Strain measurement in thin pseudomorphic SiGe layers of submicron wires using Raman spectroscopy

The internal strain in thin heteroepitaxial Si 1− x Ge x layers was investigated before and after etching the material between the remaining narrow stripes. The strong inner stress in pseudomorphic heterostructures, caused by the difference in the lattice constants of Si and Si 1− x Ge x , relaxes in small regions after removing the surrounding layer material which mediates the stress. Strain and relaxation were determined from micro-Raman measurements. These measurements were compared with calculations using a two-dimensional finite element program to predict the strain distributions in Si 1− x Ge x layers. Assuming a pure elastic relaxation of the pseudomorphic strain we have found a reasonably good agreement between the measured and calculated Raman shifts.