Epitaxial lateral overgrowth (ELO) was employed for both c -plane and a -plane GaN layers on sapphire, and a more pronounced optical improvement was observed for the a -plane GaN as evidenced by the significantly increased band edge photoluminescence (PL). Room temperature near-field scanning optical microscopy studies explicitly showed enhanced optical quality in the wing regions of the overgrown GaN due to reduced density of dislocations, and for the a -plane ELO GaN sample the wings and the windows were clearly discernible from PL mapping. Time-resolved PL measurements revealed biexponential decays with time constants that were significantly enhanced for the a -plane ELO GaN (τ1 =0.08 ns, τ2 =0.25 ns) when compared to the non-ELO control sample but were still much shorter than those for the c -plane ELO GaN (τ1 =0.26 ns, τ2 =0.90 ns). © 2006 American Institute of Physics.