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Highly Strained Si Films with Ultra-low Dislocation Density Grown on Virtual Substrates of Thin Thickness

By using compositionally graded SiGe films as virtual substrates, tensile strained Si films with the strain of 1.5% and the threading dislocation density less than 1.0 × 105 cm−2 are successfully grown in micron size windows by molecular beam epitaxy (MBE). The thickness of the virtual substrates was only 330nm. On the surface of the s-Si films no cross-hatched lines resulting from misfit dislocations could be observed. We attribute these results to the edge-induced strain relaxation of the epitaxial films in windows, and the patterned virtual substrates with compositionally graded SiGe films.