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

Abstract

Mis®t 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 of mis®t dislocations directly near island edges. Dislocation introduction in the islands has a signi®cant 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 mis®t is not completely accommodated before the layer becomes continuous. Subsequent strain relaxation occurs by the introduction of glissile pairs of 608 dislocations, which then combine to form sessile 908 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 mis®t dislocations, spaced about 4 nm apart. Subsequent in-situ annealing induces the non-conservative motion of the mis®t dislocations on the (001) plane to homogenize the spacing and, thus, to reduce the energy of the con®guration.