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

Abstract

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 4.2–500K temperature range under excitation within the 3.8–6.0eV. 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 2.54eV emission and the weaker 2.46eV 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.