Dislocation propagation in GaN films formed by epitaxial lateral overgrowth

We have investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) the relationship between surface morphological e volution and dislocation propagation in GaN films formed by epitaxial later al overgrowth (ELO) in hydride vapour phase epitaxy. The SEM observations r evealed that step and terrace structures were formed on (0001) surfaces of the films both in the earlier and the later stages of growth, suggesting th e occurrence of step-flow growth during ELO. Bending dislocations with late rally propagated segments were frequently observed in the ELO films and the ir morphology led to a reduction in threading dislocation density in the fi lm surface regions. Systematic TEM observations were performed to reveal th e detailed structure of the bending dislocations. Comparison between the SE M and the TEM results showed that the lateral propagation of the dislocatio n was closely related to the appearance of the {1 (1) over bar 01} facets. A mechanism for dislocation propagation is discussed that explains the obse rved dislocation structure and surface step morphology.