Analysis of polar direction of AlN grown on (0001) sapphire and 6H-SiC substrates by high-temperature metal-organic vapor phase epitaxy using coaxial impact collision ion scattering spectroscopy

High-crystalline quality AlN layers with an atomically flat surface are grown on (0001) sapphire and 6H-SiC substrates by metal-organic vapor phase epitaxy at 1400 degrees C without a low-temperature buffer layer. The polar direction of the AlN layers is determined by coaxial impact-collision ion scattering spectroscopy (CAICISS). For AlN growth on the sapphire substrate, trimethylaluminum (TMAl) is supplied for 10 sec before introducing ammonia (NH3). For AlN growth on the SiC substrate, the TMAl and NH3 are supplied simultaneously. The CAICISS spectrum of each AlN layer is analyzed by measuring the dependence of the Al atoms' signal intensity on the angle of ion beam incidence considering the shadowing and focusing effects for determining the polar direction of the AlN layer. The CAICISS spectra clearly indicate the polar direction of the AlN layers, both of which are found to have the Al-polarity. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim