Plasma-assisted MBE growth of GaN and InGaN on different substrates

We investigate structural and optical properties of GaN and InGaN on sapphire and neodymium gallate substrates, deposited by MBE using a novel RF and conventional ECR nitrogen activators. The GaN/NdGaO3 layer demonstrates higher luminescence efficiency compared with GaN/Al2O3. Dislocation density in GaN/NdGaO3, estimated using X-ray diffraction measurements, is much less than that in the layers on sapphire substrate (the dominant vertical screw dislocation density is 10(4) or less). The layers demonstrate a direct correlation between the dislocation density and incorporation of oxygen and other contaminations determined by secondary ion mass spectroscopy measurements, with the lowest impurity concentration located in the GaN/NdGaO3 epilayers. All the layers grown by the novel nitrogen source exhibit negligible yellow photoluminescence band independently of the substrate type. (C) 1999 Elsevier Science B.V. All rights reserved.