Observation of the Fermi-edge singularity in n-doped single asymmetric quantum wells: the influence of residual acceptors

The investigation of the evolution of the photoluminescence spectra, in single asymmetric quantum wells (SAQWs), from a typical emission spectrum to a Fermi-edge singularity, is carried out as a function of both the optical excitation intensity and the temperature. The three samples used here are n-doped, low carrier density (below 5 x 10(11) cm(-2)), GaAs/Al0.35Ga0.65As SAQWs grown by molecular beam epitaxy. The strong collective recombination of electrons with different k states up to the Fermi wave vector as well as the optical signature of the Fermi-edge singularity is observed in two samples containing residual accepters inside the GaAs SAQW. In contrast, a third sample containing no experimental evidence of residual accepters in the GaAs SAQW shows no optical signature of the Fermi-edge singularity. (C) 2001 Elsevier Science B.V. All rights reserved.