NATURE AND ORIGIN OF PURE EDGE DISLOCATIONS IN LOW MISMATCHED EPITAXIAL STRUCTURES

A study of pure edge misfit dislocations (L-MDs) in SiGe/Si, Ge/GaAs, GaAlAsP/GaAs, GaAlAsSb/GaSb and InGaAsP/InP epitaxial structures grown by different techniques has been performed. A model for the formation of L-MDs from the parallel 60 degrees-MDs pre-existing at the interfa ce is proposed. The common dislocation node for these initial 60 degre es-MDs, arising as a result of the dislocation reactions in crossing p oints of the MDs, is a starting point for L-MD generation. Initial MDs with appropriate Burgers vectors may be located at the interface at a distance of up to 0.5 mu m apart. The process of L-MD propagation is accompanied by a shift of dislocations from the interface upwards into the epilayer or downwards into the substrate. The behavior of L-MDs i s discussed in terms of dislocation mobility in the epitaxial layer at the growth temperature in heterostructures.