The Fermi Edge Correlation Singularity in Absorption Spectra of Modulation Doped Quantum Wells.
01 January 1988
The large concentrations of free carriers (electrons or holes) present in modulation doped quantum well (MDQW) samples have important effects on their optical properties. We discuss here the temperature dependent optical absorption and luminescence spectra of GaAs/AlGaAs and InGaAs/InAlAs n-doped MDQWs with emphasis on the peak seen at the edge of the absorption spectra of these samples. We present here a many-body calculation of the elctron-hole correlation enhancement, which identifies this peak with the Mahan exciton - the result of the Coulomb interaction between the photoexcited hole in the valence band and the sea of electrons in the conduction band. This calculation accounts for the strong dependence of the absorption edge peak on both the temperature and the carrier concentration, in good qualitative agreement with our data and with previously published results. We also analyze the changes induced by the carriers on the subband structure through self-consistent calculations, and we conclude that in these symmetric structures the changes are small for achievable carrier densities.