Recovery of radiation damage in CdTe and CdZnTe Detectors

The exposure of CdTe:Cl and Cd_0.9Zn_0.1Te detectors to increasing doses of ionizing radiation seriously affects their spectroscopic performance. We have investigated the recovery process of the detectors by means of photon (²⁴¹Am and ⁵⁷Co) spectroscopy and PICTS (photo-induced current transient spectroscopy) analyses, by studying the evolution with time of their spectroscopic performance and correlating it with the presence of defective states in the material. In our recovery processes, the temperatures of the annealing stages varied from room temperature to 380 K, while the time scale varied from 1 hour to 4 years. We have observed a clear improvement of the material detecting properties with time at room temperature only after long times (years) and for detectors that had not been severely degraded by the irradiation. Thermal treatments were necessary to recover heavier damage. The recovery effect can be associated to the decrease in concentration of some specific defective states, thus assessing the crucial role they play in controlling the charge collection