Electron Mobility in Semiconducting Strontium Titanate

Abstract

The electron Hall mobility has been measured in semiconducting SrTi${\mathrm{O}}_{3}$ over the temperature range from 1.6 to 550\ifmmode^\circ\else\textdegree\fi{}K. Electron concentrations in the range from 1\ifmmode\times\else\texttimes\fi{}${10}^{17}$ to 2.5\ifmmode\times\else\texttimes\fi{}${10}^{19}$ ${\mathrm{cm}}^{\ensuremath{-}3}$ were obtained by reduction or by doping with niobium. The niobium donor centers remain fully ionized down to the lowest temperatures investigated. The low-temperature mobility in niobium-doped SrTi${\mathrm{O}}_{3}$ is approximately 4 times larger than in reduced SrTi${\mathrm{O}}_{3}$ over the concentration range investigated, and mobility values up to 2.2\ifmmode\times\else\texttimes\fi{}${10}^{4}$ ${\mathrm{cm}}^{2}$/V sec were measured in niobium-doped samples having electron concentrations of approximately 2\ifmmode\times\else\texttimes\fi{}${10}^{17}$ ${\mathrm{cm}}^{\ensuremath{-}3}$. The mobility results are compared with the behavior expected for scattering by ionized defects and polar optical lattice modes at low and high temperatures, respectively.