Ballistic electrons in GaAs and ZnS

Abstract

Ballistic electron scattering and transport in the compound semiconductors GaAs and ZnS are simulated by a Monte Carlo program based on the electron interaction with polar-optical and acoustic phonons, intervalley and interband scattering as well as impact ionization. These scattering processes are considered for higher electron energies and proved in a multiple energy band model of the materials in crystalline fcc-zinkblende structure. The energy band structure and the related density of states are calculated by the empirical pseudopotential method. The scattering processes were considered as intra- and inter-valley transitions within and between nonparabolic bands and in terms of effective mass tensors. A first check of the scattering and transport simulation is applied to electron drift velocity and mobility calculations demonstrating the well-known Gunn effect in these materials. Then, the high electric field transport is aimed at the avalanching process as well as at vacuum emission experiments as a direct spectroscopy of ballistic electrons. MC simulations as well as experimental vacuum emission spectroscopy show the presence of high energy electrons up to 6.5 eV in ZnS supporting the excitation mechanisms in thin film electroluminescence devices.