Microscopic evaluation of spatial variations in material and charge transport properties of CdZnTe radiation detectors

The material uniformity and charge transport properties in CdZnTe radiation detectors are investigated by various non-destructive room temperature techniques. High-resolution secondary electron microscopy shows evidence of Te-enriched regions near the metal contacts. Photoluminescence (PL) mapping is used to image material defects and variations in Zn composition. Close to the electrodes PL spectra show strong defect-activated emission which is not observed in the material bulk. Ion-beam-induced-charge (IBIC) microscopy using a 2 μm resolution focussed proton beam is used to investigate the spatial variation in charge transport across detectors. Localized regions of poor charge collection efficiency seen in the IBIC images correlate with material defects observed in PL such as tellurium precipitates. The effects of these material defects in terms of the spectroscopic performance of the detectors to X-ray and γ-ray irradiation is discussed.