It was recalled that micro-pipes in 6H- and 4H-samples, grown by using the modified Lely technique, and nanopipes in GaN, grown via metal-organic vapor-phase epitaxy onto sapphire, had been attributed to Frank growth dislocations which had an empty core due to their large Burgers vectors. Such so-called killer defects had a deleterious influence upon device performance. A formation mechanism was proposed here for nanopipes and micro-pipes in hexagonal semiconductors.

P.Pirouz: Philosophical Magazine A, 1998, 78[3], 727-36