Nanoscale laterally epitaxial overgrown GaN layers were investigated on Si (111) substrate. Nanoporous SiO2 films on the surfaces of GaN/Si (111) were fabricated by inductively coupled plasma etching using anodic alumina templates as etch masks. GaN was grown over the nanoporous SiO2 layer using metalorganic chemical vapour deposition. Supersaturation of the source material was investigated to realize a continuous and smooth film. Nanoscale laterally epitaxial overgrown GaN layers were found to result in a significant reduction of threading dislocation density ≈108/cm2, characterized by atomic force microscopy and cross-sectional transmission electron microscopy. High quality GaN nano-rod arrays has also been demonstrated and investigated on Si (111) substrates. Nanoscale overgrowth was a promising method to improve the quality of GaN semiconductor materials for the commercialization of GaN devices on Si substrates. Orders of Magnitude Reduction in Dislocation Density in GaN Grown on Si (111) by Nano Lateral Epitaxial Overgrowth. K.Y.Zang, S.J.Chua: Physica Status Solidi C, 2008, 5[6], 1585-8