The effect of image forces in GaN pyramidal nanorod structures was investigated in order to develop dislocation-free light-emitting diodes. A model based upon the eigenstrain method and non-local stress was used to demonstrate that the pyramidal nanorod efficiently ejected dislocations from the structure. Two possible regimes of filtering behavior were found: cap-dominated and base-dominated. The cap-dominated regime was shown to be the more effective filtering mechanism. Optimal ranges of fabrication parameters that favoured a dislocation-free light-emitting diodes were predicted and corroborated using available experimental evidence. The filtering probability was summarized as a function of practical processing parameters: the nanorod radius and height. The results suggested an optimal nanorod geometry with a radius of some 50b (26nm) and a height of some 125b (65nm), in which b was the magnitude of the Burgers vector for the GaN system studied. A filtering probability of greater than 95% was predicted for the optimal geometry.

GaN Nanostructure Design for Optimal Dislocation Filtering. Z.Liang, R.Colby, I.H.Wildeson, D.A.Ewoldt, T.D.Sands, E.A.Stach, R.E.García: Journal of Applied Physics, 2010, 108[7], 074313