Epitaxy: example 4 Using the critical thickness graph, estimate the maximum thickness for the Si and Ge epitaxial layers shown in the diagram to ensure they are defect-free. Assume the substrate is SiGe with a Ge composition of 40% and is fully relaxed. Si Ge Si Gen , substrate mismatch strain = (%) 10 SIGe on SI 151 critical thickness h, (nm) Ge composition