Modeling silicon-germanium interdiffusion by the vacancy exchange and interstitial mechanisms

We present a comprehensive model for the interdiffusion of silicon (Si) and germanium (Ge) in single quantum well (SQW) structures. The model includes the vacancy exchange mechanism as well as interstitial diffusion. We explicitly account for lattice site conservation and the effect of Ge on the various material properties. We use well-established values from the literature without need of any adjustable parameters. The model fits experimental data for up to 25% Ge over the temperature range 800-1,200 degrees C under inert and oxidizing conditions. At high temperatures, nitriding anneals are also considered. We find that diffusion is dominated at temperatures below similar to 1,050 degrees C by the vacancy exchange mechanism, whereas the silicon interstitial dominates the diffusion at higher temperatures at least up to 15% Ge.