Non‐Polar a‐Plane AlN Growth on Nitrided r‐Plane Sapphire by Ga–Al Liquid‐Phase Epitaxy

Abstract

Growth of non‐polar AlN layers is important to realize high‐efficiency deep‐ultraviolet light‐emitting diodes. In this study, a‐plane AlN layers are fabricated by a combination of thermal nitridation and Ga–Al liquid‐phase epitaxy (LPE). Thermal nitridation at 1603 and 1623 K provides a‐plane AlN thin films with smooth surfaces on r‐plane sapphire substrates. However, these AlN films contain a double domain structure. Nitridation of r‐plane sapphire with an off‐cut angle can effectively eliminate the double domain structure. Moreover, a‐plane AlN films are grown homoepitaxially on the nitrided r‐plane sapphire substrates by Ga–Al LPE. Thus, a single‐domain non‐polar AlN film is successfully grown on nitrided r‐plane sapphire with an off‐cut angle.