Dissociated V-shaped dislocation model for the relaxation of strained single heterostructures

An energy equilibrium model for the prediction of the critical layer thickness of strained single heterostructures, based on relaxation by generation of dissociated V-shaped dislocations, is derived. In this model the dislocations in the layers under tensile as well as under compressive stress are assumed to be extended. The theoretical relation between the thickness and the lattice mismatch is compared with experimental results and with other equilibrium models as proposed in the literature. It is found that a good description of the critical thickness is given by the models assuming nucleation of semicircular perfect dislocation loops and nucleation of dissociated V-shaped dislocations. From kinetic and energetic considerations it is made clear that the model for dissociated V-shaped dislocations is preferred to the model for semicircular perfect loops.