Epitaxial lateral overgrowth of GaN on nano-cavity patterned sapphire substrates

•We propose an epitaxial growth of GaN on nano-cavity patterned sapphire substrates.•Polystyrene sphere patterning was used to fabricate nano-cavities on the substrate.•Nanoscale epitaxial lateral overgrowth of GaN over the nano-cavities was studied.•Nano-cavity is effective in defect reduction, stress relief, and light scattering.