Growth of thick a‐plane GaN on r‐plane sapphire by direct synthesis method

Thick film growth of nonpolar a-plane GaN was carried out on r-plane sapphire by direct synthesis method for a substrate of homoepitaxy of a-plane GaN. A 30 μm thick a-plane GaN film was obtained at growth temperature at 1050 °C with a low-temperature buffer layer deposited at 700 °C. The surface was smooth but has some pits. Without a buffer layer, 20 μm thick a-plane GaN with much fewer pits was obtained. The best FWHM of XRD peak in ω-mode obtained was less than 700 arcsec. This film can be used as a substrate for a-plane III-nitrides growth.