DEFECT STATES IN ZNSE SINGLE-CRYSTALS IRRADIATED WITH GAMMA-RAYS

Defect states in ZnSe single crystals induced by Co-60 gamma-ray irradiation have been investigated with deep-level transient spectroscopy (DLTS) and optical deep-level transient spectroscopy (ODLTS). 5-MeV-electron-irradiated crystals have also been examined for comparison. With DLTS measurements it is found that two electron traps at E(c) - 0.27 eV and E(c) - 0.49 eV are newly introduced, and the concentration of an electron trap at E(c) - 0.30 eV, which exists in unirradiated ZnSe, is increased by gamma-ray or electron irradiation. Two additional electron traps located at E(c) - 0.15 eV and E(c) - 0.79 eV are also observed, and are unique to the gamma-ray and the 5-Mev-electron-irradiated material, respectively. In ODLTS spectra a newly introduced hole trap at E(v) + 0.71 eV and the increase in the concentration of a trap at E(v) + 0.19 eV are observed in the ZnSe irradiated with gamma-ray or 5 MeV electron. It is concluded that the electron trap at E(c) - 0.30 eV and the hole trap at E(v) + 0.71 eV are attributed to a Se and Zn vacancy-associated defect in the ZnSe single crystal, respectively. The hole trap at E(v) + 0.19 eV is tentatively identified as arising from an impurity Se vacancy complex.