Heteroepitaxial AlN growth on c-plane sapphire substrates by ammonia-free high temperature metalorganic chemical vapor deposition

AlN films were hetero-epitaxially grown on c-plane sapphire substrates by ammonia-free high temperature metalorganic chemical vapor deposition (AFHT-MOCVD). The dependence of the AlN growth rate on the flow rate of source gases (H-2, N-2 and trimethylaluminum (TMA)) and the growth temperature were systematically investigated. The maximum AlN growth rate up to ~4.0 mu m/hour was obtained at the present growth conditions. Based on the experimental results, the possible mechanisms in the AFHT-MOCVD growth concerning the gas reactions are qualitatively discussed. The as-grown AlN epilayers were characterized by high-resolution X-ray diffraction (HRXRD), scanning electron microscope (SEM) and scanning transmission electron microscope (STEM). The narrow full width at half maximum (FWHM) values of symmetric (0002) and asymmetric (10-12) AlN diffractions are obtained ((0002): 211 arcsec, (10-12): 325 arcsec from a ~3 mu m thick AlN epilayer), showing the potential of the growth technique for the high quality AlN growth.