FIRST-PRINCIPLES STUDY OF THE AS-MEDIATED GROWTHS OF SI AND GE ON SI(100)

We study the mechanism of the As-mediated epitaxial growths of Ge and Si on Si(100) surfaces through first-principles pseudopotential calcul ations. On an As-monolayer-covered Si(100) surface, individual Ge or S i adatoms are found to incorporate rapidly into subsurface As sites wi th minimum surface diffusion. The segregation of As is initiated by th e substitutional adsorptions of individual Ge or Si adatoms. Because o f the rapid adatom incorporation, adatom mobility is drastically reduc ed, compared with the growth without surfactants, resulting in a high density of two-dimensional islands. The inclusion of gradient correcti ons to the LDA energies does not change our results.