Diffusion and segregation in inhomogeneous media and the ${\mathrm{Ge}}_{\mathrm{x}}$${\mathrm{Si}}_{1\mathrm{-}\mathrm{x}}$ heterostructure

A theoretical groundwork has been laid for modeling dopant diffusion and distribution in semiconductor heterostructures. The driving force for the diffusion of a dopant is no longer simply given by its concentration gradient as in homogeneous semiconductors, but by the gradient of its chemical potential that derives from several contributions to the free energy of the solid solution, including two sources of strain energy and the variation of band gap with the composition of the heterostructure. Expressions for dopant flux and segregation are given.