Hot-electron transport for many-valley semiconductors by the method of nonequilibrium statistical operators

Abstract

The method of the nonequilibrium statistical operator has been generalized to study high-field electron transport in many-valley semiconductors. For steady state, the balance equations for momenta, energies, and populations of the hot electrons in various valleys are derived. Taking n-type silicon as an example, we calculate the drift velocity, electron temperatures, and repopulations of both cold and hot valleys as functions of electric field (1--${10}^{5}$ V/cm) at several temperatures between T=8 K and T=300 K. By applying the electric field parallel to the 〈111〉, 〈100〉, and 〈110〉 crystallographic directions, the anisotropic effect for the drift velocity has been investigated. Furthermore, when considering the transient repopulation effect for a given sample with certain length, a negative-differential-mobility region has been obtained. It is shown that our results are not only in excellent agreement with the results of Monte Carlo method but also quantitatively comparable with experimental data in all temperature ranges.