Influence of Nucleation Layers on MOVPE Growth of Semipolar (\(11{\bar{2}}2\)) GaN on m-Plane Sapphire

The influence of the underlying nucleation layer on the properties of semipolar \((11{\bar{2}}2)\) GaN grown on m-plane sapphire by metalorganic vapor-phase epitaxy has been investigated. \((11{\bar{2}}2)\) GaN epilayers of ~ 1 μm thickness were grown using four different initiating sequences: low-temperature AlN and GaN, and high-temperature AlN buffer layers, and directly (high-temperature GaN). The choice of nucleation layer had a pronounced effect on the surface morphology and crystal quality of the overlying GaN epilayer. In comparison, direct growth of \((11{\bar{2}}2)\) GaN without any buffer layer provided the best crystal quality with a rocking-curve \(\omega \) full-width at half-maximum (FWHM) value of 720 arcsec along the \([11{\bar{2}}{\bar{3}}]\) direction and relatively enhanced near-band-edge photoluminescence emission, thus showing this direct growth process to be a simple route for synthesis of semipolar \((11{\bar{2}}2)\) GaN layers.