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Gradual variation method for thick GaN heteroepitaxy by hydride vapour phase epitaxy

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Chinese Physics B 2011年第9期20卷 439-444页

作者：杜彦浩吴洁君罗伟科 John Goldsmith 韩彤陶岳彬杨志坚于彤军张国义 research centre for wide-gap semiconductors School of PhysicsPeking University Beijing Yanyuan research centre Sino Nitride Semiconductor LTD

Two strain-state samples of GaN, labelled the strain-relief sample and the quality-improved sample, were grown by hydride vapour phase epitaxy （HVPE）, and then characterized by high-resolution X-ray diffraction, photoluminescence and optical microscopy. Two strain states of GaN in HVPE, like 3D and 2[） growth modes in metal-organic chemical vapour deposition （MOCVD）, provide an effective way to solve the heteroepitaxial problems of both strain relief and quality improvement. The gradual variation metbod （GVM）, developed based on the two strain states, is characterized by growth parameters＇ gradual variation alternating between the strain-relief growth conditions and the quality-improved growth conditions. In GVM, the introduction of the strain-relief amplitude, which is defined by the range from the quality-improved growth conditions to the strain-relief growth conditions, makes the strain-relief control concise and effective. The 300-μm thick bright and crack-free GaN film grown on a two-inch sapphire proves the effectiveness of GVM.

关键词： GaN hydride vapour phase epitaxy heteroepitaxy

Investigation of yellow luminescence intensity of N-polar unintentionally doped GaN

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Chinese Physics B 2011年第3期20卷 455-459页

作者：杜大超张进成欧新秀王昊陈珂薛军帅许晟瑞郝跃 Key Laboratory of wide Band-gap semiconductors and Devices School of Microelectronics Xidian University

This paper reports that the yellow luminescence intensity of N-polar GaN Epi-layers is much lower than that of Ga-polar ones due to the inverse polarity, and reduces drastically in the N-polar unintentionally-doped GaN after etching in KOH solution. The ratio of yellow luminescence intensity to band-edge emission intensity decreases sharply with the etching time. The full width at half maximum of x-ray diffraction of （10-12） plane falls sharply after etching, and the surface morphology characterized by scanning electron microscope shows a rough surface that changes with the etching time. The mechanism for the generation of the yellow luminescence are explained in details.

关键词： N-polar GaN yellow luminescence KOH etching

Investigation of heavy ion irradiation effects on 650-V p-GaN normally-off HEMTs

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Science China(Information Sciences) 2022年第8期65卷 254-260页

作者： Yinhe WU Jincheng ZHANG Shenglei ZHAO Zhaoxi WU Zhongxu WANG Bo MEI Chao DUAN Dujun ZHAO Weihang ZHANG Zhihong LIU Yue HAO Key Laboratory of wide Band-gap semiconductors and Devices School of MicroelectronicsXidian University China Aerospace Components Engineering Center

In this study, we investigate heavy ion irradiation effects on commercial 650 V p-GaN normallyoff HEMTs. Ge and Cl ions are used to irradiate the GaN devices in the experiments. Ge and Cl ion beam irradiation have little impact on the output characteristics of GaN devices. After heavy ion irradiation, the leakage currents between source and drain electrodes increase significantly under off-state, decreasing the breakdown voltage(BVDS) sharply. Additionally, Ge and Cl ion irradiation have little effect on the trap states under the gate electrode; thus, the gate leakage currents increase slightly. Many line-shaped crystal defects extending from the surface to the GaN buffer layer can be captured using a transmission electron microscope after Ge/Cl ion irradiation. The buffer layers of the irradiated devices were damaged, and the leakage path was generated in the buffer layer. Defect percolation process in buffer layer is the dominant factor of irradiated high-voltage GaN device failure.

