Novel structure of GaAs-based interdigital-gated HEMT plasma devices for solid-state THz wave amplifier

Theoretical analysis of potential distribution in the interdigital-gated high electron mobility transistor (HEMT) plasma wave device was carried out. The dc I–V characteristics of capacitively coupled interdigital structure showed that uniformity of electric field under the interdigital gates was improved compared to the dc-connected interdigital gate structure. Admittance measurements of capacitively coupled interdigital gate structure in the microwave region of 10–40 GHz showed the conductance modulation by drain–source voltage. These results indicate the existence of plasma wave interactions.     

GaAs基HEMT嵌入式微加速度传感器力电耦合系数研究

设计加工了一种GaAs基高电子迁移率晶体管(HEMT)嵌入式微加速度传感器结构,通过软件仿真和实验测试相结合的方法,研究了所设计的微结构在平行于HEMT生长方向上(Z方向)不同加速度作用下敏感单元HEMT的力电耦合特性。实验结果表明:GaAs基HEMT微加速度传感器在其低量程范围内(0～15gn)敏感单元HEMT的力电耦合系数较稳定,且其力电耦合系数为10-8数量级,比常规Si压阻式加速度传感器的力电耦合系数10-10高出2个数量级。     

Advanced FIB sample preparation techniques for high resolution TEM investigations of HEMT structures

In this paper advanced sample preparation techniques based on focused ion beam (FIB) optimized for TEM investigation of high electron mobility transistor (HEMT) structures are presented. It is shown that the usage of an innovative in-situ lift-out method combined with X2 window and backside milling techniques as well as live thickness control and end point detection can significantly improve the quality of electron transparent samples required for high resolution TEM investigations. This advanced preparation flow is evaluated and demonstrated at GaN HEMT structures for atomic resolution TEM investigation.     

Material Growth and Device Fabrication of GaN-Based Blue-Violet Laser Diodes

Studies on first GaN-based blue-violet laser diodes(LDs) in China mainland are reported.High quality GaN materials as well as GaN-based quantum wells laser structures are grown by metal-organic chemical vapor deposition method.The X-ray double-crystal diffraction rocking curve measurements show the fullwidth half maximum of 180″ and 185″ for (0002) symmetric reflection and (10-12) skew reflection,respectively.A room temperature mobility of 850cm2/(V·s) is obtained for a 3μm thick GaN film.Gain guided and ridge geometry waveguide laser diodes are fabricated with cleaved facet mirrors at room temperature under pulse current injection.The lasing wavelength is 405.9nm.A threshold current density of 5kA/cm2 and an output light power over 100mW are obtained for ridge geometry waveguide laser diodes.     

GaN-based optoelectronic devices on sapphire and Si substrates

A recessed gate AlGaN/GaN high-electron mobility transistor (HEMT) on sapphire (0 0 0 1), a GaN metal-semiconductor field-effect transistor (MESFET) and an InGaN multiple-quantum well green light-emitting diode (LED) on Si (1 1 1) substrates have been grown by metalorganic chemical vapor deposition. The AlGaN/GaN intermediate layers have been used for the growth of GaN MESFET and LED on Si substrates. A two-dimensional electron gas mobility as high as 9260 cm²/V s with a sheet carrier density of 4.8×10¹² cm⁻² was measured at 4.6 K for the AlGaN/GaN heterostructure on the sapphire substrate. The recessed gate device on sapphire showed a maximum extrinsic transconductance of 146 mS/mm and a drain–source current of 900 mA/mm for the AlGaN/GaN HEMT with a gate length of 2.1 μm at 25°C. The GaN MESFET on Si showed a maximum extrinsic transconductance of 25 mS/mm and a drain–source current of 169 mA/mm with a complete pinch-off for the 2.5-μm-gate length. The LED on Si exhibited an operating voltage of 18 V, a series resistance of 300 Ω, an optical output power of 10 μW and a peak emission wavelength of 505 nm with a full-width at half-maximum of 33 nm at 20 mA drive current.     

