DIFFUSION AND SEGREGATION IN HETEROSTRUCTURES - THEORY, 2 LIMITING CASES, AND INTERNAL STRAIN

In a previous paper [Phys. Rev. Lett. 63, 2492 (1989)], the author presented a theory of dopant diffusion and segregation in semiconductor heterostructures, with special reference to the Si-GexSi1-x heterostructure. Here the theory is derived in a more rigorous procedure, leading to the discovery of a small error in the former. Furthermore, two important limiting cases in dopant concentration are analyzed, giving very different parametric dependences for the dopant chemical potential and the segregation coefficient. Finally, we address the issue of internal strain energy and its effects in chemical potentials in heterostructures. We find that the internal strain energy is generally quite small compared to the external, pseudomorphic epitaxial strain. The theory has recently been used by Hu et al. [Phys. Rev. Lett. 67, 1450 (1991)] to explain successfully their experimental results of the segregation of boron, phosphorus, and arsenic across a Si-GexSi1-x-Si heterostructure.