Enhancement of initial layer‐by‐layer growth and reduction of threading dislocation density by optimized Ga pre‐irradiation in molecular‐beam epitaxy of 2H‐AlN on 6H‐SiC(0001)

300-nm-thick AlN layers without a nucleation layer were grown on 6H-SiC (0001) vicinal substrates with 3-bilayer-height steps by rf-plasma-assisted molecular-beam epitaxy. A Ga beam was supplied for 0 to 30 seconds just before growth of AlN. The Ga pre-irradiation for 7 seconds (∼1.6 ML) was found to be effective for realization of the AlN layer-by-layer growth mode at an earlier stage of the growth and reduction of threading dislocation densities (TDD) in the AlN layers. The screw-type and edge-type TDDs were ∼106 cm-2 and 6×108 cm-2, respectively. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)