Free-electron absorption in n-doped GaN semiconductors at mid-IR wavelengths in the strong phonon-plasmon coupling regime

We have calculated the free-carrier absorption coefficient for polar III-V semiconductors with strong LO phonon-plasmon interaction. We took several mechanisms into account, which assist in the photon absorption process. At the considered doping concentrations the most important scattering mechanisms are thermal LO phonon branch scattering, impurity scattering, plasmon branch scattering and acoustic phonon scattering. For all these interaction potentials screening by conduction electrons has been included. Computations are performed for beta-GaN and alpha-GaN doped semiconductors at different mid-IR wavelengths and doping concentrations. For all considered cases the relative difference between the Drude model calculation results based on static and dynamic damping factors is typically smaller than 25-30%.