60° dislocations in (001) GaAs/Si interfaces

Abstract

The geometry of 60° dislocations at the (001) GaAs/Si. heterojunction is discussed considering transmission electron microscopy images of plan-view samples. The GaAs examined was grown by molecular beam epitaxy on to a Si substrate, which had been polished to be 4° off the exact (001) plane, towards the [110] direction. Both 60° and pure edge dislocations may be present at the interface to accommodate the lattice misfit. The Burgers vectors of all the dislocations involved are (a/2)(110). The 60° dislocations interact with the network of orthogonal edge dislocations which is present at the interface and cause displacements of the edge dislocations. Because of the tilt of the heterojunction away from the exact 〈001〉 plane, the density of these 60° dislocations along [110] direction is different from that along ]110] direction. The changes in geometry when like 60° dislocations are dissociated is described.