Very high quality AlN grown on (0001) sapphire by metal-organic vapor phase epitaxy

Very high quality AlN epitaxially grown on (0001) sapphire by metal-organic vapor phase epitaxy is investigated by atomic force microscopy, x-ray diffraction, and photospectrometry. A clear and continuously linear step-flow pattern with sawtooth shaped terrace edges is observed in atomic force microscopic images. Triple-axis x-ray rocking curves show a full width at half maximum of 11.5 and 14.5arcsec for the (002) and (004) reflections, respectively. KOH etching reveals an etch-pit density of 2×107cm−2, as deduced from atomic force microscopy measurements. The optical transmission spectrum shows a sharp absorption edge with a band gap energy of 6.10eV.