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 calculations. On an As-monolayer-covered Si(100) surface, individual Ge or Si adatoms are found to incorporate rapidly into subsurface As sites with minimum surface diffusion. The segregation of As is initiated by the substitutional adsorptions of individual Ge or Si adatoms. Because of the rapid adatom incorporation, adatom mobility is drastically reduced, compared with the growth without surfactants, resulting in a high density of two-dimensional islands. The inclusion of gradient corrections to the LDA energies does not change our results.