Theoretical study of epitaxial growths on As-covered Si(100) surfaces

We investigate the energetics, diffusion, and reaction paths of Si and Ge adatoms on As-covered Si(100) surfaces through first-principles pseudopotential calculations. We find that at a monolayer coverage, individual Ge or Si adatoms incorporate rapidly into subsurface As sites with minimum surface diffusion. Thus, the segregation of As to the surface is initiated by single adatom exchange. Due to rapid adatom exchanges, the adatom mobility on surface is drastically reduced, compared to the growth mode without surfactants, resulting in a high density of two-dimensional islands. Generalized gradient corrections to the LDA energies do not alter our results