Heteroepitaxial growth of semipolar (11-22) GaN without low temperature GaN buffer layer grown on m-sapphire substrate

We investigated high quality semipolar (11-22) GaN epilayers were grown by novel 2-step growth method, which consisted of GaN (the first step) with N2 atmosphere and GaN (the second step) with H2 atmosphere at the growth temperature above 1000 ο C without low temperature (LT) GaN or high temperature (HT) AlN buffer layer. As a nucleation layer, the thickness of GaN with N2 atmosphere was varied from 0.3 to 0.1 µm. The full width at half maximum (FWHM) of X-ray ω-rocking curve (XRC) was decreased from 1088 to 951 arcsec with reducing thickness of nucleation layer. After fixing 0.1 µm-thick GaN with N2 atmosphere, semipolar GaN epilayers were grown by controlling V/III, growth pressure and growth temperature under H2 atmosphere. From these results, we could achieve the minimum XRC FWHM of 602 arcsec with increasing V/III, growth pressure, and growth temperature.