Evaluation of CZT crystals from the former Soviet Union

Vertical high-pressure Bridgman (VHPB) Cd1-xZnxTe (0.04 < x < 0.24) detecto r crystals grown in the Ukraine and Russia have been evaluated and compared to US-grown materials. Various analytical techniques were used to study th e materials for trace impurities, precipitates, crystallinity, and electric al transport properties. Relatively, high concentrations of carbon and trac e impurities such as Se, Nd and Si have been detected in the crystals. In m ost cases, the crystals showed lower resistivity than US-grown CZT. However , recent crystals grown in Russia exhibited better detector performance tha n those grown previously, and a good response to an Am-241 radioactive sour ce was found. Electron lifetimes below 1 mu s were measured in crystals hav ing significant numbers of micro-defects, compared to lifetimes of 5-15 mu s found in spectrometer grade materials produced in the US. Furthermore, th e zinc composition along the growth axis showed better homogeneity in compa rison with the US material. (C) 1999 Published by Elsevier Science B.V. All rights reserved.