Fermi-edge singularity and band-filling effects in the luminescence spectrum of Be-δ-doped GaAs

Photoluminescence studies of the quasi-two-dimensional hole gas (2DHG) at a single Be-δ-doped layer in GaAs reveal Fermi-edge enhancement and photoinduced band filling in the low-temperature emission spectra. Strong radiative recombination is observed of the 2DHG with the photocreated electrons confined by GaAs/${\mathrm{Al}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As heterointerfaces placed at both sides of the doping spike. For optical excitation with a sufficiently large penetration depth to generate electrons on both sides of the doping spike, a filling of the valence subbands with photocreated holes is found for excitation power densities exceeding a certain threshold. Excitation with light generating electrons only at the near-surface side of the doping spike does not lead to such band filling, but yields luminescence spectra which show a strong enhancement in intensity at the Fermi edge. The observation of a Fermi-edge singularity is indicative for non-k-conserving recombination of electrons weakly localized at the topmost heterointerface.