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GexSi1−x films are grown on Si by molecular beam epitaxy and analyzed by Nomarski optical interference microscopy, Rutherford ion backscattering and channeling, x-ray diffraction, and transmission electron microscopy. The full range of alloy compositions will grow smoothly on silicon. GexSi1−x films with x≤0.5 can be grown free of dislocations by means of strained-layer epitaxy where lattice mismatch is accommodated by tetragonal strain. Critical thickness and composition values are tabulated for strained-layer growth. Multiple strained layers are combined to form a GexSi1−x/Si strained-layer superlattice.

We have studied the growth of GexSi1−x alloys on Si(110) surfaces. For this growth normal, there are only two inclined {111} glide planes intersecting the interfacial plane. Both intersections are along the same in-plane [11̄0] direction, thus classic a/2〈110〉{111} glide misfit dislocations can form along only one interfacial direction. This produces an orthorhombic unit cell following strain relaxation by misfit dislocations. At sufficiently high stresses, previously unobserved misfit dislocation structures are activated. The critical thickness for misfit dislocation introduction is found to be shifted to lower Ge compositions with respect to growth on the (100) surface, consistent with a higher angular factor resolving the interfacial component of the dislocation Burgers vector in the (110) system.

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