Evaluation of CZT crystals from the former Soviet Union

Vertical high-pressure Bridgman (VHPB) Cd1-xZnxTe (0.04<x<0.24) detector crystals grown in the Ukraine and Russia have been evaluated and compared to US-grown materials. Various analytical techniques were used to study the materials for trace impurities, precipitates, crystallinity, and electrical transport properties. Relatively, high concentrations of carbon and trace impurities such as Se, Nd and Si have been detected in the crystals. In most cases, the crystals showed lower resistivity than US-grown CZT. However, recent crystals grown in Russia exhibited better detector performance than those grown previously, and a good response to an 241Am radioactive source was found. Electron lifetimes below 1 μs were measured in crystals having significant numbers of micro-defects, compared to lifetimes of 5–15 μs found in spectrometer grade materials produced in the US. Furthermore, the zinc composition along the growth axis showed better homogeneity in comparison with the US material.