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1.
Effects of SiNx on two-dimensional electron gas and current collapse of AlGaN/GaN high electron mobility transistors 下载免费PDF全文
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. 相似文献
2.
The degradation mechanism of an AIGaN/GaN high electron mobility transistor under step-stress 下载免费PDF全文
Step-stress experiments are performed in this paper to investigate the degradation mechanism of an AIGaN/GaN high electron mobility transistor (HEMT). It is found that the stress current shows a recoverable decrease during each voltage step and there is a critical voltage beyond which the stress current starts to increase sharply in our experiments. We postulate that defects may be randomly induced within the A1GaN barrier by the high electric field during each voltage step. But once the critical voltage is reached, the trap concentration will increase sharply due to the inverse piezoelectric effect. A leakage path may be introduced by excessive defect, and this may result in the permanent degradation of the A1GaN/GaN HEMT. 相似文献
3.
Effect of Si doping in wells of A1GaN/GaN superlattice on the characteristics of epitaxial layer 下载免费PDF全文
An A1GaN/GaN superlattice grown on the top of a GaN buffer induces the broadening of the full width at half maximum of (102) and (002) X-ray diffraction rocking curves. With an increase in the Si-doped concentration in the GaN wells, the full width at half maximum of the (102) rocking curves decreases, while that of the (002) rocking curves increases. A significant increase of the full width at the half maximum of the (002) rocking curves when the doping concentration reaches 2.5 × 10^19 cm-3 indicates the substantial increase of the inclined threading dislocation. High level doping in the A1GaN/GaN superlattice can greatly reduce the biaxial stress and optimize the surface roughness of the structures grown on the top of it. 相似文献
4.
Low-leakage-current AIGaN/GaN HEMTs on Si substrates with partially Mg-doped GaN buffer layer by metal organic chemical vapor deposition 下载免费PDF全文
High-performance low-leakage-current A1GaN/GaN high electron mobility transistors (HEMTs) on silicon (111) sub- strates 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 onμe. A 1μ m 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 A1GaN/GaN HEMTs on Si featuring the same dimension and structure. The RF characteristics of 0.25-μ m gate length T-shaped gate HEMTs were also investigated. 相似文献
5.
Cao Meng-Yi ;Lu Yang ;Wei Jia-Xing ;Chen Yong-He ;Li Wei-Jun ;Zheng Jia-Xin ;Ma Xiao-Hua ;Hao Yue 《中国物理 B》2014,(8):452-456
In this paper, a new current expression based on both the direct currect (DC) characteristics of the A1GaN/GaN high election mobility transistor (HEMT) and the hyperbolic tangent function tanh is proposed, by which we can describe the kink effect of the A1GaN/GaN HEMT well. Then, an improved EEHEMT model including the proposed current expression is presented. The simulated and measured results of Ⅰ-Ⅴ, S-parameter, and radio frequency (RF) large-signal characteristics are compared for a self-developed on-wafer A1GaN/GaN HEMT with ten gate fingers each being 0.4-μm long and 125-p-m wide (Such an A1GaN/GaN HEMT is denoted as A1GaN/GaN HEMT (10 × 125 μm)). The improved large signal model simulates the Ⅰ-Ⅴ characteristic much more accurately than the original one, and its transconductance and RF characteristics are also in excellent agreement with the measured data. 相似文献
6.
The influence of A1GaN/GaN superlattices as electron blocking layers on the performance of blue InGaN light-emitting diodes 下载免费PDF全文
P-A1GaN/P-GaN superlattices are investigated in blue InGaN light-emitting diodes as electron blocking layers. The simulation results show that efficiency droop is markedly improved due to two reasons: (i) enhanced hole concentration and hole carrier transport efficiency in A1GaN/GaN superlattices, and (ii) enhanced blocking of electron overflow between multiple quantum-wells and A1CaN/GaN superlattices. 相似文献
7.
Xu Sheng-Rui Hao Yue Zhang Jin-Cheng Zhou Xiao-Wei Cao Yan-Rong Ou Xin-Xiu Mao Wei Du Da-Chao Wang Hao 《中国物理 B》2010,(10):458-462
Morphology of nonpolar (1120) a-plane GaN epilayers on r-plane (1102) sapphire substrate grown by low-pressure metal-organic vapour deposition was investigated after KOH solution etching. Many micron- and nano-meter columns on the a-plane GaN surface were observed by scanning electron microscopy. An etching mechanism model is proposed to interpret the origin of the peculiar etching morphology. The basal stacking fault in the a-plane GaN plays a very important role in the etching process. 相似文献
8.
Effects of interface roughness on photoluminescence full width at half maximum in GaN/AIGaN quantum wells 下载免费PDF全文
Low temperature photoluminescence (PL) measurements have been performed for a set of GaN/AlxGal xN quantum wells (QWs). The experimental results show that the optical full width at half maximum (FWHM) increases relatively rapidly with increasing A1 composition in the AlxGal xN barrier, and increases only slightly with increasing GaN well width. A model considering the interface roughness is used to interpret the experimental results. In the model, the FWHM's broadening caused by the interface roughness is calculated based on the triangle potential well approximation. We find that the calculated results accord with the experimental results well. 相似文献
9.
