Local strain in SiGe/Si heterostructures analyzed by X-ray microdiffraction

We have investigated, using X-ray microdiffraction, local strain and crystalline texture in SiGe layers fabricated under various growth conditions on Si(001) substrates. Two-dimensional reciprocal space maps and contour maps in a series of the X-ray rocking curves were taken from the SiGe layers with misfit dislocations having either a 60° or pure-edge character. Quantitative analysis for fine structures observed in the diffraction peak revealed that crystal domains with sizes ranging from 50 nm to 200 nm at tilt angles from 0.00° to 0.42° with respect to the Si[001] direction are formed in the layer relaxed with 60° dislocations. Furthermore, nonuniformity of crystalline texture having a size of 2 to 4 μm was also detected. On the other hand, no remarkable domain structures were detected from diffraction profiles when the sample is predominantly strain-relaxed by pure-edge dislocations. In this case, homogeneous strain distribution with reduced mosaicity is realized in the micrometer-sized regions.