Résumé
Deep ultraviolet micro-Raman scattering was employed to monitor high-temperature processing of AlGaN films under resonant excitation conditions, giving rise to enhanced first and second-order Raman scattering. High-temperature treatments at 1100 degrees C result in changes in the second-order Raman scattering signal and monitor the emergence of microscopic defects during the high-temperature processing. The second-order Raman spectrum was analyzed to gain insight into the AlGaN phonon density of states. For annealing temperatures higher than 1150 degrees C, the Al0.72Ga0.28N film decomposes: a low- and a high-aluminum composition AlxGa1-xN phase emerge. At 1100 degrees C, prior to the Al0.72Ga0.28N decomposition, deep UV Raman scattering detects the built-up of strain in the Al0.72Ga0.28N film.