Long propagating nanopipes in thick HVPE layers were analyzed by means of transmission electron microscopy. They were observed to behave like screw-component threading dislocations, terminated surface steps as hexagonal pits, and led to the possibility of spiral growth. The formation of a nanopipe was observed by the trapping of a screw dislocation at a pinhole that opened into an empty core. The mechanism of formation of nanopipes was expected to be linked to the growth kinetics of screw dislocations in the early stages of growth of highly strained material.

Nanopipes in Thick GaN Films Grown at High Growth Rate. E.Valcheva, T.Paskova, P.O.Å.Persson, B.Monemar: Physica Status Solidi A, 2002, 194[2], 532-5