On the formation of edge dislocations in In_xGa_1−xAs/GaAs heterostructures with x < 0·20

Abstract

A model for the formation of edge dislocations in In_xGa_1−xAs/GaAs heterostructures (with x < 0.20) is proposed. Each edge dislocation is the result of the combination of two 60[ddot] misfit dislocations which have glided from the interface into the substrate. This type of combination is very commonly observed in the immediate vicinity of annihilation and junction reactions between other 60[ddot] dislocations in the interface. This is explained by analysing the forces acting on the dislocations. These forces are either attractive forces between misfit dislocations with appropriate Burgers vectors that tend to expel them into the substrate, or forces which tend to keep the dislocations in the interface (return force F _r exerted by the interface and line tension force F _l). When the misfit dislocations lie in the interface, the attractive forces are much lower than forces F _r and F _l. On the contrary, in the immediate vicinity of annihilation and junction reactions, dislocation segments are expelled into the substrate and are then brought closer to each other, so that the attractive forces locally become high enough to balance forces F _r and F _l.