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Effect of a high temperature AlN buffer layer grown by initially alternating supply of ammonia on AlGaN/GaN heterostuctures

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Journal of Semiconductors 2009年第9期30卷 1-4页

作者：段焕涛郝跃张进成 Key Laboratory of Fundamental Science for National Defense on Wide Band-Gap Semiconductor Technology School of MicroelectronicsXidian University

The effect of a high temperature AlN buffer layer grown by the initially alternating supply of ammonia （IASA） method on AlGaN/GaN heterostructures was studied. The use of AlN by the IASA method can effectively increase the crystalline quality and surface morphology of GaN. The mobility and concentration of 2DEG of AlGaN/GaN heterostuctures was also ameliorated.

关键词： metal-organic vaporphase epitaxy aluminum nitride gallium nitride AlGaN/GaN heterostructures

Effect of nucleation layer morphology on crystal quality,surface morphology and electrical properties of AlGaN/GaN heterostructures

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Journal of Semiconductors 2009年第10期30卷 68-70页

作者：段焕涛郝跃张进城 Key Laboratory of Fundamental Science for National Defense on Wide Band-Gap Semiconductor Technology School of Microelectronics Xidian University

Nucleation layer formation is a key factor for high quality gallium nitride（GaN）growth on a sapphire *** found that the growth rate substantially affected the nucleation layer morphology,thereby having a great impact on the crystal quality,surface morphology and electrical properties of AlGaN/GaN heterostructures on sapphire substrates.A nucleation layer with a low growth rate of 2.5 nm/min is larger and has better coalescence than one grown at a high growth rate of 5 nm/***/GaN heterostructures on a nucleation layer with low growth rate have better crystal quality,surface morphology and electrical properties.

关键词： MOCVD AlGaN/GaN nucleation layer

高温AlN插入层对AlGaN/GaN异质结材料和HEMTs器件电学特性的影响

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物理学报 2009年第7期58卷 4925-4930页

作者：倪金玉郝跃张进成段焕涛张金风西安电子科技大学微电子学院宽禁带半导体材料与器件重点实验室西安710071

研究了在GaN缓冲层中插入40 nm厚高温AlN层的GaN外延层和AlGaN/GaN异质结材料,AlN插入层可以增加GaN层的面内压应力并提高AlGaN/GaN高电子迁移率晶体管(HEMTs)的电学特性.在精确测量布拉格衍射角的基础上定量计算了压应力的大小.增加的... 详细信息

研究了在GaN缓冲层中插入40 nm厚高温AlN层的GaN外延层和AlGaN/GaN异质结材料,AlN插入层可以增加GaN层的面内压应力并提高AlGaN/GaN高电子迁移率晶体管(HEMTs)的电学特性.在精确测量布拉格衍射角的基础上定量计算了压应力的大小.增加的压应力一方面通过增强GaN层的压电极化电场,提高了AlGaN/GaN异质结二维电子气(2DEG)面密度,另一方面使AlGaN势垒层对2DEG面密度产生的两方面影响相互抵消.同时,这种AlN插入层的采用降低了GaN与AlGaN层之间的晶格失配,改善了AlGaN/GaN异质结界面特性,有利于减弱界面粗糙度散射,提高2DEG迁移率.利用这种插入层结构的AlGaN/GaN异质结材料研制了栅长为1μm的HEMTs器件,其最大漏电流和最大跨导比常规HEMTs器件分别提高了42%和20%.

关键词：高温AlN插入层 AlGaN/GaN异质结二维电子气应力

背势垒层结构对AlGaN/GaN双异质结载流子分布特性的影响

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物理学报 2009年第5期58卷 3409-3415页

作者：张进成郑鹏天董作典段焕涛倪金玉张金凤郝跃西安电子科技大学微电子学院宽带隙半导体技术国防重点学科实验室宽禁带半导体材料与器件教育部重点实验室西安710071

首先通过一维自洽求解薛定谔/泊松方程,研究了AlGaN/GaN双异质结构中AlGaN背势垒层Al组分和厚度对载流子分布特性的影响.其次利用低压MOCVD方法在蓝宝石衬底上生长出具有不同背势垒层的AlGaN/GaN双异质结构材料,通过汞探针CV测试验证了... 详细信息

首先通过一维自洽求解薛定谔/泊松方程,研究了AlGaN/GaN双异质结构中AlGaN背势垒层Al组分和厚度对载流子分布特性的影响.其次利用低压MOCVD方法在蓝宝石衬底上生长出具有不同背势垒层的AlGaN/GaN双异质结构材料,通过汞探针CV测试验证了理论计算的正确性.理论计算和实验结果均表明,随着背势垒层Al组分的提高和厚度的增加,主沟道中的二维电子气面密度逐渐减小,寄生沟道的二维电子气密度逐渐增加;背势垒层Al组分的提高和厚度的增加能有效的增强主沟道的二维电子气限域性,但是却带来了较高的寄生沟道载流子密度,因此,在AlGaN/GaN双异质结构的设计时,需要在主沟道二维电子气限域性的提高和寄生沟道载流子密度抑制之间进行折中考虑.