Electrothermal Monte Carlo simulation of submicron wurtzite GaN/AlGaN HEMTs

We present results from the simulation of the electrothermal behaviour of submicron wurtzite GaN/AlGaN High Electron Mobility Transistors (HEMTs). The simulator uses an iterative procedure which couples a Monte Carlo simulation with a fast Fourier series solution of the Heat Diffusion Equation (HDE). The results demonstrate the dependence of the extent of the thermal droop observed in the I_ds-V_ds characteristics and the device peak temperature on the device bias. The paper also investigates the effect of the inclusion of thermal self-consistency on the device microscopic properties and studies the dependence of the device electrothermal characteristics on the type of substrate material used.     

Design and process development of a novel multi-wafer OMVPE reactor for growing very uniform GaAs and AlGaAs epitaxial layers

A unique multi-wafer OMVPE reactor with capability to produce atomic-layer abrupt-ness is demonstrated. Uniform GaAs and AlGaAs epitaxial layers were grown on four two-inch wafers or one three- or four-inch wafer. Thickness variation across a three-inch wafer was less than ±2%, while the variation of Al solid composition was less than ±1%. Multiple AlGaAs/GaAs quantum wells ranging in size from 10Å to 140Å were grown with heterointerface roughness less than one monolayer. The electrical properties of HEMT device were studied. Variations of sheet carrier concentration and electron mobility were ±6% and ±5% respectively across a three-inch wafer. The carrier con-centration profile, mobility spectrum and device characteristics of DH-HEMT are also presented. These results indicate that this OMVPE reactor can grow good device struc-tures for microwave and millimeter-wave power device applications.     

X波段四路合成氮化镓功率放大器

本文利用自主研制的SiC 衬底的,栅宽为2.5mm的AlGaN/GaN HEMT器件,设计完成了X波段氮化镓合成固态放大器模块。模块由AlGaN/GaN HEMT器件,Wilkinson功率合成/分配器,偏置电路和微带匹配电路构成。为了使放大器稳定,在每一路放大器的输入端和输出端加入了RC 稳定网络,在栅极和直流输入之间加上稳定电阻,并且利用3/4 λ 枝接的威尔金森功率合成/分配器,从而有效消除其自激和低频串扰问题。在连续波条件下(直流偏置电压为Vds=27V,Vgs=-4.0V),放大器在8GHz频率下线性增益为5dB,最大效率为17.9%,输出功率最大可为42.93dBm,此时放大器增益压缩为3dB。四路合成放大器的合成效率是67.5%。通过分析,发现了放大器合成效率的下降是由每路放大器特性的不一致、功率合成网络的损耗以及电路制造误差所造成。     

增强型GaN绝缘栅HEMT线性电荷控制解析模型

基于MIS理论和含极化的泊松方程,应用费米能级与二维电子气密度线性近似,并考虑计入了绝缘体/AlGaN界面的陷阱或离子电荷,导出建立了适用于增强型且兼容耗尽型AlGaN/GaN绝缘栅HEMT的线性电荷控制解析模型。研究表明,Insulator/AlGaN界面陷阱密度在1013cm-2数量级;基于该模型的器件转移特性的理论结果与器件的实测转移特性数据比较符合。该模型可望用于器件性能评估和设计优化。     

一种基于微结构的GaAs HEMT的压阻系数

GaAs HEMT(高电子迁移率晶体管)位于微结构悬臂梁根部附近的最大应力处。介绍了GaAs HEMT和微结构的设计加工,并通过实验研究了GaAs HEMT在平行于HEMT生长方向(Z方向)单轴应力作用下的力电耦合特性。测试结果表明:GaAs HEMT不同偏压下压阻系数不同,且它的最大压阻系数为(1.72±0.33)×10-7Pa-1,比Si高出三个数量级。