High-resolution electron microscopic studies were made of the (001) epitaxy of heterojunctions before and after lengthy vacuum annealing. The annealed interface structure consisted of a periodic array of perfect edge Lomer misfit dislocations with spacings which corresponded to a strain-free thin film. This represented the equilibrium microstructure. The as-deposited films were very thick, and were 3 or 4 orders of magnitude greater in thickness than the critical value. The latter was equal to less than a monolayer for large lattice mismatch systems. The microstructure corresponded to a metastable distribution of defects in that the thin-film residual strain was almost zero, and neighboring defects could react so as to create Lomer misfits. Various defects existed in the form of perfect misfit dislocations at the interface, and extended defects in the thin film. The extended defects resulted from the formation of stacking faults which were bounded by Shockley or Frank partials, and more complicated defect structures which were due to the interaction of perfect and partial dislocations on intersecting slip planes.

A.F.Schwartzman, R.Sinclair: Journal of Electronic Materials, 1991, 20[10], 805-14