Effect of graded buffer design on the defect structure in InGaAs/GaAs (111)B heterostructures

In this work, the defective structure of InGaAs/GaAs (111)B has been studied, using different types of substrate misorientation and incorporating different types of graded buffer layers. The formation of deformation twins has been observed to be independent of misorientation direction, but with a distribution dependent on the substrate misorientation angle. Samples grown on 2° misoriented substrates showed long twins with the majority of them formed with only one {111} variant. The use of a step-graded structure achieved a threading dislocation (TD) density improvement, although it was not able to alter the density of plastic relaxation occurring through twins. Twin nucleation occurred at the surface, being controlled by the superficial step density and not by the relaxation sequence of the structure. In the perpendicular direction to the off-cut, the linearly graded layer structures showed a higher twin density and no misfit dislocations (MD) were observed. A diffraction pattern study indicated an epilayer tilt in the off-cut direction with respect to the substrate. This additional tilt, probably due to the introduction of dislocations with a preferential Burgers vector, produced a superficial step density increase and, therefore, strain relief occurred by twins in preference to MDs.     

Design and Manufacture of the Synthesized Furnace New Type GaAs Polycrystal for High Pressure

在分析原卧式砷化镓多晶合成炉缺陷的基础上．借鉴其它进口砷化镓单晶炉体部分结构优点,综合创新设计等制造出立式砷化镓多晶合成炉。经过300多炉次砷化镓多晶合成,证实新型砷化镓合成炉具有装、取料方便、电极不易沉积砷、炉体清洁快速等优点。由于提高了新合成炉密闭性及增强了石墨系统稳定性,从而保证了砷化镓多晶合成产品的一致性。     

GaAs/InP的键合界面热应力分析

采用双层条状金属热应力模型,用MATLAB方法对退火过程中GaAs/InP晶片间的应力和双轴弹性形变能进行模拟和分析。结果表明:将InP剪薄至200μm,GaAs剪薄至175μm,剪应力取得了一个相对的小值,而剥离应力更是被完全消除,这时正应力也相对较小。而按照一定的比例适度剪薄两侧晶片的厚度,可以使得两侧的双轴形变能减小到原来的一半以下。通过减薄键合晶片的厚度可以得到较好的键合质量。另外,不管那一种应力都随退火温度的升高而快速增加,所以实验中一定保持低的退火温度,通常小于300°C为宜。     

2～20GHz分布式单片放大器设计

介绍了一种采用0.15μm GaAs PHEMT工艺设计加工的2～20 GHz宽带单片放大器,为了提高电路的整体增益和带宽,在设计电路时采用两级级联分布式结构。此种电路结构不仅能够增加整体电路的增益和带宽,还可以提高电路的反向隔离,获得更低的噪声系数。利用Agilent ADS仿真设计软件对整体电路的原理图和版图进行仿真优化设计。后期电路在中国电子科技集团公司第十三研究所砷化镓工艺线上加工完成。电路性能指标:在2～20 GHz工作频率范围内,小信号增益>13.5 dB;输入输出回波损耗<-9 dB;噪声系数<4.0 dB;P-1>13 dBm。放大器的工作电压5 V,功耗400 mW,芯片面积为3.00 mm×1.6 mm。     

基区设计对InGaP/GaAs HBT热稳定性的影响

研究了不同基区设计对多发射极指结构功率InGaP/GaAs异质结双极型晶体管热稳定性的影响。以发生电流增益崩塌的临界功率密度为热稳定性判定标准,推导了热电反馈系数Φ、集电极电流理想因子η和热阻Rth与基区掺杂浓度NB、基区厚度dB的理论公式。基于TCAD虚拟实验,观测了不同基区掺杂浓度和不同基区厚度分别对InGaP/GaAs HBT热稳定性的影响。结合理论公式,对仿真实验曲线进行了分析。结果表明,基区设计参数对热稳定性有明显的影响,其影响规律不是单调变化的。通过基区外延层参数的优化设计,可以改进多指HBT器件的热稳定性,从而为多指InGaP/GaAs HBT热稳定性设计提供了一个新的途径。     

Validated front contact grid simulation for GaAs solar cells under concentrated sunlight