关键词： heavy ions irradiation p-GaN normally-off HEMTs line-shaped crystal defects leakage path defect percolation process

Frequency Response of Modulated Electroluminescence of Light-Emitting Diodes

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Chinese Physics Letters 2011年第10期28卷 244-247页

作者： FENG Lie-Feng LI Yang LI Ding WANG Cun-Da ZHANG Guo-Yi YAO Dong-Sheng LIU Wei-Fang XING Peng-Fei Department of Applied Physics Tianjin UniversityTianjin 300072 research Center for wide-band gap semiconductors School of PhysicsPeking UniversityBeijing 100871

Frequency responses of modulated electroluminescence(EL)of light-emitting diodes were measured using a testing *** increasing frequency of the ac signal,the relative light intensity(RLI)clearly ***,a peculiar asynchrony between the RLI and ac small-signal is *** frequencies higher than 10 kHz,the RLI clearly lags behind the ac signal and the absolute value of the lagging angle is nearly proportional to the signal *** the classical recombination model of light-emitting diodes under ac small-signal modulation,these abnormal characteristics of modulated EL can be clearly explained.

关键词： diodes absolute testing

Optical Defect in GaN-Based Laser Diodes Detected by Cathodoluminescence

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Chinese Physics Letters 2008年第12期25卷 4342-4344页

作者：赵璐冰吴洁君徐科包魁杨志坚潘尧波胡晓东张国义 research Center for wide gap semiconductors Peking University State Key Laboratory for Artificial Microstrueture and Microscopic Physics School of Physics Peking University Beijing 100871

GaN-based laser diodes （LDs） with 399 nm wavelength are grown on sapphire substrates by metal organic chemical vapour deposition （MOCVD）. Electroluminescence spectra of the fabricated LDs show that the LDs from some grown wafers failed to emit laser. The SEM and XRD results show the similar surface morphology and interface qualities of multi quantum wells （MQWs） and super-lattices between LDs that succeed and fail to emit laser. However, the cathodoluminescence （CL） measurements reveal a kind of optical defect rather than structural defect in un-emitted LDs. Further depth-dependent CL imaging observation indicates that such optical defects originate from the MQWs to the surface of LDs as a non-irradiative recombination centre that should cause the failure of laser emitting of LDs.

关键词： field emission molybdenum dioxide enhancement factor

Strain Effect on Photoluminescences from InGaN MQWs with Different Barriers Grown by MOCVD

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Chinese Physics Letters 2007年第5期24卷 1365-1367页

作者：于彤军康香宁潘尧波秦志新陈志忠杨志坚张国义 research Center for wide Band gap semiconductors Peking University 100871 State Key Laboratory of Artificial Microstructure and Microscopic Physics School of Physics Peking University Beijing 100871

InGaN/GaN MQWs, InGaN/AlGaN MQWs and InGaN/AlInGaN MQWs are grown on （0001） sapphire substrates by MOCVD. Membrane samples are fabricated by laser lift-off technology. The photoluminescence spec-ra of membranes show a blue shift of peak positions in InGaN/GaN MQWs, a red shift of peak positions in InGaN/AlGaN MQWs and no shift of peak positions in InGaN/AIlnGaN MQWs from those of samples with substrates. Different changes in Raman scattering spectra and HR-XRD （0002） profile of InGaN/AlInGaN MQWs, from those of InGaN/GaN MQWs and InGaN/AlGaN MQWs, are observed. The fact that the strain changes differently among InGaN MQWs with different barriers is confirmed. The AIlnGaN barrier could adjust the residual stress for the least strain-induced electric field in InGaN/AIlnGaN quantum wells.

关键词： MULTIPLE-QUANTUM WELLS SAPPHIRE

Effects of the flow rate of hydrogen on the growth of graphene

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International Journal of Minerals,Metallurgy and Materials 2015年第1期22卷 102-110页

作者： Yong-gui Shi Yue Hao Dong Wang Jin-cheng Zhang Peng Zhang Xue-fang Shi Dang Han Zheng Chai Jing-dong Yan School of Microelectronics Xidian University State Key Discipline Laboratory of wide Band-gap semiconductors and Devices Xidian University School of Technical Physics Xidian University

