Self-surfactant effect of As on a GaAs 111/A surface

We have theoretically investigated the effects of Ga- and As-adatom adsorption on a GaAs 111.A surface to reveal the epitaxial growth mechanism by using first-principles calculations. We found that the formation of Ga–Ga and Ga–As coupled structures make the Ga-vacancy site stable, while our previous study showed that the site is not the most stable site for one Ga-adatom adsorption. We also found that the Ga–As coupled structure is more stable than the Ga–Ga coupled structure, clearly indicating that As has a stronger stabilization effect on the Ga-vacancy site for a Ga atom. The GaAs lattice is maintained by the As adsorption in a self-organizing manner. Accordingly, As acts as a self-surfactant element. The importance of As suggested by the present calculations is consistent with the experimentally known fact that rather high As pressure is needed for the growth of the GaAs epitaxial layers on a GaAs 111.A surface. q2000 Elsevier Science B.V. All rights reserved.