Defect structures were studied in GaAs/InGaAs/GaAs heterostructures, before and after thermal processing. Cathodoluminescence techniques permitted the non-destructive examination of bulk specimens, while transmission electron microscopy could be used to establish the details of dislocation configurations. In each as-grown specimen, the thickness of the InGaAs layer was above its critical value; so that 60° misfit dislocations were already present. It was shown that new pure edge (90°) dislocations formed at the interfaces during thermal processing at 1040K. Their Burgers vectors were a/2<101>, perpendicular to their <010> directions. It was noted that, although individual 90° misfit dislocations were more effective relievers of strain than were 60° dislocations, the self-energy of an array of such dislocations was higher and 60° misfit dislocations therefore formed first. A model for the formation of 90° edge misfit dislocations was proposed in which the climb of vacancy-producing jogs on pre-existing 60° dislocations left a trailing dislocation dipole.

Edge-Type Misfit Dislocations Produced by Thermal Processing of Pre-Relaxed InGaAs/GaAs Heterostructures. X.W.Liu, A.A.Hopgood, B.F.Usher, H.Wang, N.S.Braithwaite: Journal of Applied Physics, 2000, 88[10], 5975-80