Various types of growth instabilities in coherent epitaxy

Abstract

The instability of coherent epitaxial systems Ge/Si(0 0 1) is investigated. The qualitatively different features observed at low misfit (1 or 2%) and at larger misfit (more than 3%) are explained by a different type of nucleation of new terraces. At high misfit they are nucleated on the upper edge of existing steps and this triggers the sudden formation of three-dimensional bumps. At lower misfits, new terraces are nucleated near the centres of existing terraces and growth proceeds as in a pure crystal. The instability takes place at later times as an effect of kinetic roughness.