Thermodynamics of diffusion under pressure and stress: Relation to point defect mechanisms

A thermodynamic formalism is developed for illuminating the predominant point defect mechanism of self- and impurity diffusion in silicon and is used to provide a rigorous basis for point defect-based interpretation of diffusion experiments in biaxially strained epitaxial layers in the Si-Ge system. A specific combination of the hydrostatic and biaxial stress dependences of the diffusivity is +/- 1 times the atomic volume, deepending upon whether the predominant mechanism involves vacancies or interstitials. Experimental results for Sb diffusion in biaxially strained Si-Ge films and ab initio calculations of the activation volume for Sb diffusion by a vacancy mechanism are in quantitative agreement with no free parameters. Key parameters are identified that must be measured or calculated for a quantitative test of interstitial-based mechanisms. (C) 1997 American Institute of Physics.