We report the results of systematic studies of the influence of the growth temperature on the morphology of GaAs/ (Al0.3Ga0.7)As quantum well interfaces. A combination of highly selective etching and subsequent atomic force microscopy measurements was used to investigate the interface morphology. A mesoscopic island structure was observed for the first time on heterostructure interfaces grown by molecular beam epitaxy. At high growth temperatures additional mesoscopic islands are grown on smooth macroscopic extended terraces, this phenomena is the dominant contribution to the inhomogeneously broadened exciton luminescence linewidth. (C) 2002 Elsevier Science B.V. All rights reserved.