Comparative investigation of semipolar (11-22) GaN grown on patterned (113) Si with different V/III ratios via MOCVD

We report on the growth of high-quality semi-polar (11-22) GaN with a smooth surface on a patterned Si (113) substrate by delicately tuning the V/III ratio in a three-step approach. The 2 mu m wide stripe SiO2 is first prepared by photolithography on the Si (113), and trenches were etched in Si (113) using KOH to expose Si (1-11) sidewalls. Subsequently, an AlN layer is grown on the (1-11) surface to prevent Ga-melting back etching, finally a high-temperature GaN layer and a low-temperature GaN layer are deposited. Scanning electron microscopy showed that the sample with V/III ratio for each step is 700/1500/1500 has the most smooth surface, and atomic force microscopy also showed that the root means square of the sample was only 5.2 nm (2 mu m x 2 mu m). The orientation of the GaN are examined by high resolution x-ray diffraction. In addition, x-ray rocking curve not only proved that GaN has anisotropy, but also demonstrated the existence of strain in the samples. The room temperature Raman and photoluminescence spectra confirmed the strain in the samples and showed a very low density of basal plane stacking faults.