Interface Structure of Ge/Si Superlattices Determined by X-Ray Absorption Fine Structure

We illustrate the usefulness of the Extended X-ray Absorption Fine Structure (EXAFS) technique to determine the amount of interface mixing and strain condition in the study of (SimGen)p short-period superlattices. It is found that for n < 4, the number of Ge and Si nearest neighbours to Ge atoms is consistent with ~25% interfacial mixing and that the Ge-Ge bond length corresponds to that of coherently strained Ge. The Si-Ge bond length is shorter, close to that of a strained Si0.25Ge0.75 alloy. For n > 4, the Ge-Ge bond length and the number of Si-Ge nearest neighbours increase significantly consistent with partial relaxation and interdiffusion. Raman scattering spectroscopy and x-ray reflectometry measurements are also presented and are consistent with the conclusions of the EXAFS analysis.