Time and thermal recovery of irradiated CdZnTe detectors

摘要

The exposure of Cd_(0.9)Zn_(0.1)Te detectors to increasing doses/fluences of ionizing radiation seriously affects their spectroscopic performance. We have investigated the recovery process of irradiated detectors by means of photon spectroscopy (~(241)Am and ~(57)Co) and PICTS (photo-induced current transient spectroscopy) analyses, to study the evolution with time of their spectroscopic performance and to correlate it with the presence of defective states in the material. The temperatures of the annealing stages in our recovery process varied from room temperature to 380 K, while the time scale varied from 1 h to 4 years. We have observed an improvement of the material detecting properties with time at room temperature only after a long time (years) and for detectors that had not been severely degraded by the irradiation. Preliminary results on thermal treatments are also reported as they proved necessary to recover heavier damage. The recovery effect can be associated with a decrease in concentration of a few specific defective states, thus assessing the crucial role they play in determining the charge collection processes in the material.