describe the DC current-voltage (I-V) relationship in scaled III-nitride high electron mobility transistors (HEMTs) in which transport within the channel is quasi-ballistic in nature. Following Landauer's transport theory and charge calculation based on two-dimensional electrostatics that incorporates negative momenta states from the drain terminal, an analytic expression for current as a function of terminal voltages is developed. The model interprets the non-linearity of access regions in non-self-aligned HEMTs. Effects of Joule heating with temperature-dependent thermal conductivity are incorporated in the model in a self-consistent manner. With a total of 26 input parameters, the analytic model offers reduced empiricism compared to existing GaN HEMT models. To verify the model, experimental I-V data of InAlN/GaN with InGaN back-barrier HEMTs with channel lengths of 42 and 105 nm are considered. Additionally, the model is validated against numerical I-V data obtained from DC hydrodynamic simulations of an unintentionally doped AlGaN-on-GaN HEMT with 50-nm gate length. The model is also verified against pulsed I-V measurements of a 150-nm T-gate GaN HEMT. Excellent agreement between the model and experimental and numerical results for output current, transconductance, and output conductance is demonstrated over a broad range of bias and temperature conditions.

Epitaxial ZnO gate dielectrics deposited by RF sputter for AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors

Science.gov (United States)

Yoon, Seonno; Lee, Seungmin; Kim, Hyun-Seop; Cha, Ho-Young; Lee, Hi-Deok; Oh, Jungwoo

2018-01-01

Radio frequency (RF)-sputtered ZnO gate dielectrics for AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors (MOS-HEMTs) were investigated with varying O2/Ar ratios. The ZnO deposited with a low oxygen content of 4.5% showed a high dielectric constant and low interface trap density due to the compensation of oxygen vacancies during the sputtering process. The good capacitance-voltage characteristics of ZnO-on-AlGaN/GaN capacitors resulted from the high crystallinity of oxide at the interface, as investigated by x-ray diffraction and high-resolution transmission electron microscopy. The MOS-HEMTs demonstrated comparable output electrical characteristics with conventional Ni/Au HEMTs but a lower gate leakage current. At a gate voltage of -20 V, the typical gate leakage current for a MOS-HEMT with a gate length of 6 μm and width of 100 μm was found to be as low as 8.2 × 10-7 mA mm-1, which was three orders lower than that of the Ni/Au Schottky gate HEMT. The reduction of the gate leakage current improved the on/off current ratio by three orders of magnitude. These results indicate that RF-sputtered ZnO with a low O2/Ar ratio is a good gate dielectric for high-performance AlGaN/GaN MOS-HEMTs.

Investigation of enhancement-mode AlGaN/GaN nanowire channel high-electron-mobility transistor with oxygen-containing plasma treatment

Science.gov (United States)

He, Yunlong; Wang, Chong; Mi, Minhan; Zhang, Meng; Zhu, Qing; Zhang, Peng; Wu, Ji; Zhang, Hengshuang; Zheng, Xuefeng; Yang, Ling; Duan, Xiaoling; Ma, Xiaohua; Hao, Yue

2017-05-01

A novel enhancement-mode (E-mode) AlGaN/GaN high-electron-mobility transistor (HEMT) has been fabricated, by combining nanowire channel (NC) structure fabrication and N2O (or O2) plasma treatment. A comparison of two NC-HEMTs with different plasma treatments has been made. The NC-HEMT with N2O plasma treatment shows an output current of 610 mA/mm and a peak transconductance of 450 mS/mm. The DIBL of the NC-HEMT with N2O plasma treatment is as low as 2 mV/V, and an SS of 70 mV/decade is achieved. The device exhibits an intrinsic current gain cutoff frequency f T of 19 GHz and a maximum oscillation frequency f max of 58 GHz.

High-Power Electron Accelerators for Space (and other) Applications

Energy Technology Data Exchange (ETDEWEB)

Nguyen, Dinh Cong [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lewellen, John W. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2016-05-23

This is a presentation on high-power electron accelerators for space and other applications. The main points covered are: electron beams for space applications, new designs of RF accelerators, high-power high-electron mobility transistors (HEMT) testing, and Li-ion battery design. In summary, the authors have considered a concept of 1-MeV electron accelerator that can operate up to several seconds. This concept can be extended to higher energy to produce higher beam power. Going to higher beam energy requires adding more cavities and solid-state HEMT RF power devices. The commercial HEMT have been tested for frequency response and RF output power (up to 420 W). Finally, the authors are testing these HEMT into a resonant load and planning for an electron beam test in FY17.

Significant performance enhancement in AlGaN/GaN high electron mobility transistor by high-κ organic dielectric

International Nuclear Information System (INIS)

Ze-Gao, Wang; Yuan-Fu, Chen; Cao, Chen; Ben-Lang, Tian; Fu-Tong, Chu; Xing-Zhao, Liu; Yan-Rong, Li

2010-01-01

The electrical properties of AlGaN/GaN high electron mobility transistor (HEMT) with and without high-κ organic dielectrics are investigated. The maximum drain current I D max and the maximum transconductance g m max of the organic dielectric/AlGaN/GaN structure can be enhanced by 74.5%, and 73.7% compared with those of the bare AlGaN/GaN HEMT, respectively. Both the threshold voltage V T and g m max of the dielectric/AlGaN/GaN HEMT are strongly dielectric-constant-dependent. Our results suggest that it is promising to significantly improve the performance of the AlGaN/GaN HEMT by introducing the high-κ organic dielectric. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Temperature Effects on The Electrical Characteristics of In0.15Ga0.85As Pseudomorphic High-Electron-Mobility Transistors

Directory of Open Access Journals (Sweden)

BECHLAGHEM Fatima Zohra

2017-10-01

Full Text Available Nowadays, GaAs-based HEMTs and pseudomorphic HEMTs are speedily replacing conventional MESFET technology in military and commercial applications including, communication, radar and automotive technologies having need of high gain, and low noise figures especially at millimeter-wave frequencies. In this work, a short gate length pseudomorphic HEMT "p-HEMT" on GaAs substrate is treated. As temperature dependence study is a very important part of the complete characterization on active devices, the impact of temperature variation on the electrical properties of our 30nm short gate length pseudomorphic high-electron mobility In0.15Ga0.85As device is investigated. All our static DC device characteristics and RF response have been obtained using a device simulator that is Silvaco software to examine temperature impact on our device output current, transconductance and cutoff frequency. The 30nm gate pseudomorphic HEMT reported here exhibit superior DC and RF performances, Our results reveals a maximum drain-source current IDS up to 537.16 mA/mm, a peak extrinsic transconductance Gm of 345.4 mS/mm, a cutoff frequency Ft of 285.9 GHz, and a maximum frequency Fmax of 1580 GHz at room temperature.

Effect of gate length on breakdown voltage in AlGaN/GaN high-electron-mobility transistor

International Nuclear Information System (INIS)

Luo Jun; Zhao Sheng-Lei; Mi Min-Han; Zhang Jin-Cheng; Ma Xiao-Hua; Hao Yue; Chen Wei-Wei; Hou Bin

2016-01-01

The effects of gate length L G on breakdown voltage V BR are investigated in AlGaN/GaN high-electron-mobility transistors (HEMTs) with L G = 1 μm∼ 20 μm. With the increase of L G , V BR is first increased, and then saturated at L G = 3 μm. For the HEMT with L G = 1 μm, breakdown voltage V BR is 117 V, and it can be enhanced to 148 V for the HEMT with L G = 3 μm. The gate length of 3 μm can alleviate the buffer-leakage-induced impact ionization compared with the gate length of 1 μm, and the suppression of the impact ionization is the reason for improving the breakdown voltage. A similar suppression of the impact ionization exists in the HEMTs with L G > 3 μm. As a result, there is no obvious difference in breakdown voltage among the HEMTs with L G = 3 μm∼20 μm, and their breakdown voltages are in a range of 140 V–156 V. (paper)

Novel model of a AlGaN/GaN high electron mobility transistor based on an artificial neural network

International Nuclear Information System (INIS)

Cheng Zhi-Qun; Hu Sha; Liu Jun; Zhang Qi-Jun

2011-01-01

In this paper we present a novel approach to modeling AlGaN/GaN high electron mobility transistor (HEMT) with an artificial neural network (ANN). The AlGaN/GaN HEMT device structure and its fabrication process are described. The circuit-based Neuro-space mapping (neuro-SM) technique is studied in detail. The EEHEMT model is implemented according to the measurement results of the designed device, which serves as a coarse model. An ANN is proposed to model AlGaN/GaN HEMT based on the coarse model. Its optimization is performed. The simulation results from the model are compared with the measurement results. It is shown that the simulation results obtained from the ANN model of AlGaN/GaN HEMT are more accurate than those obtained from the EEHEMT model. (condensed matter: structural, mechanical, and thermal properties)

Thermal instability and the growth of the InGaAs/AlGaAs pseudomorphic high electron mobility transistor system

International Nuclear Information System (INIS)

Pellegrino, Joseph G.; Qadri, Syed B.; Mahadik, Nadeemullah A.; Rao, Mulpuri V.; Tseng, Wen F.; Thurber, Robert; Gajewski, Donald; Guyer, Jonathan

2007-01-01

The effects of temperature overshoot during molecular beam epitaxy growth on the transport properties of conventionally and delta-doped pseudomorphic high electron mobility transistor (pHEMT) structures have been examined. A diffuse reflectance spectroscopy (DRS)-controlled versus a thermocouple (TC)-controlled, growth scheme is compared. Several advantages of the DRS-grown pHEMTs over the TC-controlled version were observed. Modest improvements in mobility, on the order of 2%-3%, were observed in addition to a 20% reduction in carrier freeze-out for the DRS-grown pHEMTs at 77 K

ONR D&I Electronics Technology Programs

National Research Council Canada - National Science Library

Moon, Jeong

2008-01-01

Program Status: One of the D&I program goals is to develop greatly improved field-plated MMW GaN HEMT devices with high ft/fmax, which will improve gain/PAE and output power of GaN HEMT MMIC PAs simultaneously...

Concept development of "compassion fatigue" in clinical nurses: Application of Schwartz-Barcott and Kim's hybrid model

Directory of Open Access Journals (Sweden)

Mahdieh Sabery

2017-06-01

Full Text Available Compassion fatigue is not a new concept in nursing; yet, it is not well known and there is no fixed clear definition of the term. The ambiguity surrounding how to define compassion fatigue has challenged its measurement and evaluation. Thus, any attempt to determine attributes of this underdeveloped concept and studying it in a new socio-cultural context requires concept development. The purpose of this study is to clarify the concept of compassion fatigue through concept development and to produce a vivid and tentative definition of this concept in clinical practice. Concept development was conducted using a three-step hybrid concept analysis including theoretical, fieldwork, and final analysis phases according to Schwartz-Barcott and Kim's method. We reviewed and analyzed 48 articles that met the inclusion criteria. Following, the first author conducted 13 interviews with clinical nurses followed by an inductive content analysis. Finally, a comprehensive definition of compassion fatigue in nurses was attained. Compassion fatigue in nurses can be explained as a cumulative and progressive process of absorption of the patient’s pain and suffering formed from the sympathetic and caring interactions with the patients and their families. The physical, emotional, intellectual, spiritual, social, and organizational consequences of compassion fatigue are so extensive that they threaten the existential integrity of the nurse. Context-based variables (culture, family, and community such as personality features like devotion behaviors and commitment towards the patient, exposure to multiple stressors, organizational challenges, and lack of self-care are factors associated with an increased risk of compassion fatigue. Concept development of compassion fatigue is the first step in the protection of nurses against the destructive consequences of compassion fatigue and to improve quality of care.

Comparative analysis of the effects of tantalum doping and annealing on atomic layer deposited (Ta2O5)x(Al2O3)1−x as potential gate dielectrics for GaN/AlxGa1−xN/GaN high electron mobility transistors

International Nuclear Information System (INIS)

Partida-Manzanera, T.; Roberts, J. W.; Sedghi, N.; Potter, R. J.; Bhat, T. N.; Zhang, Z.; Tan, H. R.; Dolmanan, S. B.; Tripathy, S.

2016-01-01

This paper describes a method to optimally combine wide band gap Al 2 O 3 with high dielectric constant (high-κ) Ta 2 O 5 for gate dielectric applications. (Ta 2 O 5 ) x (Al 2 O 3 ) 1−x thin films deposited by thermal atomic layer deposition (ALD) on GaN-capped Al x Ga 1−x N/GaN high electron mobility transistor (HEMT) structures have been studied as a function of the Ta 2 O 5 molar fraction. X-ray photoelectron spectroscopy shows that the bandgap of the oxide films linearly decreases from 6.5 eV for pure Al 2 O 3 to 4.6 eV for pure Ta 2 O 5 . The dielectric constant calculated from capacitance-voltage measurements also increases linearly from 7.8 for Al 2 O 3 up to 25.6 for Ta 2 O 5 . The effect of post-deposition annealing in N 2 at 600 °C on the interfacial properties of undoped Al 2 O 3 and Ta-doped (Ta 2 O 5 ) 0.12 (Al 2 O 3 ) 0.88 films grown on GaN-HEMTs has been investigated. These conditions are analogous to the conditions used for source/drain contact formation in gate-first HEMT technology. A reduction of the Ga-O to Ga-N bond ratios at the oxide/HEMT interfaces is observed after annealing, which is attributed to a reduction of interstitial oxygen-related defects. As a result, the conduction band offsets (CBOs) of the Al 2 O 3 /GaN-HEMT and (Ta 2 O 5 ) 0.16 (Al 2 O 3 ) 0.84 /GaN-HEMT samples increased by ∼1.1 eV to 2.8 eV and 2.6 eV, respectively, which is advantageous for n-type HEMTs. The results demonstrate that ALD of Ta-doped Al 2 O 3 can be used to control the properties of the gate dielectric, allowing the κ-value to be increased, while still maintaining a sufficient CBO to the GaN-HEMT structure for low leakage currents

A two-dimensional fully analytical model with polarization effect for off-state channel potential and electric field distributions of GaN-based field-plated high electron mobility transistor

International Nuclear Information System (INIS)

Mao Wei; She Wei-Bo; Zhang Chao; Zhang Jin-Cheng; Zhang Jin-Feng; Liu Hong-Xia; Yang Lin-An; Zhang Kai; Zhao Sheng-Lei; Chen Yong-He; Zheng Xue-Feng; Hao Yue; Yang Cui; Ma Xiao-Hua

2014-01-01

In this paper, we present a two-dimensional (2D) fully analytical model with consideration of polarization effect for the channel potential and electric field distributions of the gate field-plated high electron mobility transistor (FP-HEMT) on the basis of 2D Poisson's solution. The dependences of the channel potential and electric field distributions on drain bias, polarization charge density, FP structure parameters, AlGaN/GaN material parameters, etc. are investigated. A simple and convenient approach to designing high breakdown voltage FP-HEMTs is also proposed. The validity of this model is demonstrated by comparison with the numerical simulations with Silvaco—Atlas. The method in this paper can be extended to the development of other analytical models for different device structures, such as MIS-HEMTs, multiple-FP HETMs, slant-FP HEMTs, etc. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Novel model of a AlGaN/GaN high electron mobility transistor based on an artificial neural network

Science.gov (United States)

Cheng, Zhi-Qun; Hu, Sha; Liu, Jun; Zhang, Qi-Jun

2011-03-01

In this paper we present a novel approach to modeling AlGaN/GaN high electron mobility transistor (HEMT) with an artificial neural network (ANN). The AlGaN/GaN HEMT device structure and its fabrication process are described. The circuit-based Neuro-space mapping (neuro-SM) technique is studied in detail. The EEHEMT model is implemented according to the measurement results of the designed device, which serves as a coarse model. An ANN is proposed to model AlGaN/GaN HEMT based on the coarse model. Its optimization is performed. The simulation results from the model are compared with the measurement results. It is shown that the simulation results obtained from the ANN model of AlGaN/GaN HEMT are more accurate than those obtained from the EEHEMT model. Project supported by the National Natural Science Foundation of China (Grant No. 60776052).

Metalorganic chemical vapor deposition growth and thermal stability of the AlInN/GaN high electron mobility transistor structure

International Nuclear Information System (INIS)

Yu, Hongbo; Ozturk, Mustafa; Demirel, Pakize; Cakmak, Huseyin; Bolukbas, Basar; Caliskan, Deniz; Ozbay, Ekmel

2011-01-01

The Al x In 1−x N barrier high electron mobility transistor (HEMT) structure has been optimized with varied barrier composition and thickness grown by metalorganic chemical vapor deposition. After optimization, a transistor structure comprising a 7 nm thick nearly lattice-matched Al 0.83 In 0.17 N barrier exhibits a sheet electron density of 2.0 × 10 13 cm −2 with a high electron mobility of 1540 cm 2 V −1 s −1 . An Al 0.83 In 0.17 N barrier HEMT device with 1 µm gate length provides a current density of 1.0 A mm −1 at V GS = 0 V and an extrinsic transconductance of 242 mS mm −1 , which are remarkably improved compared to that of a conventional Al 0.3 Ga 0.7 N barrier HEMT. To investigate the thermal stability of the HEMT epi-structures, post-growth annealing experiments up to 800 °C have been applied to Al 0.83 In 0.17 N and Al 0.3 Ga 0.7 N barrier heterostructures. As expected, the electrical properties of an Al 0.83 In 0.17 N barrier HEMT structure showed less stability than that of an Al 0.3 Ga 0.7 N barrier HEMT to the thermal annealing. The structural properties of Al 0.83 In 0.17 N/GaN also showed more evidence for decomposition than that of the Al 0.3 Ga 0.7 N/GaN structure after 800 °C post-annealing

Influence of 60Co gamma radiation on fluorine plasma treated enhancement-mode high-electron-mobility transistor

International Nuclear Information System (INIS)

Quan Si; Hao Yue; Ma Xiao-Hua; Yu Hui-You

2011-01-01

AlGaN/GaN depletion-mode high-electron-mobility transistor (D-HEMT) and fluorine (F) plasma treated enhancement-mode high-electron-mobility transistor (E-HEMT) are exposed to 60 Co gamma radiation with a dose of 1.6 Mrad (Si). No degradation is observed in the performance of D-HEMT. However, the maximum transconductance of E-HEMT is increased after radiation. The 2DEG density and the mobility are calculated from the results of capacitance-voltage measurement. The electron mobility decreases after fluorine plasma treatment and recovers after radiation. Conductance measurements in a frequency range from 10 kHz to 1 MHz are used to characterize the trapping effects in the devices. A new type of trap is observed in the F plasma treated E-HEMT compared with the D-HEMT, but the density of the trap decreases by radiation. Fitting of G p /ω data yields the trap densities D T = (1 − 3) × 10 12 cm −2 · eV −1 and D T = (0.2 − 0.8) × 10 12 cm −2 · eV −1 before and after radiation, respectively. The time constant is 0.5 ms-6 ms. With F plasma treatment, the trap is introduced by etch damage and degrades the electronic mobility. After 60 Co gamma radiation, the etch damage decreases and the electron mobility is improved. The gamma radiation can recover the etch damage caused by F plasma treatment. (interdisciplinary physics and related areas of science and technology)

Hâkim Tasarım ve Ekşi Sözlük: İnternet’in Dönüşümünü Anlamak

Directory of Open Access Journals (Sweden)

Babacan Taşdemir

2014-02-01

Full Text Available Son yıllarda bir yanda devletler, diğer yanda sermaye kuruluşları, siyasi, idari ve ticari amaçları ile İnternet ortamını gittikçe daha fazla kolonileştirmektedirler. Bu da siyasi ve ticari baskılardan azade bir özgürlük alanı olarak görülen İnternet’e ilişkin toplumsal beklentilere zıt bir durum ortaya çıkarmaktadır. Çalışmamız, İnternet’teki bu dönüşümü üretim gücü ve üretim ilişkileri kavramları üzerinden eleştirel bir gözle değerlendirmeyi önermektedir. Dönüşüm, ‘Teknolojik Değişimin Döngüsel Modeli’ndeki ‘mayalanma dönemi’ ve ‘hâkim tasarım’ kavramlarının sunduğu potansiyelden faydalanılarak açıklanmaya çalışılmaktadır.  Burada ‘mayalanma dönemi’ ile İnternette ifade özgürlüğü açısından daha uygun olan ilk dönemlere, ‘hâkim tasarım’ ile ise yerleşik üretim ve iktidar ilişkilerinin daha fazla nüfuz ettiği yakın döneme gönderme yapılmaktadır. Ekşi Sözlük örneği ile de savlarını destekleyen çalışmamız, üç kategori üzerinden örnek olaylarla Sözlük’ün dönüşümünü değerlendirmektedir: İş çevreleriyle ticari ilişkilere bağlı dönüşüm, İnternet’in düzenlenmesine dair hukuki çerçeve ve kamu otoriteleri ile ilişkilere bağlı olarak geçirilen dönüşüm, Sözlük kullanıcıları ve sahipleri arasındaki örgütsel ilişkinin değişimi dolayımında geçirilen dönüşüm. Sonuç olarak, İnternet’in ‘mayalanma döneminde’, yani görece serbest bir ortamda, Ekşi Sözlük popülaritesini ve saygınlığını, yaratıcı ve muhalif duruş ile karakterize olan bir ifade alanı olarak kazansa da, zaman içinde tamamen kâr merkezli bir işletmeye dönüşmektedir. Böylece bir yandan pazarlama stratejilerinin ana mecralarından biri diğer yandan da politik baskıya tabii sıradan bir forum ve paylaşım sitesi haline gelmektedir. Sözlük’ün gelişimine ilişkin örnek olaylar ele

The operation cutoff frequency of high electron mobility transistor measured by terahertz method

International Nuclear Information System (INIS)

Zhu, Y. M.; Zhuang, S. L.

