R-plane Sapphire Substrate for Non-polar GaN Film

R-plane sapphire used for epitaxial growth of non-polar GaN film was grown by the temperature gradient technique (TGT) method and chemical mechanical method was used to polish the r-plane sapphire substrate. The crystallization quality,optical property and surface roughness of as-obtained r-plane sapphire substrate were investigated. The average full width at half maximum (FWHM) of the substrate is 19.4arcsec and the dislocation density is 5.6×103cm-2. The transmission of the substrate is higher than 80% when the wavelength is longer than 300nm and the optical homogeneity is 6.6×10-5. The average surface roughness of the r-plane sapphire substrate is 0.49nm. The results indicate that as-obtained r-plane sapphire substrate meets the basic standard of GaN substrate.