Electron Mobility in Semiconducting Strontium Titanate

The electron Hall mobility has been measured in semiconducting SrTi${\mathrm{O}}_3$ over the temperature range from 1.6 to 550°K. Electron concentrations in the range from 1×${10}^{17}$ to 2.5×${10}^{19}$ ${\mathrm{cm}}^{-3\mathrm{}}$ 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×${10}^4$ ${\mathrm{cm}}^2$/V sec were measured in niobium-doped samples having electron concentrations of approximately 2×${10}^{17}$ ${\mathrm{cm}}^{-3\mathrm{}}$. 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.