Structural and optical characterization of (11‐22) semipolar GaN on m ‐plane sapphire without low temperature buffer layer

We reported the high quality semipolar (11‐22) GaN grown on m‐sapphire by using the novel two‐step growth method without low temperature GaN or AlN buffer layer. It is found that macroscopic surface morphology of semipolar GaN epilayer was very smooth, while microscopic surface structure was arrowhead‐like surface structure toward the direction of [1‐21‐1]. Anisotropic crystal properties of semipolar GaN/m‐sapphire were also observed by two incident directions of X‐ray beam. Therefore, we suggested that the anisotropic crystal properties and arrow‐head like surface structure would be caused by heteroepitaxial crystallograhpic difference between semipolar GaN and m‐sapphire. Additionally, photoluminescence (PL) measurements showed the strong bandedge emission of n‐type semipolar GaN without yellow luminescence (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)