Dislocation filtering in GaN by selective area growth through a nanoporous template was examined both by transmission electron microscopy and numerical modelling. These nanorods grew epitaxially from the (00•1)-oriented GaN underlayer through the approximately 100nm thick template and naturally terminate with hexagonal pyramid-shaped caps. It was demonstrated that for a certain window of geometric parameters a threading dislocation growing within a GaN nanorod was likely to be excluded by the strong image forces of the nearby free surfaces. Approximately 3000 nanorods were examined in cross-section, including growth through 50 and 80nm diameter pores. The very few threading dislocations not filtered by the template turn toward a free surface within the nanorod, exiting less than 50nm past the base of the template. The potential active region for light-emitting diode devices based on these nanorods would were entirely free of threading dislocations for all samples examined. A greater than 2 orders of magnitude reduction in threading dislocation density could be surmised from a data set of this size. A finite element-based implementation of the eigenstrain model was employed to corroborate the experimentally observed data and examine a larger range of potential nanorod geometries, providing a simple map of the different regimes of dislocation filtering for this class of GaN nanorods.

Dislocation Filtering in GaN Nanostructures. R.Colby, Z.Liang, I.H.Wildeson, D.A.Ewoldt, T.D.Sands, R.E.García, E.A.Stach: Nano Letters, 2010, 10[5], 1568-73