Hot free-electron absorption in nonparabolic III–V semiconductors at mid-infrared wavelengths

Abstract

A quantum mechanical model based on the second order perturbation theory was constructed for the calculation of the free-electron absorption coefficient in nonparabolic III–V semiconductors. The implemented model allows for the calculation of the absorption changes when the free-electron gas temperature differs from the lattice temperature. Several mechanisms, which assist in the photon absorption process, were taken into account. At the considered lattice and electron temperature range and doping concentrations, the most important scattering mechanisms are impurity scattering, thermal and hot longitudinal optical phonon scattering, and finally acoustic phonon scattering. For all the interaction potentials we included the effect of screening by the conduction electrons. The model was developed in a fully consistent nonparabolic way. The electron dispersion relation as well as the interaction probabilities feature nonparabolic effects. Computations are performed for GaAs, InAs, and InSb at different mid-IR wavelengths, doping concentrations, and lattice and electron temperatures. Our nonparabolic hot-electron model is validated with experimental results available in the literature. It turns out that our model is much more accurate and consistent than other more relaxed models. The competition between different hot free-electron absorption mechanisms is discussed.