CdTe and CdZnTe detectors behavior in X-ray computed tomography conditions

The application of CdTe and CdZnTe 2D array detectors for medical X-ray Com puted Tomography (XCT) is investigated. Different metallic electrodes have been deposited on High-Pressure Bridgman Method CdZnTe and on Traveling Hea ter Method CdTe:Cl. These detectors are exposed to X-rays in the CT irradia tion conditions and are characterized experimentally in current mode. Detec tors performances such as sensitivity and response speed are studied. They are correlated with charge trapping and de-trapping. The trapped carrier sp ace charges may influence the injection from the electrodes. This enables o ne to get information on the nature of the predominant levels involved. The performances achieved are encouraging: dynamic ranges higher than 4 decade s and current decreases of 3 decades in 4 ms after X-ray beam cut-off are o btained. Nevertheless, these detectors are still limited by high trap densi ties responsible for the memory effect that makes them unsuitable for XCT. (C) 2000 Elsevier Science B.V. Ail rights reserved.