Plan-view and cross-sectional transmission electron microscopic studies were made of columnar defects in nitride films which had been epitaxially grown onto (00•1) sapphire. They were identified as being open-core (00•1) Burgers vector dislocations. Their behavior along the film thickness alternated between open-core sections (nano-pipes) and closed-core sections. This alternating behavior was observed within the first 0.5 from the interface with the sapphire.

P.Vennéguès, B.Beaumont, M.Vaille, P.Gibart: Applied Physics Letters, 1997, 70[18], 2434-6