Recovery of radiation damage in CdTe and CdZnTe detectors

The time and thermal recovery of the spectroscopic capabilities of CdZnTe and CdTe detectors, irradiated with different doses of various ionizing radiations, such as electrons, low-energy neutrons, high-energy neutrons and protons, have been investigated by PICTS (Photo Induced Transient Spectroscopy) measurements, by leakage current analyses and by 241Am and 57Co gamma spectroscopy. The time recovery has been studied by testing at different time intervals the detectors after they had been stored at room temperature in the dark for up to 4 years after irradiation. The evolution of the spectroscopic properties correlated with the evolution of the defective states provided clear indications of the role played by some of the identified defects in the degradation of the detectors’ properties. Most of the detectors show a good recovery of their spectroscopic capabilities with time, even though only in few cases a complete recovery could be observed. In order to accelerate the radiation damage recovery and to study its thermal activation energy, we have also performed annealing treatments on selected detectors. The effects of different thermal ramps and of biasing have been considered. Both isothermal and isochronal annealing stages have been performed to assess the most favorable time/temperature ratio that could be applied to better restore the starting spectroscopic properties of the irradiated detectors.