X-Ray Irradiation Effects on the Trapping Properties of Cd(1-x)ZnxTe Detectors

A high degree of control of the material charge transport and trapping properties is one of the crucial issues for a successful application of Cd-based compounds as room-temperature X- and γ-ray detectors. The behaviour of detectors when exposed to prolonged or intense radiation fields may be significantly altered due to the interaction between the impinging beam and the electronic structure of the atoms. The formation of electrically active defects following such irradiation alters the charge compensation processes that are responsible for the high resistivity of the material and ultimately affects the macroscopic performance of the detector. This contribution deals with the irradiation of Cd(1-x)ZnxTe based detectors with X-rays of 40keV energy using a Mo and a W anode to simulate the damage resulting from a prolonged exposure to diagnostic apparatuses for mammography and general purpose medical imaging. We investigated the effects induced by high X-ray doses by correlating γ-spectroscopy, current-voltage analyses and photo-induced current spectroscopy (PICTS). The evolution of the detector performance with the increasing radiation dose and the effects of the two different X-ray energies have been analysed and compared to previous results obtained on γ-ray (60Co) irradiated detectors to shine more light on the microscopic mechanism underlying the defect formation processes in Cd(1-x)ZnxTe . The formation of intrinsic defects is likely to be the major outcome of X-ray irradiation and we investigated the origin and nature of the dominant electrically active defects induced.