60-DEGREES MISFIT DISLOCATION ARRAYS AT A GASB-GAAS(001) INTERFACE

Abnormal growth and relaxation of a GaSb film on GaAs(001) is studied by transmission electron microscopy. Irregularly shaped and abnormally large GaSb islands are relaxed by 60-degrees misfit dislocations. Having the same sign, these dislocations form a regular array which has been rarely observed in (001)-grown large-lattice-mismatched semiconductor heterostructures. The GaSb film consequently becomes tilted with respect to the substrate to remove the long-range stress field resulting from the vertical edge component of the Burgers vector of the 60-degrees dislocations. The measured angle of tilt agrees reasonably with the absence of a long-range stress field. The vicinality of the substrate does not necessarily induce 60-degrees dislocations, but it promotes 60-degrees dislocations to be a particular sign.