Growth of InGaN films on c-plane sapphire substrates with an AlN nucleation layer by using metal-organic chemical-vapor deposition

In this study, we report on the crystal quality of InGaN epifilms with different indium fractions grown at different growth temperatures on c-plane sapphire substrates with an AlN nucleation layer by using low-pressure metal-organic chemical-vapor deposition (MOCVD). High-resolution X-ray diffraction (HRXRD), atom force microscopy (AFM), photoluminescence (PL) and Raman scattering measurements were employed to study the crystal quality, optical properties and strain condition of InGaN epifilms with increasing indium fraction (from 4.36% to 15.36%). Results show that InGaN epitaxial layers can be realized with a higher indium fraction at a lower temperature by inserting an AlN nucleation layer between the sapphire substrate and the GaN buffer layer and that the obtained InGaN epifilms have an improved crystal quality and a lower threading dislocation density.