Dislocation studies in VCz GaAs by laser scattering tomography

Laser scattering images of decorated dislocations in the as-grown state of semi-insulating VCz GaAs are presented. They show the state of dislocation patterns in the temperature range of about 800-1100 degreesC. The courses o f the dislocations can be classified in nearly straight lines, plane curved lines and spatially curved lines. The appearance of plane curved lines is striking. A well-developed cellular structure appears in the wafer centre. The cells are globularly shaped. A substructured dislocation network was di scovered in their walls. Separate dislocation lines and incomplete cells ex ist at half the radius of the wafer. In the peripheral region dislocation t angelings and lineages are present. The lineages contain an enormous number of slip lines within one of the {1 1 1} planes, Everywhere in the crystal certain I I I glide planes are strongly populated by plane curved dislocati ons. However, other planes, not belonging to the basic glide systems are po pulated too. The LST results confirm that the majority of dislocations is d ue to stress. The plane population of glide planes give hints to the direct ion of the shear stress. (C) 2001 Elsevier Science B.V. All rights reserved .