四结叠层太阳电池中AlGaAs/GaAs隧穿结的特性和表现

III-V族化合物叠层太阳电池是具有超高转换效率的第三代新型太阳电池。四结叠层电池GaInP/GaAs/InGaAs/Ge,各子电池的带隙分别为1.8, 1.4, 1.0, 0.7(ev)。为了使各子电池之间电流匹配,在各子电池之间以隧穿结互相连接。本文主要探索研究了四结叠层电池GaInP/GaAs/InGaAs/Ge隧穿结的特性,三个隧穿结的材料选取,探讨了隧穿结对整体叠层电池的特性的补偿作用,对各子电池电流密度的影响,以及在此基础上对整体电池效率的增加。选用AlGaAs/GaAs作为隧穿结运用PC1D进行电池的整体模拟仿真,得到各子电池电流密度分别为16.02mA/cm²,17.12 mA/cm²,17.75 mA/cm²,17.45 mA/cm²,电池在AM0下的开路电压Voc为3.246V,转换效率为33.9%。     

AlGaAs/GaAs tunnel junctions in a 4-J tandem solar cell

TheⅢ-Ⅴcompound tandem solar cell is a third-generation new style solar cell with ultra-high efficiency. The energy band gaps of the sub-cells in a GaInP/GaAs/InGaAs/Ge 4-J tandem solar cell are 1.8,1.4,1.0 and 0.7 eV,respectively.In order to match the currents between sub-cells,tunnel junctions are used to connect the sub-cells.The characteristics of the tunnel junction,the material used in the tunnel junction,the compensation of the tunnel junction to the overall cell’s characteristics,the tunnel junction’s influence on the current density of sub-cells and the efficiency increase are discussed in the paper.An AlGaAs/GaAs tunnel junction is selected to simulate the cell’s overall characteristics by PC1D,current densities of 16.02,17.12,17.75 and 17.45 mA/cm² are observed,with a V_oc of 3.246 V,the energy conversion efficiency under AM0 is 33.9%.     

Fabrication and characterization of AlGaAs/GaAs heterojunction bipolar transistors

The fabrication and characterization of MBE-grown AlGaAs/GaAs heterojunction bipolar transistors (HBT's) are described, A Be redistribution profile in the HBT epi-layer at the emitter-base heterojunction interface is investigated using secondary ion mass spectrometry, A relatively high substrate temperature of 650°C during growth can be employed by introducing a 100-Å undoped spacer layer between the emitter and base layer. A simple wafer characterization method using phototransistors is demonstrated for accurately predicting current gain in a three-terminal device. A dc current gain of up to 230 is obtained for the fabricated HBT with a heavy base doping of 1 × 10¹⁹/cm³. A gain-bandwidth product fTof 25 GHz is achieved with a 4.5-µm-width emitter HBT.     

Fabrication of an optoelectronic AlGaAs/GaAs waveguide neuron

A novel optical waveguide neuron is fabricated. It accepts two inputs, applies adjustable weights to them, sums the weighted inputs, and thresholds the sum to issue one output. An AlGaAs/GaAs p-i-n diode waveguide with a Wannier-Stark superlattice in the core is used. Two modulators and one saturable absorber are monolithically integrated on a 5-μm rib waveguide Y-junction combiner. A simple self-aligned single-mask liftoff technique with wet chemical etching is used. At 780 nm the weights vary from 1 to -25 dB/mm for reverse bias below 7 V, and a 25-dB thresholding nonlinearity is obtained     

Fabrication and Simulation of an AlGaAs/GaAs Ultra-Thin Base NDR HBT

A novel mesa ultra-thin base AlGaAs/GaAs HBT is designed and fabricated with wet chemical selective etch technique and monitor electrode technique.It has a particular and obvious voltage-controlled NDR whose PVCR is larger than 120.By use of device simulation,the cause of NDR is that increasing collector voltage makes the ultra-thin base reach through and the device transforms from a bipolar state to a bulk barrier state.In addition,the simulated cutoff frequency is about 60～80GHz.     

