Sb segregation effects have been studied in structures grown by organometallic vapor phase epitaxy. The structures are formed by periodic exposure of the GaAs (0 0 1) surface to trimethylantimony (TMSb), followed by GaAs growth. Reflectance-difference spectra obtained during growth show a strong influence of Sb on the surface reconstruction, reducing the concentration of As dimers. Transmission electron microscope images and X-ray diffraction (XRD) Measurements show that a periodic multiple quantum well (MQW) structure is formed by the TMSb/GaAs growth sequence. A fraction of the deposited Sb is incorporated as a one monolayer thick Sb-rich quantum well in each period. The incorporation of impurity Sb, as the GaAs layers are grown, results in the formation of a graded GaAs1-xSbx barrier layer above each QW layer. The impurity profile inferred from XRD measurements is in good agreement with a one-dimensional segregation model based on the partitioning of Sb between the growing barrier layer and a surface floating layer. The Sb floating layer is shown to desorb under exposure to tertiarybutylarsine. (C) 2003 Elsevier Science B.V. All rights reserved.