Improvement of structural quality of AlN layers grown on c-plane sapphire substrate by metal-organic vapor phase epitaxy using post-growth annealing with trimethylgallium

AlN layers were grown on a c-plane sapphire substrate by metal-organic vapor phase epitaxy (MOVPE) at 1350 & DEG;C. The structural quality of the grown AlN layers was drastically improved by post-growth annealing in mixed hydrogen, ammonia, and trimethylgallium ambiance at 1350 & DEG;C. As a first step, we grew the AlN layers exhibiting a double-domain structure with an in-plane rotation angle of & SIM;4 & DEG;. Then, the domain structure was changed from double to single by the post-growth annealing. After 20 min post-growth annealing, the surface possessed an atomically flat step-and-terrace structure with a root-mean-square value of & SIM;0.11 nm measured across 5 x 5 mu m(2). The full-width at half maximum values for 0002 and 1014 AlN reflections using x-ray diffraction were as small as & SIM;75 and & SIM;280 arcsec, respectively. Since this work provides a simple continuous MOVPE growth procedure to improve the structural quality of AlN/sapphire, it is advantageous to the industrial fabrication of AlxGa1-xN-based ultraviolet light-emitters.