Ammonia-free high temperature metalorganic vapor phase epitaxy (AFHT-MOVPE): a new approach to high quality AlN growth
We propose a new growth technique, ammonia-free high temperature metalorganic vapor phase epitaxy (AFHT-MOVPE), for high quality AlN growth. Nitrogen (N2) gas, instead of ammonia (NH3) gas in the conventional MOVPE growth technique, is used together with hydrogen (H2) gas and trimethylaluminum (TMA) in AlN growth. Basic growth features and AlN epilayer characteristics, such as the H2 gas effect on the growth, the AlN growth features, the lattice polarity of an AlN epilayer and the AlN epilayer structural qualities, are investigated to capture the whole image of the new growth technique. It is found that H2 plays a role in AlN growth, where AlN growth takes place only with the introduction of H2 into the growth chamber. The Al-polar AlN epilayers with high structural quality have been successfully grown on the sapphire c-plane (0001) substrate. High resolution X-ray diffraction (HRXRD) rocking curve measurements show the full width at half maximum (FWHM) values of the symmetric (002) and the asymmetric (102) diffraction peaks of 298 and 420 arcsec from an ∼2.5 μm-thick AlN epilayer, respectively, which are comparable to or better than those grown by the conventional MOVPE technique. Our results show a potential feature of the proposed technique in the growth of high quality AlN as a template, which is greatly important for optical and electronic power device applications.