Nonequilibrium total dielectric function approach to the electron Boltzmann equation for inelastic scattering in doped polar semiconductors

Abstract

This paper describes a simple and general method for deriving the inelastic collision term in the electron Boltzmann equation for scattering from a coupled electron-phonon system, and applies the method to the case of doped polar semiconductors. In the Born approximation, the inelastic differential scattering rate $W^{inel}$ can be expressed in terms of the nonequilibrium total dynamic dielectric function, which includes both electronic and lattice contributions. Within the random-phase approximation $W^{inel}$ separates into two components: an electron-electron interaction containing the nonequilibrium distribution function for excitations of the electron gas, and a Fröhlich interaction including the phonon distribution function and self-energy due to polarization of the electrons. Each of these two interactions is screened by only the electronic part of the total dielectric function which contains the high frequency dielectric constant, unlike commonly used expressions which contain the static dielectric constant. Detailed balance between plasmons and electron-hole pairs in steady state is used to eliminate the nonequilibrium plasmon distribution from the Boltzmann equation, resulting in a dynamically screened electron-electron collision term. The phonon self-energy modifies the longitudinal optical phonon dispersion so that two hybrid normal modes contribute to the electron-phonon collision term.