Graphene samples with different morphologies were fabricated on the inside of copper enclosures by low pressure chemical vapor deposition and tuning the flow rate of hydrogen. It is found that the flow rate of hydrogen greatly influences the growth of graphene. Ther-modynamic analysis indicates that a higher flow rate of hydrogen is favorable to the formation of good quality graphene with regular mor-phology. However, the mass-transfer process of methane dominates the growth driving force. At very low pressure, mass-transfer proceeds by Knudsen diffusion, and the mass-transfer flux of methane decreases as the flow rate of hydrogen increases, leading to a decrease in the growth driving force. At a higher pressure, mass-transfer proceeds by Fick＇s diffusion, and the mass-transfer flux of methane is dominated by the gas velocity, whose variation determines the growth driving force variation of graphene.

关键词： graphene crystal growth morphology diffusion mass transfer chemical vapor deposition

Effects of growth temperature and metamorphic buffer on electron mobility of InAs film grown on Si substrate by molecular beam epitaxy

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Chinese Physics B 2019年第2期28卷 428-433页

作者： Jing Zhang Hongliang Lv Haiqiao Ni Shizheng Yang Xiaoran Cui Zhichuan Niu Yimen Zhang Yuming Zhang School of Microelectronics Xidian University and the State Key Discipline Laboratory of wide Band gap Semiconductor Technology State Key Laboratory for Superlattices and Microstructures Institute of semiconductors Chinese Academy of Sciences

The growth of the InAs film directly on the Si substrate deflected from the plane(100) at 4° towards(110) has been performed using a two-step procedure. The effect of the growth and annealing temperature on the electron mobility and surface topography has been investigated for a set of samples. The results show that the highest electron mobility is4640 cm^2/V·s in the sample, in which the 10-nm InAs nucleation layer is grown at a low temperature of 320 ℃ followed by ramping up to 560 ℃, and the nucleation layer was annealed for 15 min and the second layer of InAs is grown at 520 ℃.The influence of different buffer layers on the electron mobility of the samples has also been investigated, which shows that the highest electron mobility of 9222 cm^2/V·s at 300 K is obtained in the sample grown on a thick and linearly graded InGaAlAs metamorphic buffer layer deposited at 420 ℃.

关键词： InAs Si high electron mobility growth temperature InGaAlAs metamorphic buffer

Design and simulation of reverse-blocking Schottky-drain AlN/AlGaN HEMTs with drain field plate

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Science China(Information Sciences) 2022年第2期65卷 155-161页

作者： Dujun ZHAO Zhaoxi WU Chao DUAN Bo MEI Zhongyang LI Zhongxu WANG Qing TANG Qing YANG Yinhe WU Weihang ZHANG Zhihong LIU Shenglei ZHAO Jincheng ZHANG Yue HAO Key Laboratory of wide Band-gap semiconductors and Devices School of MicroelectronicsXidian University China Aerospace Components Engineering Center Chengdu Yaguang Electronics Co. Ltd.

In this paper, Schottky-drain reverse-blocking Al N/Al Ga N HEMTs with drain field plate(FP)have been investigated by Silvaco-ATLAS tools. For HEMTs without FP, with the increase of Al mole fraction in Al Ga N channel from 0 to 0.5, the reverse-blocking voltage increases from-158 V to-720 *** using the drain field plate technique, a second electric field peak is introduced and the reverse-blocking voltage can be improved. Combined with the optimization of the Si N passivation thickness, optimal electric field management can be achieved to obtain the highest reverse-blocking voltage devices. Since HEMTs with different Al mole fractions possess different critical electric field values, the optimal Si N thickness are *** the increase of the Al mole fraction from 0 to 0.5, the reverse-blocking voltage increases from-510 V to-4500 V for HEMTs using drain FP and optimal Si N passivation thickness, and a high power figure-of-merit of 1.171 GW/cm~2 is achieved. Al Ga N channel HEMTs with Al mole fraction demonstrate great potential for power applications.

关键词： reverse-blocking voltage AlN/AlGaN HEMTs Schottky-drain field plate optimal passivation thickness