A Microstructural Comparison of the Initial Growth of AIN and GaN Layers on Basal Plane Sapphire and SiC Substrates by Low Pressure Metalorganic Chemical Vapor DepositonThe initial growth by low pressure metalorganic chemical vapor deposition and subsequent thermal annealing of AIN and GaN epitaxial layers on SiC and sapphire substrates is examined using high resolution transmission electron microscopy and atomic force microscopy.