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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 asdeposited 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. [ABSTRACT FROM AUTHOR]

High crystalline quality of AlN layers are commonly grown at temperatures above 1200 °C. However, this work revealed that introducing a rough surface of AlN layer, defined as dislocation filtering (DF) herein, can improve the crystalline quality of 1.5 μm thick AlN layers grown at 1175 °C via metal organic vapor phase epitaxy technique. With 7 slm of ammonia flow during the DF growth, the lowest threading dislocation density (TDD) of ∼2.9 × 109 cm−2 was obtained. The result was associated to the formation of 3D growths which become reasonably smaller, denser, and more uniformly distributed with increasing ammonia flow up to 7 slm. The 3D growths were suggested to promote lateral growth that can increase the possibility for TD inclination and hence, mutual annihilation. The 3D growths characteristic disappeared when the ammonia flow was 10 slm. The optimized AlN layer that was obtained with 7 slm of ammonia flow exhibited an atomically smooth surface with a few deep trenches and improved transparency. Meanwhile, the calculated in-plane tensile strain for the AlN layers grown on DF with 1–7 slm of ammonia was about 3 times higher than the AlN layer without DF. However, no evidence of microcracks on the surface was observed. • With 7 slm ammonia flow during DF (dislocation filtering) growth, the lowest TDD of AlN was ∼2.9 × 109 cm−2. • AlN surface and transparency improved with DF, especially with 5 and 7 of ammonia flow. • In general, DF increased tensile strain but no microcracks was observed. [ABSTRACT FROM AUTHOR]