Low-signature Cadmium Zinc Telluride CZT defect inspection by IR, ultrasound, etch pit density, and x-ray topography

Widespread utilization of Cadmium Zinc Telluride (CZT) in nuclear radiation detectors is currently limited by the cost of high spectroscopic quality material. Yield of devices is limited by non-uniformity in the charge collection efficiency associated crystal defects that occur during synthesis. An inspection method suitable for grading CZT parts during an early stage of device manufacturing is sought. We have implemented a combination of UT and IR imaging of CZT wafers that is successful to map sub-grain boundaries, twins and tellurium inclusions greater than 10-micron diameter. However, point defects and dislocations are below the imaging resolution of the system. It is the goal of this system to study defect density in UT and IR clear areas of CZT wafers and establish an opportunity for low signature defect mapping.