Single crystalline AlN epitaxial layers have been grown on and (0001) sapphire and 6H-SiC substrates by MOVPE technique at high temperatures in the range of 1340-1500°C. The structural qualities of the high temperature grown AlN layers were found to be good as evidenced by X-ray diffraction analyses results. By transmission electron microscopic analysis, dislocation densities of the layers were found to be 6.2 × 107 cm−2 or lower and the formation of dislocation loops was confirmed. High temperature bridge layers of AlN and AlxGa1−xN layers were grown on linear-groove patterned sapphire based AlN templates and 6H-SiC substrates. AlxGa1−xN bridge layers exhibited different growth behaviours depending on the direction of groove patterns on the sub-strates.