Electronic properties of traps induced by γ-irradiation in CdTe and CdZnTe detectors

The knowledge of a detector response to different types of radiation sources is becoming a key issue for its employment in many medical, space and scientific applications. Nevertheless, a clear understanding of the effects of irradiation on the material properties is still a long way ahead and, therefore, we have started a thorough investigation of room temperature CdTe and CdZnTe detectors exposed to γ-ray irradiation. As-grown detectors have been exposed to increasing γ-ray doses, up to the virtual death of the detector, which occurs at a dose of 30 kGy. The modifications in the detector performance have been investigated by dark-current measurements and quantitative spectroscopic analyses at low and medium energies. The deep levels present in the material have been identified by means of Photo-Induced Current Transient Spectroscopy (PICTS) analyses. The evolution of the trap parameters with increasing irradiation dose has been monitored and a comparison of the results obtained from CdTe and CdZnTe detectors allows to achieve a better insight into the modifications of the material properties and performances after γ-ray exposure.