Growth of High-Quality AlN and AlGaN Films on Sputtered AlN/Sapphire Templates via High-Temperature Annealing

We investigated the fabrication and characterization of AlN and AlGaN epilayers grown on sputtered and annealed AlN/sapphire templates by metal organic vapor phase epitaxy. The surfaces of the AlN homoepilayers exhibited clear step-terrace structures with minimal root mean square roughness values. X-ray rocking curve (XRC) measurements showed that the AlN homoepilayers had smaller (1012)-plane full width at half maximum (FWHM) values (192 arcsec) than the AlN/sapphire templates did (214 arcsec), and that they had larger (0002)-plane FWHM values (97 arcsec) than the AlN/sapphire templates (22 arcsec). The latter results may be due to the wafer curvature increasing as the AlN layer thickness increases. We also present results for the growth of AlGaN heteroepilayers with different AlN compositions on AlN/sapphire templates that either did or did not contain AlN regrowth layers. High-AlN mole fraction AlGaN heteroepilayers had larger (0002)-plane FWHM values and smaller (102)-plane FWHM values than low-AlN mole fraction AlGaN. Furthermore, the presence of an AlN regrowth layer tended to have a negative effect on the high-AlN mole fraction AlGaN layers. The above results are discussed using lattice mismatch, wafer curvature, surface condition, and growth temperature parameters.