Organometallic vapor phase lateral epitaxy and coalescence of GaN layers originating from GaN stripes deposited within 3-&mgr;m-wide windows spaced 3 &mgr;m apart and contained inSiO2masks on GaN/AlN/6H–SiC(0001) substrates are reported. The extent and microstructural characteristics of the lateral overgrowth were a strong function of stripe orientation. A high density of threading dislocations, originating from the interface of the underlying GaN with the AlN buffer layer, were contained in the GaN grown in the window regions. The overgrowth regions, by contrast, contained a very low density of dislocations. The coalesced layers had a rms surface roughness of 0.25 nm. ©1997 American Institute of Physics.