A MOLECULAR-DYNAMICS STUDY OF THE CRITICAL THICKNESS OF GE LAYERS ON SI SUBSTRATES

Epitaxial growth can occur layer-by layer or by islanding. The mode of growth depends on the surface energies of the substrate and the epilayer. In cases of the growth of strained layers, the strain energy of the film also needs to be taken into account. This may result in the formation of misfit dislocations at the interface. Also where strain effects are important, initial layer-by-layer growth can become three-dimensional through islanding. Using the method of molecular dynamics and a many-body description of interatomic forces, we have made a study of the comparative energies of strained-relieved epilayers as well as (111) faceted islands of Ge on Si(001). We conclude that the critical thickness for this system is around 3 monolayers.