Density Dependence of the Exciton Energy in Semiconductors

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Abstract
We investigate both experimentally and theoretically the excitonic absorption in ZnSe in a temperature range between 2 and 60 K with increasing densities of carriers. For higher temperatures a weak redshift of the exciton resonance is found which turns into a blueshift for lower temperatures. While the widely used simplified treatment of the scattering processes within a static screening approximation fails completely to describe this thermally induced crossover, it can be explained by the interplay between Coulomb-Hartree-Fock renormalizations and carrier-carrier and carrier-polarization scattering including the dynamical screening.