关键词： AlGaN/GaN 双异质结构限域性寄生沟道晶体管

An X-band GaN combined solid-state power amplifier

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Journal of Semiconductors 2009年第9期30卷 57-61页

作者：陈炽郝跃冯辉杨林安马晓华段焕涛胡仕刚 Key Laboratory of Wide Band-Gap Semiconductor Materials and Device School of MicroelectronicsXidian University

Based on a self-developed A1GaN/GaN HEMT with 2.5 mm gate width technology on a SiC substrate, an X-band GaN combined solid-state power amplifier module is fabricated. The module consists of an AIGaN/GaN HEMT, Wilkinson power couplers, DC-bias circuit and microstrip line. For each amplifier, we use a bipolar DC power source. Special RC networks at the input and output and a resistor between the DC power source and the gate of the transistor at the input are used for cancellation of self-oscillation and crosstalk of low-frequency of each amplifier. At the same time, branches of length 3λ/4 for Wilkinson power couplers are designed for the elimination of self-oscillation of the two amplifiers. Microstrip stub lines are used for input matching and output matching. Under Vds = 27 V, Vgs = -4.0 V, CW operating conditions at 8 GHz, the amplifier module exhibits a line gain of 5.6 dB with power added efficiency of 23.4%, and output power of 41.46 dBm （14 W）, and the power gain compression is 3 dB. Between 8 and 8.5 GHz, the variation of output power is less than 1.5 dB.

关键词： AlGaN/GaN HEMT solid-state power amplifiers output power gain compression power added efficiency

The effects of vicinal sapphire substrates on the properties of AlGaN/GaN heterostructures

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Chinese Physics B 2009年第12期18卷 5457-5461页

作者：许志豪张进成张忠芬朱庆玮段焕涛郝跃 Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices School of MicroelectronicsXidian University

A1GaN/GaN heterostructures on vicinal sapphire substrates and just-oriented sapphire substrates （0001） are grown by the metalorganic chemical vapor deposition method. Samples are studied by high-resolution x-ray diffraction, atomic force microscopy, capacitance-voltage measurement and the Van der Panw Hall-effect technique. The investigation reveals that better crystal quality and surface morphology of the sample are obtained on the vicinal substrate. Fur- thermore, the electrical properties are also improved when the sample is grown on the vicinal substrate. This is due to the fact that the use of vicinal substrate can promote the step-flow mode of crystal growth, so many macro-steps are formed during crystal growth, which causes a reduction of threading dislocations in the crystal and an improvement in the electrical properties of the AlGaN/GaN heterostructure.

关键词： GaN AlGaN/GaN heterostructures vicinal substrate

Stress,structural and electrical properties of Si-doped GaN film grown by MOCVD

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Journal of Semiconductors 2009年第12期30卷 13-17页

作者：许志豪张进成段焕涛张忠芬朱庆玮徐浩郝跃 Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices School of MicroelectronicsXidian University

The stresses, structural and electrical properties of n-type Si-doped GaN films grown by metaiorganic chemical vapor deposition （MOCVD） are systemically studied. It is suggested that the main stress relaxation is induced by bending dislocations in low doping samples. But for higher doping samples, as the Si doping concentration increases, the in-plane stresses in the grown films are quickly relaxed due to the rapid increase of the edge dislocation densities. Hall effect measurements reveal that the carrier mobility first increases rapidly and then decreases with increasing Si doping concentration. This phenomenon is attributed to the interaction between various scattering process. It is suggested that the dominant scattering process is defect scattering for low doping samples and ionized impurity scattering for high doping samples.

关键词： Si-doped GaN stress relaxation defect electrical properties

High-electric-field-stress-induced degradation of SiN passivated AlGaN/GaN high electron mobility transistors

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Chinese Physics B 2009年第4期18卷 1601-1608页

作者：谷文萍段焕涛倪金玉郝跃张进城冯倩马晓华 School of Microelectronics Xidian University China Key Lab of Ministry of Education for Wide Band-Gap Semiconductor Materials and Devices

AlGaN/GaN high electron mobility transistors （HEMTs） are fabricated by employing SiN passivation, this paper investigates the degradation due to the high-electric-field stress. After the stress, a recoverable degradation has been found, consisting of the decrease of saturation drain current IDsat, maximal transconductance gm, and the positive shift of threshold voltage VTH at high drain-source voltage VDS. The high-electric-field stress degrades the electric characteristics of AlGaN/GaN HEMTs because the high field increases the electron trapping at the surface and in AlGaN barrier layer. The SiN passivation of AlGaN/GaN HEMTs decreases the surface trapping and 2DEC depletion a little during the high-electric-field stress. After the hot carrier stress with VDS = 20 V and VGS= 0 V applied to the device for 104 sec, the SiN passivation decreases the stress-induced degradation of IDsat from 36% to 30%. Both on-state and pulse-state stresses produce comparative decrease of IDsat, which shows that although the passivation is effective in suppressing electron trapping in surface states, it does not protect the device from high-electric-field degradation in nature. So passivation in conjunction with other technological solutions like cap layer, prepassivation surface treatments, or field-plate gate to weaken high-electric-field degradation should be adopted.

关键词： AlGaN/GaN high electron mobility transistors surface states traps in AlGaN passivation

Characterization of GaN grown on 4H-SiC and sapphire by Raman spectroscopy and high resolution XRD

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Journal of Semiconductors 2009年第7期30卷 24-28页

作者：段焕涛谷文萍张进成郝跃陈炽倪金玉许昇瑞 Key Laboratory of Fundamental Science for National Defense on Wide Band-Gap Semiconductor Technology School of Microelectronics Xidian University

The crystal quality, stress and strain of GaN grown on 4H-SiC and sapphire are characterized by high resolution X-ray diffraction（HRXRD） and Raman *** large stress in GaN leads to the generation of a large number of *** Raman stress is determined by the results of *** position and line shape of the A1 longitudinal optical（LO） phonon mode is used to determine the free carrier concentration and electron mobility in *** differences between free carrier concentration and electron mobility in GaN grown on sapphire and 4H-SiC are analyzed.

关键词： metalorganic vapor phase epitaxy GaN Raman XRD