.ingap / Gaas Micro-structure Materials Gsmbe Growth And Characteristics Of Hbt And Solar Cell Devices

Chen Xiaojie (Majoring in Microelectronics and Solid State Electronics) Directed by Prof. Aizhen Li In this work, high quality GaAs-. AlGaAs InGaP epilayers and Lattice-matched N-p-n Ino.4gGao.5 1P/GaAs heterojunction bipolar transistor materials with 6Onm heavily beryllium doped base and Snm undoped spacers have been grown by gas source molecular beam epitaxy. The mismatch between high crystalline quality 1n0?9Ga051P epilayer and GaAs substrate is in order of magnitude of l0~. The effects of substrate temperature, AsH3 and PH3 switching, and the flux ratio of Indium to Gallium during growth procedure have been investigated. Discrete prototype HBT devices with conventional mesa structure have been fabricated on the grown wafer by using selective wet chemical etching technique and photolithographic process. AuGeNi/Au was used for the emitter and collector contacts, and Cr/Au was used for the base contact. The turn-on voltages of BE heterojunction and BC junction are 1.0 and 0.65 V, and the reverse breakdown voltages are 10 and 12 V, respectively. The common-emitter current-voltage characteristics show a maximum current gain of 320 at collector current density of 280A1cm2. Potential distributions in the Space Charge Region of InGaP/GaAs abrupt heteroj unction with undoped spacer, transferring current ingredients in HBT devices, and the effects of undoped spacer to device performance have also been discussed. In the AlGaAs/GaAs space solar cell project, key factors to solar cell efficiency, such as the reverse leakage current, series resistance and parallel resistance have been studied by simulating equivalent circuit. The optimized device process of p-n Alo.85Gao.15As/GaAs solar cells have been investigated. AuBe/Au and AuGeNi/Au were evaporated and metallized to form ohmic contacts of front grids and back electrodes, respectively. Heavily-doped GaAs cap layers were removed by the NH4OH:H202:H3P04:H20 selective etching solution. Double-layered ZnS/MgF2 anti-reflection layers were evaporated on the Alog5Ga0.15As window layers. A maximum efficiency of the fabricated 2x2cm2 solar cell achieved 22.23% under 1 sun AMO condition.