Short-range deformation-potential interaction and its application to ultrafast processes in semiconductors

Abstract

The authors have developed a semi-empirical model for the short-range deformation-potential (DP) interaction in bulk (elemental or compound) semiconductors (not semiconductor alloys), which governs the transfer of carriers between different equivalent or non-equivalent conduction band (CB) valleys. Their formalism treats the electron-phonon interaction in the rigid-ion approximation and uses parametrized models for describing electrons (empirical local pseudopotential method) and phonons (shell models). The parameters for electrons and phonons were taken from the literature and no additional parameter was introduced to model the electron-phonon coupling. This model, when applied to the scattering times of electrons between different CB valleys in GaAs, gives reasonable agreement with a number of recent ultrafast optical experiments and resolves apparent contradictions between them. The present model can also be used in Monte-Carlo simulations of electronic transport under high-field conditions. The authors' main conclusion is that the simple formula for intervalley scattering due to Conwell (based on parabolic CB valleys for the electrons, an Einstein model for the phonons, and a single coupling constant describing the interaction) can only qualitatively explain most experiments and leads to differing values of the strength of the DP interaction. The full electronic band structure and all six phonon modes have to be taken into account in order to obtain a consistent picture.