Acceptor-bound excitons in GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As symmetric coupled-double-quantum-well structures

The effect of an electric-field perturbation on excitons bound to Be acceptors in symmetric coupled-double-quantum-well (CDWQ) structures has been studied with photoluminescence (PL) and photoluminescence excitation spectroscopy. The Be acceptors were positioned in the central region of each well. With an electric field perpendicular to the well layers, interwell and intrawell free excitons are observed in the PL spectra of CDQW’s. In weakly coupled DQW’s, interwell and intrawell excitons bound to neutral acceptors can be observed simultaneously. Only one (interwell) bound exciton is observed in a strongly coupled system. Interwell and intrawell bound excitons are found to have the same bound-exciton (BE) binding energies. This indicates that it is mainly the hole of the exciton which is attracted by the neutral acceptor impurity. No variations of BE binding energies with the strength of the electric field were observed for the weakly coupled DQW’s, while the binding energy increased with the electric field in a strongly coupled DQW. It was found that the BE binding energies at zero electric field in CDQW’s are equal to those obtained for center-doped single-quantum-well structures with the same well widths.