Macroscopic effects and microscopic origins of gamma-ray irradiation on In-doped CdZnTe crystal

The effects of gamma-ray irradiation, exposed to a ⁶⁰Co source with a dose of 2.7 kGy, on In-doped CdZnTe (CdZnTe:In) crystal were investigated. We combined the “macroscopic” electrical properties of CdZnTe:In sample, evaluated by current–voltage (I–V) measurements at different temperature, with the “microscopic” origins of electrically active defects induced by gamma-irradiation, characterized by thermally stimulated current spectroscopy. It reveals that the bulk resistivity at room temperature have increased from 2.7 × 10⁹ Ω cm for the as-grown CdZnTe:In sample to 5.9 × 10⁹ Ω cm for the irradiated sample. Since the microscopic origins of these macroscopic effects are linked to the electrically active defects within the material, five main defect states (I, II, III, IV and V) were characterized and identified in the CdZnTe:In crystal. In particular, the introduction of gamma-irradiation altered the trap concentrations of these defect states, such as the rapidly decreasing concentration of region I. Besides, the gamma-ray irradiation caused a further deepening of E_DD level (region V) from the value of 0.717 ± 0.004 eV for the as-grown sample to the value of 0.749 ± 0.004 eV for the irradiated sample. The microscopic origin of E_DD level was identified with Te_Cd²⁺ below the conduction band minimum, which is responsible for the pinning of E_F level near the mid-gap, and thus for the observed high-resistivity performance of CdZnTe:In.