β-Ga2O3(010) homo-epitaxial growth was performed by plasma-assisted molecular beam epitaxy. Under Ga-rich conditions and for growth temperatures above 650 °C, the growth rate was independent of the Ga/O ratio (>1). A high growth rate of 2.2 nm/min for β-Ga2O3(010) was achieved by optimizing the O flux between 650 and 750 °C. Under Ga-rich conditions between growth temperatures of 500–900 °C, smooth surfaces with rms roughness below 1 nm were realized. We found that the slightly Ga-rich conditions between 650 and 750 °C were optimal for β-Ga2O3(010) growth with a smooth surface and a high growth rate.

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300-nm-thick AlN layers were grown directly on 6H-SiC(0001) with six Si–C bilayer-height (1.5 nm) steps by rf-plasma-assisted molecular-beam epitaxy (MBE). 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 6×104 and 4×108 cm-2, 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 8×107 cm-2.

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