Optimization of selenium in CdZnTeSe quaternary compound for radiation detector applications

Abstract

X- and gamma-ray detectors are increasingly becoming an essential tool for science and technology in various fields, including homeland security, nonproliferation, nuclear security, medical imaging, astrophysics, and high energy physics. Cd1−xZnxTe1−ySey (CZTS) is emerging as a next-generation compound semiconductor for such applications. CZTS was found to possess a very low concentration of Te inclusions and free from sub-grain boundary networks. Being a quaternary compound with varying alloy compositions, optimization of the composition was performed to determine the minimum amount of selenium required to produce CZTS with reduced defects. The optimized composition was found to be x = 0.10 and y = 0.02, i.e., Cd0.9Zn0.1Te0.98Se0.02, for excellent material properties as a radiation detector. The resulting material was free from sub-grain boundary networks and with a highly reduced concentration of Te inclusions. The bulk dark resistivity obtained was in the range of 1-3 × 1010 Ω cm with the highest achieved mobility-lifetime product of ∼6.6 × 10−3 cm2/V for the optimized CZTS composition. Impurity analyses were performed by the glow discharge mass spectroscopy technique, and the results showed relatively high impurity concentrations compared to commercial detector-grade CdZnTe. Thus, CZTS has room for further improvement with additional purification of the starting materials.