MIGRATION OF GA ATOMS DURING SI MOLECULAR-BEAM EPITAXIAL-GROWTH ON A GA-ADSORBED SI(111) SURFACE

Ga atom migration during Si molecular beam epitaxial growth on a Ga-adsorbed Si(111) square-root 3 x square-root 3 surface is investigated by microprobe reflection high-energy electron diffraction. Ga atom migration in the depth direction (surface segregation) and termination of Si dangling bonds by Ga atoms cause a reduction of the production rate of two-dimensional nuclei and an enhancement of surface diffusion of Si atoms during Si-MBE. This improves the crystallinity of Si-grown films. Ga atom migration in the lateral direction is also investigated using a partially Ga-adsorbed surface. The Ga-adsorbed areas are preserved during Si-MBE at low substrate temperature (approximately 300-degrees-C), and during annealing of the sample at high substrate temperature (approximately 600-degrees-C). The adsorbed areas clearly change during Si-MBE at high substrate temperature (approximately 600-degrees-C). This indicates that Ga atoms migrate in the lateral direction on the surface when interchange between Si atoms and Ga atoms occurs in the surface segregation process of Ga atoms during Si-MBE.