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采用金属有机物化学气相沉积法(MOCVD)生长GaAs/Al0.3Ga0.7As量子阱材料,制备300μm×300μm台面,内电极压焊点面积为20μm×20μm,外电极压焊点面积为80μm×80μm的单元样品两种。用变温液氮制冷系统对样品进行77~300K暗电流特性测试。结果显示,器件暗电流曲线呈现出正负偏压的不对称性。利用高分辨透射扫描电镜(HRTEM)获得样品纳米尺度横断面高分辨像,分析结果表明:样品横断面处存在不同程度的位错及不均匀性。说明样品内部穿透位错造成相位分离是引起量子阱光电性能变差的根本原因,不同生长次序中AlGaAs与GaAs界面的不对称性与掺杂元素的扩散现象加剧了暗电流曲线的不对称性。
The GaAs / Al0.3Ga0.7As quantum well material is grown by metal organic chemical vapor deposition (MOCVD) to prepare a 300 μm × 300 μm mesa. The area of the internal electrodes is 20 μm × 20 μm, the area of the external electrodes is 80 μm × 80 μm Two kinds of unit samples. The samples were tested for dark current characteristics of 77 ~ 300K with variable temperature liquid nitrogen refrigeration system. The results show that the device dark current curve shows a positive and negative bias asymmetry. High-resolution transmission electron microscopy (HRTEM) was used to obtain nanoscale cross-sectional high-resolution images of the samples. The results show that there are different degrees of dislocations and inhomogeneities in the cross-section of the samples. It is indicated that the phase separation caused by dislocation within the sample is the fundamental reason that leads to the poor photoelectric property of quantum well. The asymmetry of AlGaAs and GaAs interface and the diffusion of doping elements in different growth order aggravate the asymmetry of dark current curve .