Irradiation-induced defects in Cd _0.9Zn _0.1Te:Al

The effects of gamma-irradiation, produced by a ⁶⁰Co source with a dose of 2.7 kGy, on defect levels in a Cd _0.9Zn _0.1Te:Al (CZT:Al) crystal were investigated by thermally stimulated current spectroscopy. Nine observed defect levels were identified, and the irradiation-induced variations of trap signatures for these levels, i.e., the thermal activation energy, concentration, and capture cross-section, have been evaluated using simultaneous multiple peak analysis. In addition, the dark-current spectra dominated by the deep donor (EDD) level have been certified. By fitting plots of the logarithm of dark current ln(IDC) versus 1/kT, the EDD level is determined to be 0.554 ± 0.001 eV and 0.792 ± 0.004 eV before and after gamma-irradiation, respectively. One month after irradiation, the EDD level moved slightly to 0.782 ± 0.003 eV. This result indicates that the EDD level is closer to the middle of the bandgap of CZT:Al after irradiation, which should be responsible for Fermi-level pinning near the middle of the bandgap, leading to high resistivity. This is consistent with the resistivity variation of CZT:Al at room temperature from the original value of 7.5 9 10 ⁹ ω cm before irradiation to the irradiated value of 5.6 9 10 ¹⁰ ω cm as determined by current-voltage measurements.