Ion beam assisted pulsed laser deposition of epitaxial aluminum nitride thin films on sapphire substrates

Epitaxial aluminum nitride films were grown on c- and r-plane oriented sapphire substrates by pulsed laser deposition technique. Additionally the influence of nitrogen/argon ion bombardment during film growth was studied. By X-ray diffraction measurements only the hexagonal wurzite structure of AlN was found. The epitaxial relationship between film and substrate was investigated by X-ray diffraction texture measurements. On c-plane oriented sapphire the wurzite c-axis is perpendicular to the substrate surface. On r-plane oriented sapphire not only an a-axis orientation but also a tilt of the hexagonal c-axis by 30° off the surface normal has been observed. Ion irradiation can improve epitaxy on c-plane oriented sapphire at a certain energy, depending on the angle of incidence. From the dechanneling dependence in Rutherford backscattering spectroscopy channeling spectra defect clusters, like stacking faults, are considered as dominating defects.