Improved CdZnTe detectors grown by vertical Bridgman process

The gamma ray (Co-57) and a particle (Am-241) detector response of Cd1-xZnxTe crystals grown by vertical Bridgman technique was studied under both positive and negative bias conditions. Post-growth processing was utilized to produce a high-resistivity material with improved charge-collection properties. Samples of various Zn concentrations were investigated by I-V measurements and thermally stimulated spectroscopies to determine the ionization energies of deep levels in the band gap. When the post-processing conditions were optimized the low-energy tailing of the gamma-ray photopeaks was significantly reduced and an energy resolution of under 5% was achieved for the 122 keV gamma-photon line in crystals with x=0.2 Zn content at room temperature. A peak to background ratio of 14:1 for the 122 keV photopeak from Co-57 was observed on the best sample, using a standard planar detection geometry. The low-energy 14.4 keV X-ray line could also be observed and distinguished from the noise.