Based on the facts that: (a) the transverse acoustic vibrational branch frequency is softened at the Brillouin zone boundaries of crystalline GaAs; (b) at the surface, the Ga-As bond is stronger than Ga-Te bond; and (c) the requirement that the final bond orientation of the Te surfactant should be rotated by 90degrees with respect to its initial orientation, we carried out a model study of an exchange process in epitaxial growth of GaAs (100). Even with very restrictive conditions imposed on the atomic movements, this study explains why Te is an effective surfactant for this type of growth. (C) 2002 Elsevier Science B.V. All rights reserved.