300nm-thick AlN layers were grown directly onto 6H-SiC(00•1) with six Si–C bilayer-height (1.5nm) steps by rf-plasma-assisted molecular-beam epitaxy. To avoid unintentional active-nitrogen exposure, AlN was grown just after the nitrogen plasma ignition. By combining optimized Ga pre-deposition and no active-nitrogen exposure, layer-by-layer growth was realized from the first layer of AlN. Screw-type and edge-type threading dislocation densities in the AlN layer were reduced to 6 x 104 and 4 x 108/cm2, respectively. Most of the edge-type dislocations were located at the step edge of the SiC substrate. The dislocation density of the AlN grown on the terrace of the SiC substrate was as low as 8 x 107/cm2.

Reduction of Threading Dislocation Density in 2H-AlN Grown on 6H-SiC(0001) by Minimizing Unintentional Active-Nitrogen Exposure before Growth. H.Okumura, T.Kimoto, J.Suda: Applied Physics Express, 2011, 4[2], 025502