Nonpolar (1120) GaN films are grown on the etched a-plane GaN substrates via metalorganic vapor phase epitaxy. High-resolution X-ray diffraction analysis shows great decreases in the full width at half maximum of the samples grown on etched substrates compared with those of the sample without etching, both on-axis and off-axis, indicating the reduced dislocation densities and improved crystalline quality of these samples. The spatial mapping of the E2 (high) phonon mode demonstrates the smaller line width with a black background in the wing region, which testifies the reduced dislocation densities and enhanced crystalline quality of the epitaxial lateral overgrowth areas. Raman scattering spectra of the E2 (high) peaks exhibit in-plane compressive stress for all the overgrowth samples, and the E2 (high) peaks of samples grown on etched substrates shift toward the lower frequency range, indicating the relaxations of in-plane stress in these GaN films. Furthermore, room temperature photoluminescence measurement demonstrates a significant decrease in the yellow-band emission intensity of a-plane GaN grown on etched templates, which also illustrates the better optical properties of these samples. 相似文献
10.
High electronic density is achieved by polarization doping without an impurity dopant in graded AIGaN films. Low specific contact resistance is studied on the polarization-doped A1GaN/GaN heterojunctions by using the transmission line method (TLM). The sheet density of polarization-doped A1GaN/GaN heterojunction is 6 × 10 14 cm-2 at room temperature. The linearly graded material structure is demonstrated by X-ray diffraction. The cartier concentration and mobility are characterized by a temperature-dependent Hall measurement. Multiple-layer metal (Ti/A1/Ti/Au) is deposited and annealed at 650 ℃ to realize the Ohmic contacts on the graded A1GaN/GaN heterojunctions. 相似文献
11.
The effects of V/Ill growth flux ratio on a-plane GaN films grown on r-plane sapphire substrates with an InGaN interlayer are investigated. The surface morphology, crystalline quality, strain states, and density of basal stacking faults were found to depend heavily upon the V/III ratio. With decreasing V/III ratio, the surface morphology and crystal quality first improved and then deteriorated, and the density of the basal-plane stacking faults also first decreased and then increased. The optimal V/III ratio growth condition for the best surface morphology and crystalline quality and the smallest basal-plane stacking fault density of a-GaN films are found. We also found that the formation of basal-plane stacking faults is an effective way to release strain. 相似文献
12.
Characterization of Al2O3/GaN/AIGaN/GaN metal- insulator-semiconductor high electron mobility transistors with different gate recess depths* 下载免费PDF全文
Ma Xiao-Hua Pan Cai-Yuan Yang Li-Yuan Yu Hui-You Yang Ling Quan Si Wang Hao Zhang Jin-Cheng Hao Yue 《中国物理 B》2011,(2):458-464
In this paper, in order to solve the interface-trap issue and enhance the transconductance induced by high-k dielectric in metal-insulator-semiconductor (MIS) high electron mobility transistors (HEMTs), we demonstrate better performances of recessed-gate A1203 MIS-HEMTs which are fabricated by Fluorine-based Si3N4 etching and chlorine- based A1CaN etching with three etching times (15 s, 17 s and 19 s). The gate leakage current of MIS-HEMT is about three orders of magnitude lower than that of A1GaN/CaN HEMT. Through the recessed-gate etching, the transconductanee increases effectively. When the recessed-gate depth is 1.02 nm, the best interface performance with Tit----(0.20--1.59) p~s and Dit :(0.55-1.08)x 1012 cm-2.eV- 1 can be obtained. After chlorine-based etching, the interface trap density reduces considerably without generating any new type of trap. The accumulated chlorine ions and the N vacancies in the AIGaN surface caused by the plasma etching can degrade the breakdown and the high frequency performances of devices. By comparing the characteristics of recessed-gate MIS-HEMTs with different etching times, it is found that a low power chlorine-based plasma etching for a short time (15 s in this paper) can enhance the performances of MIS-HEMTs effectively. 相似文献
13.
In this paper, we present a high-efficiency S-band gallium nitride (GaN) power amplifier (PA). This amplifier is fabri- cated based on a self-developed GaN high-electron-mobility transistor (HEMT) with 10 mm gate width on SiC substrate. Harmonic manipulation circuits are presented in the amplifier. The matching networks consist of microstrip lines and discrete components. Open-circuited stub lines in both input and output are used to tune the 2rid harmonic wave and match the GaN HEMT to the highest efficiency condition. The developed amplifier delivers an output power of 48.5 dBm (70 W) with a power-added efficiency (PAE) of 72.2% at 2 GHz in pulse condition. When operating at 1.8-2.2 GHz (20% relative bandwidth), the amplifier provides an output power higher than 48 dBm (,-~ 65 W), with a PAE over 70% and a power gain above 15 dB. When operating in continuous-wave (CW) operating conditions, the amplifier gives an output power over 46 dBm (40 W) with PAE beyond 60% over the whole operation frequency range. 相似文献
14.
