Quantum Theory of Free Carrier Absorption

Publisher Website
Google Scholar
Abstract
The theory of photon absorption by free carriers in degenerate semiconductors is given taking into account the influence of nonparabolic energy bands and the effects of scattering by impurities, phonons, and plasmons. Analytical formulas for the imaginary part of the dielectric function, ϵ2(ω), are derived. The quality of the asymptotic expansions of ϵ2(ω) for low and high photon energies to approximate ϵ2(ω) over a wide range of frequencies is investigated numerically. It is found that within a few percent the classical Drude theory gives an excellent approximation for photon energies up to twice the Fermi energy of the electrons. In the opposite case, the approximation for high photon energies gives a rather poor approximation of ϵ2(ω) near the Fermi energy, except for ionized impurity scattering.