电极材料对碘化汞(α-HgI_2)晶体I-V特性的影响

I-V Characteristics of Mercuric Iodide Crystal with Different Contacts

利用Aligent4155型CVIV测试仪分别对Au/HgI2、AuCl3(Au)/HgI2、C(石墨)/HgI2接触的I-V特性进行了测定,对比研究了不同电极材料与α-HgI2晶体所形成的接触特性,并利用热电子发射理论对实验结果进行了分析。结果表明,AuCl3和C均能与HgI2形成良好的欧姆接触,其欧姆特性系数分别为1.0291和0.9380,接触电阻分别为3.0×108Ω和1.0×108Ω;而溅射Au与HgI2接触的欧姆特性较差,欧姆系数约为0.8341,接触电阻为3.5×109Ω。这说明AuCl3在HgI2表面形成了重掺杂,产生显著的隧道电流,从而形成了较理想的欧姆接触。C(石墨)化学性能稳定,电极制备工艺没有影响晶体表面质量,因此C(石墨)/HgI2接触电阻最小,并具有良好的欧姆特性。而溅射Au过程中由于温度升高引起晶体表面HgI2分子的挥发,造成晶体表面质量下降,导致Au/HgI2接触的欧姆特性变差。

I-V characteristics of HgI2 crystal wafers with different contacting layers, such as sputtering Au, chloroauric acid decomposed Au, colloidal graphite, were studied using Aligent4155 CVIV instrument, and analyzed according to thermoionic emission model. The results indicate that the fitting data, b, according to I = aV^b and representing ohmic contacts are 1. 0291 and 0. 9380, and the contact resistances are 3.0 × 10^8Ω and 1.0 × 10^8Ω for AuCl3 （Au）/HgI2 and C （graphite）/HgI2, respectively, while 0.8341 and 3.5 × 10^9Ω for sputtered Au. Heavily doped layer might be formed at HgI2 surface during decomposed process of AuCl3 which produced obvious tunnel current and idea ohmic contacts. Colloidal graphite had better chemical stability and craft of electrode fabrication did not deteriorate surface quality of HgI2 crystal wafers. Thus, C/HgI2 had lower contact resistance and better ohmic porperties. The higher temperature during sputtering of Au contacts leading to HgI2 volatilization deteriorated the interface quality of HgI2 crystal wafers, which formed no ohmic contacts.