High-resolution x-ray diffraction measurements of SiGe/Si structures

High-resolution x-ray diffraction is an excellent probe of strain relaxation in complex SiGe structures. The high flux provided by synchrotron sources enables us to make extensive reciprocal space map measurements and evaluate many samples. The diffraction peak positions of each layer in a step-graded structure, measured for two different reflections, yield quantitative values for the relaxation and alloy composition in the layer. Grazing-incidence diffraction allows us to determine the in-plane structure of very thin layers, which have thickness-broadened peaks at conventional diffraction geometries. We demonstrate the power of these techniques with two examples.