Observation of the 2s state excitons in (111)-oriented GaAs/${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As quantum-well structures

Transitions associated with the 2s excited-state heavy-hole excitons have been observed in the low-temperature photoluminescence excitation spectra of (111)-oriented GaAs/${\mathrm{Al}}_{0.3}$ ${\mathrm{Ga}}_{0.7}$As multiple quantum wells. The binding energy of the 1s heavy-hole excitons has been found to be about 10% larger in (111)-oriented quantum wells than that in (100)-oriented ones.