In a common approach, the electric behavior of a solar cell is modeled by dividing it into smaller sub‐circuits and solving the resulting network by a circuit simulator. In this paper detailed network simulations are presented for a GaAs single‐junction solar cell. All resistive losses and losses influencing the diode saturation currents, such as recombination in the depletion region or at the perimeter are taken into account. With this model the maximum power point of a solar cell can be calculated for one‐sun and for higher illumination intensities. The results were validated experimentally using suitable test structures. This includes solar cell devices with varying dimensions, grid finger spacing and lengths. An excellent agreement between theoretical and experimental results was obtained. The network simulation model allows determining the optimum size and concentration ratio at which a solar cell operates at its maximum efficiency. In the case of a GaAs single‐junction solar cell this global efficiency maximum was found for an area of 1 mm² and at a concentration ratio of 450 suns. Under these conditions the largest loss mechanisms are the finger shading with 36.1% and the emitter resistance losses with 21.5% of the total power losses. Copyright © 2010 John Wiley & Sons, Ltd.     

Demonstration of a nipi‐diode photovoltaic

The simulation, growth, processing, and characterization of a three‐period GaAs n‐type/intrinsic/p‐type/intrinsic … (nipi) doping solar cell is demonstrated. A V‐groove etching process is characterized and used to expose the multiple n‐type and p‐type layers for electrical connection made by interdigitated grid‐finger electrodes. A five‐layer photolithographic process flow is developed and used to make 1 × 1 cm² devices with varying grid‐finger separation. Device simulations of the structure indicate that strong rectification can be achieved in the parallel‐connected three period nipi GaAs solar cell structure provided the necessary semiconductor doping compensation is achieved in the region near the metal‐semiconductor interfaces. Experimentally, the improvements observed in the open circuit voltage, short circuit current, and ideality of the devices following thermal annealing suggests the formation of barriers near the contacts, which support the simulation results. A comparison of the short circuit current and series resistance under illumination indicate a tradeoff between shadowing and series resistance, which may be overcome with modification to the device structure. Ultimately, these results show promise towards the development of high efficiency solar cells or radioisotope batteries, and offer a novel device structure for the incorporation of nano‐structures such as quantum wells or quantum dots. Copyright © 2010 John Wiley & Sons, Ltd.     

GaAs器件电磁脉冲效应实验与毁伤机理研究

介绍了GaAs低噪声器件电磁脉冲效应实验响应的易损敏感端,对所确定的敏感端注入电磁脉冲方渡,研究了器件在静态时的损伤阈值.根据GaAs器件易损性薄弱环节,从GaAs器件的结构、内部缺陷等出发,探索电磁脉冲对GaAs器件易损性薄弱环节的损毁机理.通过对毁伤实验分析,进一步阐述了电磁脉冲对器件存在潜在不稳定性失效,对器件和整机系统设计者和使用者具有一定的参考意义.GaAs微波低噪声器件在EMP正脉冲注入情况下,获得的损伤阈值约为3.024μJ.在EMP负脉冲注入情况下,损伤阈值约为10.02μJ.初步认为GaAs FET的正脉冲EMP比负脉冲EMP更易损伤.     

美、日、欧宽带隙半导体技术发展研究

美国、日本和欧盟等国在SiC、GaN和金刚石等宽带隙半导体器件与电路研究中已取得多项里程碑性的进展,这些飞速发展已经证实宽带隙半导体是当之无愧的新一代半导体材料,并将替代Si和GaAs应用于相控阵雷达、高保密通信及其他重要设施等诸多国防和航空领域.概述了SiC和GaN等宽带隙半导体在军事、宇航及其他恶劣环境应用中优于Si和GaAs等传统半导体技术的具体体现.介绍了美国、日本和欧盟在发展宽带隙半导体技术上的重大举措及其在器件开发与研究中的最新进展.着重探讨了美、日、欧等发达国家实施的宽带隙半导体技术发展计划及其对其军事、航天及其他重要设施产生的深远影响.     

InGaAs/GaAs应变量子阱激光器MOCVD生长研究

采用金属有机物化学气相淀积(MOCVD)方法生长了InGaAs/GaAs应变量子阱(QW),通过降低生长温度、提高生长速度以及采用应变缓冲层(SBL)结构,改善了应变QW生长表面质量和器件荧光(PL)谱特性,实验表明,通过优化工艺条件和采用SBL等手段提高了应变QW质量。生长的QW结构用于1054 nm激光器的制作,经测试,器件具有较低的阈值电流和较高的单面斜率效率,性能较好。