Influence of the electron-hole spatial separation on the magnetoluminescence measurements of the fractional-quantum-Hall-effect energy gaps

Specially designed single GaAs-${\mathrm{Al}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As heterojunctions with two monolayers of acceptors located at different distances from the interface have been studied by luminescence experiments. Using a time-resolved technique we distinguished the two channels of luminescence corresponding to radiative recombination of two-dimensional electrons with holes bound to acceptors from these two monolayers. Comparison of the fractional-quantum-Hall-effect (FQHE) energy gaps derived from these two recombination channels allows us to measure the corrections to the FQHE gaps associated with the finite e-h spatial separation.