Interface properties of AlxGa1−xN/AlN heterostructures from optical waveguiding information

Abstract

A complete optical characterization using the prism coupling technique is proposed for AlGaN/AlN heterostructures grown on sapphire substrates by metalorganic vapor-phase epitaxy. In this study, we have qualified the film behavior and the substrate-to-layer interface directly from the measured optical data. The experimental and theoretical approach used for this purpose is described in detail. The results have clearly shown essential changes in the refractive index profile at the interface, which may be related to structural defects, and indicate a good agreement with the trends observed by transmission electron microscopy analysis.