Fabrication of 2-D photonic bandgap structures in GaAs/AlGaAs

The authors report the first realisation of a two-dimensional photonic bandgap structure with a period of λ₀/2n in the GaAs/AlGaAs material system. The structure consists of a honeycomb lattice with a wall thickness of ~30 nm and a period of 160 nm. It was found that, to realise patterns of such small size and periodicity, it is crucial to control the shape of the exposed features     

碳掺杂AlGaAs的MOCVD生长及808 nm大功率激光器

用 CCl4 作为掺杂剂 ,进行了掺碳 Al Ga As层的 LP-MOCVD生长 ,并对其掺杂特性进行了研究 ,分析了各生长参数对掺杂的影响 ;研制了碳掺杂 Al Ga As限制层 80 8nm大功率半导体激光器 ;激光器单面连续波输出功率大于 1 W,功率效率为 0 .7W/ A。     

GaAs/AlGaAs and InGaAs/AlGaAs MODFET inverter simulations

Although MODFET's have exhibited the fastest switching speed for any digital circuit technology, there is as yet no clear consensus on optimal inverter design rules. We therefore have developed a comprehensive MODFET device model that accurately accounts for such high gate bias effects as transconductance degradation and increased gate capacitance. The device model, which agrees with experimental devices fabricated in this laboratory, is used in the simulation of direct-coupled FET logic (DCFL) inverters with saturated resistor loads. Based on simulation results, the importance of large driver threshold voltage not only for small propagation delay times but for wide logic swings and noise margins is demonstrated. Furthermore, minimum delay times are found to occur at small supply voltages as seen experimentally. Both of these results are attributed to the reduction of detrimental high gate bias effects. The major effect of reducing the gate length on delay time is to decrease the load capacitance of the gate. Using 0.25-µm gates, delay times of 5 and 3.6 ps at 300 and 77 K, respectively, are predicted. Finally, the recently introduced In-GaAs/AlGaAs MODFET's are shown to have switching speeds superior to those of conventional GaAs/AlGaAs MODFET's.     

High-electric-field effects and degradation of AlGaAs/GaAs power HFETs: a numerical study

This work presents a numerical study of high-field degradation and reliability issues of AlGaAs/GaAs power HFETs. A commercial two-dimensional drift–diffusion tool is used to investigate electric-field distributions, the effects of electron capture at the device surface under hot-carrier conditions, and the impact of drain recess scaling on such effects. Wherever experimental data are available for direct comparison, a good match is observed with our simulations. The main results of this study are (1) a validation of the hypothesis that attributes the main high-field degradation effects to electron capture over the gate–drain access region, and (2) design indications pointing out to the possibility of a reverse correlation between the gate–drain breakdown voltage and the device hot-carrier reliability.     

单量子阱GaAs/AlGaAs半导体激光器

本文介绍了用分子束外延法制作的梯度折射率分别限制式单量子阱GaAs/AlGaAs半导体激光器。该器件具有较低的阈值电流密度和单模运转特性,连续输出功率可达55mw。     

Ultra-submicrometer-gate AlGaAs/GaAs HEMTs

Ultra-submicrometer-gate AlGaAs/GaAs high-electron-mobility transistors (HEMTs) that have gate lengths ranging from 25 to 85 nm and were fabricated using electron-beam lithographic techniques on epitaxial wafers grown by molecular beam epitaxy are discussed. These devices show that velocity overshoot and short-gate geometry effects play an important role for the gate lengths less than 100 nm. The maximum intrinsic transconductance is 215 mS/mm, and the effective saturated electron velocity reaches 3×10⁷ cm/s for a 30-nm HEMT     

超亚微米栅AlGaAs/GaAs HEMT

在分子束外延生长的外延晶片上,用电子束刻蚀技术制作了超亚微米栅AlGaAs/GaAs高电子迁移率晶体管(HEMT),其栅长分布为25～85nm。该器件表明,速度过冲和短栅几何效应对栅长小于100nm的器件起着重要的作用。栅长为30nm的HEMT的最大本征跨导为215mS/mm,有效饱和电子速度可达3×10~7cm/s。     

AlGaAs/GaAs/AlGaAs DHBT's for high-temperature stable circuits

High-temperature devices are required for a large number of industrial applications. In order to demonstrate the feasibility of a high temperature operating circuit on GaAs an operational amplifier was designed and fabricated. A corresponding technology for transistors and circuits for operation up to 300°C with AlGaAs/GaAs/AlGaAs DHBT's is presented. For the amplifier circuit an open loop gain of 49.5 dB at room temperature and 35.8 dB at 200°C was measured, which is in good agreement with the circuit simulation. High temperature stability has been proven by a storage test at 400°C over 1000 h for the ohmic contact metallization and 200 h for the transistors     

