Growing oriented AlN films on sapphire substrates by plasma-enhanced atomic layer deposition

The possibility of growing oriented AlN films on Al$_2$O$_3$ substrates at temperatures below 300$^\circ$C by plasma-enhanced atomic layer deposition was examined. The samples were subjected to X-ray phase analysis and ellipsometry. It was demonstrated that the refraction index of films deposited with plasma exposures longer than 20 s was 2.03 $\pm$ 0.03. The (0002) and (0004) reflections at 2$\Theta$ angles of 35.7$^\circ$ and 75.9$^\circ$ were present in the X-ray diffraction patterns of these samples. These reflections are typical of the hexagonal AlN polytype. The full width at half maximum of the rocking curve of reflection (0002) in the best sample was 162 $\pm$ 11 arcsec.