Elastic Electron Scattering in Symmetry‐Induced Zero‐Gap Semiconductors

Relaxation times for elastic electron scattering in the symmetry‐induced zero‐gap semi‐conductors of zincblende structure are calculated, taking into account the nonparabolic character of the conduction band both in the density of states and the electron wave functions. The calculation is based on the band structure proposed by Groves and Paul and uses exact k · p solutions for the three‐level model of Γ8, Γ6, and Γ7 levels. Electron scattering by charged impurities and heavy holes, optical phonons (screened polar interaction) and acoustic phonons is considered. Spin‐flip transitions play an important role for all scattering modes. An anomalous q‐dependence of the static dielectric function due to low energy excitations between the Γ8 heavy hole and conduction bands is shown to have small effect on the ionized impurity scattering at low temperatures. It is demonstrated that transverse modes give a large contribution to acoustic scattering. In all cases the Γ8 symmetry of the band‐edge and the nonparabolicity of the band at higher energies have essential effect on the scattering processes.