GaAs (100) substrates prepared in a quartz chamber under a H-2/As-4 flux, and then exposed to air were used for the subsequent growth of GaAs-AlGaAs single quantum wells by molecular beam epitaxy. The substrates prepared by this method showed atomically at surfaces corroborated by atomic force microscopy analysis. Quantum wells grown directly on these substrates without a GaAs buffer layer exhibited narrow and intense photoluminescence peaks, an indication of a high quality material. The secondary ion mass spectroscopy analysis showed oxygen and carbon traces on the. first AlGaAs barrier layer grown after air exposure with no effects on the quantum wells optical emissions. From the results we conclude that the prepared GaAs surfaces are useful for the epitaxial growth of high quality quantum structures. (C) 2008 Elsevier B. V. All rights reserved.