On the role and modeling of compressive strain in Si-Ge interdiffusion for SiGe heterostructures

摘要

The role of compressive strain on Si-Ge interdiffusion in epitaxial SiGe heterostructures was systematically investigated both by experiments and by theoretical analysis. The Ge fraction x_(Ge) range (0.36-0.75) studied in this work extended to a wider Ge regime. With x-ray diffraction and Raman spectroscopy measurements, it was demonstrated that the epitaxial SiGe structures were kept pseudomorphic during the annealing. Complete theoretical analysis was presented to address the strain impact on the interdiffusion driving force, the interdiffusivity prefactor and the activation energy. The strain derivative of the interdiffusivity q', was shown to be temperature dependent, q' was quantitatively extracted from the experimental data in the Ge content range (0.36-0.75) and the temperature range (720-880 ℃), and is shown to have the form of q' = (-0.081T + 110) eV/unit strain, where T is temperature in Kelvin.