Photorefractive properties of nonstoichiometric Bi_(12)GeO_(20) crystals

摘要

We have grown Bi_(12)GeO_(20) single crystals from melts of different GeO_2 content. The absorption of the crystals increases with decreasing GeO_2 content in the melt. Furthermore, the samples show a significant variation of the photoconductivity and the effective trap density. Our results can be described by a one-center model with the intrinsic antisite defect Bi_(Ge) (Bi~(3+/4+) on Ge site associated with a hole) as dominant photorefractive center.