INTERACTIONS OF MISFIT DISLOCATIONS IN INXGA1-XAS/GAAS INTERFACES

The interactions between 60-degrees misfit dislocations with identical Burgers vectors have been examined by transmission electron microscopy in In(x)Ga1-xAs/GaAs strained-layer superlattices. The corresponding annihilation reaction at the crossing point of two perpendicular dislocations results in an asymmetric configuration with one inclined tip which has glided out of the interface plane towards the substrate. This is incompatible with the model proposed by Hagen and Strunk for the multiplication of misfit dislocations. This model is based on the occurrence of dislocation tips gliding towards the epilayer free surface with the help of the image forces exerted by this surface. Calculations of all the forces acting on interacting dislocations have thus been made taking into account the dissociated character of these dislocations. It is shown that image forces are negligible in the present case and that the occurrence of dislocation tips gliding towards the substrate can be explained by misfit stress forces that are generally higher than the mutual interaction elastic forces.