A comparison of point defects in Cd_(1-x)Zn_xTe_(1-y)Se_y crystals grown by Bridgman and traveling heater methods

摘要

In this paper, the properties of point defects in Cd_(1-x)Zn_xTe_(1-x)Se_y (CZTS) radiation detectors are characterized using deep-level transient spectroscopy and compared between materials grown using two different methods, the Bridgman method and the traveling heater method. The nature of the traps was analyzed in terms of their capture cross-sections and trap concentrations, as well as their effects on the measured charge-carrier trapping and de-trapping times, and then compared for the two growth techniques. The results revealed that Se addition to CdZnTe can reduce the V~-~Cd concentration. In Travelling Heater Method (THM) and Bridgman Method (BM) grown CZTS detectors, besides a few similarities in the shallow and medium energy traps, there were major differences in the deep traps. It was observed that the excess-Te and lower growth-temperature conditions in THM-grown CZTS led to a complete compensation of V~-_cd and two additional traps (attributed to Te~-_i and Te_(Cd)~(++) appearing at around E_v + 0.26 eV and E_c - 0.78 eV, respectively). The 1.1-eV deep trap related to large Te secondary phases was a dominant trap in the BM-grown CZTS crystals. In addition to i-DLTS data, the effects of point defects induced due to different processing techniques on the detector's resistivity, spectral response to gammas, and µx product were determined.