Journal of Crystal Growth, Vol.231, No.1-2, 22-30, 2001
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 of 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 discovered in their walls. Separate dislocation lines and incomplete cells exist at half the radius of the wafer. In the peripheral region dislocation tangelings 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 dislocations. However, other planes, not belonging to the basic glide systems are populated too. The LST results confirm that the majority of dislocations is due to stress. The plane population of glide planes give hints to the direction of the shear stress.
Keywords:crystal structure;defects;light scattering tomography;Czochralski method;semiconducting gallium arsenide