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

A quantum mechanical model based on the second order perturbation theory wa s constructed for the calculation of the free-electron absorption coefficie nt in nonparabolic III-V semiconductors. The implemented model allows for t he calculation of the absorption changes when the free-electron gas tempera ture differs from the lattice temperature. Several mechanisms, which assist in the photon absorption process, were taken into account. At the consider ed lattice and electron temperature range and doping concentrations, the mo st important scattering mechanisms are impurity scattering, thermal and hot longitudinal optical phonon scattering, and finally acoustic phonon scatte ring. For all the interaction potentials we included the effect of screenin g by the conduction electrons. The model was developed in a fully consisten t nonparabolic way. The electron dispersion relation as well as the interac tion probabilities feature nonparabolic effects. Computations are performed for GaAs, InAs, and InSb at different mid-IR wavelengths, doping concentra tions, 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 a bsorption mechanisms is discussed. (C) 1999 American Institute of Physics. [S0021-8979(99)02807-8].