Temperature-dependent conductivity of metallic doped semiconductors

We have analyzed the temperature dependence of the electrical conductivity of a series of metallic samples of Ge: Sb in the temperature range 10 mK to 1 K. We find a temperature dependence that is consistent with a sum of the behaviors predicted by Coulomb interactions and localization theories. The observed density dependence of the Coulomb contribution is consistent with theory but its magnitude differs by a factor of up to 4 if intervalley scattering is neglected. With our fitting procedure the dominant inelastic scattering process is electron-electron with a density dependence in reasonable agreement with theory. The magnitude of this scattering is enhanced by a factor of 2 over the prediction for weak scattering but is much too small to be properly described by existing strong-scattering theories.