Spatially resolved Raman spectroscopy of a step graded Ge _xSi_1-x strain relief structure

The structure of a strain relief region between a Si substrate and a low dislocation density Ge film has been measured by Raman spectroscopy. The composition of the structure has been determined with ≅1000 Å resolution in the growth direction, and the upper portions shown to be largely relaxed. The presence of microscopic inhomogeneities in these alloys is suggested.