2014-01-01

Commonly, the cutoff frequency of high electron mobility transistor (HEMT) can be measured by vector network analyzer (VNA), which can only measure the sample exactly in low frequency region. In this paper, we propose a method to evaluate the cutoff frequency of HEMT by terahertz (THz) technique. One example shows the cutoff frequency of our HEMT is measured at ∼95.30 GHz, which is reasonable agreement with that estimated by VNA. It is proved THz technology a potential candidate for the substitution of VNA for the measurement of high-speed devices even up to several THz.

Botulinum toxin detection using AlGaN /GaN high electron mobility transistors

Science.gov (United States)

Wang, Yu-Lin; Chu, B. H.; Chen, K. H.; Chang, C. Y.; Lele, T. P.; Tseng, Y.; Pearton, S. J.; Ramage, J.; Hooten, D.; Dabiran, A.; Chow, P. P.; Ren, F.

2008-12-01

Antibody-functionalized, Au-gated AlGaN /GaN high electron mobility transistors (HEMTs) were used to detect botulinum toxin. The antibody was anchored to the gate area through immobilized thioglycolic acid. The AlGaN /GaN HEMT drain-source current showed a rapid response of less than 5s when the target toxin in a buffer was added to the antibody-immobilized surface. We could detect a range of concentrations from 1to10ng/ml. These results clearly demonstrate the promise of field-deployable electronic biological sensors based on AlGaN /GaN HEMTs for botulinum toxin detection.

Simulation and experimental study of high power microwave damage effect on AlGaAs/InGaAs pseudomorphic high electron mobility transistor

International Nuclear Information System (INIS)

Yu Xin-Hai; Chai Chang-Chun; Liu Yang; Yang Yin-Tang; Xi Xiao-Wen

2015-01-01

The high power microwave (HPM) damage effect on the AlGaAs/InGaAs pseudomorphic high electron mobility transistor (pHEMT) is studied by simulation and experiments. Simulated results suggest that the HPM damage to pHEMT is due to device burn-out caused by the emerging current path and strong electric field beneath the gate. Besides, the results demonstrate that the damage power threshold decreases but the energy threshold slightly increases with the increase of pulse-width, indicating that HPM with longer pulse-width requires lower power density but more energy to cause the damage to pHEMT. The empirical formulas are proposed to describe the pulse-width dependence. Then the experimental data validate the pulse-width dependence and verify that the proposed formula P = 55τ −0.06 is capable of quickly and accurately estimating the HPM damage susceptibility of pHEMT. Finally the interior observation of damaged samples by scanning electron microscopy (SEM) illustrates that the failure mechanism of the HPM damage to pHEMT is indeed device burn-out and the location beneath the gate near the source side is most susceptible to burn-out, which is in accordance with the simulated results. (paper)

Evaluation of thermal resistance constitution for packaged AlGaN/GaN high electron mobility transistors by structure function method

International Nuclear Information System (INIS)

Zhang Guang-Chen; Feng Shi-Wei; Zhou Zhou; Li Jing-Wan; Guo Chun-Sheng

2011-01-01

The evaluation of thermal resistance constitution for packaged AlGaN/GaN high electron mobility transistor (HEMT) by structure function method is proposed in this paper. The evaluation is based on the transient heating measurement of the AlGaN/GaN HEMT by pulsed electrical temperature sensitive parameter method. The extracted chip-level and package-level thermal resistances of the packaged multi-finger AlGaN/GaN HEMT with 400-μm SiC substrate are 22.5 K/W and 7.2 K/W respectively, which provides a non-invasive method to evaluate the chip-level thermal resistance of packaged AlGaN/GaN HEMTs. It is also experimentally proved that the extraction of the chip-level thermal resistance by this proposed method is not influenced by package form of the tested device and temperature boundary condition of measurement stage. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

pH sensor using AlGaN/GaN high electron mobility transistors with Sc2O3 in the gate region

International Nuclear Information System (INIS)

Kang, B. S.; Wang, H. T.; Ren, F.; Gila, B. P.; Abernathy, C. R.; Pearton, S. J.; Johnson, J. W.; Rajagopal, P.; Roberts, J. C.; Piner, E. L.; Linthicum, K. J.

2007-01-01

Ungated AlGaN/GaN high electron mobility transistors (HEMTs) exhibit large changes in current upon exposing the gate region to polar liquids. The polar nature of the electrolyte introduced leds to a change of surface charges, producing a change in surface potential at the semiconductor/liquid interface. The use of Sc 2 O 3 gate dielectric produced superior results to either a native oxide or UV ozone-induced oxide in the gate region. The ungated HEMTs with Sc 2 O 3 in the gate region exhibited a linear change in current between pH 3 and 10 of 37 μA/pH. The HEMT pH sensors show stable operation with a resolution of <0.1 pH over the entire pH range. The results indicate that the HEMTs may have application in monitoring pH solution changes between 7 and 8, the range of interest for testing human blood

Analysis of the coexisting pathways for NO and N2O formation in Chernozem using the (15)N-tracer SimKIM-Advanced model.

Science.gov (United States)

Stange, Claus Florian; Spott, Oliver; Russow, Rolf

2013-01-01

The nitrogen (N) cycle consists of a variety of microbial processes. These processes often occur simultaneously in soils, but respond differently to local environmental conditions due to process-specific biochemical restrictions (e.g. oxygen levels). Hence, soil nitrogen cycling (e.g. soil N gas production through nitrification and denitrification) is individually affected through these processes, resulting in the complex and highly dynamic behaviour of total soil N turnover. The development and application of methods that facilitate the quantification of individual contributions of coexisting processes is a fundamental prerequisite for (i) understanding the dynamics of soil N turnover and (ii) implementing these processes in ecosystem models. To explain the unexpected results of the triplet tracer experiment (TTE) of Russow et al. (Role of nitrite and nitric oxide in the processes of nitrification and denitrification in soil: results from (15)N tracer experiments. Soil Biol Biochem. 2009;41:785-795) the existing SimKIM model was extended to the SimKIM-Advanced model through the addition of three separate nitrite subpools associated with ammonia oxidation, oxidation of organic nitrogen (Norg), and denitrification, respectively. For the TTE, individual treatments with (15)N ammonium, (15)N nitrate, and (15)N nitrite were conducted under oxic, hypoxic, and anoxic conditions, respectively, to clarify the role of nitric oxide as a denitrification intermediate during N2O formation. Using a split nitrite pool, this analysis model explains the observed differences in the (15)N enrichments in nitric oxide (NO) and nitrous oxide (N2O) which occurred in dependence on different oxygen concentrations. The change from oxic over hypoxic to anoxic conditions only marginally increased the NO and N2O release rates (1.3-fold). The analysis using the model revealed that, under oxic and hypoxic conditions, Norg-based N2O production was the dominant pathway, contributing to 90 and 50�

Kim Magrini | NREL

Science.gov (United States)

System Control software Education Ph.D., Physical Chemistry, University of Colorado at Boulder, 1984-1989 But Converges During Decomposition-Transformation," Soil Biology and Biochemistry (2013) " Catalytic Conditioning of Biomass-Derived Syngas," Topics in Catalysis (2012) "Transformation of

Study on the electrical degradation of AlGaN/GaN MIS-HEMTs induced by residual stress of SiNx passivation

Science.gov (United States)

Bai, Zhiyuan; Du, Jiangfeng; Liu, Yong; Xin, Qi; Liu, Yang; Yu, Qi

2017-07-01

In this paper, we report a new phenomenon in C-V measurement of different gate length MIS-HEMTs, which can be associated with traps character of the AlGaN/GaN interface. The analysis of DC measurement, frequency dependent capacitance-voltage measurements and simulation show that the stress from passivation layer may induce a decrease of drain output current Ids, an increase of on-resistance, serious nonlinearity of transconductance gm, and a new peak of C-V curve. The value of the peak is reduced to zero while the gate length and measure frequency are increasing to 21 μm and 1 MHz, respectively. By using conductance method, the SiNx/GaN interface traps with energy level of EC-0.42 eV to EC-0.45 eV and density of 3.2 × 1012 ∼ 5.0 × 1012 eV-1 cm-2 is obtained after passivation. According to the experimental and simulation results, formation of the acceptor-like traps with concentration of 3 × 1011 cm-2 and energy level of EC-0.37 eV under the gate on AlGaN barrier side of AlGaN/GaN interface is the main reason for the degradation after the passivation. He is currently an Associate Professor with State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Microelectronics and Solid-State Electronics, UESTC. He is the author of over 30 peer-reviewed journal papers and more than 20 conference papers. He has also hold over 20 patents. His research interests include Gallium Nitride based high-voltage power switching devices, microwave and millimeter-wave power devices and integrated technologies. Dr. Yu was a recipient of the prestigious Award of Science and Technology of China

Selective epitaxial growth of monolithically integrated GaN-based light emitting diodes with AlGaN/GaN driving transistors

International Nuclear Information System (INIS)

Liu, Zhaojun; Ma, Jun; Huang, Tongde; Liu, Chao; May Lau, Kei

2014-01-01

In this Letter, we report selective epitaxial growth of monolithically integrated GaN-based light emitting diodes (LEDs) with AlGaN/GaN high-electron-mobility transistor (HEMT) drivers. A comparison of two integration schemes, selective epitaxial removal (SER), and selective epitaxial growth (SEG) was made. We found the SER resulted in serious degradation of the underlying LEDs in a HEMT-on-LED structure due to damage of the p-GaN surface. The problem was circumvented using the SEG that avoided plasma etching and minimized device degradation. The integrated HEMT-LEDs by SEG exhibited comparable characteristics as unintegrated devices and emitted modulated blue light by gate biasing

Comparative analysis of the effects of tantalum doping and annealing on atomic layer deposited (Ta{sub 2}O{sub 5}){sub x}(Al{sub 2}O{sub 3}){sub 1−x} as potential gate dielectrics for GaN/Al{sub x}Ga{sub 1−x}N/GaN high electron mobility transistors

Energy Technology Data Exchange (ETDEWEB)

Partida-Manzanera, T., E-mail: sgtparti@liv.ac.uk [Centre for Materials and Structures, School of Engineering, University of Liverpool, Liverpool, L69 3GH (United Kingdom); Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), Innovis, 2 Fusionopolis way, Singapore 138634 (Singapore); Roberts, J. W.; Sedghi, N.; Potter, R. J. [Centre for Materials and Structures, School of Engineering, University of Liverpool, Liverpool, L69 3GH (United Kingdom); Bhat, T. N.; Zhang, Z.; Tan, H. R.; Dolmanan, S. B.; Tripathy, S. [Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), Innovis, 2 Fusionopolis way, Singapore 138634 (Singapore)

2016-01-14

This paper describes a method to optimally combine wide band gap Al{sub 2}O{sub 3} with high dielectric constant (high-κ) Ta{sub 2}O{sub 5} for gate dielectric applications. (Ta{sub 2}O{sub 5}){sub x}(Al{sub 2}O{sub 3}){sub 1−x} thin films deposited by thermal atomic layer deposition (ALD) on GaN-capped Al{sub x}Ga{sub 1−x}N/GaN high electron mobility transistor (HEMT) structures have been studied as a function of the Ta{sub 2}O{sub 5} molar fraction. X-ray photoelectron spectroscopy shows that the bandgap of the oxide films linearly decreases from 6.5 eV for pure Al{sub 2}O{sub 3} to 4.6 eV for pure Ta{sub 2}O{sub 5}. The dielectric constant calculated from capacitance-voltage measurements also increases linearly from 7.8 for Al{sub 2}O{sub 3} up to 25.6 for Ta{sub 2}O{sub 5}. The effect of post-deposition annealing in N{sub 2} at 600 °C on the interfacial properties of undoped Al{sub 2}O{sub 3} and Ta-doped (Ta{sub 2}O{sub 5}){sub 0.12}(Al{sub 2}O{sub 3}){sub 0.88} films grown on GaN-HEMTs has been investigated. These conditions are analogous to the conditions used for source/drain contact formation in gate-first HEMT technology. A reduction of the Ga-O to Ga-N bond ratios at the oxide/HEMT interfaces is observed after annealing, which is attributed to a reduction of interstitial oxygen-related defects. As a result, the conduction band offsets (CBOs) of the Al{sub 2}O{sub 3}/GaN-HEMT and (Ta{sub 2}O{sub 5}){sub 0.16}(Al{sub 2}O{sub 3}){sub 0.84}/GaN-HEMT samples increased by ∼1.1 eV to 2.8 eV and 2.6 eV, respectively, which is advantageous for n-type HEMTs. The results demonstrate that ALD of Ta-doped Al{sub 2}O{sub 3} can be used to control the properties of the gate dielectric, allowing the κ-value to be increased, while still maintaining a sufficient CBO to the GaN-HEMT structure for low leakage currents.

Engineering the Ideal Array (BRIEFING CHARTS)

Science.gov (United States)

2007-03-05

48 V, f = 10 GHz GaN HEMT Transistor i t Dramatically higher: • Output power • Efficiency • Bandwidth GaN HEMT Power Amplifier lifi ...functions – RF amplifiers – 4-bit phase shifters – Amplitude controllers – Summing network – Power control – Latches for phase state – Address

Visible-blind and solar-blind detection induced by defects in AlGaN high electron mobility transistors

Science.gov (United States)

Armstrong, Andrew M.; Klein, Brianna; Allerman, Andrew A.; Douglas, Erica A.; Baca, Albert G.; Crawford, Mary H.; Pickrell, Greg W.; Sanchez, Carlos A.

2018-03-01

Visible- and solar-blind detection was demonstrated using Al0.45Ga0.55N/Al0.30Ga0.70N and Al0.85Ga0.25N/Al0.70Ga0.30N high electron mobility transistors (HEMTs), respectively. Peak responsivities (S) of 3.9 × 106 A/W in the saturation mode and 6.2 × 104 A/W in the pinch-off mode were observed for the visible-blind Al0.45Ga0.55N/Al0.30Ga0.70N HEMT, and a peak S of 4.9 × 104 A/W was observed for the solar-blind Al0.85Ga0.15N/Al0.70Ga0.30N HEMT in the saturation mode. Spectrally resolved photocurrent investigation indicated that sub-bandgap absorption by defect states was the primary origin of the HEMTs' photoresponse. Defect-mediated responsivity caused slow photocurrent rise and fall times, but electrical pulsing was used to improve the bandwidth at the cost of optical gain. Operating HEMTs in this dynamic mode achieved a 25 Hz bandwidth with S = 2.9 × 105 A/W in accumulation and S = 2.0 × 104 A/W in pinch-off for visible-blind detection and S = 5.1 × 103 A/W for solar-blind detection.

A STUDY OF METABOLIC SYNDROME IN PATIENTS UNDERGOING CORONARY ANGIOGRAPHY AT KIMS HOSPITAL, HUBBALLI, KARNATAKA, INDIA

Directory of Open Access Journals (Sweden)

Chandrashekar K

2018-01-01

Full Text Available BACKGROUND Coronary heart disease has become an epidemic since 20th century. Deaths due to the same are increasing of around 17.5 million deaths in year 2012. The deaths are increasing more in developing countries and metabolic syndrome is a cluster of disorders, which are promoting the development of coronary artery diseases. The disorders include central obesity, insulin resistance, dyslipidaemia and hypertension. Increasing prevalence, changing lifestyle and progression of the disease without obvious symptoms had led to increasing morbidity and mortality. The non-infectious epidemic of the century is posing great challenges to healthcare and research in development of more infrastructure and funds to prevent and treat the disease. MATERIALS AND METHODS A total of 100 patients diagnosed with CAD and posted for Coronary Angiogram (CAG in ICCU at KIMS Hospital, Hubballi, were studied over a period of one and a half year. Cases were categorised according to ATPIII and new IDF criteria for metabolic syndrome and compared. Clinical evaluation, ECG, lipid profile and 2D-echo was done. Statistical analysis done using unpaired t-test, Mann-Whitney tests, Chi-square test and Kappa statistics. RESULTS Of the total 100, 57 had metabolic syndrome by either ATP criteria or IDF criteria. Kappa=0.859 (p-value 150 mg/dL and DM or FBS >100 mg/dL (p value <0.001. The mean values of SBP (144.0 vs. 120.8, DBP (85.6 vs. 73.8 and waist circumference (95.4 vs. 87.7 was statistically significant (p value <0.01 between patients with metabolic syndrome and without metabolic syndrome with IDF criteria (p value <0.001. It was observed LAD (28.1% was the most common vessel involved individually. There was no much significance related to metabolic syndrome. Incidence of CAD was more common in patients with metabolic syndrome than other group. CONCLUSION The prevalence of metabolic syndrome was high in patients with CAD. Both metabolic syndrome definitions identify subset

El individuo en el cambio: la transformación de las relaciones bilaterales entre la República de Corea y la República Popular Democrática de Corea, bajo la figura del presidente surcoreano Kim Dae-Jung

OpenAIRE

Perilla Moreno, Jairo Andrés

2017-01-01

Este artículo busca interpretar el proceso mediante el cual las ideas y presupuestos políticos y sociales del expresidente surcoreano Kim Dae-Jung, permitieron una transformación significativa de las relaciones bilaterales entre Corea del Sur y Corea del Norte, durante su periodo presidencial entre los años 1998 y 2003. Inicialmente, dichas relaciones estuvieron caracterizadas por una incesante tensión militar como resultado de la Guerra de Corea, escenario dentro del cual apareció la figura ...

Metal oxide, Group V-VI chalcogenides and GaN/AlGaN photodetectors

Science.gov (United States)

Hasan, Md. Rezaul

. Position of gate pad defined the center point of the image without tilting the image as the geometry of the gate pads were parallel to each other. And there was no effect of gate pad bonding wire orientation because of the larger width of gate pads. For the GaN/AlGaNHEMT, the effect of Al mole fraction in AlGaN layer and the effect of gate oxide on the DC and low frequency noise characterization was studied. MOSHEMT with SiO2 improved the Id(on)/I d(off) ratio up to more than 8 orders, while it is only 10 times in conventional HEMT. It was shown that the gate leakage and isolation leakage suppression efficiency improved dramatically with the oxide. Subthreshold swing (SS) of MOS-HEMTs with different Al mole fraction (from 20% to 35%) vary slightly from 72 mV/decade to 79 mV/decade, but the conventional GaN/AlGaN HEMT showed SS of 2.4V/decade. Low frequency noise study revealed the difference in transport mechanism between HEMT and MOS-HEMTs. By using Carrier Number Fluctuation (CNF) model on the measured data, it was found that the noise is predominantly coming from the surface states. While generation-recombination is very prominent in conventional HEMT, it is very weak and insignificant in both MOS-HEMTs at much higher frequencies. This study reveals that very high number of surface states assisting the tunneling in schottky/AlGaN barrier is responsible for unusually high leakage and higher noise level in conventional HEMT. Leakage level is improved from mA/mm range for HEMT to pA/mm range for MOS-HEMTs. Leakage suppression improvement and minimization of noise level can be mainly attributed to high quality SiO2. Hooge's constant was in the order of 5-6x10-3 in MOS-HEMTs, which is 5x10 -2 for conventional HEMT indicating much lower noise level in the MOS-HEMTs. (Abstract shortened by ProQuest.).

Study on GaN buffer leakage current in AlGaN/GaN high electron mobility transistor structures grown by ammonia-molecular beam epitaxy on 100-mm Si(111)

International Nuclear Information System (INIS)

Ravikiran, L.; Radhakrishnan, K.; Ng, G. I.; Munawar Basha, S.; Dharmarasu, N.; Agrawal, M.; Manoj kumar, C. M.; Arulkumaran, S.

