Growth of high-quality GaN on (1 0 0) Ga2O3 substrates by facet-controlled MOVPE

•Detailed optimization of epitaxial growth of GaN on (1 0 0) β-Ga2O3 via MOVPE.•Demonstration of high quality GaN by 3-step MOVPE using an intermediate facet-control layer.•Comprehensive structural and optical characterization of GaN on (1 0 0) β-Ga2O3.•Influence of variation of the thickness of the LT GaN, and the thickness and growth temperature of the facet layer studied. We report a comprehensive study of the growth of GaN layers on (1 0 0)-oriented Ga2O3 substrates by metalorganic vapour phase epitaxy (MOVPE), especially the improvement on using an intermediate facet-control layer between the low-temperature buffer and the high-temperature GaN layer compared to the usual two-step growth process. We examined in detail the effects of substrate nitridation, carrier gas, and variation of the thickness of the low-temperature buffer GaN layer, and the thickness and growth temperature of the facet layer. This optimization allowed us to obtain GaN layers on (1 0 0)-oriented Ga2O3 with high structural and optical quality, as shown by high-resolution X-ray diffraction, electron microscopy, optical absorption, and luminescence measurements.