Study of growth defects in CZT and their influence on detector uniformity

The main problems involved in applying Cadmium Zinc Telluride (CZT) to detectors are the crystal perfection required and the difficulty in making reliable surface electrical contacts to the material. Our efforts have focused on the development of interconnect techniques and testing methods which will allow us to explore the interaction of defects with detector properties. Local stoichiometry variations and other local disordering make it very hard to find a systematic correlation between performance and material defects in the macroscopic scale. In order to understand the factors limiting the energy resolution of CZT detectors, our efforts were directed to the area of material characterization and detector testing using the National Synchrotron Light Source (NSLS). NSLS provides us with a highly collimated high intensity X-ray beam, which is employed to investigate micron-scale detector performance mapping and the correlation between microscopic defects and fluctuations in collected charge. Some results were already published and more are presented and correlated to X-ray diffraction topography (XDT) measurements. XDT at the beamline X17B1 is used to investigate more systematically the origins of the mosaicity that can give us information about the defect distribution and strains in bulk CZT crystals.