Sidewall lateral epitaxial overgrowth (SLEO) is a technique to reduce the extended defect densities in non-polar III-nitrides in a single re-growth by employing lateral overgrowth from sidewalls of an etched nitride through the mask openings. The technique involved depositing a stripe patterned mask over a-plane (11 (2) over bar0) GaN along < 1 (1) over tilde 00 >(GaN) and creating vertical {0001}c-plane sidewalls by etching of nitride through the openings in the mask at a depth so that in the first growth stage, coalescence was achieved from the sidewalls before the growth of defected material trench bottom impeded lateral sidewall growth. After achieving the first-stage coalescence from the sidewalls, the material was grown over in two subsequent stages-growing up through the window openings, and then over the mask region until a smooth coalesced film was achieved. In this paper, we describe the effect of growth variables on material quality in all three stages of growth evolution in SLEO until coalescence. With the SLEO technique, threading dislocation densities of 10(6)-10(7) cm(-2) and stacking fault densities Of 10(3)-10(4)cm(-1) were achieved in non-polar a-plane (11 (2) over bar0) GaN grown over r-plane sapphire. (c) 2007 Elsevier B.V. All rights reserved.