Raman scattering in strained Si1-xGex layers under hydrostatic pressure
The Si-Si Raman mode in Si1-xGex layers pseudomorphically strained to Si and in bulk Si1-xGex was investigated as a function of externally applied hydrostatic pressure. The experiments demonstrate that bulk elastic properties can be derived from the pressure-dependent Raman investigations of thin strained hetero-epitaxial layers. Our experimental results are favourably analysed using linear interpolation for the components of elastic stiffness tensor of the Si1-xGexcompounds. It was found that the pressure derivative of strained Si1-xGex increases with the Ge concentration. Our analysis suggests that the Gruneisen parameter for strained Si1-xGex is higher than expected from linear interpolation between the Si and the Ge values and that it has slight negative pressure dependence.