Strain relaxation and dislocation introduction in lattice-mismatched InAs/GaP heteroepitaxy

Abstract

Misfit dislocation development in the lattice-mismatched InAs/GaP system was studied by transmission electron microscopy. InAs is 11% lattice mismatched with GaP, and the majority of strain relaxation during initial growth occurs by the introduction in misfit dislocations directly near island edges. Dislocation introduction in the islands has a significant impact on the island morphology and the prevailing state of strain. The island aspect ratio decreases with increasing dislocation content, which rapidly leads to island coalescence. However, the misfit is not completely accommodated before the layer becomes continuous. Subsequent strain relaxation occurs by the introduction of glissile pairs of 60° dislocations, which then combine to form sessile 90° segments at the interface. This latter mechanism is seen during early growth but becomes more pronounced after island coalescence occurs. Complete strain relaxation results in a two-dimensional network of predominantly edge misfit dislocations, spaced about 4 nm apart. Subsequent in-situ annealing induces the non-conservative motion of the misfit dislocations on the (001) plane to homogenize the spacing and, thus, to reduce the energy of the configuration.