Determination of germanium content and relaxation in Si1-xGex/Si layers byRaman spectroscopy and X-ray diffractometry

We determine the germanium content and degree of relaxation in heteroepitax ial Si1-xGex/Si layers through a combination of Raman spectroscopy and X-ra y diffractometry. Our method uses the lattice constant nl of the partially relaxed layer, as determined by double-crystal X-ray diffractometry, in com bination with the Raman shift of the Si-Si vibrational mode. Samples with a Ge content of 0.20 < x < 0.35 and different relaxation values of 0 < R < 0 .7 were chosen to verify the accuracy of the method. The lattice constant a (perpendicular to) was determined within an error range of +/-5 x 10(-4) An gstrom using the angular distance between the 004 X-ray diffraction peaks o f the epi-layer and substrate recorded in symmetrical Bragg geometry. With this value a, and the Raman line shift of the Si-Si phonon, the values for the degree of relaxation and the Ge content are determined graphically from a chart based on a simple phenomenological model. The values obtained for x and R were validated independently by X-ray diffractometry and agree to w ithin +/-0.01 for x and +/-0.02 for R.