Thick AlN layers grown on micro-scale patterned sapphire substrates with sputter-deposited annealed AlN films by hydride vapor-phase epitaxy

•Thick AlN layers without cracks were grown by hydride vapor phase epitaxy.•Undesired misaligned AlN growth can be prevented at appropriate growth temperature.•Optimized patterned sapphire substrate geometries can realize rapid coalescence. Misaligned crystallite growth is found on the sidewalls of dome-shaped patterns which hinders the coalescence of the c-plane AlN layer growing on the c-axis-oriented sapphire plane. In this study, thick AlN layers without cracks were grown by hydride vapor-phase epitaxy on micro-scale patterned sapphire substrates using annealed sputter-deposited AlN with a thickness of 200 nm. It was observed that undesired misaligned AlN growth can be prevented by selecting an appropriate growth temperature. A two-step approach was used to promote the lateral growth and coalescence of AlN. A relatively smooth surface without discontinuities and holes was obtained. The influence of the multi-oriented sapphire facets provided by micro-scale patterned sapphire substrates was investigated. According to the geometry of the misaligned crystallites, the grown AlN deviating from the c-axis on the near sapphire r-plane sidewalls has less influence on the coalescence of AlN, compared to the near n-plane sidewalls.