Raman investigation of strain in Si/SiGe heterostructures: Precise determination of the strain-shift coefficient of Si bands

Raman scattering experiments were carried out on Si/SiGe heterostructures. The strain in both the top Si layer, and the Si1-xGex buffer layers with various Ge compositions was evaluated using several excitation sources, together with x-ray diffraction and secondary ion mass spectrometry. The strain-shift coefficient, which is a necessary quantity to evaluate the strain by Raman spectroscopy, was precisely determined. The dependence of the Si-Si band frequency on the Ge composition in the SiGe alloy was also examined. We found that the strained top-Si layers with a thickness below 25 nm experience coherent growth on Si1-xGex buffer layers with composition x < 0.35. (c) 2006 American Institute of Physics.