Temperature dependence of the photorefractive effect in Bi12GeO20

The temperature dependence of the photorefractive effect in undoped and Ga-doped Bi12GeO20 (BGO) crystals was measured over the temperature range from 40 to 300 K. From comparison of the decay curves of the laser-induced grating with thermally stimulated current and photoconductivity curves, we conclude that the major decay step between, similar to 100 and similar to 160 K, is due to the thermal release of trapped electrons from a distribution of traps centered near 0.3 eV, in both types of EGO sample. Additional thermal decay steps, between similar to 200 and similar to 300 K, correlate with other electron traps, in the energy range from similar to 0.4 to similar to 0.7 eV. (C) 1998 American Institute of Physics. [S0021-8979(98)06116-7]