Electric Field Dependence of Conduction by Electrons in Nearly Pure Germanium

We have measured dc resistivity and its dependence on the electric field strength of 3-cm microwaves in $n$-type germanium and compared the data with values determined from numerical solutions of the Boltzmann equation. The variation of resistivity with temperature was sensitive to ion concentration and approached $T^{1.75}$ for the purer samples. An optical scattering coefficient of 0.55 times acoustical, chosen to give this exponent theoretically, also gave agreement with measurements of field dependence of resistivity and of its variation with microwave frequency for the purer samples.