The use of the coherent potential approximation was proposed for the description of interdiffusion across the Si/Ge interfaces of SimGen superlattices. A generalization of the Kubo-Greenwood formula for optical conductivity within the coherent potential approximation was used to describe quantitatively the effect of interface diffusion upon the opto-electronic properties of the superlattices. The latter were described, within the tight-binding approximation, by using an orthogonal basis set which included interactions up to third-nearest neighbors. The results were in very good agreement with other theoretical approaches, and with recent experimental measurements of the optical absorption coefficient and the optical transitions in Si4Ge4 and SimGe10-m superlattices. This suggested that the present approach was computationally efficient and accurate.

I.A.Papadogonas, A.N.Andriotis, E.N.Economou: Physical Review B, 1997, 55[16], 10760-75