Temperature dependence of the photorefractive effect in Bi12GeO20

A study was conducted on the temperature dependence of the photorefractive effect in undoped and Ga-doped Bi12GeO20 (BGO) crystals over the temperature of 40 to 300 K. Comparison of the decay curves of the laser-induced grating with thermally stimulated current and photoconductivity curves suggested that the major decay steps were due to the thermal release of trapped electrons from a distribution of traps near 0.3 eV. This indicated that the photorefractive effect in BGO is caused by trapping of electrons at the localized energy states.