Equivalence of Lei and Ting balance equations for nonlinear electronic transport and a Boltzmann approach

We discuss the connection between the Greens-function approach to nonlinear electronic transport in semiconductors proposed recently by Lei and Ting [Phys. Rev. B 32, 1112 (1985)] and the description of high-field transport based on the familiar nonlinear Boltzmann equation. We show that their balance equations are identical to those one obtains from the Boltzmann equation by assuming that the carrier distribution function is a displaced Fermi-Dirac distribution at the electron temperature Te.