Photostimulated Defect Creation Processes in the Undoped and Bi3+-Doped Ca3Ga2Ge3O12 Garnets

The thermally stimulated luminescence characteristics of UV-irradiated microcrystalline powders of the undoped and Bi3+-doped Ca3Ga2Ge3O12 garnets are investigated in the 80-510 K temperature range after selective irradiation in the 4.1-5.7 eV energy range. The dependences of these characteristics on the irradiation energy, temperature, and duration, as well as on the emission energy, are obtained. The origin of the electron and hole centers of different types responsible for the observed thermally stimulated luminescence glow curve peaks is clarified, and the depths of the corresponding electron traps are determined. The electron-hole recombination processes, resulting in the appearance of the intrinsic and Bi3+-related luminescence, are investigated. The mechanisms of the processes responsible for the photostimulated creation of various electron and hole centers under irradiation of the undoped and Bi3+-doped Ca3Ga2Ge3O12 garnets in the band-to-band transition region and in the energy ranges of the intrinsic and Bi-related absorption bands are proposed.