2015-01-01

The effect of carbon doping on the structural and electrical properties of GaN buffer layer of AlGaN/GaN high electron mobility transistor (HEMT) structures has been studied. In the undoped HEMT structures, oxygen was identified as the dominant impurity using secondary ion mass spectroscopy and photoluminescence (PL) measurements. In addition, a notable parallel conduction channel was identified in the GaN buffer at the interface. The AlGaN/GaN HEMT structures with carbon doped GaN buffer using a CBr 4 beam equivalent pressure of 1.86 × 10 −7 mTorr showed a reduction in the buffer leakage current by two orders of magnitude. Carbon doped GaN buffers also exhibited a slight increase in the crystalline tilt with some pits on the growth surface. PL and Raman measurements indicated only a partial compensation of donor states with carbon acceptors. However, AlGaN/GaN HEMT structures with carbon doped GaN buffer with 200 nm thick undoped GaN near the channel exhibited good 2DEG characteristics

Detection of prostate-specific antigen with biomolecule-gated AlGaN/GaN high electron mobility transistors

Science.gov (United States)

Li, Jia-dong; Cheng, Jun-jie; Miao, Bin; Wei, Xiao-wei; Xie, Jie; Zhang, Jin-cheng; Zhang, Zhi-qiang; Wu, Dong-min

2014-07-01

In order to improve the sensitivity of AlGaN/GaN high electron mobility transistor (HEMT) biosensors, a simple biomolecule-gated AlGaN/GaN HEMT structure was designed and successfully fabricated for prostate specific antigen (PSA) detection. UV/ozone was used to oxidize the GaN surface and then a 3-aminopropyl trimethoxysilane (APTES) self-assembled monolayer was bound to the sensing region. This monolayer serves as a binding layer for attachment of the prostate specific antibody (anti-PSA). The biomolecule-gated AlGaN/GaN HEMT sensor shows a rapid and sensitive response when the target prostate-specific antigen in buffer solution was added to the antibody-immobilized sensing area. The current change showed a logarithm relationship against the PSA concentration from 0.1 pg/ml to 0.993 ng/ml. The sensitivity of 0.215% is determined for 0.1 pg/ml PSA solution. The above experimental result of the biomolecule-gated AlGaN/GaN HEMT biosensor suggested that this biosensor might be a useful tool for prostate cancer screening.

Detection of prostate-specific antigen with biomolecule-gated AlGaN/GaN high electron mobility transistors

International Nuclear Information System (INIS)

Li, Jia-dong; Miao, Bin; Wei, Xiao-wei; Xie, Jie; Wu, Dong-min; Cheng, Jun-jie; Zhang, Jin-cheng; Zhang, Zhi-qiang

2014-01-01

In order to improve the sensitivity of AlGaN/GaN high electron mobility transistor (HEMT) biosensors, a simple biomolecule-gated AlGaN/GaN HEMT structure was designed and successfully fabricated for prostate specific antigen (PSA) detection. UV/ozone was used to oxidize the GaN surface and then a 3-aminopropyl trimethoxysilane (APTES) self-assembled monolayer was bound to the sensing region. This monolayer serves as a binding layer for attachment of the prostate specific antibody (anti-PSA). The biomolecule-gated AlGaN/GaN HEMT sensor shows a rapid and sensitive response when the target prostate-specific antigen in buffer solution was added to the antibody-immobilized sensing area. The current change showed a logarithm relationship against the PSA concentration from 0.1 pg/ml to 0.993 ng/ml. The sensitivity of 0.215% is determined for 0.1 pg/ml PSA solution. The above experimental result of the biomolecule-gated AlGaN/GaN HEMT biosensor suggested that this biosensor might be a useful tool for prostate cancer screening. (paper)

Study on GaN buffer leakage current in AlGaN/GaN high electron mobility transistor structures grown by ammonia-molecular beam epitaxy on 100-mm Si(111)

Energy Technology Data Exchange (ETDEWEB)

Ravikiran, L.; Radhakrishnan, K., E-mail: ERADHA@e.ntu.edu.sg; Ng, G. I. [NOVITAS-Nanoelectronics, Centre of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Munawar Basha, S.; Dharmarasu, N.; Agrawal, M.; Manoj kumar, C. M.; Arulkumaran, S. [Temasek Laboratories@NTU, Nanyang Technological University, Singapore 637553 (Singapore)

2015-06-28

The effect of carbon doping on the structural and electrical properties of GaN buffer layer of AlGaN/GaN high electron mobility transistor (HEMT) structures has been studied. In the undoped HEMT structures, oxygen was identified as the dominant impurity using secondary ion mass spectroscopy and photoluminescence (PL) measurements. In addition, a notable parallel conduction channel was identified in the GaN buffer at the interface. The AlGaN/GaN HEMT structures with carbon doped GaN buffer using a CBr{sub 4} beam equivalent pressure of 1.86 × 10{sup −7} mTorr showed a reduction in the buffer leakage current by two orders of magnitude. Carbon doped GaN buffers also exhibited a slight increase in the crystalline tilt with some pits on the growth surface. PL and Raman measurements indicated only a partial compensation of donor states with carbon acceptors. However, AlGaN/GaN HEMT structures with carbon doped GaN buffer with 200 nm thick undoped GaN near the channel exhibited good 2DEG characteristics.

Improved linearity and reliability in GaN metal-oxide-semiconductor high-electron-mobility transistors using nanolaminate La2O3/SiO2 gate dielectric

Science.gov (United States)

Hsu, Ching-Hsiang; Shih, Wang-Cheng; Lin, Yueh-Chin; Hsu, Heng-Tung; Hsu, Hisang-Hua; Huang, Yu-Xiang; Lin, Tai-Wei; Wu, Chia-Hsun; Wu, Wen-Hao; Maa, Jer-Shen; Iwai, Hiroshi; Kakushima, Kuniyuki; Chang, Edward Yi

2016-04-01

Improved device performance to enable high-linearity power applications has been discussed in this study. We have compared the La2O3/SiO2 AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors (MOS-HEMTs) with other La2O3-based (La2O3/HfO2, La2O3/CeO2 and single La2O3) MOS-HEMTs. It was found that forming lanthanum silicate films can not only improve the dielectric quality but also can improve the device characteristics. The improved gate insulation, reliability, and linearity of the 8 nm La2O3/SiO2 MOS-HEMT were demonstrated.

Characteristics in AlN/AlGaN/GaN Multilayer-Structured High-Electron-Mobility Transistors

International Nuclear Information System (INIS)

Gui-Zhou, Hu; Ling, Yang; Li-Yuan, Yang; Si, Quan; Shou-Gao, Jiang; Ji-Gang, Ma; Xiao-Hua, Ma; Yue, Hao

2010-01-01

A new multilayer-structured AlN/AlGaN/GaN heterostructure high-electron-mobility transistor (HEMT) is demonstrated. The AlN/AlGaN/GaN HEMT exhibits the maximum drain current density of 800 mA/mm and the maximum extrinsic transconductance of 170 mS/mm. Due to the increase of the distance between the gate and the two-dimensional electron-gas channel, the threshold voltage shifts slightly to the negative. The reduced drain current collapse and higher breakdown voltage are observed on this AlN/AlGaN/GaN HEMT. The current gain cut-off frequency and the maximum frequency of oscillation are 18.5 GHz and 29.0 GHz, respectively. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Magneto-transport characterization of e-beam-induced damage in GaAs-AlGaAs heterostructures

International Nuclear Information System (INIS)

Fink, T.; Smith, D.D.; Braddock, W.D.

1989-01-01

This paper reports the effect of electron irradiation as a function of energy on the 2D EG transport properties of high electron mobility transistor (HEMT) structures at liquid helium temperature measured. High mobility HEMT structures were molecular beam epitaxy (MBE) grown with a 2D EG channel approximately 850 angstrom below the surface. A Cambridge EBMF 10.5 was used for electron irradiation with electron energies between 2.5 and 20 keV. The HEMT structures were fabricated into Hall bar geometry. Damage is assessed by changes in the 2D EG concentrations, as determined from Shubnikov-de Haas (SdH) oscillations in a magnetic field from 0 to 8.5 Telsa, and changes in the zero field Hall mobilities

Ultralow nonalloyed Ohmic contact resistance to self aligned N-polar GaN high electron mobility transistors by In(Ga)N regrowth

International Nuclear Information System (INIS)

Dasgupta, Sansaptak; Nidhi,; Brown, David F.; Wu, Feng; Keller, Stacia; Speck, James S.; Mishra, Umesh K.

2010-01-01

Ultralow Ohmic contact resistance and a self-aligned device structure are necessary to reduce the effect of parasitic elements and obtain higher f t and f max in high electron mobility transistors (HEMTs). N-polar (0001) GaN HEMTs, offer a natural advantage over Ga-polar HEMTs, in terms of contact resistance since the contact is not made through a high band gap material [Al(Ga)N]. In this work, we extend the advantage by making use of polarization induced three-dimensional electron-gas through regrowth of graded InGaN and thin InN cap in the contact regions by plasma (molecular beam epitaxy), to obtain an ultralow Ohmic contact resistance of 27 Ω μm to a GaN 2DEG.

Current linearity and operation stability in Al2O3-gate AlGaN/GaN MOS high electron mobility transistors

Science.gov (United States)

Nishiguchi, Kenya; Kaneki, Syota; Ozaki, Shiro; Hashizume, Tamotsu

2017-10-01

To investigate current linearity and operation stability of metal-oxide-semiconductor (MOS) AlGaN/GaN high electron mobility transistors (HEMTs), we have fabricated and characterized the Al2O3-gate MOS-HEMTs without and with a bias annealing in air at 300 °C. Compared with the as-fabricated (unannealed) MOS HEMTs, the bias-annealed devices showed improved linearity of I D-V G curves even in the forward bias regime, resulting in increased maximum drain current. Lower subthreshold slope was also observed after bias annealing. From the precise capacitance-voltage analysis on a MOS diode fabricated on the AlGaN/GaN heterostructure, it was found that the bias annealing effectively reduced the state density at the Al2O3/AlGaN interface. This led to efficient modulation of the AlGaN surface potential close to the conduction band edge, resulting in good gate control of two-dimensional electron gas density even at forward bias. In addition, the bias-annealed MOS HEMT showed small threshold voltage shift after applying forward bias stress and stable operation even at high temperatures.

GaN MOSHEMT employing HfO2 as a gate dielectric with partially etched barrier

Science.gov (United States)

Han, Kefeng; Zhu, Lin

2017-09-01

In order to suppress the gate leakage current of a GaN high electron mobility transistor (GaN HEMT), a GaN metal-oxide-semiconductor high electron mobility transistor (MOSHEMT) is proposed, in which a metal-oxide-semiconductor gate with high-dielectric-constant HfO2 as an insulating dielectric is employed to replace the traditional GaN HEMT Schottky gate. A 0.5 μm gate length GaN MOSHEMT was fabricated based on the proposed structure, the {{{Al}}}0.28{{{Ga}}}0.72{{N}} barrier layer is partially etched to produce a higher transconductance without deteriorating the transport characteristics of the two-dimensional electron gas in the channel, the gate dielectric is HfO2 deposited by atomic layer deposition. Current-voltage characteristics and radio frequency characteristics are obtained after device preparation, the maximum current density of the device is 900 mA mm-1, the source-drain breakdown voltage is 75 V, gate current is significantly suppressed and the forward gate voltage swing range is about ten times higher than traditional GaN HEMTs, the GaN MOSHEMT also demonstrates radio frequency characteristics comparable to traditional GaN HEMTs with the same gate length.

Isolated photosystem I reaction centers on a functionalized gated high electron mobility transistor.

Science.gov (United States)

Eliza, Sazia A; Lee, Ida; Tulip, Fahmida S; Mostafa, Salwa; Greenbaum, Elias; Ericson, M Nance; Islam, Syed K

2011-09-01

In oxygenic plants, photons are captured with high quantum efficiency by two specialized reaction centers (RC) called Photosystem I (PS I) and Photosystem II (PS II). The captured photon triggers rapid charge separation and the photon energy is converted into an electrostatic potential across the nanometer-scale (~6 nm) reaction centers. The exogenous photovoltages from a single PS I RC have been previously measured using the technique of Kelvin force probe microscopy (KFM). However, biomolecular photovoltaic applications require two-terminal devices. This paper presents for the first time, a micro-device for detection and characterization of isolated PS I RCs. The device is based on an AlGaN/GaN high electron mobility transistor (HEMT) structure. AlGaN/GaN HEMTs show high current throughputs and greater sensitivity to surface charges compared to other field-effect devices. PS I complexes immobilized on the floating gate of AlGaN/GaN HEMTs resulted in significant changes in the device characteristics under illumination. An analytical model has been developed to estimate the RCs of a major orientation on the functionalized gate surface of the HEMTs. © 2011 IEEE

Isolated Photosystem I Reaction Centers on a Functionalized Gated High Electron Mobility Transistor

Energy Technology Data Exchange (ETDEWEB)

Eliza, Sazia A. [University of Tennessee, Knoxville (UTK); Lee, Ida [ORNL; Tulip, Fahmida S [ORNL; Islam, Syed K [University of Tennessee, Knoxville (UTK); Mostafa, Salwa [University of Tennessee, Knoxville (UTK); Greenbaum, Elias [ORNL; Ericson, Milton Nance [ORNL

2011-01-01

In oxygenic plants, photons are captured with high quantum efficiency by two specialized reaction centers (RC) called Photosystem I (PS I) and Photosystem II (PS II). The captured photon triggers rapid charge separation and the photon energy is converted into an electrostatic potential across the nanometer-scale nm reaction centers. The exogenous photovoltages from a single PS I RC have been previously measured using the technique of Kelvin force probe microscopy (KFM). However, biomolecular photovoltaic applications require two-terminal devices. This paper presents for the first time, a micro-device for detection and characterization of isolated PS I RCs. The device is based on an AlGaN/GaN high electron mobility transistor (HEMT) structure. AlGaN/GaN HEMTs show high current throughputs and greater sensitivity to surface charges compared to other field-effect devices. PS I complexes immobilized on the floating gate of AlGaN/GaN HEMTs resulted in significant changes in the device characteristics under illumination. An analytical model has been developed to estimate the RCs of a major orientation on the functionalized gate surface of the HEMTs.

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

Broadband 0.25-um Gallium Nitride (GaN) Power Amplifier Designs

Science.gov (United States)

2017-08-14

networking, and sensor systems of interest to Department of Defense applications, particularly for next-generation radar systems. Broadband, efficient, high...simulations of MMIC (3–6 GHz, 28 V/180 mA) 1.75-mm HEMT power amplifier ............................................... 13 Fig. 20 Simple schematic...design simple , a single 1.75-mm high-electron-mobility transistor (HEMT) was used for a preliminary ideal design of the broadband power amplifier

Electron velocity of 6 × 107 cm/s at 300 K in stress engineered InAlN/GaN nano-channel high-electron-mobility transistors

International Nuclear Information System (INIS)

Arulkumaran, S.; Manoj Kumar, C. M.; Ranjan, K.; Teo, K. L.; Ng, G. I.; Shoron, O. F.; Rajan, S.; Bin Dolmanan, S.; Tripathy, S.

2015-01-01

A stress engineered three dimensional (3D) Triple T-gate (TT-gate) on lattice matched In 0.17 Al 0.83 N/GaN nano-channel (NC) Fin-High-Electron-Mobility Transistor (Fin-HEMT) with significantly enhanced device performance was achieved that is promising for high-speed device applications. The Fin-HEMT with 200-nm effective fin-width (W eff ) exhibited a very high I Dmax of 3940 mA/mm and a highest g m of 1417 mS/mm. This dramatic increase of I D and g m in the 3D TT-gate In 0.17 Al 0.83 N/GaN NC Fin-HEMT translated to an extracted highest electron velocity (v e ) of 6.0 × 10 7  cm/s, which is ∼1.89× higher than that of the conventional In 0.17 Al 0.83 N/GaN HEMT (3.17 × 10 7  cm/s). The v e in the conventional III-nitride transistors are typically limited by highly efficient optical-phonon emission. However, the unusually high v e at 300 K in the 3D TT-gate In 0.17 Al 0.83 N/GaN NC Fin-HEMT is attributed to the increase of in-plane tensile stress component by SiN passivation in the formed NC which is also verified by micro-photoluminescence (0.47 ± 0.02 GPa) and micro-Raman spectroscopy (0.39 ± 0.12 GPa) measurements. The ability to reach the v e  = 6 × 10 7  cm/s at 300 K by a stress engineered 3D TT-gate lattice-matched In 0.17 Al 0.83 N/GaN NC Fin-HEMTs shows they are promising for next-generation ultra-scaled high-speed device applications

Electron velocity of 6 × 10{sup 7 }cm/s at 300 K in stress engineered InAlN/GaN nano-channel high-electron-mobility transistors

Energy Technology Data Exchange (ETDEWEB)

Arulkumaran, S., E-mail: SArulkumaran@pmail.ntu.edu.sg; Manoj Kumar, C. M.; Ranjan, K.; Teo, K. L. [Temasek Laboratories@NTU, Nanyang Technological University, Research Techno Plaza, 50 Nanyang Drive, Singapore 637553 (Singapore); Ng, G. I., E-mail: eging@ntu.edu.sg [School of Electrical and Electronics Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Shoron, O. F.; Rajan, S. [Electrical and Computer Engineering Department, The Ohio State University, Columbus, Ohio 43210 (United States); Bin Dolmanan, S.; Tripathy, S. [Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology, and Research), 3 Research Link, Singapore 117602 (Singapore)

2015-02-02

A stress engineered three dimensional (3D) Triple T-gate (TT-gate) on lattice matched In{sub 0.17}Al{sub 0.83}N/GaN nano-channel (NC) Fin-High-Electron-Mobility Transistor (Fin-HEMT) with significantly enhanced device performance was achieved that is promising for high-speed device applications. The Fin-HEMT with 200-nm effective fin-width (W{sub eff}) exhibited a very high I{sub Dmax} of 3940 mA/mm and a highest g{sub m} of 1417 mS/mm. This dramatic increase of I{sub D} and g{sub m} in the 3D TT-gate In{sub 0.17}Al{sub 0.83}N/GaN NC Fin-HEMT translated to an extracted highest electron velocity (v{sub e}) of 6.0 × 10{sup 7 }cm/s, which is ∼1.89× higher than that of the conventional In{sub 0.17}Al{sub 0.83}N/GaN HEMT (3.17 × 10{sup 7 }cm/s). The v{sub e} in the conventional III-nitride transistors are typically limited by highly efficient optical-phonon emission. However, the unusually high v{sub e} at 300 K in the 3D TT-gate In{sub 0.17}Al{sub 0.83}N/GaN NC Fin-HEMT is attributed to the increase of in-plane tensile stress component by SiN passivation in the formed NC which is also verified by micro-photoluminescence (0.47 ± 0.02 GPa) and micro-Raman spectroscopy (0.39 ± 0.12 GPa) measurements. The ability to reach the v{sub e} = 6 × 10{sup 7 }cm/s at 300 K by a stress engineered 3D TT-gate lattice-matched In{sub 0.17}Al{sub 0.83}N/GaN NC Fin-HEMTs shows they are promising for next-generation ultra-scaled high-speed device applications.

Reduced thermal resistance in AlGaN/GaN multi-mesa-channel high electron mobility transistors

Energy Technology Data Exchange (ETDEWEB)

Asubar, Joel T., E-mail: joel@rciqe.hokudai.ac.jp; Yatabe, Zenji; Hashizume, Tamotsu [Research Center for Integrated Quantum Electronics (RCIQE) and Graduate School of Information Science and Technology, Hokkaido University, Sapporo (Japan); Japan Science and Technology Agency (JST), CREST, 102-0075 Tokyo (Japan)

2014-08-04

Dramatic reduction of thermal resistance was achieved in AlGaN/GaN Multi-Mesa-Channel (MMC) high electron mobility transistors (HEMTs) on sapphire substrates. Compared with the conventional planar device, the MMC HEMT exhibits much less negative slope of the I{sub D}-V{sub DS} curves at high V{sub DS} regime, indicating less self-heating. Using a method proposed by Menozzi and co-workers, we obtained a thermal resistance of 4.8 K-mm/W at ambient temperature of ∼350 K and power dissipation of ∼9 W/mm. This value compares well to 4.1 K-mm/W, which is the thermal resistance of AlGaN/GaN HEMTs on expensive single crystal diamond substrates and the lowest reported value in literature.

