The morphology and asymmetric strain relief behaviour of InAs films on GaAs (110) grown by molecular beam epitaxy

Abstract 30, 60 and 400 A thick InAs layers on GaAs (110) grown by MBE were studied using both TEM and X-ray diffraction techniques. Two different strain relief mechanisms, directly associated with (110) surface geometry, were observed in the two orthogonal directions [1 1 0] and [001]. In the [1 1 0] direction, the strain relief was via the nucleation of a regular array of Lomer type dislocations which have line direction u = [001] and Burgers vector b = 1 2 a [1 1 0] , whereas the relief in the [100] direction was via the generation of 60° type dislocations with u = [1 1 0] and b = 1 2 a 〈101〉 and 1 2 〈011〉 . The density of the latter was film thickness dependent. As a consequence, the overall strain relief of the InAs layers was thickness dependent and asymmetric in the thinner layers. The 60° type dislocations also give rise to local tilt about the [1 1 0] direction with large overall tilt in the thicker layer (400 A).