Photo-Hall Effect in Strontium Titanate

Abstract

The photoconductivity and the Hall mobility of photo-electrons in pure SrTiO₃ single crystals have been measured over the temperature range from 10 to 230°K. The measurements have used the conventional dc method and continuous illumination, but have suffered from no effect of space charge owing to the large dielectric constant of SrTiO₃. A large anomaly in the photoconductivity temperature dependence has been observed around 47°K. At corresponding temperatures the Hall mobility exhibits a slight anomaly. These anomalies are due to a ferroelectric transition of a small fraction of sample around 47°K. The Hall mobility μ_H exhibits a power-law temperature dependence of the form μ_H=1.25×10⁸T⁻³ cm²/volt·sec over the temperature range from 30 to 230°K and is proportional to T^−3⁄2 below 30°K, where T is the absolute temperature. These temperature dependences can be explained in terms of the mixed scattering by the intra-valley acoustical modes and the inter-valley optical modes.