Ultrasensitive detection of Hg2+ using oligonucleotide-functionalized AlGaN/GaN high electron mobility transistor

International Nuclear Information System (INIS)

Cheng, Junjie; Li, Jiadong; Miao, Bin; Wu, Dongmin; Wang, Jine; Pei, Renjun; Wu, Zhengyan

2014-01-01

An oligonucleotide-functionalized ion sensitive AlGaN/GaN high electron mobility transistor (HEMT) was fabricated to detect trace amounts of Hg 2+ . The advantages of ion sensitive AlGaN/GaN HEMT and highly specific binding interaction between Hg 2+ and thymines were combined. The current response of this Hg 2+ ultrasensitive transistor was characterized. The current increased due to the accumulation of Hg 2+ ions on the surface by the highly specific thymine-Hg 2+ -thymine recognition. The dynamic linear range for Hg 2+ detection has been determined in the concentrations from 10 −14 to 10 −8 M and a detection limit below 10 −14 M level was estimated, which is the best result of AlGaN/GaN HEMT biosensors for Hg 2+ detection till now.

Gate length scaling effect on high-electron mobility transistors devices using AlGaN/GaN and AlInN/AlN/GaN heterostructures.

Science.gov (United States)

Liao, S Y; Lu, C C; Chang, T; Huang, C F; Cheng, C H; Chang, L B

2014-08-01

Compared to AlGaN/GaN HEMT with 0.15 μm T-gate length, the AlInN/AlN/GaN one exhibits much higher current density and transconductance of 1558 mA/mm at Vd = 2 V and 330 mS/mm, respectively. The high extrinsic ft and fmax of 82 GHz and 70 GHz are extracted from AlInN/AlN/GaN HEMT. Besides, we find that the transconductance roll-off is significant in AlGaN/GaN, but largely improved in AlInN/AlN/GaN HEMT, suggesting that the high carrier density and lattice-matched epitaxial heterostructure is important to reach both large RF output power and high operation frequency, especially for an aggressively gate length scaling.

Breakdown mechanisms in AlGaN/GaN high electron mobility transistors with different GaN channel thickness values

International Nuclear Information System (INIS)

Ma Xiao-Hua; Zhang Ya-Man; Chen Wei-Wei; Wang Xin-Hua; Yuan Ting-Ting; Pang Lei; Liu Xin-Yu

2015-01-01

In this paper, the off-state breakdown characteristics of two different AlGaN/GaN high electron mobility transistors (HEMTs), featuring a 50-nm and a 150-nm GaN thick channel layer, respectively, are compared. The HEMT with a thick channel exhibits a little larger pinch-off drain current but significantly enhanced off-state breakdown voltage (BV off ). Device simulation indicates that thickening the channel increases the drain-induced barrier lowering (DIBL) but reduces the lateral electric field in the channel and buffer underneath the gate. The increase of BV off in the thick channel device is due to the reduction of the electric field. These results demonstrate that it is necessary to select an appropriate channel thickness to balance DIBL and BV off in AlGaN/GaN HEMTs. (paper)

Investigation of plasmonic resonances in the two-dimensional electron gas of an InGaAs/InP high electron mobility transistor

Science.gov (United States)

Cleary, Justin W.; Peale, Robert E.; Saxena, Himanshu; Buchwald, Walter R.

2011-05-01

The observation of THz regime transmission resonances in an InGaAs/InP high electron mobility transistor (HEMT) can be attributed to excitation of plasmons in its two-dimensional electron gas (2DEG). Properties of grating-based, gate-voltage tunable resonances are shown to be adequately modeled using commercial finite element method (FEM) software when the HEMT layer structure, gate geometry and sheet charge concentration are taken into account. The FEM results are shown to produce results consistent with standard analytical theories in the 10-100 cm-1 wavenumber range. An original analytic formula presented here describes how the plasmonic resonance may change in the presence of a virtual gate, or region of relatively high free charge carriers that lies in the HEMT between the physical grating gate and the 2DEG. The virtual gate and corresponding analytic formulation are able to account for the red-shifting experimentally observed in plasmonic resonances. The calculation methods demonstrated here have the potential to greatly aid in the design of future detection devices that require specifically tuned plasmonic modes in the 2DEG of a HEMT, as well as giving new insights to aid in the development of more complete analytic theories.

Improved linearity in AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors with nonlinear polarization dielectric

International Nuclear Information System (INIS)

Gao, Tao; Xu, Ruimin; Kong, Yuechan; Zhou, Jianjun; Kong, Cen; Dong, Xun; Chen, Tangsheng

2015-01-01

We demonstrate highly improved linearity in a nonlinear ferroelectric of Pb(Zr 0.52 Ti 0.48 )-gated AlGaN/GaN metal-insulator-semiconductor high electron mobility transistor (MIS-HEMT). Distinct double-hump feature in the transconductance-gate voltage (g m -V g ) curve is observed, yielding remarkable enhancement in gate voltage swing as compared to MIS-HEMT with conventional linear gate dielectric. By incorporating the ferroelectric polarization into a self-consistent calculation, it is disclosed that in addition to the common hump corresponding to the onset of electron accumulation, the second hump at high current level is originated from the nonlinear polar nature of ferroelectric, which enhances the gate capacitance by increasing equivalent dielectric constant nonlinearly. This work paves a way for design of high linearity GaN MIS-HEMT by exploiting the nonlinear properties of dielectric

N-polar GaN/AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistor formed on sapphire substrate with minimal step bunching

Science.gov (United States)

Prasertsuk, Kiattiwut; Tanikawa, Tomoyuki; Kimura, Takeshi; Kuboya, Shigeyuki; Suemitsu, Tetsuya; Matsuoka, Takashi

2018-01-01

The metal-insulator-semiconductor (MIS) gate N-polar GaN/AlGaN/GaN high-electron-mobility transistor (HEMT) on a (0001) sapphire substrate, which can be expected to operate with lower on-resistance and more easily work on the pinch-off operation than an N-polar AlGaN/GaN HEMT, was fabricated. For suppressing the step bunching and hillocks peculiar in the N-polar growth, a sapphire substrate with an off-cut angle as small as 0.8° was introduced and an N-polar GaN/AlGaN/GaN HEMT without the step bunching was firstly obtained by optimizing the growth conditions. The previously reported anisotropy of transconductance related to the step was eliminated. The pinch-off operation was also realized. These results indicate that this device is promising.

Highly selective and sensitive phosphate anion sensors based on AlGaN/GaN high electron mobility transistors functionalized by ion imprinted polymer.

Science.gov (United States)

Jia, Xiuling; Chen, Dunjun; Bin, Liu; Lu, Hai; Zhang, Rong; Zheng, Youdou

2016-06-09

A novel ion-imprinted electrochemical sensor based on AlGaN/GaN high electron mobility transistors (HEMTs) was developed to detect trace amounts of phosphate anion. This sensor combined the advantages of the ion sensitivity of AlGaN/GaN HEMTs and specific recognition of ion imprinted polymers. The current response showed that the fabricated sensor is highly sensitive and selective to phosphate anions. The current change exhibited approximate linear dependence for phosphate concentration from 0.02 mg L(-1) to 2 mg L(-1), the sensitivity and detection limit of the sensor is 3.191 μA/mg L(-1) and 1.97 μg L(-1), respectively. The results indicated that this AlGaN/GaN HEMT-based electrochemical sensor has the potential applications on phosphate anion detection.

Impact of barrier thickness on transistor performance in AlN/GaN high electron mobility transistors grown on free-standing GaN substrates

International Nuclear Information System (INIS)

Deen, David A.; Storm, David F.; Meyer, David J.; Bass, Robert; Binari, Steven C.; Gougousi, Theodosia; Evans, Keith R.

2014-01-01

A series of six ultrathin AlN/GaN heterostructures with varied AlN thicknesses from 1.5–6 nm have been grown by molecular beam epitaxy on free-standing hydride vapor phase epitaxy GaN substrates. High electron mobility transistors (HEMTs) were fabricated from the set in order to assess the impact of barrier thickness and homo-epitaxial growth on transistor performance. Room temperature Hall characteristics revealed mobility of 1700 cm 2 /V s and sheet resistance of 130 Ω/□ for a 3 nm thick barrier, ranking amongst the lowest room-temperature sheet resistance values reported for a polarization-doped single heterostructure in the III-Nitride family. DC and small signal HEMT electrical characteristics from submicron gate length HEMTs further elucidated the effect of the AlN barrier thickness on device performance.

Impact of barrier thickness on transistor performance in AlN/GaN high electron mobility transistors grown on free-standing GaN substrates

Energy Technology Data Exchange (ETDEWEB)

Deen, David A., E-mail: david.deen@alumni.nd.edu; Storm, David F.; Meyer, David J.; Bass, Robert; Binari, Steven C. [Electronics Science and Technology Division, Naval Research Laboratory, Washington, DC 20375-5347 (United States); Gougousi, Theodosia [Physics Department, University of Maryland Baltimore County, Baltimore, Maryland 21250 (United States); Evans, Keith R. [Kyma Technologies, Raleigh, North Carolina 27617 (United States)

2014-09-01

A series of six ultrathin AlN/GaN heterostructures with varied AlN thicknesses from 1.5–6 nm have been grown by molecular beam epitaxy on free-standing hydride vapor phase epitaxy GaN substrates. High electron mobility transistors (HEMTs) were fabricated from the set in order to assess the impact of barrier thickness and homo-epitaxial growth on transistor performance. Room temperature Hall characteristics revealed mobility of 1700 cm{sup 2}/V s and sheet resistance of 130 Ω/□ for a 3 nm thick barrier, ranking amongst the lowest room-temperature sheet resistance values reported for a polarization-doped single heterostructure in the III-Nitride family. DC and small signal HEMT electrical characteristics from submicron gate length HEMTs further elucidated the effect of the AlN barrier thickness on device performance.

Design and characterisation of high electron mobility transistors for use in a monolithic GaAs X-ray imaging sensor

International Nuclear Information System (INIS)

Boardman, D.A.; Sellin, P.J.

2001-01-01

A new design of monolithic GaAs pixel detector is proposed for medical and synchrotron applications. In this device a semi-insulating GaAs wafer will be used as both the detector element and the substrate for the integrated charge readout matrix. The charge readout matrix consists of High Electron Mobility Transistors (HEMTs), which are grown epitaxially onto the GaAs substrate. Experimental characterisation of HEMTs has been carried out and their suitability for the proposed imaging device is assessed. Temperature measurements on initial devices showed the threshold voltage to be stable from room temperature down to -15 degree sign C. HEMT designs with lower leakage current that operate in enhancement mode have been fabricated and modelled using the Silvaco simulation package. These optimised devices have been fabricated using a gate recess, and exhibit enhancement mode operation and significantly reduced gate leakage currents

2016 International Workshop on Nitride Semiconductors (IWN 2016)

Science.gov (United States)

2017-01-01

Hollow -Cathode Plasma-Assisted Atomic Layer Deposition- Impact of Film Thickness PS1.53 Xu Yang The Influence of Residual Boron in Reactor on the...Recombination Rates & Efficiency of lnGaN Quantum Wells Simulations of Dislocation Core in Pyramidal Plane of n- & p- Doped Wurtzite GaN & AIGaN Ab Initio...GaN MOS-HEMT Effect of Surface Plasma Treatments on Hysteresis and Threshold Voltage Stability in AIGaN/GaN Metal-Semiconductor- Insulator (MIS) HEMTs

Standards of Justice for Human Being and Doing in Kim Stanley Robinson’s 2312 and C. S. Friedman’s This Alien Shore

Directory of Open Access Journals (Sweden)

Claire P. Curtis

2017-09-01

Full Text Available The creation of superior societies and communities in which bodies live better and thrive depends on richly detailed accounts of imagined societies including flexible theories of justice that can be used to evaluate them. Both Kim Stanley Robinson’s '2312' (2012 and C. S. Friedman’s 'This Alien Shore' (1998 attempt to rethink what bodies can do and be, by exploring ways of living together among those with different, and differently compatible, bodies. The novels are set in future spacefaring societies away from the Earth, which nevertheless struggle with the fact of Earth’s existence. Each novel describes radical cognitive and bodily change: chosen alteration in '2312' and environmental transformation in 'This Alien Shore'. In each novel, the body, and what bodies can do and be, is a central issue. But how might we evaluate the societies these novels describe to gauge their contributions to articulating desires for a better way of being? In this article I employ Martha Nussbaum’s ‘capabilities approach’ (encompassing life, bodily health, bodily integrity, senses, emotions, reason, affiliation, play, other species, control over environment to think about justice in the articulation of evaluative standards. In so doing the analysis I develop addresses some key questions raised by these novels, including: Whose body will matter? Will there be bodily norms? How will communities confront different bodily abilities? How can we enhance our own thinking about how to live in and among bodies? How does (and should the idea of the body politic change when our expectations about bodies changes?

Ultrasensitive detection of Hg{sup 2+} using oligonucleotide-functionalized AlGaN/GaN high electron mobility transistor

Energy Technology Data Exchange (ETDEWEB)

Cheng, Junjie [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031 (China); Division of Nanobiomedicine, Key Laboratory for Nano-Bio Interface Research, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123 (China); Li, Jiadong; Miao, Bin; Wu, Dongmin, E-mail: dmwu2008@sinano.ac.cn [i-Lab, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215125 (China); Key Laboratory of Nanodevices and Applications, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123 (China); Wang, Jine; Pei, Renjun, E-mail: rjpei2011@sinano.ac.cn [Division of Nanobiomedicine, Key Laboratory for Nano-Bio Interface Research, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123 (China); Wu, Zhengyan, E-mail: zywu@ipp.ac.cn [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031 (China)

2014-08-25

An oligonucleotide-functionalized ion sensitive AlGaN/GaN high electron mobility transistor (HEMT) was fabricated to detect trace amounts of Hg{sup 2+}. The advantages of ion sensitive AlGaN/GaN HEMT and highly specific binding interaction between Hg{sup 2+} and thymines were combined. The current response of this Hg{sup 2+} ultrasensitive transistor was characterized. The current increased due to the accumulation of Hg{sup 2+} ions on the surface by the highly specific thymine-Hg{sup 2+}-thymine recognition. The dynamic linear range for Hg{sup 2+} detection has been determined in the concentrations from 10{sup −14} to 10{sup −8} M and a detection limit below 10{sup −14} M level was estimated, which is the best result of AlGaN/GaN HEMT biosensors for Hg{sup 2+} detection till now.

Advances in Hydrogen, Carbon Dioxide, and Hydrocarbon Gas Sensor Technology Using GaN and ZnO-Based Devices

Directory of Open Access Journals (Sweden)

Jenshan Lin

2009-06-01

Full Text Available In this paper, we review our recent results in developing gas sensors for hydrogen using various device structures, including ZnO nanowires and GaN High Electron Mobility Transistors (HEMTs. ZnO nanowires are particularly interesting because they have a large surface area to volume ratio, which will improve sensitivity, and because they operate at low current levels, will have low power requirements in a sensor module. GaN-based devices offer the advantage of the HEMT structure, high temperature operation, and simple integration with existing fabrication technology and sensing systems. Improvements in sensitivity, recoverability, and reliability are presented. Also reported are demonstrations of detection of other gases, including CO2 and C2H4 using functionalized GaN HEMTs. This is critical for the development of lab-on-a-chip type systems and can provide a significant advance towards a market-ready sensor application.

Advances in Hydrogen, Carbon Dioxide, and Hydrocarbon Gas Sensor Technology Using GaN and ZnO-Based Devices.

Science.gov (United States)

Anderson, Travis; Ren, Fan; Pearton, Stephen; Kang, Byoung Sam; Wang, Hung-Ta; Chang, Chih-Yang; Lin, Jenshan

2009-01-01

In this paper, we review our recent results in developing gas sensors for hydrogen using various device structures, including ZnO nanowires and GaN High Electron Mobility Transistors (HEMTs). ZnO nanowires are particularly interesting because they have a large surface area to volume ratio, which will improve sensitivity, and because they operate at low current levels, will have low power requirements in a sensor module. GaN-based devices offer the advantage of the HEMT structure, high temperature operation, and simple integration with existing fabrication technology and sensing systems. Improvements in sensitivity, recoverability, and reliability are presented. Also reported are demonstrations of detection of other gases, including CO(2) and C(2)H(4) using functionalized GaN HEMTs. This is critical for the development of lab-on-a-chip type systems and can provide a significant advance towards a market-ready sensor application.

Improved linearity in AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors with nonlinear polarization dielectric

Energy Technology Data Exchange (ETDEWEB)

Gao, Tao [Fundamental Science on EHF Laboratory, University of Electronic Science and Technology of China (UESTC), Chengdu 611731 (China); Science and Technology on Monolithic Integrated Circuits and Modules Laboratory, Nanjing Electronic Devices Institute, Nanjing 210016 (China); Xu, Ruimin [Fundamental Science on EHF Laboratory, University of Electronic Science and Technology of China (UESTC), Chengdu 611731 (China); Kong, Yuechan, E-mail: kycfly@163.com; Zhou, Jianjun; Kong, Cen; Dong, Xun; Chen, Tangsheng [Science and Technology on Monolithic Integrated Circuits and Modules Laboratory, Nanjing Electronic Devices Institute, Nanjing 210016 (China)

2015-06-15

We demonstrate highly improved linearity in a nonlinear ferroelectric of Pb(Zr{sub 0.52}Ti{sub 0.48})-gated AlGaN/GaN metal-insulator-semiconductor high electron mobility transistor (MIS-HEMT). Distinct double-hump feature in the transconductance-gate voltage (g{sub m}-V{sub g}) curve is observed, yielding remarkable enhancement in gate voltage swing as compared to MIS-HEMT with conventional linear gate dielectric. By incorporating the ferroelectric polarization into a self-consistent calculation, it is disclosed that in addition to the common hump corresponding to the onset of electron accumulation, the second hump at high current level is originated from the nonlinear polar nature of ferroelectric, which enhances the gate capacitance by increasing equivalent dielectric constant nonlinearly. This work paves a way for design of high linearity GaN MIS-HEMT by exploiting the nonlinear properties of dielectric.

Low-resistance gateless high electron mobility transistors using three-dimensional inverted pyramidal AlGaN/GaN surfaces

International Nuclear Information System (INIS)

So, Hongyun; Senesky, Debbie G.

2016-01-01

In this letter, three-dimensional gateless AlGaN/GaN high electron mobility transistors (HEMTs) were demonstrated with 54% reduction in electrical resistance and 73% increase in surface area compared with conventional gateless HEMTs on planar substrates. Inverted pyramidal AlGaN/GaN surfaces were microfabricated using potassium hydroxide etched silicon with exposed (111) surfaces and metal-organic chemical vapor deposition of coherent AlGaN/GaN thin films. In addition, electrical characterization of the devices showed that a combination of series and parallel connections of the highly conductive two-dimensional electron gas along the pyramidal geometry resulted in a significant reduction in electrical resistance at both room and high temperatures (up to 300 °C). This three-dimensional HEMT architecture can be leveraged to realize low-power and reliable power electronics, as well as harsh environment sensors with increased surface area

High Temperature Terahertz Detectors Realized by a GaN High Electron Mobility Transistor

Science.gov (United States)

Hou, H. W.; Liu, Z.; Teng, J. H.; Palacios, T.; Chua, S. J.

2017-04-01

In this work, a high temperature THz detector based on a GaN high electron mobility transistor (HEMT) with nano antenna structures was fabricated and demonstrated to be able to work up to 200 °C. The THz responsivity and noise equivalent power (NEP) of the device were characterized at 0.14 THz radiation over a wide temperature range from room temperature to 200 °C. A high responsivity Rv of 15.5 and 2.7 kV/W and a low NEP of 0.58 and 10 pW/Hz0.5 were obtained at room temperature and 200 °C, respectively. The advantages of the GaN HEMT over other types of field effect transistors for high temperature terahertz detection are discussed. The physical mechanisms responsible for the temperature dependence of the responsivity and NEP of the GaN HEMT are also analyzed thoroughly.

Low-resistance gateless high electron mobility transistors using three-dimensional inverted pyramidal AlGaN/GaN surfaces

Energy Technology Data Exchange (ETDEWEB)

So, Hongyun, E-mail: hyso@stanford.edu [Department of Aeronautics and Astronautics, Stanford University, Stanford, California 94305 (United States); Senesky, Debbie G. [Department of Aeronautics and Astronautics, Stanford University, Stanford, California 94305 (United States); Department of Electrical Engineering, Stanford University, Stanford, California 94305 (United States)

2016-01-04

In this letter, three-dimensional gateless AlGaN/GaN high electron mobility transistors (HEMTs) were demonstrated with 54% reduction in electrical resistance and 73% increase in surface area compared with conventional gateless HEMTs on planar substrates. Inverted pyramidal AlGaN/GaN surfaces were microfabricated using potassium hydroxide etched silicon with exposed (111) surfaces and metal-organic chemical vapor deposition of coherent AlGaN/GaN thin films. In addition, electrical characterization of the devices showed that a combination of series and parallel connections of the highly conductive two-dimensional electron gas along the pyramidal geometry resulted in a significant reduction in electrical resistance at both room and high temperatures (up to 300 °C). This three-dimensional HEMT architecture can be leveraged to realize low-power and reliable power electronics, as well as harsh environment sensors with increased surface area.

