Growth mechanism of c-axis-oriented AlN on (001) diamond substrates by metal-organic vapor phase epitaxy

Abstract: Wurtzite AlN layers are grown on a (001) diamond substrate by metal-organic vapor phase epitaxy. The microstructure and growth mechanism of the AlN layer are examined using atomic force microscopy, X-ray diffractometry, and transmission electron microscopy. At the initial stage of AlN growth, AlN crystalline particles with various orientations are randomly nucleated on the (001) diamond surface. At the second step of growth, AlN grains predominantly oriented along the c-axis grow, incorporate the randomly oriented AlN grains, and then grow further. At the final step of growth, a continuous AlN layer with a c-axis-oriented two-domain structure is obtained on the (001) diamond substrate. Microstructural analysis reveals that either the AlN domain or AlN domain is aligned on the [110] diamond direction. The growth mechanism governs by the higher growth rate of the AlN grains along the [0001] direction than along other directions at high growth temperatures up to 1270°C. [Copyright &y& Elsevier]