NATURE OF DISLOCATIONS PROMOTING GROWTH IN LIQUID-PHASE EPITAXY OF GALLIUM-ARSENIDE

Dislocations promoting growth in the course of liquid phase epitaxy (L PE) of GaAs layers on GaAs substrates are analysed by X-ray topography . The Burgers vectors are determined by comparing double-crystal back- reflection images with calculated misorientations taking into account surface relaxation. Any dislocation which generates a spiral of elemen tary steps is found to have a Burgers vector component parallel to the macroscopic growth direction. The nature of these growth promoting di slocations may be between pure screw and pure edge type. Defects which might be responsible for the generation of the observed concentric gr owth step patterns are below the detection limit of current X-ray topo graphy.