Comparison of 1s-2s exciton-energy splittings between (001) and (111) GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As quantum wells

We have observed 2s excitonic emission from (111)-oriented GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As quantum wells. This observation enables us to make an accurate comparison of the 1s-2s exciton-energy splittings in the photoluminescence spectra of (111) quantum wells with those of (001) quantum wells. It is found that the binding energies of heavy-hole excitons are smaller in (111) quantum wells than in (001) quantum wells with the same well widths. This result is qualitatively consistent with theoretical predictions based on an effective-mass approximation.