E. Dogheche et al., Prism coupling technique for optical characterization of LP-MOVPE AlxGa1-xN thin film waveguides, PHYS ST S-A, 176(1), 1999, pp. 347-350
In this paper. the optical properties of low-pressure metalorganic vapor ph
ase epitaxy (LP-MOVPE) grown aluminum gallium nitride thin films have been
determined using the prism coupling technique. This method allowed us first
to very accurately determine the film thickness and its refractive index (
n(0) = 2.3240). Optical attenuation has been evaluated to be around 2 dB cm
(-1) for 1.2 mu m thick multimode planar structures. As second, we have rec
onstructed the refractive index profile by using an original formalism suit
able for thin film applications. The information provided from this study h
as allowed us to study the film homogeneity and the substrate to layer inte
rface. In some cases, the optical results have clearly shown a modification
of material behavior at the interface, which may be related to structural
defects, in agreement with transmission electron microscopy (TEM) analysis.