Non-destructive characterization and selection of X/γ-ray detector-grade CdZnTe crystals

Infrared (IR) transmission spectra and IR microscopy images were measured to evaluate the sliced CdZnTe crystals grown under different starting charges using modified vertical Bridgman method. Upon comparing the corresponding electric properties and charge transport performance, IR absorption within the wave-number range from 500 to 2500 cm^-1 was potentially attributed to the free carrier absorption caused by the ionized impurities. The size and density of Te particles were not sensitive to IR transmission spectra over the same wave-number range. However, the electric field was modified around isolated Te particles, in such a way that the impurities gettering in the Te inclusions. With respect to the high resistive CdZnTe crystals, IR transmission measurements demonstrated that the mean transmittance is higher than 60% in the wave-number region from 500 to 4000 cm^-1. IR microscopy shown the typical diameters of Te particles present in the material were in the range of 6-9 μm, and the density of the particles was 1-4×105 cm^-3. The obtained electron mobility lifetime product (μτ)e value was in the range of 1-3×10^-3 cm²·V^-1 by using well-known alpha particle spectra at room temperature. The fabricated CdZnTe thin planar detector showed the typical energy resolution was approximately 5.7% for the 59.5 keV peak at room temperature, without any additional signal processing.