Modeling germanium diffusion in Si1−xGex/Si superlattice structures

We present a model for the interdiffusion of silicon (Si) and germanium (Ge) in silicon germanium/silicon (Si1−xGex/Si) superlattice (SL) structures. Both a vacancy exchange mechanism and an interstitial diffusion mechanism are considered in the proposed model. The effects of Ge on the diffusion properties of the SL are also considered and the conservation of lattice site constraints is accounted for. Output from the model is compared to experimental Ge interdiffusion profiles for samples annealed in the temperature range 770–1125 °C in inert ambient and in some cases in oxidizing ambient, where the experimental samples contained Ge fractions up to 30%. For anneal temperatures up to 1075 °C a vacancy exchange mechanism is sufficient to describe the interdiffusion mechanism in Si1−xGex/Si SL structures. For higher anneal temperatures interstitial diffusion mechanism dominates the interdiffusion process.