InP MMIC Chip Set for Power Sources Covering 80-170 GHz

Science.gov (United States)

Ngo, Catherine

2001-01-01

We will present a Monolithic Millimeter-wave Integrated Circuit (MMIC) chip set which provides high output-power sources for driving diode frequency multipliers into the terahertz range. The chip set was fabricated at HRL Laboratories using a 0.1-micrometer gate-length InAlAs/InGaAs/InP high electron mobility transistor (HEMT) process, and features transistors with an f(sub max) above 600 GHz. The HRL InP HEMT process has already demonstrated amplifiers in the 60-200 GHz range. In this paper, these high frequency HEMTs form the basis for power sources up to 170 GHz. A number of state-of-the-art InP HEMT MMICs will be presented. These include voltage-controlled and fixed-tuned oscillators, power amplifiers, and an active doubler. We will first discuss an 80 GHz voltage-controlled oscillator with 5 GHz of tunability and at least 17 mW of output power, as well as a 120 GHz oscillator providing 7 mW of output power. In addition, we will present results of a power amplifier which covers the full WRIO waveguide band (75-110 GHz), and provides 40-50 mW of output power. Furthermore, we will present an active doubler at 164 GHz providing 8% bandwidth, 3 mW of output power, and an unprecedented 2 dB of conversion loss for an InP HEMT MMIC at this frequency. Finally, we will demonstrate a power amplifier to cover 140-170 GHz with 15-25 mW of output power and 8 dB gain. These components can form a power source in the 155-165 GHz range by cascading the 80 GHz oscillator, W-band power amplifier, 164 GHz active doubler and final 140-170 GHz power amplifier for a stable, compact local oscillator subsystem, which could be used for atmospheric science or astrophysics radiometers.

Depth-resolved ultra-violet spectroscopic photo current-voltage measurements for the analysis of AlGaN/GaN high electron mobility transistor epilayer deposited on Si

International Nuclear Information System (INIS)

Ozden, Burcu; Yang, Chungman; Tong, Fei; Khanal, Min P.; Mirkhani, Vahid; Sk, Mobbassar Hassan; Ahyi, Ayayi Claude; Park, Minseo

2014-01-01

We have demonstrated that the depth-dependent defect distribution of the deep level traps in the AlGaN/GaN high electron mobility transistor (HEMT) epi-structures can be analyzed by using the depth-resolved ultra-violet (UV) spectroscopic photo current-voltage (IV) (DR-UV-SPIV). It is of great importance to analyze deep level defects in the AlGaN/GaN HEMT structure, since it is recognized that deep level defects are the main source for causing current collapse phenomena leading to reduced device reliability. The AlGaN/GaN HEMT epi-layers were grown on a 6 in. Si wafer by metal-organic chemical vapor deposition. The DR-UV-SPIV measurement was performed using a monochromatized UV light illumination from a Xe lamp. The key strength of the DR-UV-SPIV is its ability to provide information on the depth-dependent electrically active defect distribution along the epi-layer growth direction. The DR-UV-SPIV data showed variations in the depth-dependent defect distribution across the wafer. As a result, rapid feedback on the depth-dependent electrical homogeneity of the electrically active defect distribution in the AlGaN/GaN HEMT epi-structure grown on a Si wafer with minimal sample preparation can be elucidated from the DR-UV-SPIV in combination with our previously demonstrated spectroscopic photo-IV measurement with the sub-bandgap excitation.

A study on multiple defect states in low-carbon doped GaN layers and its correlation with AlGaN/GaN high electron mobility transistor operation

International Nuclear Information System (INIS)

Tanaka, Takeshi; Shiojima, Kenji; Otoki, Yohei; Tokuda, Yutaka

2014-01-01

A study on defect states in relatively low-carbon doped GaN is presented. A large current collapse was observed in AlGaN/GaN high electron mobility transistor (HEMT) operation when the device channel was doped with carbon of 1 × 10 17 cm −3 . Deep level transient spectroscopy measurements showed a positive and even negative correlation between the densities of carbon and those of shallow trap states. Along with their small concentrations, shallow traps could not be associated with the collapse of the HEMT. Photo capacitance measurements yielded large signal at very deep levels of 1.6 and 2.4 eV in carbon doped GaN. Especially, the 2.4 eV deep trap was estimated to be acceptor type and related to some indirect states that the minority carrier transient spectroscopy could not characterize. A 20% of doped carbon was allocated to the very deep traps, and the large current collapse was attributed to these carbon-related states. - Highlights: • Systematic study on role of carbon in AlGaN/GaN HEMT structures was attempted. • Large current collapse was observed at HEMT operation in carbon doped channel. • Photo capacitance measurements yielded large signal at very deep levels. • The large current degradation was attributed to the carbon-related deep traps

Depth-resolved ultra-violet spectroscopic photo current-voltage measurements for the analysis of AlGaN/GaN high electron mobility transistor epilayer deposited on Si

Energy Technology Data Exchange (ETDEWEB)

Ozden, Burcu; Yang, Chungman; Tong, Fei; Khanal, Min P.; Mirkhani, Vahid; Sk, Mobbassar Hassan; Ahyi, Ayayi Claude; Park, Minseo, E-mail: park@physics.auburn.edu [Department of Physics, Auburn University, Auburn, Alabama 36849 (United States)

2014-10-27

We have demonstrated that the depth-dependent defect distribution of the deep level traps in the AlGaN/GaN high electron mobility transistor (HEMT) epi-structures can be analyzed by using the depth-resolved ultra-violet (UV) spectroscopic photo current-voltage (IV) (DR-UV-SPIV). It is of great importance to analyze deep level defects in the AlGaN/GaN HEMT structure, since it is recognized that deep level defects are the main source for causing current collapse phenomena leading to reduced device reliability. The AlGaN/GaN HEMT epi-layers were grown on a 6 in. Si wafer by metal-organic chemical vapor deposition. The DR-UV-SPIV measurement was performed using a monochromatized UV light illumination from a Xe lamp. The key strength of the DR-UV-SPIV is its ability to provide information on the depth-dependent electrically active defect distribution along the epi-layer growth direction. The DR-UV-SPIV data showed variations in the depth-dependent defect distribution across the wafer. As a result, rapid feedback on the depth-dependent electrical homogeneity of the electrically active defect distribution in the AlGaN/GaN HEMT epi-structure grown on a Si wafer with minimal sample preparation can be elucidated from the DR-UV-SPIV in combination with our previously demonstrated spectroscopic photo-IV measurement with the sub-bandgap excitation.

GaN-Based High-k Praseodymium Oxide Gate MISFETs with P2S5/(NH42SX + UV Interface Treatment Technology

Directory of Open Access Journals (Sweden)

Chao-Wei Lin

2012-01-01

Full Text Available This study examines the praseodymium-oxide- (Pr2O3- passivated AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs with high dielectric constant in which the AlGaN Schottky layers are treated with P2S5/(NH42SX + ultraviolet (UV illumination. An electron-beam evaporated Pr2O3 insulator is used instead of traditional plasma-assisted chemical vapor deposition (PECVD, in order to prevent plasma-induced damage to the AlGaN. In this work, the HEMTs are pretreated with P2S5/(NH42SX solution and UV illumination before the gate insulator (Pr2O3 is deposited. Since stable sulfur that is bound to the Ga species can be obtained easily and surface oxygen atoms are reduced by the P2S5/(NH42SX pretreatment, the lowest leakage current is observed in MIS-HEMT. Additionally, a low flicker noise and a low surface roughness (0.38 nm are also obtained using this novel process, which demonstrates its ability to reduce the surface states. Low gate leakage current Pr2O3 and high-k AlGaN/GaN MIS-HEMTs, with P2S5/(NH42SX + UV illumination treatment, are suited to low-noise applications, because of the electron-beam-evaporated insulator and the new chemical pretreatment.

Evaluation of thermal performance of all-GaN power module in parallel operation

International Nuclear Information System (INIS)

Chou, Po-Chien; Cheng, Stone; Chen, Szu-Hao

2014-01-01

This work presents an extensive thermal characterization of a single discrete GaN high-electron-mobility transistor (HEMT) device when operated in parallel at temperatures of 25 °C–175 °C. The maximum drain current (I D max ), on-resistance (R ON ), pinch-off voltage (V P ) and peak transconductance (g m ) at various chamber temperatures are measured and correlations among these parameters studied. Understanding the dependence of key transistor parameters on temperature is crucial to inhibiting the generation of hot spots and the equalization of currents in the parallel operation of HEMTs. A detailed analysis of the current imbalance between two parallel HEMT cells and its consequential effect on the junction temperature are also presented. The results from variations in the characteristics of the parallel-connected devices further verify that the thermal stability and switching behavior of these cells are balanced. Two parallel HEMT cells are operated at a safe working distance from thermal runaway to prevent destruction of the hottest cell. - Highlights: • This work reveals the sorting process of GaN devices for parallel operation. • The variations of I D max , R ON , V P , and g m with temperature are established. • The temperature-dependence parameters are crucial to prevent hot spots generation. • Safe working operation prevents thermal runaway and hottest cell destruction

Microwave and Millimeter-Wave Signal Power Generation

DEFF Research Database (Denmark)

Hadziabdic, Dzenan

Among the major limitations in high-speed communications and highresolution radars is the lack of efficient and powerful signal sources with low distortion. Microwave and millimeter-wave (mm-wave) signal power is needed for signal transmission. Progress in signal generation stems largely from...... distortion and high PAE were observed. The estimated output power of 42.5 dBm and PAE of 31.3% are comparable to the state-of-the-art results reported for GaN HEMT amplifiers. Wireless communication systems planned in the near future will operate at E-band, around 71-86 GHz, and require mm-wave-PAs to boost...... the application of novel materials like galliumnitride (GaN) and silicon-carbide (SiC) and fabrication of indiumphosphide (InP) based transistors. One goal of this thesis is to assess GaN HEMT technology with respect to linear efficient signal power generation. While most reports on GaN HEMT high-power devices...

AlGaN/GaN high electron mobility transistors with a low sub-threshold swing on free-standing GaN wafer

Directory of Open Access Journals (Sweden)

Xinke Liu

2017-09-01

Full Text Available This paper reported AlGaN/GaN high electron mobility transistors (HEMTs with low sub-threshold swing SS on free-standing GaN wafer. High quality AlGaN/GaN epi-layer has been grown by metal-organic chemical vapor deposition (MOCVD on free-standing GaN, small full-width hall maximum (FWHM of 42.9 arcsec for (0002 GaN XRD peaks and ultralow dislocation density (∼104-105 cm-2 were obtained. Due to these extremely high quality material properties, the fabricated AlGaN/GaN HEMTs achieve a low SS (∼60 mV/decade, low hysteresis of 54 mV, and high peak electron mobility μeff of ∼1456 cm2V-1s-1. Systematic study of materials properties and device characteristics exhibits that GaN-on-GaN AlGaN/GaN HEMTs are promising candidate for next generation high power device applications.

Surface morphology of Al0.3Ga0.7N/Al2O3-high electron mobility transistor structure.

Science.gov (United States)

Cörekçi, S; Usanmaz, D; Tekeli, Z; Cakmak, M; Ozçelik, S; Ozbay, E

2008-02-01

We present surface properties of buffer films (AIN and GaN) and Al0.3Gao.zN/Al2O3-High Electron Mobility Transistor (HEMT) structures with/without AIN interlayer grown on High Temperature (HT)-AIN buffer/Al2O3 substrate and Al2O3 substrate. We have found that the GaN surface morphology is step-flow in character and the density of dislocations was about 10(8)-10(9) cm(-2). The AFM measurements also exhibited that the presence of atomic steps with large lateral step dimension and the surface of samples was smooth. The lateral step sizes are in the range of 100-250 nm. The typical rms values of HEMT structures were found as 0.27, 0.30, and 0.70 nm. HT-AIN buffer layer can have a significant impact on the surface morphology of Al0.3Ga0.7N/Al2O3-HEMT structures.

Piezotronic effect tuned AlGaN/GaN high electron mobility transistor

Science.gov (United States)

Jiang, Chunyan; Liu, Ting; Du, Chunhua; Huang, Xin; Liu, Mengmeng; Zhao, Zhenfu; Li, Linxuan; Pu, Xiong; Zhai, Junyi; Hu, Weiguo; Wang, Zhong Lin

2017-11-01

The piezotronic effect utilizes strain-induced piezoelectric polarization charges to tune the carrier transportation across the interface/junction. We fabricated a high-performance AlGaN/GaN high electron mobility transistor (HEMT), and the transport property was proven to be enhanced by applying an external stress for the first time. The enhanced source-drain current was also observed at any gate voltage and the maximum enhancement of the saturation current was up to 21% with 15 N applied stress (0.18 GPa at center) at -1 V gate voltage. The physical mechanism of HEMT with/without external compressive stress conditions was carefully illustrated and further confirmed by a self-consistent solution of the Schrödinger-Poisson equations. This study proves the cause-and-effect relationship between the piezoelectric polarization effect and 2D electron gas formation, which provides a tunable solution to enhance the device performance. The strain tuned HEMT has potential applications in human-machine interface and the security control of the power system.

Reduction of skin effect losses in double-level-T-gate structure

Energy Technology Data Exchange (ETDEWEB)

Mikulics, M., E-mail: m.mikulics@fz-juelich.de; Hardtdegen, H.; Arango, Y. C.; Adam, R.; Fox, A.; Grützmacher, D. [Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, D-52425 Jülich (Germany); Jülich-Aachen Research Alliance, JARA, Fundamentals of Future Information Technology, D-52425 Jülich (Germany); Gregušová, D.; Novák, J. [Institute of Electrical Engineering, Slovak Academy of Sciences, SK-84104 Bratislava (Slovakia); Stanček, S. [Department of Nuclear Physic and Technique, Slovak University of Technology, SK-81219 Bratislava (Slovakia); Kordoš, P. [Institute of Electronics and Photonics, Slovak University of Technology, SK-81219 Bratislava (Slovakia); Sofer, Z. [Department of Inorganic Chemistry, Institute of Chemical Technology, Technická 5, Prague 6 (Czech Republic); Juul, L.; Marso, M. [Faculté des Sciences, de la Technologie et de la Communication, Université du Luxembourg, L-1359 Luxembourg (Luxembourg)

2014-12-08

We developed a T-gate technology based on selective wet etching yielding 200 nm wide T-gate structures used for fabrication of High Electron Mobility Transistors (HEMT). Major advantages of our process are the use of only standard photolithographic process and the ability to generate T-gate stacks. A HEMT fabricated on AlGaN/GaN/sapphire with gate length L{sub g} = 200 nm and double-stacked T-gates exhibits 60 GHz cutoff frequency showing ten-fold improvement compared to 6 GHz for the same device with 2 μm gate length. HEMTs with a double-level-T-gate (DLTG) structure exhibit up to 35% improvement of f{sub max} value compared to a single T-gate device. This indicates a significant reduction of skin effect losses in DLTG structure compared to its standard T-gate counterpart. These results agree with the theoretical predictions.

Direct label-free electrical immunodetection of transplant rejection protein biomarker in physiological buffer using floating gate AlGaN/GaN high electron mobility transistors.

Science.gov (United States)

Tulip, Fahmida S; Eteshola, Edward; Desai, Suchita; Mostafa, Salwa; Roopa, Subramanian; Evans, Boyd; Islam, Syed Kamrul

2014-06-01

Monokine induced by interferon gamma (MIG/CXCL9) is used as an immune biomarker for early monitoring of transplant or allograft rejection. This paper demonstrates a direct electrical, label-free detection method of recombinant human MIG with anti-MIG IgG molecules in physiologically relevant buffer environment. The sensor platform used is a biologically modified GaN-based high electron mobility transistor (HEMT) device. Biomolecular recognition capability was provided by using high affinity anti-MIG monoclonal antibody to form molecular affinity interface receptors on short N-hydroxysuccinimide-ester functionalized disulphide (DSP) self-assembled monolayers (SAMs) on the gold sensing gate of the HEMT device. A floating gate configuration has been adopted to eliminate the influences of external gate voltage. Preliminary test results with the proposed chemically treated GaN HEMT biosensor show that MIG can be detected for a wide range of concentration varying from 5 ng/mL to 500 ng/mL.

Electron mobility of two-dimensional electron gas in InGaN heterostructures: Effects of alloy disorder and random dipole scatterings

Science.gov (United States)

Hoshino, Tomoki; Mori, Nobuya

2018-04-01

InGaN has a smaller electron effective mass and is expected to be used as a channel material for high-electron-mobility transistors. However, it is an alloy semiconductor with a random distribution of atoms, which introduces additional scattering mechanisms: alloy disorder and random dipole scatterings. In this work, we calculate the electron mobility in InGaN- and GaN-channel high-electron-mobility transistors (HEMTs) while taking into account acoustic deformation potential, polar optical phonon, alloy disorder, and random dipole scatterings. For InGaN-channel HEMTs, we find that not only alloy disorder but also random dipole scattering has a strong impact on the electron mobility and it significantly decreases as the In mole fraction of the channel increases. Our calculation also shows that the channel thickness w dependence of the mobility is rather weak when w > 1 nm for In0.1Ga0.9N-channel HEMTs.

High Magnetic Field in THz Plasma Wave Detection by High Electron Mobility Transistors

Science.gov (United States)

Sakowicz, M.; Łusakowski, J.; Karpierz, K.; Grynberg, M.; Valusis, G.

The role of gated and ungated two dimensional (2D) electron plasma in THz detection by high electron mobility transistors (HEMTs) was investigated. THz response of GaAs/AlGaAs and GaN/AlGaN HEMTs was measured at 4.4K in quantizing magnetic fields with a simultaneous modulation of the gate voltage UGS. This allowed us to measure both the detection signal, S, and its derivative dS/dUGS. Shubnikov - de-Haas oscillations (SdHO) of both S and dS/dUGS were observed. A comparison of SdHO observed in detection and magnetoresistance measurements allows us to associate unambiguously SdHO in S and dS/dUGS with the ungated and gated parts of the transistor channel, respectively. This allows us to conclude that the entire channel takes part in the detection process. Additionally, in the case of GaAlAs/GaAs HEMTs, a structure related to the cyclotron resonance transition was observed.

Dry etching of MgCaO gate dielectric and passivation layers on GaN

International Nuclear Information System (INIS)

Hlad, M.; Voss, L.; Gila, B.P.; Abernathy, C.R.; Pearton, S.J.; Ren, F.

2006-01-01

MgCaO films grown by rf plasma-assisted molecular beam epitaxy and capped with Sc 2 O 3 are promising candidates as surface passivation layers and gate dielectrics on GaN-based high electron mobility transistors (HEMTs) and metal-oxide semiconductor HEMTs (MOS-HEMTs), respectively. Two different plasma chemistries were examined for etching these thin films on GaN. Inductively coupled plasmas of CH 4 /H 2 /Ar produced etch rates only in the range 20-70 A/min, comparable to the Ar sputter rates under the same conditions. Similarly slow MgCaO etch rates (∼100 A/min) were obtained with Cl 2 /Ar discharges under the same conditions, but GaN showed rates almost an order of magnitude higher. The MgCaO removal rates are limited by the low volatilities of the respective etch products. The CH 4 /H 2 /Ar plasma chemistry produced a selectivity of around 2 for etching the MgCaO with respect to GaN

Hâkim Seyyid Mehmed And His Book Called Nazire-i Hilye-i Hâkanî / HÂKİM SEYYİD MEHMED EFENDİ’NİN “NAZİRE-İ HİLYE-İ HÂKANΔ ADLI ESERİ

Directory of Open Access Journals (Sweden)

Yakup POYRAZ (M.A.H.

2007-08-01

Full Text Available As a result of the deep divine love people had for our Prophet, various literarytypes such as mevlit and na’t appeared. Of these types, hilye is one of the morepopular ones. Hilyes describe our Prophet physically and morally and theyusually convey the divine love poets have for him. The best-known hilye inTurkish literature, Hilye-i Hâkanî, was written by Hâkanî Mehmet Bey in 16thcentury. One of the nazires written in this hilye belongs to Hâkim SeyyidMehmed who was an 8th century poet. This nazire is usually regarded as one ofthe best in Hilye-i Hâkanî. In this article investigated Hilye-i Hâkanî and madeuseful form to literature.

