Growth of AlN by the Chemical Vapor Reaction Process

AlN was grown by a chemical vapor reaction process with metallic Al and ammonium chloride as source precursors. A detailed parameter study was performed for direct growth on sapphire substrates. Specular films were obtained with optimum ammonium chloride supply for a given temperature. Due to lack of optimization of initial growth conditions, these specular films on sapphire contained polycrystalline inclusions. These inclusions were successfully avoided by regrowing on metalorganic chemical vapor deposition (MOCVD)-grown AlN templates. Inversion domains which existed in the MOCVD templates were eliminated at the interface of regrowth although the density of edge-type dislocations was not reduced, and remained at 9.3×109 cm-2. Growth on grooved sapphire resulted in AlN domains with their c-axis perpendicular to the sidewalls of the grooves. The top free surface which was inclined by about 20° to the basal plane of the sapphire substrate was m-plane. The top portion of this domain showed reduced dislocation density, as low as 8×108 cm-2.