Partial dislocations, columnar growth, clustering, and pinhole formation in ultrathin film semiconductor heterostructures

Island growth of partially ionic semiconductor films (such as GaAs or CuBr) on covalent substrates (such as Ge) may produce not only misfit dislocations but also partial dislocations and antiphase boundaries because of randomization of the translational diatomic phase registry of the ionic phase during multiple island nucleation. It is suggested that such partial dislocations may play an important role in the asymmetry of epitaxial crystal growth of Ge on GaAs compared to GaAs on Ge observed in recent MBE experiments, and may explain nontransitivity of band-edge discontinuities.