Keeping Kim; How the Kim Conundrum Best Serves American Interests in the Asia Pacific

Science.gov (United States)

2018-04-18

Bombs South Korea’s Yeonpyeong Island," The Telegraph, November 23. 2010. http://www.telegraph.co.uk/news/worldnews/asia...southkorea/8153000/North-Korea- bombs -South-Koreas- Yeonpyeong-Island.html (accessed 01/05/2017, 2017). 25 A key initiative during the Sunshine Policy was...tr ad in g pa rt ne r Sa m e et hn ic ity ; di ff er en t sy st em o f go ve rn an ce So ve re ig nt y iss ue s a lw ay s co ns id er ed

Enhancement of the 2DEG density in AlGaAs/InGaAs/GaAs P-HEMTs structures grown by MBE on (311)A and (111)A GaAs substrates

International Nuclear Information System (INIS)

Rekaya, S.; Sfaxi, L.; Bouzaiene, L.; Maaref, H.; Bru-Chevallier, C.

2008-01-01

The pseudomorphic high electron mobility transistor (P-HEMT) structure materials Al 0.33 Ga 0.7 As/In 0.1 Ga 0.9 As/GaAs have been grown by molecular beam epitaxy (MBE) on (311)A and (111)A GaAs substrates. The epitaxy of strain heterostructure on high index GaAs substrate has led to new growth phenomena, material properties and device applications. The photoluminescence (PL) spectra of the structures have been measured at low temperature. The dominant emission in the PL spectra is due to the recombination from the first electron (e1) subband to the first heavy-hole (hh1) subband (E 11 : e1-hh1). This feature (E 11 ) is a relatively broad peak and has a typical asymmetric line shape. The transformation of the PL spectra in the close vicinity of the Fermi edge (E F ) under different excitation densities gives strong evidence for the Fermi Edge Singularity (FES) existence. The density of the quasi-two-dimensional electron gas (2DEG) determined by PL study (n s PL ), is in sufficient agreement with the values found from Hall measurements n s Hall at 77 K. The results prove an increase of the electron density in sample grown on GaAs (111)A and (311)A rather than in equivalent sample grown on (001) GaAs substrate. This effect is in good agreement with our theoretical prediction, which is based on a self-consistent solution of the coupled Schroedinger and Poisson equations

Strain-effect transistors: Theoretical study on the effects of external strain on III-nitride high-electron-mobility transistors on flexible substrates

Energy Technology Data Exchange (ETDEWEB)

Shervin, Shahab; Asadirad, Mojtaba [Department of Mechanical Engineering, University of Houston, Houston, Texas 77204-4006 (United States); Materials Science and Engineering Program, University of Houston, Houston, Texas 77204 (United States); Kim, Seung-Hwan; Ravipati, Srikanth; Lee, Keon-Hwa [Department of Mechanical Engineering, University of Houston, Houston, Texas 77204-4006 (United States); Bulashevich, Kirill [STR Group, Inc., Engels av. 27, P.O. Box 89, 194156, St. Petersburg (Russian Federation); Ryou, Jae-Hyun, E-mail: jryou@uh.edu [Department of Mechanical Engineering, University of Houston, Houston, Texas 77204-4006 (United States); Materials Science and Engineering Program, University of Houston, Houston, Texas 77204 (United States); Texas Center for Superconductivity at the University of Houston (TcSUH), University of Houston, Houston, Texas 77204 (United States)

2015-11-09

This paper presents strain-effect transistors (SETs) based on flexible III-nitride high-electron-mobility transistors (HEMTs) through theoretical calculations. We show that the electronic band structures of InAlGaN/GaN thin-film heterostructures on flexible substrates can be modified by external bending with a high degree of freedom using polarization properties of the polar semiconductor materials. Transfer characteristics of the HEMT devices, including threshold voltage and transconductance, are controlled by varied external strain. Equilibrium 2-dimensional electron gas (2DEG) is enhanced with applied tensile strain by bending the flexible structure with the concave-side down (bend-down condition). 2DEG density is reduced and eventually depleted with increasing compressive strain in bend-up conditions. The operation mode of different HEMT structures changes from depletion- to enchantment-mode or vice versa depending on the type and magnitude of external strain. The results suggest that the operation modes and transfer characteristics of HEMTs can be engineered with an optimum external bending strain applied in the device structure, which is expected to be beneficial for both radio frequency and switching applications. In addition, we show that drain currents of transistors based on flexible InAlGaN/GaN can be modulated only by external strain without applying electric field in the gate. The channel conductivity modulation that is obtained by only external strain proposes an extended functional device, gate-free SETs, which can be used in electro-mechanical applications.

Kim Davis: A Mother's Dilemma.

Science.gov (United States)

Hudecki, Michael S.

2000-01-01

Presents a discussion case in which parents must decide whether or not to enroll their sons in an experimental treatment program for muscular dystrophy. Identifies teaching objectives and discusses the key issues of the case--muscle structure and function, muscular dystrophy, scientists and money, scientific method and the FDA, and family health…

Rapid detection of cardiac troponin I using antibody-immobilized gate-pulsed AlGaN/GaN high electron mobility transistor structures

Science.gov (United States)

Yang, Jiancheng; Carey, Patrick; Ren, Fan; Wang, Yu-Lin; Good, Michael L.; Jang, Soohwan; Mastro, Michael A.; Pearton, S. J.

2017-11-01

We report a comparison of two different approaches to detecting cardiac troponin I (cTnI) using antibody-functionalized AlGaN/GaN High Electron Mobility Transistors (HEMTs). If the solution containing the biomarker has high ionic strength, there can be difficulty in detection due to charge-screening effects. To overcome this, in the first approach, we used a recently developed method involving pulsed biases applied between a separate functionalized electrode and the gate of the HEMT. The resulting electrical double layer produces charge changes which are correlated with the concentration of the cTnI biomarker. The second approach fabricates the sensing area on a glass slide, and the pulsed gate signal is externally connected to the nitride HEMT. This produces a larger integrated change in charge and can be used over a broader range of concentrations without suffering from charge-screening effects. Both approaches can detect cTnI at levels down to 0.01 ng/ml. The glass slide approach is attractive for inexpensive cartridge-type sensors.

Precise thickness control in recess etching of AlGaN/GaN hetero-structure using photocarrier-regulated electrochemical process

Science.gov (United States)

Kumazaki, Yusuke; Uemura, Keisuke; Sato, Taketomo; Hashizume, Tamotsu

2017-05-01

The photocarrier-regulated electrochemical (PREC) process was developed for fabricating recessed-gate AlGaN/GaN high-electron-mobility transistors (HEMTs) for normally off operation. The PREC process is based on photo-assisted electrochemical etching using low-energy chemical reactions. The fundamental photo-electrochemical measurements on AlGaN/GaN heterostructures revealed that the photo-carriers generated in the top AlGaN layer caused homogeneous etching of AlGaN with a smooth surface, but those generated in the GaN layer underneath caused inhomogeneous etching that roughens the surface. The concept of the PREC process is to supply the photo-carriers generated only in the AlGaN layer by selecting proper conditions on light wavelength and voltage. The phenomenon of self-termination etching has been observed during the PREC process, where the etching depth was controlled by light intensity. The recessed-gate AlGaN/GaN HEMT fabricated with the PREC process showed positive threshold voltage and improvement in transconductance compared to planar-gate AlGaN/GaN HEMTs.

Threading dislocation movement in AlGaN/GaN-on-Si high electron mobility transistors under high temperature reverse bias stressing

Directory of Open Access Journals (Sweden)

W. A. Sasangka

2016-09-01

Full Text Available Dislocations are known to be associated with both physical and electrical degradation mechanisms of AlGaN/GaN-on-Si high electron mobility transistors (HEMTs. We have observed threading dislocation movement toward the gate-edges in AlGaN/GaN-on-Si HEMT under high reverse bias stressing. Stressed devices have higher threading dislocation densities (i.e. ∼5 × 109/cm2 at the gate-edges, as compared to unstressed devices (i.e. ∼2.5 × 109/cm2. Dislocation movement correlates well with high tensile stress (∼1.6 GPa at the gate-edges, as seen from inverse piezoelectric calculations and x-ray synchrotron diffraction residual stress measurements. Based on Peierls stress calculation, we believe that threading dislocations move via glide in 〈 11 2 ¯ 0 〉 / { 1 1 ¯ 00 } and 〈 11 2 ¯ 0 〉 / { 1 1 ¯ 01 } slip systems. This result illustrates the importance of threading dislocation mobility in controlling the reliability of AlGaN/GaN-on-Si HEMTs.

Density-dependent electron transport and precise modeling of GaN high electron mobility transistors

Energy Technology Data Exchange (ETDEWEB)

Bajaj, Sanyam, E-mail: bajaj.10@osu.edu; Shoron, Omor F.; Park, Pil Sung; Krishnamoorthy, Sriram; Akyol, Fatih; Hung, Ting-Hsiang [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Reza, Shahed; Chumbes, Eduardo M. [Raytheon Integrated Defense Systems, Andover, Massachusetts 01810 (United States); Khurgin, Jacob [Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Rajan, Siddharth [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Department of Material Science and Engineering, The Ohio State University, Columbus, Ohio 43210 (United States)

2015-10-12

We report on the direct measurement of two-dimensional sheet charge density dependence of electron transport in AlGaN/GaN high electron mobility transistors (HEMTs). Pulsed IV measurements established increasing electron velocities with decreasing sheet charge densities, resulting in saturation velocity of 1.9 × 10{sup 7 }cm/s at a low sheet charge density of 7.8 × 10{sup 11 }cm{sup −2}. An optical phonon emission-based electron velocity model for GaN is also presented. It accommodates stimulated longitudinal optical (LO) phonon emission which clamps the electron velocity with strong electron-phonon interaction and long LO phonon lifetime in GaN. A comparison with the measured density-dependent saturation velocity shows that it captures the dependence rather well. Finally, the experimental result is applied in TCAD-based device simulator to predict DC and small signal characteristics of a reported GaN HEMT. Good agreement between the simulated and reported experimental results validated the measurement presented in this report and established accurate modeling of GaN HEMTs.

Density-dependent electron transport and precise modeling of GaN high electron mobility transistors

International Nuclear Information System (INIS)

Bajaj, Sanyam; Shoron, Omor F.; Park, Pil Sung; Krishnamoorthy, Sriram; Akyol, Fatih; Hung, Ting-Hsiang; Reza, Shahed; Chumbes, Eduardo M.; Khurgin, Jacob; Rajan, Siddharth

2015-01-01

We report on the direct measurement of two-dimensional sheet charge density dependence of electron transport in AlGaN/GaN high electron mobility transistors (HEMTs). Pulsed IV measurements established increasing electron velocities with decreasing sheet charge densities, resulting in saturation velocity of 1.9 × 10 7  cm/s at a low sheet charge density of 7.8 × 10 11  cm −2 . An optical phonon emission-based electron velocity model for GaN is also presented. It accommodates stimulated longitudinal optical (LO) phonon emission which clamps the electron velocity with strong electron-phonon interaction and long LO phonon lifetime in GaN. A comparison with the measured density-dependent saturation velocity shows that it captures the dependence rather well. Finally, the experimental result is applied in TCAD-based device simulator to predict DC and small signal characteristics of a reported GaN HEMT. Good agreement between the simulated and reported experimental results validated the measurement presented in this report and established accurate modeling of GaN HEMTs

Plasma-assisted Molecular Beam Epitaxy of N-polar InAlN-barrier High-electron-mobility Transistors.

Science.gov (United States)

Hardy, Matthew T; Storm, David F; Katzer, D Scott; Downey, Brian P; Nepal, Neeraj; Meyer, David J

2016-11-24

Plasma-assisted molecular beam epitaxy is well suited for the epitaxial growth of III-nitride thin films and heterostructures with smooth, abrupt interfaces required for high-quality high-electron-mobility transistors (HEMTs). A procedure is presented for the growth of N-polar InAlN HEMTs, including wafer preparation and growth of buffer layers, the InAlN barrier layer, AlN and GaN interlayers and the GaN channel. Critical issues at each step of the process are identified, such as avoiding Ga accumulation in the GaN buffer, the role of temperature on InAlN compositional homogeneity, and the use of Ga flux during the AlN interlayer and the interrupt prior to GaN channel growth. Compositionally homogeneous N-polar InAlN thin films are demonstrated with surface root-mean-squared roughness as low as 0.19 nm and InAlN-based HEMT structures are reported having mobility as high as 1,750 cm 2 /V∙sec for devices with a sheet charge density of 1.7 x 10 13 cm -2 .

InAlAs/InGaAs Pseudomorphic High Eelectron Mobility Transistors Grown by Molecular Beam Epitaxy on the InP Substrate

International Nuclear Information System (INIS)

Huang Jie; Guo Tian-Yi; Zhang Hai-Ying; Xu Jing-Bo; Fu Xiao-Jun; Yang Hao; Niu Jie-Bin

2010-01-01

A novel PMMA/PMGI/ZEP520 trilayer resist electron beam lithograph (EBL) technology is successfully developed and used to fabricate the 150 nm gate-length In 0.7 Ga 0.3 As/In 0.52 Al 0.48 As Pseudomorphic HEMT on an InP substrate, of which the material structure is successfully designed and optimized. A perfect profile of T-gate is successfully obtained. These fabricated devices demonstrate excellent dc and rf characteristics: the transconductance G m , maximum saturation drain-to-source current I DSS , threshold voltage V T , maximum current gain frequency f T derived from h 21 , maximum frequency of oscillation derived from maximum available power gain/maximum stable gain and from unilateral power-gain of metamorphic InGaAs/InAlAs high electron mobility transistors (HEMTs) are 470 mS/mm, 560 mA/mm, −1.0 V, 76 GHz, 135 GHz and 436 GHz, respectively. The excellent high frequency performances promise the possibility of metamorphic HEMTs for millimeter-wave applications. (cross-disciplinary physics and related areas of science and technology)

Suppression of surface-originated gate lag by a dual-channel AlN/GaN high electron mobility transistor architecture

Science.gov (United States)

Deen, David A.; Storm, David F.; Scott Katzer, D.; Bass, R.; Meyer, David J.

2016-08-01

A dual-channel AlN/GaN high electron mobility transistor (HEMT) architecture is demonstrated that leverages ultra-thin epitaxial layers to suppress surface-related gate lag. Two high-density two-dimensional electron gas (2DEG) channels are utilized in an AlN/GaN/AlN/GaN heterostructure wherein the top 2DEG serves as a quasi-equipotential that screens potential fluctuations resulting from distributed surface and interface states. The bottom channel serves as the transistor's modulated channel. Dual-channel AlN/GaN heterostructures were grown by molecular beam epitaxy on free-standing hydride vapor phase epitaxy GaN substrates. HEMTs fabricated with 300 nm long recessed gates demonstrated a gate lag ratio (GLR) of 0.88 with no degradation in drain current after bias stressed in subthreshold. These structures additionally achieved small signal metrics ft/fmax of 27/46 GHz. These performance results are contrasted with the non-recessed gate dual-channel HEMT with a GLR of 0.74 and 82 mA/mm current collapse with ft/fmax of 48/60 GHz.

A Study of China’s Possible Military Intervention in the Event of a Sudden Change in North Korea

Science.gov (United States)

2011-06-10

Kim Jong - nam , Kim Jong -chul or Kim Jong -un as Kim‘s successor. Some have asserted that there might not be a third generation of Kim ...The power struggle between Kim Jong - nam (eldest son) who is residing in China and Kim Jong -un has been observed in many places over time. Kim 29... Jong - nam , who is known to be receiving Chinese support, revealed his opposition to a third generation of dynastic succession in

Effects of SiNx on two-dimensional electron gas and current collapse of AlGaN/GaN high electron mobility transistors

International Nuclear Information System (INIS)

Fan, Ren; Zhi-Biao, Hao; Lei, Wang; Lai, Wang; Hong-Tao, Li; Yi, Luo

2010-01-01

SiN x is commonly used as a passivation material for AlGaN/GaN high electron mobility transistors (HEMTs). In this paper, the effects of SiN x passivation film on both two-dimensional electron gas characteristics and current collapse of AlGaN/GaN HEMTs are investigated. The SiN x films are deposited by high- and low-frequency plasma-enhanced chemical vapour deposition, and they display different strains on the AlGaN/GaN heterostructure, which can explain the experiment results. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Pyongyangi leedi Macbeth tõmbab niite Põhja-Koreas / Yuriko Koike

Index Scriptorium Estoniae

Koike, Yuriko

2010-01-01

Põhja-Korea liidri Kim Jong-il'i õest Kim Kyong-hui'st. Autori, Jaapani endise kaitseministri väitel on hakatud uskuma, et Kim Jong-il võib igal hetkel määrata just Kim Kyong-hui üleminekuaja valitsejaks, kes peab korraldama tema surma järel kolmanda põlvkonna Kimi võimuletuleku, kuid Kim Kyong-hui võib ise ihata saada Kim Jong-ili mantlipärijaks

Urine Kidney Injury Molecule-1: A Potential Non-invasive Biomarker for Patients with Renal Cell Carcinoma

Science.gov (United States)

Zhang, Ping L.; Mashni, Joseph W.; Sabbisetti, Venkata S.; Schworer, Charles M.; Wilson, George D.; Wolforth, Stacy C.; Kernen, Kenneth M.; Seifman, Brian D.; Amin, Mitual B.; Geddes, Timothy J.; Lin, Fan; Bonventre, Joseph V.; Hafron, Jason M.

2014-01-01

Objective To evaluate the use of urine KIM-1 as a biomarker for supporting a diagnosis of kidney cancers before operation. Methods A total of 19 patients were enrolled in the study based on preoperative imaging studies. Pre-operative and follow-up (1 month) uKIM-1 levels were measured and normalized with uCr levels and renal tumors were stained for KIM-1 using immunohistochemical techniques. Results The percentage of KIM-1 positive staining RCC cells ranged from 10 to 100% and the staining intensity ranged from 1+ to 3+. Based on the KIM-1 staining, 19 cases were divided into the KIM-1-negative staining group (n =7) and the KIM-1-positive group (n = 12). Serum creatinine (sCR) levels were significantly elevated after nephrectomy in both groups. In the KIM-1 negative group, uKIM-1/uCr remained at a similar level before (0.37 ± 0.1 ng/mg Cr) and after nephrectomy (0.32 ± 0.01 ng/mg Cr). However, in the KIM-1 positive group, elevated uKIM-1/uCr at 1.20 ± 0.31 ng/mg Cr was significantly reduced to 0.36± 0.1 ng/mg Cr, which was similar to the pre-operative uKIM-1/uCr (0.37 ± 0.1 ng/mg Cr) in the KIM-1 negative group. Conclusion Our study showed significant reduction in uKIM-1/uCr after nephrectomy, suggesting that urine KIM-1 may serve as a surrogate biomarker for kidney cancer and a non-invasive pre-operative measure to evaluate the malignant potential of renal masses. PMID:23979814

Optimization design on breakdown voltage of AlGaN/GaN high-electron mobility transistor

Science.gov (United States)

Yang, Liu; Changchun, Chai; Chunlei, Shi; Qingyang, Fan; Yuqian, Liu

2016-12-01

Simulations are carried out to explore the possibility of achieving high breakdown voltage of GaN HEMT (high-electron mobility transistor). GaN cap layers with gradual increase in the doping concentration from 2 × 1016 to 5 × 1019 cm-3 of N-type and P-type cap are investigated, respectively. Simulation results show that HEMT with P-doped GaN cap layer shows more potential to achieve higher breakdown voltage than N-doped GaN cap layer under the same doping concentration. This is because the ionized net negative space charges in P-GaN cap layer could modulate the surface electric field which makes more contribution to RESURF effect. Furthermore, a novel GaN/AlGaN/GaN HEMT with P-doped GaN buried layer in GaN buffer between gate and drain electrode is proposed. It shows enhanced performance. The breakdown voltage of the proposed structure is 640 V which is increased by 12% in comparison to UID (un-intentionally doped) GaN/AlGaN/GaN HEMT. We calculated and analyzed the distribution of electrons' density. It is found that the depleted region is wider and electric field maximum value is induced at the left edge of buried layer. So the novel structure with P-doped GaN buried layer embedded in GaN buffer has the better improving characteristics of the power devices. Project supported by the National Basic Research Program of China (No. 2014CB339900) and the Open Fund of Key Laboratory of Complex Electromagnetic Environment Science and Technology, China Academy of Engineering Physics (No. 2015-0214.XY.K).

Investigation of AlGaN/GaN high electron mobility transistor structures on 200-mm silicon (111) substrates employing different buffer layer configurations.

