Extended defects in As-grown CdZnTe

Abstract

We characterized samples cut from different locations in as-grown CdZnTe (CZT) ingots, using Automated Infrared (IR) Transmission Microscopy and White Beam X-ray Diffraction Topography (WBXDT), to locate and identify the extended defects in them. Our goal was to define the distribution of these defects throughout the entire ingot and their effects on detectors' performance as revealed by the pulse-height spectrum. We found the highest-and the lowest-concentration of Te inclusions, respectively, in the head and middle part of the ingot, which could serve as guidance in selecting samples.Crystals with high concentration of Te inclusions showed high leakage current and poor performance, because the accumulated charge loss around trapping centers associated with Te inclusions distorts the internal electric field, affects the carrier transport properties inside the crystal, and finally degrades the detector's performance. In addition, other extended defects revealed by the WBXDT measurements severely reduced the detector's performance, since they trap large numbers of electrons, leading to a low signal for the pulse-height spectrum, or none whatsoever. Finally, we fully correlated the detector's performance with our information on the extended defects gained from both the IR-and the WBXDT-measurements.

Change in the bulk resistivity of CdZnTe with selected near IR light

“…This result is supported by Xu et al who found that a higher concentration of SP leads to a higher bulk leakage current. 14 The increase in leakage current was attributed to the narrow bad gap of Te (~0.3eV), producing a noticeable gain in electrical conductivity with increasing SP.…”