The surface diffusion of Al adatoms during metalorganic vapour phase epitaxy of AlN was investigated, using sapphire substrates with different misorientations. It was found that the diffusion length during modified migration-enhanced epitaxy was about 40nm and comparable to that of conventional migration-enhanced epitaxy under the current growth conditions. The enhancement of the diffusion length by alternating supply of source precursors was also demonstrated. The screw dislocation density in the modified-migration-enhanced epitaxially grown AlN was extracted to be as low as 2.2 x 106/cm2 from X-ray diffraction, while the chemical etching by KOH solution revealed an etch pit density of 1.0 x 106/cm2, both of which indicated its superior structural properties. The chemical etching also revealed that the grown AlN had Al polarity.

Surface Diffusion during Metalorganic Vapor Phase Epitaxy of AlN. R.G.Banal, M.Funato, Y.Kawakami: Physica Status Solidi C, 2009, 6[2], 599-602