Defect structures in films which had been grown using hydride vapor-phase epitaxy were characterized by using transmission electron microscopy. Growth was obtained on SiO2-stripe patterned GaN layers that had been grown, by metal-organic vapor-phase epitaxy, onto sapphire substrates. Cross-sectional transmission electron microscopy unambiguously revealed that most of the dislocations, which originated from threading dislocations that were aligned vertically in the metal-organic vapor-phase epitaxial layer, propagated laterally around the SiO2 mask, in the hydride vapor-phase epitaxial film, before the film thickness attained 5μ. This change in the propagation direction prevented the dislocations from crossing the film, to the surface region, and thus led to a sharp reduction in the threading dislocation density of thicker films.

A.Sakai, H.Sunakawa, A.Usui: Applied Physics Letters, 1997, 71[16], 2259-61