Epitaxial lateral overgrowth (ELO) process has limited use in GaN devices due to the uneasiness of regrowth or the likeliness of contamination from the ELO mask, even though it is a method to reduce the dislocation density in GaN grown on sapphire substrate. Here we introduce a maskless and single-step ELO process using a high-dose N+-ion implantation. We employed a high-dose N+-ion implantation as an ELO mask instead of usual dielectric material such as SixNy or SiO2. The GaN layer was laterally grown over the ion implanted array formed in a stripe pattern of 4-μm-width, resulting in a complete coalescence after 30 min. TEM and photoluminescence analysis confirmed the reduced dislocation density of the ELO grown GaN layer.