Luminescence and defects creation processes in Bi3+-doped gallium garnets

Abstract

Microcrystalline powders of Y3Ga5O12:Bi and Gd3Ga5O12:Bi are investigated by the X-ray diffraction, scanning electron microscopy, time-resolved photoluminescence, and thermally stimulated luminescence methods in a wide temperature range (4.2–500 K). The results are compared with those obtained recently for the Lu3Ga5O12:Bi powder. The presence of the ultraviolet (UV) emission of a Bi3+ ion and the visible (VIS) emission of an exciton localized around the Bi3+ ion is confirmed for all the investigated gallium garnets. The processes of photostimulated creation of electron and hole centers taking place under irradiation in the 4–6 eV energy range are investigated. The origin of the hole centers responsible for the UV and VIS electron recombination luminescence is clarified. Electron transitions between the energy levels of Bi3+ ions and the Bi3+ → Ga3+oct, Bi3+ → Ga3+tetr, and Bi3+ → Y3+ or Bi3+ → Gd3+ electron transfer transitions are found to appear in the photo- and thermoluminescence excitation spectra. The Bi3+ energy level positions in the band gap are determined. Their influence on the luminescence and photostimulated creation of electron and hole centers is discussed.