Recent progress in n-type CdZnTe arrays for gamma-ray spectroscopy

Abstract

This study focuses on the characterization of n-type CdZnTe gamma-ray spectrometers, which are designed for pixelated imaging array. The intentionally doped n-type CdZnTe crystals are grown by IMARAD Imaging Systems by a modified horizontal Bridgman technique. Imaging arrays, which are produced by IMARAD with ohmic contacts are compared with arrays with different types of contacts, fabricated at Technion-Israel Institute of Technology. We investigate the performance of n-type MSM spectrometers fabricated with several types of contacts: ohmic anodes and cathode, rectifying anodes and cathode as well as mixed (i.e., ohmic anodes and rectifying cathode). The DC characteristics are correlated with the detector dark noise and the spectral performance. The study presents the significant recent advance in the technology of room-temperature semiconductor gamma-ray spectrometers. It also gives physical insight to the parameters that determine the performance of n-type CdZnTe spectrometers. The comparison between spectrometers with different contacts may indicate whether the high performance of IMARAD arrays depends upon electron injection from the cathode, as previously suggested, or to adequate hole mobility-lifetime products in the n-type CdZnTe material, as suggested here.