Regular step bunching and ordering of Ge islands on vicinal Si surfaces

摘要

We describe the structural properties of regular surface steps, SiGe wire structures and periodic 2-dimensional arrays of Ge islands prepared by self-organized growth during molecular beam epitaxy on miscut Si(001) and Si(113) substrates. Biatomic surface steps on vicinal Si(001) induce a reduced critical thickness for Ge island formation and a weak alignment of islands along the steps. Deposition of a SiGe/Si multilayer results in pronounced step bunching and SiGe accumulation in wire-like, vertically correlated stripes with a typical lateral periodicity of 100 nm. The resulting 1-dimensional local strain fields cause a long-range alignment of islands in rows after deposition of Ge. The strain-mediated repulsive interaction between neighboring islands results in a 2-dimensional, closely packed array with hexagonal unit cell. The lateral ordering of islands reduces size fluctuations and suppresses ripening. Even more regular step-bunched surfaces and wire-like SiGe structures are observed from SiGe/Si multilayers on vicinal Si(113). Formation of ordered islands with deposition of Ge on such 1-dimensional Si(113) templates is not observed so far.