Fermi-energy-edge singularity in quantum wells containing more than one occupied subband

Abstract

A study of the Fermi-energy-edge singularity in asymmetric modulation-doped quantum wells is reported. It is shown that high densities of free carriers in filled n=1 electron subbands have no significant influence on the edge singularity in partly occupied n=2 subbands, demonstrating the weakness of intersubband Coulomb-scattering processes. The enhancement of oscillator strength at the Fermi energy is of very similar magnitude to that for excitonic transitions in undoped quantum wells.