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.