The performance effects of crystal boundaries in cadmium zinc telluride radiation spectrometers

The specific performance effects of extended crystal defects in cadmium zinc telluride (CZT) radiation spectrometers have been investigated. While it is generally accepted that defects such as grain boundaries and decorated twins can have a significant deleterious impact on the performance of semiconductor radiation spectrometers, the detailed mechanisms of degradation have been previously unexplored. Because of the difficulties of the high pressure Bridgman (HPB) growth process, CZT materials generally contain a large number of such defects, and the yield of defect-free crystals is comparatively low. High-resolution gamma-ray response mapping has been combined with analytical spectral simulations to relate the anomalies in the measured detector response to the likely originating defect. Examples of several different types of boundaries have been examined in a range of commercial CZT detectors, with the relevant parameters of the boundary being its trapping or channeling nature and the properties of the material on each side of the boundary