Science.gov (United States)

Lee, H-P; Perozek, J; Rosario, L D; Bayram, C

2016-11-21

AlGaN/GaN high electron mobility transistor (HEMT) structures are grown on 200-mm diameter Si(111) substrates by using three different buffer layer configurations: (a) Thick-GaN/3 × {Al x Ga 1-x N}/AlN, (b) Thin-GaN/3 × {Al x Ga 1-x N}/AlN, and (c) Thin-GaN/AlN, so as to have crack-free and low-bow (GaN HEMT structures. The effects of buffer layer stacks (i.e. thickness and content) on defectivity, stress, and two-dimensional electron gas (2DEG) mobility and 2DEG concentration are reported. It is shown that 2DEG characteristics are heavily affected by the employed buffer layers between AlGaN/GaN HEMT structures and Si(111) substrates. Particularly, we report that in-plane stress in the GaN layer affects the 2DEG mobility and 2DEG carrier concentration significantly. Buffer layer engineering is shown to be essential for achieving high 2DEG mobility (>1800 cm 2 /V∙s) and 2DEG carrier concentration (>1.0 × 10 13  cm -2 ) on Si(111) substrates.

Dielectric and barrier thickness fluctuation scattering in Al2O3/AlGaN/GaN double heterojunction high-electron mobility transistors

International Nuclear Information System (INIS)

Ji, Dong; Lu, Yanwu; Liu, Bing; Liu, Guipeng; Zhu, Qinsheng; Wang, Zhanguo

2013-01-01

The two-dimensional electron gas (2DEG) mobility limited by dielectric and barrier thickness fluctuations (TF) scattering in Al 2 O 3 /AlGaN/GaN double heterojunction high-electron mobility transistors (HEMTs) is calculated. Calculation shows that thickness fluctuation scattering is the main limitation in Al 2 O 3 /AlGaN/GaN double heterojunction HEMTs with thin Al 2 O 3 layer thicknesses. In addition, a study of 2DEG mobility as a function of 2DEG density, n s , shows that TF scattering acts as the main limitation when n s exceeds 2 × 10 12 cm −2 . The results may be used to design HEMTs to obtain higher 2DEG mobilities by modulating the dielectric layer and barrier thicknesses or 2DEG density. - Highlights: • The mobility limited by thickness fluctuation (TF) scattering is studied. • Results show that thickness fluctuation scattering is the main limitation. • Two-dimensional electron gas (2DEG) mobility is a function of 2DEG density. • TF scattering is the main limitation when 2DEG density exceeds 2 × 10 12 cm −2

Low power fluorine plasma effects on electrical reliability of AlGaN/GaN high electron mobility transistor

International Nuclear Information System (INIS)

Yang Ling; Zhou Xiao-Wei; Ma Xiao-Hua; Lv Ling; Zhang Jin-Cheng; Hao Yue; Cao Yan-Rong

2017-01-01

The new electrical degradation phenomenon of the AlGaN/GaN high electron mobility transistor (HEMT) treated by low power fluorine plasma is discovered. The saturated current, on-resistance, threshold voltage, gate leakage and breakdown voltage show that each experiences a significant change in a short time stress, and then keeps unchangeable. The migration phenomenon of fluorine ions is further validated by the electron redistribution and breakdown voltage enhancement after off-state stress. These results suggest that the low power fluorine implant ion stays in an unstable state. It causes the electrical properties of AlGaN/GaN HEMT to present early degradation. A new migration and degradation mechanism of the low power fluorine implant ion under the off-stress electrical stress is proposed. The low power fluorine ions would drift at the beginning of the off-state stress, and then accumulate between gate and drain nearby the gate side. Due to the strong electronegativity of fluorine, the accumulation of the front fluorine ions would prevent the subsequent fluorine ions from drifting, thereby alleviating further the degradation of AlGaN/GaN HEMT electrical properties. (paper)

Suppression of surface-originated gate lag by a dual-channel AlN/GaN high electron mobility transistor architecture

International Nuclear Information System (INIS)

Deen, David A.; Storm, David F.; Scott Katzer, D.; Bass, R.; Meyer, David J.

2016-01-01

A dual-channel AlN/GaN high electron mobility transistor (HEMT) architecture is demonstrated that leverages ultra-thin epitaxial layers to suppress surface-related gate lag. Two high-density two-dimensional electron gas (2DEG) channels are utilized in an AlN/GaN/AlN/GaN heterostructure wherein the top 2DEG serves as a quasi-equipotential that screens potential fluctuations resulting from distributed surface and interface states. The bottom channel serves as the transistor's modulated channel. Dual-channel AlN/GaN heterostructures were grown by molecular beam epitaxy on free-standing hydride vapor phase epitaxy GaN substrates. HEMTs fabricated with 300 nm long recessed gates demonstrated a gate lag ratio (GLR) of 0.88 with no degradation in drain current after bias stressed in subthreshold. These structures additionally achieved small signal metrics f_t/f_m_a_x of 27/46 GHz. These performance results are contrasted with the non-recessed gate dual-channel HEMT with a GLR of 0.74 and 82 mA/mm current collapse with f_t/f_m_a_x of 48/60 GHz.

Suppression of surface-originated gate lag by a dual-channel AlN/GaN high electron mobility transistor architecture

Energy Technology Data Exchange (ETDEWEB)

Deen, David A., E-mail: david.deen@alumni.nd.edu; Storm, David F.; Scott Katzer, D.; Bass, R.; Meyer, David J. [Naval Research Laboratory, Electronics Science and Technology Division, Washington, DC 20375 (United States)

2016-08-08

A dual-channel AlN/GaN high electron mobility transistor (HEMT) architecture is demonstrated that leverages ultra-thin epitaxial layers to suppress surface-related gate lag. Two high-density two-dimensional electron gas (2DEG) channels are utilized in an AlN/GaN/AlN/GaN heterostructure wherein the top 2DEG serves as a quasi-equipotential that screens potential fluctuations resulting from distributed surface and interface states. The bottom channel serves as the transistor's modulated channel. Dual-channel AlN/GaN heterostructures were grown by molecular beam epitaxy on free-standing hydride vapor phase epitaxy GaN substrates. HEMTs fabricated with 300 nm long recessed gates demonstrated a gate lag ratio (GLR) of 0.88 with no degradation in drain current after bias stressed in subthreshold. These structures additionally achieved small signal metrics f{sub t}/f{sub max} of 27/46 GHz. These performance results are contrasted with the non-recessed gate dual-channel HEMT with a GLR of 0.74 and 82 mA/mm current collapse with f{sub t}/f{sub max} of 48/60 GHz.

Mechanism of leakage of ion-implantation isolated AlGaN/GaN MIS-high electron mobility transistors on Si substrate

Science.gov (United States)

Zhang, Zhili; Song, Liang; Li, Weiyi; Fu, Kai; Yu, Guohao; Zhang, Xiaodong; Fan, Yaming; Deng, Xuguang; Li, Shuiming; Sun, Shichuang; Li, Xiajun; Yuan, Jie; Sun, Qian; Dong, Zhihua; Cai, Yong; Zhang, Baoshun

2017-08-01

In this paper, we systematically investigated the leakage mechanism of the ion-implantation isolated AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) on Si substrate. By means of combined DC tests at different temperatures and electric field dependence, we demonstrated the following original results: (1) It is proved that gate leakage is the main contribution to OFF-state leakage of ion-implantation isolated AlGaN/GaN MIS-HEMTs, and the gate leakage path is a series connection of the gate dielectric Si3N4 and Si3N4-GaN interface. (2) The dominant mechanisms of the leakage current through LPCVD-Si3N4 gate dielectric and Si3N4-GaN interface are identified to be Frenkel-Poole emission and two-dimensional variable range hopping (2D-VRH), respectively. (3) A certain temperature annealing could reduce the density of the interface state that produced by ion implantation, and consequently suppress the interface leakage transport, which results in a decrease in OFF-state leakage current of ion-implantation isolated AlGaN/GaN MIS-HEMTs.

Direct observation of 0.57 eV trap-related RF output power reduction in AlGaN/GaN high electron mobility transistors

Science.gov (United States)

Arehart, A. R.; Sasikumar, A.; Rajan, S.; Via, G. D.; Poling, B.; Winningham, B.; Heller, E. R.; Brown, D.; Pei, Y.; Recht, F.; Mishra, U. K.; Ringel, S. A.

2013-02-01

This paper reports direct evidence for trap-related RF output power loss in GaN high electron mobility transistors (HEMTs) grown by metal organic chemical vapor deposition (MOCVD) through increased concentration of a specific electron trap at EC-0.57 eV that is located in the drain access region, as a function of accelerated life testing (ALT). The trap is detected by constant drain current deep level transient spectroscopy (CID-DLTS) and the CID-DLTS thermal emission time constant precisely matches the measured drain lag. Both drain lag and CID-DLTS measurements show this state to already exist in pre-stressed devices, which coupled with its strong increase in concentration as a function of stress in the absence of significant increases in concentrations of other detected traps, imply its role in causing degradation, in particular knee walkout. This study reveals EC-0.57 eV trap concentration tracks degradation induced by ALT for MOCVD-grown HEMTs supplied by several commercial and university sources. The results suggest this defect has a common source and may be a key degradation pathway in AlGaN/GaN HEMTs and/or an indicator to predict device lifetime.

Correlation Between Two-Dimensional Electron Gas Mobility and Crystal Quality in AlGaN/GaN High-Electron-Mobility Transistor Structure Grown on 4H-SiC.

Science.gov (United States)

Heo, Cheon; Jang, Jongjin; Lee, Kyngjae; So, Byungchan; Lee, Kyungbae; Ko, Kwangse; Nam, Okhyun

2017-01-01

We investigated the correlation between the crystal quality and two-dimensional electron gas (2DEG) mobility of an AlGaN/GaN high-electron-mobility transistor (HEMT) structure grown by metal-organic chemical vapor deposition. For the structure with an AlN nucleation layer grown at 1100 °C, the 2DEG mobility and sheet carrier density were 1627 cm²/V·s and 3.23 × 10¹³ cm⁻², respectively, at room temperature. Further, it was confirmed that the edge dislocation density of the GaN buffer layer was related to the 2DEG mobility and sheet carrier density in the AlGaN/GaN HEMT.

Double pulse doped InGaAs/AlGaAs/GaAs pseudomorphic high-electron-mobility transistor heterostructures

International Nuclear Information System (INIS)

Egorov, A. Yu.; Gladyshev, A. G.; Nikitina, E. V.; Denisov, D. V.; Polyakov, N. K.; Pirogov, E. V.; Gorbazevich, A. A.

2010-01-01

Double pulse doped (δ-doped) InGaAs/AlGaAs/GaAs pseudomorphic high-electron-mobility transistor (HEMT) heterostructures were grown by molecular-beam epitaxy using a multiwafer technological system. The room-temperature electron mobility was determined by the Hall method as 6550 and 6000 cm 2 /(V s) at sheet electron densities of 3.00 x 10 12 and 3.36 x 10 12 cm -2 , respectively. HEMT heterostructures fabricated in a single process feature high uniformity of structural and electrical characteristics over the entire area of wafers 76.2 mm in diameter and high reproducibility of characteristics from process to process.

AlGaN/GaN high electron mobility transistors with implanted ohmic contacts

International Nuclear Information System (INIS)

Wang, H.T.; Tan, L.S.; Chor, E.F.

2007-01-01

Selective area silicon implantation for source/drain regions was integrated into the fabrication of molecular beam epitaxy-grown AlGaN/GaN HEMTs. Dopant activation was achieved by rapid thermal annealing at 1100 deg. C in flowing N 2 ambient for 120 s with an AlN encapsulation. Linear transmission line measurements showed that the resistance of the overlay Ti/Al/Ni/Au ohmic contacts was reduced by 61% compared to the control sample. After the Schottky Ni/Au gate formation, the typical DC characteristics displayed a higher current drive, smaller knee voltage and better gate control properties for HEMTs with implanted source and drain regions

In situ rumen degradability characteristics of rice straw, soybean ...

African Journals Online (AJOL)

In situ rumen degradability characteristics of rice straw, soybean curd residue and peppermint (Mentha piperita) in Hanwoo steer (Bos Taurus coreanae). Byong Tae Jeon, KyoungHoon Kim, Sung Jin Kim, Na Yeon Kim, Jae Hyun Park, Dong Hyun Kim, Mi Rae Oh, Sang Ho Moon ...

Scattering and mobility in indium gallium arsenide channel, pseudomorphic high electron mobility transistors (InGaAs pHEMTs)

International Nuclear Information System (INIS)

Pearson, J.L.

1999-03-01

Extensive transport measurements have been completed on deep and shallow-channelled InGaAs p-HEMTs of varying growth temperature, indium content, spacer thickness and doping density, with a view to a thorough characterisation, both in the metallic and the localised regimes. Particular emphasis was given to MBE grown layers, with characteristics applicable for device use, but low measurement temperatures were necessary to resolve the elastic scattering mechanisms. Measurements made in the metallic regime included transport and quantum mobility - the former over a range of temperatures between 1.5K to 300K. Conductivity measurements were also acquired in the strong localisation regime between about 1.5K and 100K. Experimentally determined parameters were tested for comparison with those predicted by an electrostatic model. Excellent agreement was obtained for carrier density. Other parameters were less well predicted, but the relevant experimental measurements, including linear depletion of the 2DEG, were sensitive to any excess doping above a 'critical' value determined by the model. At low temperature (1.5K), it was found that in all samples tested, transport mobility was strongly limited at all carrier densities by a large q mechanism, possibly intrinsic to the channel. This was ascribed either to scattering by the long-range potentials arising from the indium concentration fluctuations or fluctuations in the thickness of the channel layer. This mechanism dominates the transport at low carrier densities for all samples, but at high carrier density, an additional mechanism is significant for samples with the thinnest spacers tested (2.5nm). This is ascribed to direct electron interaction with the states of the donor layer, and produces a characteristic transport mobility peak. At higher carrier densities, past the peak, quantum mobility was found only to increase monotonically in value. Remote ionised impurity scattering while significant, particularly for samples

Correlation of AlGaN/GaN high-electron-mobility transistors electroluminescence characteristics with current collapse

Science.gov (United States)

Ohi, Shintaro; Yamazaki, Taisei; Asubar, Joel T.; Tokuda, Hirokuni; Kuzuhara, Masaaki

2018-02-01

We report on the correlation between the electroluminescence and current collapse of AlGaN/GaN high-electron-mobility transistors (HEMTs). Standard passivated devices suffering from severe current collapse exhibited high-intensity whitish electroluminescence confined near the drain contact. In contrast, devices with reduced current collapse resulting from oxygen plasma treatment or GaN capping showed low-intensity reddish emission across the entire gate-drain access region. A qualitative explanation of this observed correlation between the current collapse and electroluminescence is presented. Our results demonstrate that electroluminescence analysis is a powerful tool not only for identifying high-field regions but also for assessing the degree of current collapse in AlGaN/GaN HEMTs.

Retarderi na teškim vozilima

Directory of Open Access Journals (Sweden)

Joško Rapanić

2012-10-01

Full Text Available The objective of all the braking systems fitted in vehicles isto reduce the speed, as well as to keep them at a standstill. Inorder to increase the active road traffic safety, the experts inthe leading vehicle manufacturer companies are trying from day to day to find a more efficient solution of the highest possiblequality. Braking problems, i.e. problems of stopping the vehiclesare closely related to time, forces, momentum, mass andother physical quantities. This is best seen in the braking ofheavy duty vehicles, trucks, buses, where the braking efficacyis questionable due to high inertia forces caused by heavyweight and more recently relatively high speeds. Such vehiclesare fitted with system of brakes that operate on compressed airor combination of pneumatics and hydraulics, since the driverhas not got enough power to achieve appropriate braking effect.However, the biggest problems occur by trucks runningdownhill, when the braking system is operated continuously fora longer period of time. This causes heating and overheating ofthe system elements ("fading", thus reducing the braking effect.In extreme cases, particularly if the system is poorly maintained,it can eventually fail completely.Because of the mentioned reasons for difficulties in brakingof trucks, such vehicles have been recently fitted with anauxiliary slow-down system. This system is completely independentfromthe main one on the wheels and is used exclusivelyfor slowing down or for maintaining of speed.

Ajateenistusest, ausalt! / Kim Järvepõld

Index Scriptorium Estoniae

Järvepõld, Kim

2007-01-01

Ilmunud ka: Postimees : na russkom jazõke, 9. apr. 2007, lk. 7. Autor leiab, et põhiseaduslik nõue, mille järgi on kõik Eesti kodanikud kohustatud osa võtma riigikaitsest, pole vastavuses tegeliku olukorraga, ning arvab, et kohustuslik ajateenistus tuleb kaotada või viia kooskõlla põhiseadusega

Application of the Single Hardening Model in the Finite Element Program ABAQUS

DEFF Research Database (Denmark)

Jakobsen, Kim Parsberg

model, developed by Lade and Kim (Kim & Lade 1988, Lade & Kim 1988a, Lade & Kim 1988b) is implemented as a user defined material module, UMAT, in the commercial finite element program, ABAQUS. The advantages of the Single Hardening Model Iie in its ability to predict elastic and plastic displacements...

WOCSDICE '98, 22nd Workshop on Compound Semiconductor Devices and Integrated Circuits, May 24-27, 1998, Pannonia Seehotel, Zeuthen, Germany

National Research Council Canada - National Science Library

1998-01-01

.... Topics include material growth and characterization, recent developments in MESFETS, HEMTs, and HBTs, MMlC-Technology, Microwave and millimeter wave power devices, GaN- Devices, Mesoscopic devices...

WOCSDICE 1998: 22nd Workshop on Compound Semiconductor Devices and Integrated Circuits, May 24-27, 1998, Zeuthen, Germany

National Research Council Canada - National Science Library

1998-01-01

.... Topics include material growth and characterization, recent developments in MESFETS, HEMTs, and HBTs, MMlC-Technology, Microwave and millimeter wave power devices, GaN- Devices, Mesoscopic devices...

GaN-on-Silicon - Present capabilities and future directions

Science.gov (United States)

Boles, Timothy

2018-02-01

Gallium Nitride, in the form of epitaxial HEMT transistors on various substrate materials, is the newest and most promising semiconductor technology for high performance devices in the RF, microwave, and mmW arenas. This is particularly true for GaN-on-Silicon based devices and MMIC's which enable both state-of-the-art high frequency functionality and the ability to scale production into large wafer diameter CMOS foundries. The design and development of GaN-on-Silicon structures and devices will be presented beginning with the basic material parameters, growth of the required epitaxial construction, and leading to the fundamental operational theory of high frequency, high power HEMTs. In this discussion comparisons will be made with alternative substrate materials with emphasis on contrasting the inherent advantages of a silicon based system. Theory of operation of microwave and mmW high power HEMT devices will be presented with special emphasis on fundamental limitations of device performance including inherent frequency limiting transit time analysis, required impedance transformations, internal and external parasitic reactance, thermal impedance optimization, and challenges improved by full integration into monolithic MMICs. Lastly, future directions for implementing GaN-on-Silicon into mainstream CMOS silicon semiconductor technologies will be discussed.

Enhanced mobility in vertically scaled N-polar high-electron-mobility transistors using GaN/InGaN composite channels

Science.gov (United States)

Li, Haoran; Wienecke, Steven; Romanczyk, Brian; Ahmadi, Elaheh; Guidry, Matthew; Zheng, Xun; Keller, Stacia; Mishra, Umesh K.

2018-02-01

A GaN/InGaN composite channel design for vertically scaled N-polar high-electron-mobility transistor (HEMT) structures is proposed and demonstrated by metal-organic chemical vapor deposition. In a conventional N-polar HEMT structure, as the channel thickness (tch) decreases, the sheet charge density (ns) decreases, the electric field in the channel increases, and the centroid of the two-dimensional electron gas (2DEG) moves towards the back-barrier/channel interface, resulting in stronger scattering and lower electron mobility (μ). In this study, a thin InGaN layer was introduced in-between the channel and the AlGaN cap to increase the 2DEG density and reduce the electric field in the channel and therefore increase the electron mobility. The dependence of μ on the InGaN thickness (tInGaN) and the indium composition (xIn) was investigated for different channel thicknesses. With optimized tInGaN and xIn, significant improvements in electron mobility were observed. For a 6 nm channel HEMT structure, the electron mobility increased from 606 to 1141 cm2/(V.s) when the 6 nm thick pure GaN channel was replaced by the 4 nm GaN/2 nm In0.1Ga0.9N composite channel.

Nanoscale conductive pattern of the homoepitaxial AlGaN/GaN transistor.

