Characterization of Low-Defect ${\rm Cd}_{0.9}{\rm Zn}_{0.1}{\rm Te}$ and CdTe Crystals for High-Performance Frisch Collar Detectors

Low dislocation density, high-purity, and low inclusion concentration ${\rm Cd}_{0.9}{\rm Zn}_{0.1}{\rm Te}$ (CZT) and CdTe crystals were grown by a vertical Bridgman technique using in-house zone refined precursors. The grown crystals were sequentially processed using optimized chemo-mechanical processes to fabricate planar and Frisch collar detectors. Infrared transmission and scanning electron microscopy studies have shown that EIC grown CZT and CdTe crystals have significantly lower Te inclusions and defect densities than commercially available spectrometer grade crystals. The charge transport properties (electron and hole mobility-lifetime products, $\mu \tau _{e}$ & $\mu \tau _{h}$) of various detectors have been evaluated by Hecht analysis. The detectors have been tested for spectral response using 59.5 and 662 keV $\gamma $-ray sources. The CZT detectors with planar electrodes showed 2.6% FWHM at 662 keV. By adding a Frisch collar, the detectors' spectra improved significantly. The Frisch collar detectors proved to be very promising for assembling large-area arrays with excellent energy resolution at relatively low manufacturing cost.