Modeling Si-Ge Interdiffusion by a Vacancy Exchange Mechanism

The vacancy exchange mechanism was used to model the interdiffusion of Si and Ge in Si/Si1-xGex/Si single quantum well structures. Diffusion was modeled for samples grown by molecular beam epitaxy and annealed at 900°C, 1000°C and 1100°C for different times in inert and oxidizing ambients. Intrinsic self diffusivities of Si and Ge as a function of Ge fraction in the structure used as the fitting parameters match values reported in the literature. Once these parameters were fixed for the inert ambient, the diffusion behavior under oxidizing conditions was completely accounted for by the model with no additional fitting parameters. Excellent fits were obtained in all the cases.