Optical properties of low-pressure metalorganic vapor phase epitaxy Al_xGa_1-xN thin-film waveguides by prism coupling technique

Epitaxial thin films of aluminum gallium nitride (Al_xGa_1-xN) were grown by low-pressure metalorganic vapor phase epitaxy on c-oriented sapphire substrates. The prism-coupling technique was carried out to determine the optical properties of Al_0.17Ga_0.93N thin films, i.e., the refractive index, the film thickness, and the optical loss. Optical transmission measurements were additionally used to determine the dispersion of the refractive index. A demonstration of optical waveguiding was successful in an AlGaN/AlN/sapphire planar structure, the optical propagation loss was determined to be around 1.8 dB cm^-1 at 632.8 nm. An analysis of optical anisotropy using guided modes with the optical axis oriented normal to the film surface confirmed the uniaxial nature of the layer. © 1999 American Institute of Physics.