Anisotropic crystalline morphology of epitaxial thick AlN films grown on triangular-striped AlN/sapphire template

摘要

We have investigated crystalline morphology such as wafer curvature, mosaicity, and lattice tilting of an AlN film grown on a triangular-striped AlN/α-Al_2O_3 template by X-ray rocking curve (XRC) and reciprocal space map (RSM) measurements. The result of XRC for the AlN (0002) plane showed the difference of the value in the wafer curvature between the [11-20] and [1-100] directions. This indicates the anisotropic strain relaxation preferentially along [11-20] direction due to the triangular-striped structure and the voids in the AlN film. From the results of asymmetric RSMs for AlN 11-24 and 1-104 diffractions, the broadening of the reciprocal lattice spots in elliptical shape was observed. These results reflect anisotropic crystalline morphology in the AlN film. The elliptical diffraction spot for AlN 11-24 predominantly indicates the lattice tilting fluctuation around the [1-100] axes while that for AlN 1-104 indicates the lattice spacing fluctuation. Anisotropic crystalline morphology in the AlN film grown on the triangular-striped template has been clarified in combination with XRC and asymmetric RSMs.