Epitaxial Growth of Aluminum Nitride on Sapphire Using Metalorganic Chemical Vapor Deposition

Epitaxial aluminum nitride (AlN) films were grown on the basal planes of sapphire substrates using metalorganic chemical vapor deposition (MO-CVD), and the following results were obtained. (1) The substrate temperature and the trimethylaluminum (TMA) concentration dependences of the growth rate suggested that the growth process is limited by mass transport. (2) The crystalline perfection of epitaxial films is strongly affected not only by the substrate temperature but also by the gas flow pattern. (3) Single-crystal AlN films which include no misoriented grains can be grown epitaxially at ∼1200°C under carefully-controlled gas flow patterns. (4) Crystalline imperfection is caused mainly by (1 1̄01)-oriented grains which correspond to the hillocks observed in the surface morphology.