CdZnTe晶体热激电流谱分析

Thermally stimulated current (TSC) spectroscopy is a quite effective method for the defects studies in wide bandgap semiconductors, from which the physical information, i. e. defect types, activation energy (E_{a, i}), concentration (N_i) and capture cross-section (σ_i), can be given. The discrepancy and effects of heating-rate-dependent Arrhenius method and simultaneous multiple peak analysis (SIMPA) on the data processing results of TSC were studied in this work. The results indicated that Arrhenius method were more accurate in terms of the thermal activation energy of different traps. However, more heating rate, which meaned longer test cycles, were needed to maintain the accuracy. And also, this method could not deal with conditions of traps over-lap. In contrast, the SIMPA method could obtain the trap signatures (E_{a, i}, N_i, σ_i) with only one heating rate. However, parameters, i. e. β, E_{a, i}, σ_i and carrier mobility and lifetime product (μt), had significant effects on the peak position, height and width, which directly influenced the results of the fitting curve. Furthermore, the IRTM images of sample from the head of the ingots showed lower concentration of Te inclusions with belt-like distribution compared to that from the tail. Through the investigation of TSC spectroscopy, the concentration of shallow levels were much higher in the sample from the tail of the ingots than that from the head. The low temperature persistent photoconductivity (PPC) experiments showed a curvilineal variation for the tail sample. The results showed that the concentration and distribution of Te inclusions could probably result in the concentration variation of shallow trap centers, which present longer trapping time and shorter de-trapping time of optical excited carriers in crystal.