Strain relaxation in large lattice-mismatched epitaxial films, such as Ge and III-V materials on Si, introduces high threading dislocation densities. A thermodynamic model of threading dislocation density dependence upon film thickness was developed. According to this model, the quasi-equilibrium threading dislocation density of a given strain-relaxed film scales down with the inverse square of its thickness. The quasi-equilibrium threading dislocation densities in both Ge and GaAs films follow this model consistently. The model predicted the lowest possible threading dislocation density of a large lattice-mismatched film on Si (100), which was determined by the dislocation glide activation energy and the film thickness.

A Model of Threading Dislocation Density in Strain-Relaxed Ge and GaAs Epitaxial Films on Si (100). G.Wang, R.Loo, E.Simoen, L.Souriau, M.Caymax, M.M.Heyns, B.Blanpain: Applied Physics Letters, 2009, 94[10], 102115