Structural, electronic and optical properties of AlN-based oxides on Si and GaN substrates

The properties of novel high-quality AlN-based oxides suitable for device applications are presented in this paper. The process steps employed in this investigation are similar to these of SiO₂, providing new technology for group III-nitride based electronic devices. The oxides were prepared by thermal oxidation of AlN films or direct deposition of ultra-pure aluminum in a O₂-N₂ ambient on Si or GaN substrates. The structure of the films depends on deposition conditions for oxidized AlN and on composition for the Al films deposited in the N₂-O₂ ambient. The dielectric constant was evaluated to be 12.74 while the effective charge density is about 10¹¹ cm^-2 for fully oxidized AlN. The refractive index of the oxide was about 3.9 using infrared techniques. Our results indicate that the AlN-based oxides provide a wide choice of high-quality insulators for electronic and optoelectronic applications