Oblique-angle sputtered AlN nanocolumnar layer as a buffer layer in GaN-based LED

► An AlN nanocolumnar buffer layer prepared by oblique-angle (OA) deposition. ► GaN-based LED structures were grown on a sapphire substrate with an AlN nanocolumnar buffer layer. ► The OA-AlN nanocolumnar layer has a diameter of about 30-60 nm.