Defect reduction in semipolar {101̄3̄} GaN grown on m-sapphire via two-step nanoepitaxial lateral overgrowth

A method to obtain high quality semipolar {10} GaN grown on m-plane sapphire is presented. This method is similar to two-step nanoepitaxial lateral overgrowth (2S-NELOG) by combining a TiN interlayer and self-assembled SiO2 nanospheres. For the 2S-NELOG semi-GaN, the root-mean-square (RMS) roughness is 1.8 nm with a scan area of 5 × 5 μm2. The reduction of the defect density is demonstrated using high resolution X-ray diffraction (HRXRD) and transmission electron microscopy (TEM). The full widths at half maximum (FWHMs) of the on-axis X-ray rocking curves (XRCs) are 381 and 524 arcsec, respectively rocking toward the [30] direction and the [110] direction. The anisotropy of the mosaic is lower compared to planar and TiN semi-GaN. In addition, Raman analyses also show the partial relaxation of the stress in the 2S-NELOG semi-GaN.