Prism coupling technique for optical characterization of LP-MOVPE AlxGa1-xN thin film waveguides

In this paper. the optical properties of low-pressure metalorganic vapor phase 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 reconstructed the refractive index profile by using an original formalism suitable for thin film applications. The information provided from this study has allowed us to study the film homogeneity and the substrate to layer interface. 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.