Two-dimensional hole gas and Fermi-edge singularity in Be δ-doped GaAs

The subband structure of the quasi-two-dimensional hole gas (2DHG) formed at a single Be δ-doped layer in GaAs has been studied by photoluminescence spectroscopy. To confine the photogenerated minority carriers, and thus to enhance the efficiency of radiative recombination from the 2DHG, the δ-doping spike was placed in the center of an ${\mathrm{Al}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As/GaAs/${\mathrm{Al}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As double heterostructure. Recombination involving different hole subbands has been resolved which enabled us to analyze the subband occupation as a function of dopant concentration and sample temperature. In sample structures where the Fermi level is located close to unoccupied subbands, a pronounced Fermi-edge singularity (FES) is observed in the low-temperature (