MODELING OF GE SEGREGATION IN THE LIMITS OF ZERO AND INFINITE SURFACE-DIFFUSION

A model to treat Ge segregation with simultaneous growth and exchange during Si/SiGe layer growth by molecular beam epitaxy is described. Wi thin this three layer formalism, the segregating layers were treated i n two limiting cases, a solid surface model in which no surface diffus ion occurs, and a fluid surface model, in which surface diffusion is v ery fast. Simultaneous treatment of exchange and growth within the flu id surface model was the only one of the two that allowed the accumula tion of Ge in the top two layers to significantly exceed that of the b ulk in surface alloys, in agreement with experimental observations.