CLUSTER MODEL STUDY ON GAAS EPITAXIAL CRYSTAL-GROWTH BY AN ARSENIC MOLECULAR-BEAM .3. AS4 MOLECULAR-BEAM

We examined the mechanism of GaAs epitaxial crystal growth with an As4 cluster beam on the Ga-stabilized GaAs(100) surface using the cluster model and the Hartree-Fock and Moller-Plesset second-order perturbati on methods. Our results indicate that when the surface is irradiated w ith the As4 beam, the As4 cluster is adsorbed at a ditch site of the G aAs surface and dissociated: two As atoms are dissociatively adsorbed onto the surface to give a new As-layer and the other two As atoms are released into vacuum as an As2 molecule. Alternatively, two As4 clust ers can be coadsorbed on the surface and dissociated: four atoms of th e two As4 clusters are dissociatively adsorbed on the surface to give a new As-layer and the other four As atoms are released into vacuum as an As4 cluster. Thus, the present results confirm a previously propos ed reaction.