Abstract
We have illustrated the use of ultraviolet (UV) Raman scattering to investigate the thermal stability of AlGaN layers with high-aluminum content. The degradation pathway of Al0.72Ga0.28N was monitored for high-temperature treatments up to 1200 degrees C. 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, UV Raman scattering detects the buildup of a large strain in the Al0.72Ga0.28N film The crystalline quality of Al0.72Ga0.28N is unaffected up to 1000 degrees C. (C) 1999 American Institute of Physics. [S0003-6951(99)00704-4].