Commensurate and incommensurate structures in molecular beam epitaxially grown Ge<i>x</i>Si1−<i>x</i>films on Si(100)

Abstract

The transition between commensurate and incommensurate growth of GexSi1−x alloys on Si is observed directly by means of ion channeling and x-ray diffraction measurements. Molecular beam epitaxial films of thickness h up to 2500 Å thick show commensurate epitaxy for x≲50% and h≲hc, a critical thickness dependent upon x. The observed values of hc are discussed in terms of a model invoking the maximum theoretical interfacial shear strength and a barrier to misfit dislocation formation.