Modeling germanium-silicon interdiffusion in silicon germanium/silicon superlattice structures

We present a model for the interdiffusion of silicon (Si) and germanium (Ge) in SiGe/Si superlattice structures. We considered both the vacancy exchange mechanism and the interstitial diffusion to fit the experimental data available in the temperature range 850-1125°C with Ge fraction up to 27% in SiGe. We considered the effect of Ge fraction on different material properties and we explicitly account for the lattice site conservation during the simulations. We were able to obtain excellent fits for all the cases. The same sets of fitting parameters can successfully describe the interdiffusion mechanism for both inert and oxidizing anneals for samples annealed below ∼1075°C, where we find vacancy exchange mechanism dominates the interdiffusion process. For higher temperatures, Si interstitials dominate the interdiffusion mechanism.