GaAs/Al_(0.3)Ga_(0.7)As QWIP暗电流特性HRTEM研究

Dark current of GaAs/Al_(0.3)Ga_(0.7) As quantum well infrared photodetector by HRTEM

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77~300 K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 method of Metal Organic Chemical Vapor Deposition （MOCVD） was used to grow GaAs/Al0.3Ga0.7As quantum well material. Which is prepared for quantum well infrared photodetectors （QWIP）. The two sample-devices have large surface area 300μm×300μm. But its pressure welding area of inside electrode is 20μm×20μm while that of the one outside is 80μm×80μm. Refrigerating machine of liquid nitrogen was adopted to do dark current test under variable-temperature from 77 K to 300 K . The dark current was studied under different bias voltages. The results show that dark current curves is asymmetric under positive and negative bias voltage. The crystal structure is investigated by use of high-resolution transmission electron microscope （HRTEM） to determine the exact reson. Which shows that there is thread dislocation and nonuniformity in different degrees. The follows is known from above： It is the phase separation caused by the threading dislocation that leads to photoelectric performance variation essentially. At the same time, it is interfacial asymmetry between AlGaAs and GaAs in different growing＆nbsp;orders and the doping element diffusion that intensifies asymmetry of dark current.