Using time-resolved reflectance anisotropy spectroscopy (RAS) we studied in situ the dynamics of surface processes of Sb-covered GaAs(1 0 0) and InP(1 0 0) under metalorganic vapour-phase epitaxy conditions. Both Sb removal during a hydride purge and Sb incorporation during GaAs and InP overgrowth were monitored enabling the investigation of group V exchange reactions. Sb surface layers are found to be much more stable during purge with PH3 as compared to AsH3. Estimated activation energies are 2.5 eV for the Sb-P exchange processes and 1.1 eV for the Sb-As exchange reactions. These values reflect the low volatility of Sb compared to other group V adsorbates. During InP overgrowth Sb is rapidly buried at temperatures of 510degreesC and below while it is rather persistent on the surface at temperatures of 550degreesC and above. This transition indicates the existence of a highly mobile quasi-liquid InSb surface layer at temperatures above its melting point (similar to525 degreesC). (C) 2004 Elsevier B.V. All rights reserved.