Epitaxial thin films of aluminum gallium nitride (AlxGa1-xN) were grown by
low-pressure metalorganic vapor phase epitaxy on c-oriented sapphire substr
ates. The prism-coupling technique was carried out to determine the optical
properties of Al0.17Ga0.93N thin films, i.e., the refractive index, the fi
lm thickness, and the optical loss. Optical transmission measurements were
additionally used to determine the dispersion of the refractive index. A de
monstration 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 m
odes with the optical axis oriented normal to the film surface confirmed th
e uniaxial nature of the layer. (C) 1999 American Institute of Physics. [S0
003-6951(99)01926-9].