Science.gov (United States)

Pérez-Tomás, A; Catalàn, G; Fontserè, A; Iglesias, V; Chen, H; Gammon, P M; Jennings, M R; Thomas, M; Fisher, C A; Sharma, Y K; Placidi, M; Chmielowska, M; Chenot, S; Porti, M; Nafría, M; Cordier, Y

2015-03-20

The gallium nitride (GaN)-based buffer/barrier mode of growth and morphology, the transistor electrical response (25-310 °C) and the nanoscale pattern of a homoepitaxial AlGaN/GaN high electron mobility transistor (HEMT) have been investigated at the micro and nanoscale. The low channel sheet resistance and the enhanced heat dissipation allow a highly conductive HEMT transistor (Ids > 1 A mm(-1)) to be defined (0.5 A mm(-1) at 300 °C). The vertical breakdown voltage has been determined to be ∼850 V with the vertical drain-bulk (or gate-bulk) current following the hopping mechanism, with an activation energy of 350 meV. The conductive atomic force microscopy nanoscale current pattern does not unequivocally follow the molecular beam epitaxy AlGaN/GaN morphology but it suggests that the FS-GaN substrate presents a series of preferential conductive spots (conductive patches). Both the estimated patches density and the apparent random distribution appear to correlate with the edge-pit dislocations observed via cathodoluminescence. The sub-surface edge-pit dislocations originating in the FS-GaN substrate result in barrier height inhomogeneity within the HEMT Schottky gate producing a subthreshold current.

Influence of a drain field plate on the forward blocking characteristics of an AlGaN/GaN high electron mobility transistor

International Nuclear Information System (INIS)

Zhao Sheng-Lei; Yue Tong; Wang Yi; Luo Jun; Mao Wei; Ma Xiao-Hua; Hao Yue; Chen Wei-Wei

2013-01-01

In this paper, the influence of a drain field plate (FP) on the forward blocking characteristics of an AlGaN/GaN high electron mobility transistor (HEMT) is investigated. The HEMT with only a gate FP is optimized, and breakdown voltage V BR is saturated at 1085 V for gate—drain spacing L GD ≥ 8 μm. On the basis of the HEMT with a gate FP, a drain FP is added with L GD = 10 μm. For the length of the drain FP L DF ≤ 2 μm, V BR is almost kept at 1085 V, showing no degradation. When L DF exceeds 2 μm, V BR decreases obviously as L DF increases. Moreover, the larger the L DF , the larger the decrease of V BR . It is concluded that the distance between the gate edge and the drain FP edge should be larger than a certain value to prevent the drain FP from affecting the forward blocking voltage and the value should be equal to the L GD at which V BR begins to saturate in the first structure. The electric field and potential distribution are simulated and analyzed to account for the decrease of V BR

The fabrication of a back-gated high electron mobility transistor - a novel approach using MBE regrowth on an in situ ion beam patterned epilayer

International Nuclear Information System (INIS)

Linfield, E.H.; Jones, G.A.C.; Ritchie, D.A.; Thompson, J.H.

1993-01-01

A new technique for the fabrication of GaAs/AlGaAs back-gated high electron mobility transistors (HEMTs) is described in this paper. First we demonstrate that a dose of > 2 x 10 13 cm -2 Ga ions at an energy of 10 keV can be used to damage a 67 nm n + GaAs layer, rendering the implanted regions non-conducting. After implantation the epilayer has a 4 K sheet resistivity which is increased by a factor of ∼ 10 7 when compared with the original unimplanted value. This isolation procedure is then used to form a patterned back-gated HEMT by MBE regrowth on top of an in situ ion-implanted n + GaAs layer. The resulting structure is designed so that the back gate is rendered highly resistive under the regions where the ohmic contacts to the two-dimensional electron gas (2DEG) are formed, thus making shallow ohmic contacts unnecessary. The results obtained characteristic of a high-quality 2DEG with mobility limited by remote ionized impurity scattering. This technique can therefore be used as a means of controlling the 2DEG carrier concentration, whilst leaving the surface of the HEMT structure free for conventional lithographic processing. (Author)

Browse Title Index

African Journals Online (AJOL)

Items 6201 - 6250 of 11090 ... Byong Tae Jeon, KyoungHoon Kim, Sung Jin Kim, Na Yeon Kim, Jae Hyun Park, Dong Hyun Kim, Mi Rae Oh, Sang Ho Moon. Vol 10, No 65 (2011), In vitro activity of certain antimicrobial agents in combination with Augouardia letestii hexane extracts against methicillin-resistant Staphylococcus ...

Synthesis, Transfer, and Characterization of Nanoscale 2-Dimensional Materials

Science.gov (United States)

2015-09-01

Shi Y, Hamsen C, Jia X, Kim KK, Reina A, Hofmann M, Kong J. Synthesis of few-layer hexagonal boron nitride thin film by chemical vapor deposition...hexagonal boron nitride layers. Nano Letters. 2010;10(8):3209–3215. 12. Kim KK, Hsu A, Jia X, Kim SM, Shi Y, Hofmann M, Kong J. Synthesis of...microscopy. Physical Review B. 2009;80(15):155425. 33. Kim KK, Hsu A, Jia X, Kim SM, Shi Y, Hofmann M, Kong J. Synthesis of monolayer hexagonal boron

Two-Dimensional Modeling of Aluminum Gallium Nitride/Gallium Nitride High Electron Mobility Transistor

National Research Council Canada - National Science Library

Holmes, Kenneth

2002-01-01

.... This thesis studies the effects of AIGaN/GaN HEMTs' polarization, piezoelectric (PZ) and spontaneous, properties utilizing the TM commercially available Silvaco Atlas software for modeling and simulation...

Kim, czym, kiedy, gdzie i dlaczego są polscy Żydzi? Wyobrażanie, konstruowanie i zawłaszczanie Żydów polskich

Directory of Open Access Journals (Sweden)

Scott Ury

2017-12-01

Full Text Available Who, what, when, where, and why is Polish Jewry? Envisioning, constructing, and possessing Polish Jewry This article examines the different ways that various communities of scholars imagine, research and teach about “Polish Jewry.” Focusing on scholarship written in Israel, Poland and the United States over the past generation or two, the article argues that each particular community of scholars constructs a particular version of Polish Jewry and that each of these versions is deeply influenced by contemporary social, political and communal needs and demands. As a result, scholars very often end up constructing radically different versions of Polish Jewish history and society. These scholarly differences reflect many of the challenges and difficulties related to researching and writing about the history and culture of Polish Jews since 1989.   Kim, czym, kiedy, gdzie i dlaczego są polscy Żydzi? Wyobrażanie, konstruowanie i zawłaszczanie Żydów polskich Artykuł stanowi omówienie odmiennych sposobów, jakimi różne społeczności badaczy wyobrażają grupę polskich Żydów, badają ją i nauczają o niej. Na podstawie analizy działalności naukowej badaczy z Izraela, Polski i Stanów Zjednoczonych ostatnich dwóch pokoleń autor pokazuje, że każda społeczność badaczy konstruuje własny, specyficzny obraz grupy zwanej „polskimi Żydami” i że obrazy te pozostają pod przemożnym wpływem współczesnych potrzeb i wymogów o naturze społecznej, politycznej i wspólnotowej. Na skutek tych różnic uczeni tworzą często radykalnie odmienne obrazy historii i społeczeństwa polskich Żydów. Różnice stanowią odzwierciedlenie przeszkód i utrudnień, jakie po 1989 roku wiążą się z badaniem i opisywaniem historii i kultury polskich Żydów.

Characterization of N-polar AlN in GaN/AlN/(Al,Ga)N heterostructures grown by metal-organic chemical vapor deposition

Science.gov (United States)

Li, Haoran; Mazumder, Baishakhi; Bonef, Bastien; Keller, Stacia; Wienecke, Steven; Speck, James S.; Denbaars, Steven P.; Mishra, Umesh K.

2017-11-01

In GaN/(Al,Ga)N high-electron-mobility transistors (HEMT), AlN interlayer between GaN channel and AlGaN barrier suppresses alloy scattering and significantly improves the electron mobility of the two-dimensional electron gas. While high concentrations of gallium were previously observed in Al-polar AlN interlayers grown by metal-organic chemical vapor deposition, the N-polar AlN (Al x Ga1-x N) films examined by atom probe tomography in this study exhibited aluminum compositions (x) equal to or higher than 95% over a wide range of growth conditions. The also investigated AlN interlayer in a N-polar GaN/AlN/AlGaN/ S.I. GaN HEMT structure possessed a similarly high x content.

Elastic scattering by hot electrons and apparent lifetime of longitudinal optical phonons in gallium nitride

Energy Technology Data Exchange (ETDEWEB)

Khurgin, Jacob B., E-mail: jakek@jhu.edu [Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Bajaj, Sanyam; Rajan, Siddharth [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States)

2015-12-28

Longitudinal optical (LO) phonons in GaN generated in the channel of high electron mobility transistors (HEMT) are shown to undergo nearly elastic scattering via collisions with hot electrons. The net result of these collisions is the diffusion of LO phonons in the Brillouin zone causing reduction of phonon and electron temperatures. This previously unexplored diffusion mechanism explicates how an increase in electron density causes reduction of the apparent lifetime of LO phonons, obtained from the time resolved Raman studies and microwave noise measurements, while the actual decay rate of the LO phonons remains unaffected by the carrier density. Therefore, the saturation velocity in GaN HEMT steadily declines with increased carrier density, in a qualitative agreement with experimental results.

Thermal stability and in situ SiN passivation of InAlN/GaN high electron mobility heterostructures

Energy Technology Data Exchange (ETDEWEB)

Lugani, L.; Carlin, J.-F.; Py, M. A.; Grandjean, N. [ICMP, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland)

2014-09-15

We investigate the thermal stability of nearly lattice-matched InAlN layers under metal organic vapor phase epitaxy conditions for temperatures >800 °C and show that they are not fully stable. In particular, InAlN top layers undergo degradation during high temperature annealing due to a surface related process, which causes the loss of crystal quality. This strongly impacts the transport properties of InAlN/GaN HEMT heterostructures; in particular, the mobility is significantly reduced. However, we demonstrate that high thermal stability can be achieved by capping with a GaN layer as thin as 0.5 nm. Those findings enabled us to realize in situ passivated HEMT heterostructures with state of the art transport properties.

Very high channel conductivity in low-defect AlN/GaN high electron mobility transistor structures

International Nuclear Information System (INIS)

Dabiran, A. M.; Wowchak, A. M.; Osinsky, A.; Xie, J.; Hertog, B.; Cui, B.; Chow, P. P.; Look, D. C.

2008-01-01

Low defect AlN/GaN high electron mobility transistor (HEMT) structures, with very high values of electron mobility (>1800 cm 2 /V s) and sheet charge density (>3x10 13 cm -2 ), were grown by rf plasma-assisted molecular beam epitaxy (MBE) on sapphire and SiC, resulting in sheet resistivity values down to ∼100 Ω/□ at room temperature. Fabricated 1.2 μm gate devices showed excellent current-voltage characteristics, including a zero gate saturation current density of ∼1.3 A/mm and a peak transconductance of ∼260 mS/mm. Here, an all MBE growth of optimized AlN/GaN HEMT structures plus the results of thin-film characterizations and device measurements are presented

Two-Dimensional Modeling of Aluminum Gallium Nitride/Gallium Nitride High Electron Mobility Transistor

National Research Council Canada - National Science Library

Holmes, Kenneth

2002-01-01

Gallium Nitride (GaN) High Electron Mobility Transistors (HEMT's) are microwave power devices that have the performance characteristics to improve the capabilities of current and future Navy radar and communication systems...

A Compact Two-Stage 120 W GaN High Power Amplifier for SweepSAR Radar Systems

Science.gov (United States)

Thrivikraman, Tushar; Horst, Stephen; Price, Douglas; Hoffman, James; Veilleux, Louise

2014-01-01

This work presents the design and measured results of a fully integrated switched power two-stage GaN HEMT high-power amplifier (HPA) achieving 60% power-added efficiency at over 120Woutput power. This high-efficiency GaN HEMT HPA is an enabling technology for L-band SweepSAR interferometric instruments that enable frequent repeat intervals and high-resolution imagery. The L-band HPA was designed using space-qualified state-of-the-art GaN HEMT technology. The amplifier exhibits over 34 dB of power gain at 51 dBm of output power across an 80 MHz bandwidth. The HPA is divided into two stages, an 8 W driver stage and 120 W output stage. The amplifier is designed for pulsed operation, with a high-speed DC drain switch operating at the pulsed-repetition interval and settles within 200 ns. In addition to the electrical design, a thermally optimized package was designed, that allows for direct thermal radiation to maintain low-junction temperatures for the GaN parts maximizing long-term reliability. Lastly, real radar waveforms are characterized and analysis of amplitude and phase stability over temperature demonstrate ultra-stable operation over temperature using integrated bias compensation circuitry allowing less than 0.2 dB amplitude variation and 2 deg phase variation over a 70 C range.

Analysis of current instabilities of thin AlN/GaN/AlN double heterostructure high electron mobility transistors

International Nuclear Information System (INIS)

Zervos, Ch; Adikimenakis, A; Bairamis, A; Kostopoulos, A; Kayambaki, M; Tsagaraki, K; Konstantinidis, G; Georgakilas, A

2016-01-01

The current instabilities of high electron mobility transistors (HEMTs), based on thin double AlN/GaN/AlN heterostructures (∼0.5 μm total thickness), directly grown on sapphire substrates, have been analyzed and compared for different AlN top barrier thicknesses. The structures were capped by 1 nm GaN and non-passivated 1 μm gate-length devices were processed. Pulsed I–V measurements resulted in a maximum cold pulsed saturation current of 1.4 A mm −1 at a gate-source voltage of +3 V for 3.7 nm AlN thickness. The measured gate and drain lag for 500 ns pulse-width varied between 6%–12% and 10%–18%, respectively. Furthermore, a small increase in the threshold voltage was observed for all the devices, possibly due to the trapping of electrons under the gate contact. The off-state breakdown voltage of V br  = 70 V, for gate-drain spacing of 2 μm, was approximately double the value measured for a single AlN/GaN HEMT structure grown on a thick GaN buffer layer. The results suggest that the double AlN/GaN/AlN heterostructures may offer intrinsic advantages for the breakdown and current stability characteristics of high current HEMTs. (paper)

Pramana – Journal of Physics | Indian Academy of Sciences

Indian Academy of Sciences (India)

... J Jia B M Johnson S C Johnson K S Joo S Kametani J H Kang M Kann S S Kapoor S Kelly B Khachaturov A Khanzadeev J Kikuchi D J Kim H J Kim S Y Kim Y G Kim W W Kinnison E Kistenev A Kiyomichi C Klein-Boesing S Klinksiek L Kochenda V Kochetkov D Koehler T Kohama D Kotchetkov A Kozlov P J Kroon K Kurita ...

Electric Power Research in 1991

International Nuclear Information System (INIS)

1991-05-01

This book of contents are a study of desalination by Kim, Young Bu, a study on efficiency test for nuclear power security by Jo, Sung Je; Ann, Nam Sung; Kim, Ho Gi, augmentation of EMS and RYU by Jung, Tae Hoe; Shin, Young Chuel, research on application for electric cars by Yu, Ann Gue, practical use oft robot for nuclear industry by Woo, He Gone; Shin, Hen Beom, a study on the characteristics of coolant structure in generator by Choi, Beng Hwan; Song, Young Chel; Kim, Jong Hark, and research of penetration rate of appliances by Park, Hong Ho; Kim, Beng Cheal; Kim, Dong Hwen.

Piezoelectric Nanogenerators for Self-Powered Nanosystems and Nanosensors

Science.gov (United States)

2013-05-15

researchers 1. Sangmin Lee, Sung-Hwan Bae, Long Lin, Seunghyun Ahn, Chan Park, Seung Nam Cha, Young Jun Park, Hyuk Chang, Sang-Woo Kim and...Sohn, Seung Nam Cha, Dukhyun Choi * Zhong Lin Wang * Sang-Woo Kim * “ P-Type Polymer–Hybridized High-Performance Piezoelectric Nanogenerators”, Nano...Yoon Lee, † Sang-Woo Kim , *,$ Jae-Young Choi, *,† Jong Min Kim , † and Zhong Lin Wang *, “Flexible Hybrid Multi-Type Energy Scavenger”, Energy

Impact of oxide thickness on gate capacitance – Modelling and ...

Indian Academy of Sciences (India)

Department of Electronics and Communication Engineering, National ... conventional HEMT, Schottky barrier diode is formed at the gate electrode. .... term corresponds to the energy required for the electric field in the oxide layer and the.

Baseline characteristics and response to 2 years of growth hormone (GH) replacement of hypopituitary patients with GH deficiency due to adult-onset craniopharyngioma in comparison with patients with nonfunctioning pituitary adenoma: data from KIMS (Pfizer International Metabolic Database).

Science.gov (United States)

Verhelst, Johan; Kendall-Taylor, Pat; Erfurth, Eva Marie; Price, David Anthony; Geffner, Mitchell; Koltowska-Häggström, Maria; Jönsson, Peter J; Wilton, Patrick; Abs, Roger

2005-08-01

In epidemiological studies, hypopituitary adults show increased mortality compared with population controls. Patients with hypopituitarism caused by a craniopharyngioma (CP) and/or its treatment have a higher mortality than patients with other etiologies, such as a nonfunctioning pituitary adenoma (NFPA). To analyze this difference, we used the KIMS database (Pfizer International Metabolic Database) comparing CP and NFPA patients in terms of baseline characteristics and responses to GH replacement. Baseline characteristics were studied in 351 CP patients (189 men and 162 women; mean age, 42.5 yr) and compared with 370 NFPA patients, matched for age and sex (185 men and 185 women; mean age, 42.5 yr). The effects of 2 yr of GH replacement were analyzed in a subgroup of 183 CP and 209 NFPA patients. At baseline, both CP and NFPA patients had characteristic features of GH deficiency, with low serum IGF-I, increased body fat, dyslipidemia, and reduced quality of life. Male CP patients were significantly more obese (30.0 vs. 28.2 kg/m2; P = 0.0003) compared with NFPA patients, had a higher waist/hip ratio (P = 0.004), higher triglycerides (P = 0.003), and lower high-density lipoprotein cholesterol (P = 0.03). Similar, but much smaller, differences were seen in female CP compared with NFPA patients, only reaching significance for waist/hip ratio (P = 0.05) and triglycerides (P = 0.0004). CP patients had more often undergone surgery by the transcranial route (68.8% vs. 30.9%; P NFPA patients (58.7% vs. 19.8%; P NFPA patients. After 2 yr of GH replacement therapy, similar significant improvements were evident in both groups in fat-free mass, total and low-density lipoprotein cholesterol, and Quality-of-Life-Assessment in GH Deficient Adults score compared with baseline. In contrast to NFPA patients, CP patients had no significant decrease in body fat with GH therapy. In the KIMS database, patients with CP have more often undergone surgery by the transcranial route than

Design and simulation of a novel GaN based resonant tunneling high electron mobility transistor on a silicon substrate

International Nuclear Information System (INIS)

Chowdhury, Subhra; Biswas, Dhrubes; Chattaraj, Swarnabha

2015-01-01

For the first time, we have introduced a novel GaN based resonant tunneling high electron mobility transistor (RTHEMT) on a silicon substrate. A monolithically integrated GaN based inverted high electron mobility transistor (HEMT) and a resonant tunneling diode (RTD) are designed and simulated using the ATLAS simulator and MATLAB in this study. The 10% Al composition in the barrier layer of the GaN based RTD structure provides a peak-to-valley current ratio of 2.66 which controls the GaN based HEMT performance. Thus the results indicate an improvement in the current–voltage characteristics of the RTHEMT by controlling the gate voltage in this structure. The introduction of silicon as a substrate is a unique step taken by us for this type of RTHEMT structure. (paper)

Electronic Biosensors Based on III-Nitride Semiconductors.

Science.gov (United States)

Kirste, Ronny; Rohrbaugh, Nathaniel; Bryan, Isaac; Bryan, Zachary; Collazo, Ramon; Ivanisevic, Albena

2015-01-01

We review recent advances of AlGaN/GaN high-electron-mobility transistor (HEMT)-based electronic biosensors. We discuss properties and fabrication of III-nitride-based biosensors. Because of their superior biocompatibility and aqueous stability, GaN-based devices are ready to be implemented as next-generation biosensors. We review surface properties, cleaning, and passivation as well as different pathways toward functionalization, and critically analyze III-nitride-based biosensors demonstrated in the literature, including those detecting DNA, bacteria, cancer antibodies, and toxins. We also discuss the high potential of these biosensors for monitoring living cardiac, fibroblast, and nerve cells. Finally, we report on current developments of covalent chemical functionalization of III-nitride devices. Our review concludes with a short outlook on future challenges and projected implementation directions of GaN-based HEMT biosensors.

Brassia campestris L. ssp. chinensis L.var. utilis Tsen et Lee

African Journals Online (AJOL)

omodibo

2012-12-31

Dec 31, 2012 ... On the basis of morphological and cultural features, the pathogen ... Alternaria isolate from Purple-Caitai showed 99% identity with other ITS sequences of .... Cho KH, Park SH, Kim KT, Kim S, Kim JS, Park BS, Woo JG, Lee HJ.