Advances in CdZnTe and CdMnTe semiconductors for detection of radiological and nuclear threats

Cadmium zinc telluride (CdZnTe) X-rays and gamma-rays detectors have found applications in radiological and nuclear security, environmental protection, astrophysics, and nuclear medical imaging. Cadmium manganese telluride (CdMnTe) has the potential for similar success as CdZnTe in the detection of ionizing radiations. The detection of radiological and nuclear threats would greatly benefit from detector wafers with large-volume, high-performance, and low-cost of production. This paper presents recent advances in the development of CdZnTe and CdMnTe nuclear detectors with the focus on the detection of radiological and nuclear threats. Efforts on improving the performance of CdZnTe and CdMnTe detectors were made in three major areas: crystal growth, post-growth annealing, and device fabrication. In crystal growth, we optimized ampoule carbon coating for CdZnTe and eliminated detector performance-limiting secondary phase particles in CdMnTe. In post-growth annealing of CdMnTe and CdZnTe crystals, we reduced and in some cases eliminated Te inclusions. In device fabrication, we observed that chemomechanical polishing produced smoother wafer surfaces than chemical etching, but chemical etching produced a better energy resolution.