Anomalous photoconductivity in SrTiO3

We have measured the photoconductivity of insulative SrTiO3 single crystal whose band-gap is 3.2 eV. We have found that the dependence of resistivity on temperature shows metallic conduction under white light irradiation and the resistivity drops rapidly below 105 K. This temperature at which a gian t photoconductivity phenomenon occurs coincides with that of the cubic-to-t etragonal structural phase transition, suggesting that the anomalous photoc onductivity is related to the structural phase transition.