Interface roughness in quantum wells prepared with growth interruptions

We use photoluminescence to examine GaAs/(AlGa)As single quantum wells of different thickness grown by molecular beam epitaxy with and without growth interruptions. We observed distinctive peaks arising from the heavy-hole exciton splitting associated with heterointerface growth ‘‘islands.’’ Comparison of the exciton peak energies with the predictions of the theory proposed by L. C. Andreani and A. Pasquarello [Phys. Rev. B 42, 8928 (1990)] (which was supported by independent experiments) yields a constant value of 0.85 monolayers for the apparent thickness fluctuations given rise to the different exciton peaks observed from each well. This behavior strongly supports the bimodal roughness model of the heterointerface in quantum wells prepared with growth interruptions as it was recently suggested by C. A. Warwick and R. F. Kopf [Appl. Phys. Lett. 60, 386 (1992)].