Effect of extended defects in planar and pixelated CdZnTe detectors

Abstract

We evaluated a spectroscopy-grade 15×15×7 mm3 CdZnTe (CZT) crystal with a high μτ-product, >10−2 cm2/V, but impaired by microscopic extended defects, such as walls of dislocations, low-angle and sub-grain boundaries, and Te inclusions. First, we evaluated a planar detector fabricated from this crystal using a Micro-scale X-ray Detector Mapping (MXDM) technique. Then, we fabricated from the same crystal a pixel detector to study local non-uniformities of the electric field. The measured X-ray response maps confirmed the presence of non-uniformities in the charge transport, and they showed that the global- and local-distortions of the internal E-field correlated to the extended defects and space-charge buildup on the side surfaces.