Gamma Ray Spectroscopy with THM CdZnTe Detectors

Good uniformity in electron transport has been observed on Cd_0.9Zn_0.1Te crystals grown by the Traveling Heater Method (THM) using alpha-particle measurements. Excellent electron mobility-lifetime products have been measured consistently on the order of 1times 10^-2 cm²/V. A coplanar-grid detector of size 10times10times5 mm³ has been fabricated from this material, and it shows an energy resolution of 2.1% FWHM at room temperature for 662 keV gamma rays. Pseudo Frisch-Grid 3times3times5 mm³ detectors fabricated from THM Cd_0.9Zn_0.1Te materials routinely exhibit near 1% FWHM @ 662 keV and < 3% FWHM @ 122 keV at room temperature while 4% FWHM at 122 kev has also been measured on 20times20times5 mm³ monolithic pixellated devices. Other material properties have been characterized using near-IR transmission microscopy, I-V, and Hall measurements. The material shows great potential toward producing large-volume detectors with excellent spectral performance for high-resolution gamma-ray spectroscopy, with uses in homeland security, nuclear nonproliferation, scientific research, and medical imaging applications.