Modeling of Ge surface segregation in vapor-phase deposited Si_{1 - x}Ge_x thin films

Recent experimental results concerning Ge segregation in Si_{1 - x}Ge_x epitaxial thin films deposited on Si(100) substrates using Si₂H₆ and GeH₄ cannot be accounted for by a simple two-site model involving surface and bulk states. This is due to Ge enrichment in the subsurface layers. Here, we demonstrate that a simple model based on the regular solution theory, which invokes both nearest, and next-nearest neighbor interactions, can explain the Ge enrichment in the subsurface. A computer simulation using the Monte Carlo method verifies the assumptions made in the model, and both methods show excellent agreement with the experimental data.