Influence of interface localization on the binding energy of acceptor bound excitons in narrow GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As quantum wells

The role of interface roughness in bringing about localization of the free exciton in narrow GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As quantum wells is well known. In this paper we investigate the interaction of the localization potential due to interface roughness with that due to the presence of a shallow acceptor impurity. Using a selective excitation technique we are able to accurately measure the bound exciton binding energy in a narrow quantum well, thereby determining the effect of interface localization on the exciton to impurity binding energy. The binding energy decreases with increasing localization strength (due to interface roughness), a localization energy of 3 meV with respect to the free-exciton energy results in a decrease by 1.2 meV in the local binding energy of the bound exciton. The rapid diffusion of weakly localized free excitons is also demonstrated and contrasted with the absence of a similar migration process for bound excitons.