An investigation was made of the structural properties of layers, on sapphire or NdGaO3 substrates, which had been deposited by means of molecular beam epitaxy. The GaN/NdGaO3 layer exhibited a higher luminescence efficiency as compared with that of GaN/Al2O3. The dislocation density in GaN/NdGaO3, as estimated using X-ray diffraction measurements, was much lower than that in layers on sapphire substrates (the predominant vertical screw dislocation density was 104 or less). The layers exhibited a direct correlation between the dislocation density and the incorporation of O and other contaminants, as determined by means of secondary ion mass spectroscopy measurements. The lowest impurity concentration was found in GaN/NdGaO3 epilayers. All of the layers which were grown by using the novel N source exhibited a negligible yellow photoluminescence band, regardless of the substrate type.

Plasma-Assisted MBE Growth of GaN and InGaN on Different Substrates. V.V.Mamutin, S.V.Sorokin, V.N.Jmerik, T.V.Shubina, V.V.Ratnikov, S.V.Ivanov, P.S.Kopev, M.Karlsteen, U.Södervall, M.Willander: Journal of Crystal Growth, 1999, 201-202, 346-50