High-Temperature Annealing of Sputter-Deposited AlN on (001) Diamond Substrate

A novel fabrication process of hexagonal aluminum nitride (AlN)/(001) diamond by means of sputtering and high-temperature annealing is proposed. Crystallinity of the AlN is significantly improved by the annealing, leading to full width at half maximum (FWHM) of the AlN(0002) diffraction X-ray rocking curve (XRC) of 1490 arcsec for the AlN thickness of 400 nm. The in-plane epitaxial relationship in AlN/diamond structure is stabilized in the single domain of (0001) [11–20] AlN || (001) [110] diamond on single-crystal diamond substrates with off-cut angle along [110]. Transmission electron microscopy and nano-beam electron diffraction indicate the existence of an epitaxial graphite layer exhibiting an epitaxial relationship of (0001) [11–20] AlN || (1–100) [0001] graphite || (001) [110] diamond. The demonstration of single-domain hexagonal AlN/(001) diamond structure provides a cost-effective, mass production approach for realizing Al_xGa_1−xN/diamond devices for electronic and optoelectronic applications.