Optical and electrical characterization of Cadmium Telluride X-ray pad detectors

Tellurium defects in CdTe and CdZnTe detectors are known to degrade the detector performance by trapping passing charges. This causes losses in charge collection and ultimately degrades the energy resolution. The amount and size of the defects has previously been studied for small areas of these materials, and small defects (< 5 mu m) have been identified as the main cause for signal degradation. However, previous studies concentrated on the evaluation of a view regions of interest. In this study we present a system capable of scanning larger volumes of CdTe and CdZnTe and associate the locations of the found defects with the charge collection of detectors. Further, we show that the signal degradation is not uniform over the whole detector, but linked to local densities of defects. This results in variations of charge collection even within single detectors.