Origin of Bi3+-related luminescence in Gd3Ga5O12:Bi epitaxial films

Photoluminescence characteristics of Gd3Ga5O12:Bi single crystalline films with different Bi contents grown by the liquid phase epitaxy are studied by the steady-state and time-resolved luminescence spectroscopy methods in the 4.2-500 K temperature range under excitation within the 3.8-6.0 eV. No ultraviolet emission, which could be ascribed to the radiative decay of the triplet excited state of Bi3+, is observed. Only visible emission is shown to arise from the Bi3+-related luminescence centers. Both the intense 2.54 eV emission and the weaker 2.46 eV emission of Gd3Ga5O12:Bi are shown to be of exciton origin. We suggest that they are due to the radiative decay of an exciton localized around a single Bi3+ ion and a dimer {Bi3+-Bi3+} center, respectively. The characteristic parameters of the corresponding exciton states are determined. The photostimulated processes, resulting in the localized excitons formation under excitation in the Bi3+-related absorption bands, are discussed. Peculiarities of Gd3+-Bi3+ energy transfer processes in Gd3Ga5O12:Bi are investigated. The possibility of application of Bi3+-doped gadolinium gallium garnets in scintillation detectors and light emitting diodes is considered.