Recovery of radiation damage in CdTe detectors

The exposure of CdTe:Cl detectors to increasing doses/fluences of ionizing radiation seriously affects their spectroscopic performance and operation. We have investigated the recovery process of irradiated detectors by means of photon spectroscopy (241Am and 57Co) 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 time recovery processes the scale varied from 1 hour to 4 years, while the temperatures of the annealing stages varied from room temperature to 380K. We have observed an improvement of the material detecting capabilities with time at room temperature only after long times (years) and only in the case of 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 efficiency processes