GaInP/GaAs/Ge叠层太阳电池的研制及其温度依赖性分析

利用MOCVD方法制备了GaInP/GaAs/Ge叠层太阳电池。测试了I-V特性,并测试分析了该电池性能在30℃至170℃温度范围内的变化情况。测试结果表明,随着温度的升高,短路电流密度略微增大,温度系数为9.8 (μA/cm2)/℃;开路电压以系数-5.6mV/℃急剧下降;填充因子也随之下降（-0.00063 /℃）;电池的转换效率随温度升高线性减小,温度从30℃升高至 130℃时,效率从28%下降至22.1%。最后,本文对该叠层电池随着温度变化的特性给予了详细的理论分析。     

GaAs/AlGaAs太赫兹量子级联激光器的热分析

为研究太赫兹量子级联激光器(THz QCLs)中的热传输及有效散热方法,建立了二维/三维有限元热分析模型,模拟计算了GaAs/AlGaAs THz QCLs低温工作时的温度及热流分布;并讨论了源区结构参数、热沉材料及散热膜层对器件热传输的影响规律。研究结果表明,器件源区温度水平方向分布较均匀,垂直方向温差大,源区热量主要依靠热沉导出;减小源区厚度、增加腔长与减小脊宽均有利于促进热传导并降低源区温度;在器件顶部增加AlN薄膜具有显著的辅助散热效果,当薄膜厚度大于8 μm时,源区温降趋于缓慢。     

Submicron-square emitter AlGaAs/GaAs HBTs with AlGaAshetero-guardring

Successful operation of submicron-square emitter AlGaAs/GaAs HBTs is demonstrated for the first time by using a fully mesa-structure-type emitter-base junction-area definition method with an AlGaAs hetero-guardring. The hetero-guardring reduces surface recombination current at the emitter-mesa edge to 1.4 μA/μm. This is 1/10 of that for devices without the guardring. Here, dc gains of 20, 26, and 40 are achieved for 0.5 μm×0.5 μm, 0.7 μm×0.7 μm, and 0.9 μm×0.9 μm emitter HBTs, respectively. An f_T of 40 GHz, and an f_max of 30 GHz are obtained for 0.9 μm×0.9 μm at a J_C of 1.0×10⁵ A/cm²     

AlGaAs/GaAs/AlGaAs渐变异质结光致发光仿真研究

分析了AlGaAs/GaAs/AlGaAs渐变异质结的光致发光特性。根据理论及仿真结果,确定了GaAs发光的最优能带结构为双异质结P-AlGaAs/P-GaAs/P-AlGaAs或者N-AlGaAs/N-GaAs/ N-AlGaAs,并且异质结两边能带渐变。基于所选结构,研究了能带渐变及层宽对发光效率的影响。研究结果表明,外体区吸收层的能带渐变,且外体区激发层的能带不变,发光区域的载流子最多,发光能量值最大。激励光源的波长不同,各层有不同的最优宽度,为器件的整体优化提供了依据。AlGaAs/GaAs/AlGaAs渐变异质结的光致发光研究为高效率器件如太阳电池、发光二极管等的实用化设计、研制提供了有价值的参考。     

Thermal stability analysis of AlGaAs/GaAs heterojunction bipolartransistors with multiple emitter fingers

A numerical electro-thermal model was developed for AlGaAs/GaAs heterojunction bipolar transistors (HBT's) to describe the base current, current gain and output power dependence on junction temperature. The model is applied to microwave HBT devices with multi-emitter fingers. The calculated results of the common-emitter, current-voltage characteristics in the linear active region show a “current crush” effect due to inherent nonuniform junction temperature, current density and current gain distribution in the device. The formation of highly localized high temperature regions, i.e., hot spots, occur when the device is operating beyond the current-crush point. This thermally induced current instability imposes an upper limit on the power capability of HBT's. The dependence of this effect on various factors is discussed. These factors include the intrinsic parameters such as the base current ideality factor, the “apparent” valence band discontinuity, and the temperature coefficient of the emitter-base turn-on voltage, as well as the extrinsic factors such as the emitter contact specific resistance, the substrate thermal conductivity and the heat source layout     

Electron mobility in a AlGaAs/GaAs/AlGaAs quantum well

An oscillatory dependence of the electron mobility on the quantum well (QW) thickness in a AlGaAs/GaAs/AlGaAs heterostructure with double-sided modulation doping has been observed experimentally. A steep decrease in mobility with increasing electron concentration in the QW is established. The conditions for an increase in mobility on introducing a thin barrier into the QW are determined. The first experimental observation of an increase in mobility by a factor of 1.3 in a QW of thickness L=26 nm upon introducing a thin (1–1.5 nm) AlAs barrier is reported.