CdZnTe material uniformity and coplanar-grid gamma-ray detector performance

“Electron-only” detection techniques such as the coplanar-grid method are effective in overcoming some of the charge transport problems of CdZnTe and, consequently, have led to large-volume gamma-ray detectors with good energy resolution while operating at room temperature. A requirement for the success of these techniques is uniformity in electron generation and transport. Once large inhomogeneities in these properties caused by grain boundaries and other large-scale crystal defects are eliminated through simple material screening techniques, small variations remain and limit the gamma-ray energy resolution. In this paper we present the results from our characterization and analysis of these nonuniformities in commercially available CdZnTe, and we establish the relationship between the nonuniformities and the ultimate coplanar-grid gamma-ray detector performance through experimental measurements