Preparation and characterization of polycrystalline CdZnTe films for large-area, high-sensitivity X-ray detectors

This article reviews the preparation and characterization of polycrystalline CdTe and CdZnTe films to be used in large-area, high-sensitivity X-ray panel detectors intended for medical diagnostics. The films, deposited by closed-spaced sublimation, are expected to exhibit excellent efficiency at low X-ray doses because of their high sensitivity. The detectors constructed using these films incorporated a novel hybrid technique, in which zinc-doped CdTe was pre-deposited onto a ceramic substrate and then connected to a TFT circuit substrate. The sensor substrate material was specially selected to avoid both incident X-ray attenuation in the substrate and micro-cracks in the film. Zinc doping, which was used to grow the CdTe film, also served to form the heterojunction diode structure that suppressed leakage current. Moreover, the quality of a polycrystalline CdZnTe film deposited on a 9″×9″ substrate was characterized, revealing its applicability to large-area X-ray detectors. Further investigation and improvements are in progress.