X-ray scanning microscope study of strain instabilities in low mismatched SiGe alloys grown on Si(001) substrates

An X-ray scanning microscope study of self-organized morphological defects arising during the growth of thick SiGe virtual substrates grown on Si(001) surface is reported. The 200 nm microscope resolution permitted to probe the local alloy composition. The measured variations of the Ge content in the alloy demonstrate that defect formation and evolution represent a strain relief mechanism. The observed large stress concentration inside the defect and the absence of the cross-hatch pattern on its internal facets are findings in close analogy with the lateral strain relaxation of self-organized islands in heterostructures.