15.
Comparison of electrical characteristic between AIN/GaN and AIGaN/GaN heterostructure Schottky diodes 下载免费PDF全文
Ni/Au Schottky contacts on A1N/GaN and A1GaN/GaN heterostructures are fabricated. Based on the measured current-voltage and capacitance-voltage curves, the electrical characteristics of AlN/GaN Schottky diode, such as Schottky barrier height, turn-on voltage, reverse breakdown voltage, ideal factor, and the current-transport mechanism, are analyzed and then compared with those of an A1GaN/GaN diode by self-consistently solving Schrodinger's and Poisson's equations. It is found that the dislocation-governed tunneling is dominant for both AlN/GaN and AlGaN/GaN Schottky diodes. However, more dislocation defects and a thinner barrier layer for AlN/GaN heterostrncture results in a larger tunneling probability, and causes a larger leakage current and lower reverse breakdown voltage, even though the Schottky barrier height of AlN/GaN Schottky diode is calculated to be higher that of an A1GaN/GaN diode. 相似文献
16.
First-order Raman scatterings of hexagonal GaN layers deposited by the hydride vapour phase epitaxy and by metal-organic chemical vapour deposition on SiC and sapphire substrates are studied in a temperature range between 303 K and 503 K. The temperature dependences of two GaN Raman modes (A1 (LO) and E2 (high)) are obtained. We focus our attention on the temperature dependence of E2 (high) mode and find that for different types of GaN epilayers their temperature dependences are somewhat different. We compare their differences and give them an explanation. The simplified formulas we obtained are in good accordance with experiment data. The results can be used to determine the temperature of a GaN sample. 相似文献
17.
<正>Black-coloured GaN nanoparticles with an average grain size of 50 nm have been obtained by annealing GaN nanoparticles under flowing nitrogen at 1200℃for 30 min.XRD measurement result indicates an increase in the lattice parameter of the GaN nanoparticles annealed at 1200℃,and HRTEM image shows that the increase cannot be ascribed to other ions in the interstitial positions.If the as-synthesised GaN nanoparticles at 950℃are regarded as standard,the thermal expansion changes nonlinearly with temperature and is anisotropic;the expansion below 1000℃is smaller than that above 1000℃.This study provides an experimental demonstration for selecting the proper annealing temperature of GaN.In addition,a large blueshift in optical bandgap of the annealed GaN nanoparticles at 1200℃is observed,which can be ascribed to the dominant transitions from the C(Γ7) with the peak energy at 3.532 eV. 相似文献
18.
Significant performance enhancement in A1GaN/GaN high electron mobility transistor by high-κ organic dielectric 下载免费PDF全文
Wang Ze-Gao Chen Yuan-Fu Chen Cao Tian Ben-Lang Chu Fu-Tong Liu Xing-Zhao Li Yan-Rong 《中国物理 B》2010,(10):510-514
The electrical properties of A1GaN/GaN high electron mobility transistor (HEMT) with and without high-κ organic dielectrics are investigated. The maximum drain current ID max and the maximum transconductance gm max of the organic dielectric/A1CaN/GaN structure can be enhanced by 74.5%, and 73.7% compared with those of the bare A1GaN/GaN HEMT, respectively. Both the threshold voltage VT and gm 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 A1GaN/GaN HEMT by introducing the high-κ organic dielectric. 相似文献
19.
The effects of ^60Co γ-ray irradiation on the DC characteristics of enhancement-mode A1GaN/GaN high-electron-mobility transistors 下载免费PDF全文
The effects of ^60Co γ-ray irradiation on the DC characteristics of AlGaN/GaN enhancement-mode high-electron- mobility transistors (E-mode HEMTs) are investigated. The results show that having been irradiated by^60Co γ-rays at a dose of 3 Mrad (Si), the E-mode HEMT reduces its saturation drain current and maximal transconductance by 6% and 5%, respectively, and significantly increases both forward and reverse gate currents, while its threshold voltage is affected only slightly. The obvious performance degradation of E-mode A1GaN/GaN HEMTs is consistent with the creation of electronegative surface state charges in the source-gate spacer and gate-drain spacer after being irradiated. 相似文献
20.
Breakdown characteristics of AIGaN/GaN Schottky barrier diodes fabricated on a silicon substrate 下载免费PDF全文
In this work, the breakdown characteristics of AlGaN/GaN planar Schottky barrier diodes (SBDs) fabricated on the silicon substrate are investigated. The breakdown voltage (BV) of the SBDs first increases as a function of the anodeto-cathode distance and then tends to saturate at larger inter-electrode spacing. The saturation behavior of the BV is likely caused by the vertical breakdown through the intrinsic GaN buffer layer on silicon, which is supported by the post-breakdown primary leakage path analysis with the emission microscopy. Surface passivation and field plate termination are found effective to suppress the leakage current and enhance the BV of the SBDs. A high BV of 601 V is obtained with a low on-resistance of 3.15 mΩ·cm^2. 相似文献