Phonon strain shift coefficients in Si_(1-x)Ge_x alloys

摘要

A comprehensive study of the biaxial strain-induced shift of the Si_(1-x)Ge_x Raman active phonon modes is presented. High-resolution Raman measurements of Si_(1-x)Ge_x/Si heterostructures have been compared to x-ray diffraction data. Our approach, unlike previous works, is effective to decouple and quantify separately the effect of strain and composition on the phonon frequencies, yielding an accurate determination of the phonon strain shift coefficients in the entire composition range. Our results show that the strain shift coefficients are independent of the composition, a result which is in good agreement with theoretical calculations, performed within the framework of valence force-field theory.