SHALLOW TRAPS AND THE APPARENT SUBLINEAR PHOTOCONDUCTIVITY OF PHOTOREFRACTIVE BARIUM TITANATE

Abstract

We show that shallow acceptors reduce the lifetime of free holes and make the photoconducti-vity of barium titanate increase sublinearly with intensity both in the cw and pulsed illumination regimes. We also show that as-grown barium titanate crystals have quite different photorefractive properties depending on their relative density of deep donors and shallow acceptors, and we determine the depth of the shallow acceptors to be ~0.4 eV above the top of the valence bond.