A method of forming a III-V semiconductor vertical fin is provided. The method includes forming a fin mandrel on a substrate, forming a spacer layer on the substrate surrounding the fin mandrel, forming a wetting layer on each of the sidewalls of the fin mandrel, forming a fin layer on each of the wetting layers, removing the fin mandrel, removing the wetting layer on each of the fin layers, and forming a fin layer regrowth on each of the sidewalls of the fin layers exposed by removing the wetting layer from each of the fin layers.