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

A complete optical characterization using the prism coupling technique is p roposed for AlGaN/AlN heterostructures grown on sapphire substrates by meta lorganic vapor-phase epitaxy. In this study, we have qualified the film beh avior and the substrate-to-layer interface directly from the measured optic al data. The experimental and theoretical approach used for this purpose is described in detail. The results have clearly shown essential changes in t he refractive index profile at the interface, which may be related to struc tural defects, and indicate a good agreement with the trends observed by tr ansmission electron microscopy analysis. (C) 1999 American Institute of Phy sics. [S0003-6951(99)05347-4].