A Physics-Based Empirical Model for Ge Self Diffusion in Silicon Germanium Alloys

We propose a physics-based model for the Ge self diffusivity in SiGe alloys and empirically fit the model to previously reported experimental results [1-3]. The dominant mechanism for Ge self diffusion in SiGe is the vacancy exchange mechanism since the published data on Ge diffasivity are in most cases for experiments done at temperatures lower than 1050 degrees C. We added two new terms to modify the regular diffusivity equation to relate the diffusivity to the change in Ge concentration. The first term is a consequence of the change in the point defects disorder entropy [4] as a result of adding more Ge atoms to the SiGe system. The second term is to account for the change in formation and migration enthalpies of the point defects due to the change in Ge content in the alloy.