Charge Transport Properties in CZT Detectors Grown by the Vertical Bridgman Technique

The crystallinity of material remains a serious problem for CdZnTe (CZT) radiation detectors affecting their availability and cost. Point defects control the electron lifetime in the single-crystal regions, which determines the fraction of the charge signal lost due to carrier trapping in each interaction event. If carrier losses are small, the charge signals can be electronically corrected. In contrast, extended defects may result in significantly greater charge losses and, consequently, cause much greater fluctuation of the output signals, which cannot be corrected. Although not all of the interacting events are affected by the extended defects, its fraction rapidly increases with a crystals thickness and with the concentration and extent of such defects. In this paper, we present new results from testing CZT material and detectors to emphasize the roles of particular defects and their contributions to the overall device performance. We also describe possible ways to identify and reject the incomplete charge collection events caused by the extended defects