A study of p-type Ohmic contact for 4H-SiC avalanche photodetector

Abstract

对4H-SiC雪崩光电探测器的Ti/Al/Au p型欧姆接触进行了详细的研究。通过线性传输线模型(LTLM)测得经930℃退火后欧姆接触的最小比接触电阻为5.4×10~(-4)Ωcm~2。分别用扫描电子显微镜(SEM)、俄歇电子能谱(AES)、X射线光电子能谱(XPS)和X射线衍射谱(XRD)对退火前后的表面形貌、金属之间以及金-半接触界面之间相互反应及扩散情况进行测试与分析,发现了影响欧姆接触性能的主要原冈。对采用此欧姆接触制备的4H-SiC雪崩光电探测器进行测试,发现器件的击穿电压约为-55 V,此时其p型电极处的电压降仅为0.82 mV,可以满足4H-SiC雪崩光电探测器在高压下工作的需要。The p-type Ohmic contact of Ti/Al/Au multiple metal alloy for 4H-SiC avalanche photodetector(APD)was investigated and the lowest specific contact resistance of 5.4×10~(-4)Ωcm~2 was achieved by the linear transmission line method(LTLM).The scanning elec- tron microscope(SEM),Auger electron spectroscopy(AES),X-ray photoelectron spectroscopy (XPS)and Panalytical X'pert PRO X-ray diffraction(XRD)were measured to analyze the contact morphology,chemical composition and the phase formation of the samples before and after annealing.In addition,the electrical properties of 4H-SiC APDs with the same p-type Ohmic contact were also measured.Near the breakdown voltage of about-55 V,the voltage descent at p electrode was as low as 0.82 mV,which showed that the Ohmic contact can satisfy the requirement of 4H-SiC APD