Electric field-induced retardation of the drift mobility of the photocarriers in SrTiO3 crystal

Transient photocurrent of SrTiO3 induced by excitation in the fundamental absorption has been measured by the time-of-flight method at low temperatures. The drift mobilities of electrons and holes at 4 K were evaluated to be 1.10×104 and 7.0×103 mm2 s-1 V-1, respectively. The result indicates that the hole as well as the electron is highly mobile in SrTiO3 crystal and that the photo-generated carriers relax into large polarons. We have found that the drift mobilities of the carriers are retarded with increasing the electric field. The field dependence of the drift mobility may arise from the polarization induced by the carrier relaxation with the external electric field.