Agglomeration enhancement of AlN surface diffusion fluxes on a (0 0 0 1)-sapphire substrate grown by pulsed atomic-layer epitaxy techniques via MOCVD

Abstract

An atomically flat covering with a dense and crack-free surface of aluminium nitride films was successfully deposited on a sapphire-(0 0 0 1) substrate through a pulsed atomic-layer epitaxy technique via horizontal metalorganic chemical vapour deposition. The distribution of surface diffusion energy for the as-deposited pulsed atomic-layer epitaxy aluminium nitride films was examined by integrating the growth temperature at 1120 °C, 1150 °C and 1180 °C, respectively. The micrograph from field emission scanning electron microscopy and atomic force microscopy topography analyses disclosed a dense and crack-free surface with near atomically flat aluminium nitride films was obtained at 1180 °C with the smallest root mean square surface roughness of 0.98 nm. The progression of the E₂ (high) peak frequency retrieved from the Raman spectra was analysed to understand the in-plane compressive strain generated within the as-deposited aluminium nitride films. The lowest screw and mixed-edge threading dislocation densities were calculated to be 2.06 × 10⁷ and 7.33 × 10⁹ cm⁻², respectively, implying an enhancement in the kinetic mobility of the AlN surface diffusion fluxes when deposited at 1180 °C. The photoluminescence and X-ray photoemission scan spectra also presented a low inclusion of foreign impurities on the surface of the aluminium nitride film.