Low-Temperature Non-Ohmic Electron Transport in GaAs

The electric field dependence of the electrical conductivity and Hall effect in $n$-type epitaxial GaAs crystals was measured between 1.2 and 300°K. Some of the samples showed donor freeze-out, while others showed none down to the lowest temperatures. The non-Ohmic transport below 77°K was explained by a theory that included ionized-impurity and acoustic-phonon scattering, where the electron-phonon interaction was assumed to involve screened piezoelectric and deformation potentials. A treatment assuming an electron temperature and a second theory involving a direct calculation of the electron distribution function were compared with experiment. Only the theory involving a direct distribution-function calculation appears to explain the observations. A new model was proposed for the current-controlled negative resistance observed at low temperatures. This model depends upon the screening of impurity scattering and the electron-phonon interaction.