Degradation of AlGaN during high-temperature annealing monitored by ultraviolet Raman scattering

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 °C. For annealing temperatures higher than 1150 °C, the Al0.72Ga0.28N film decomposes: a low- and a high-aluminum composition AlxGa1−xN phase emerge. At 1100 °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 °C.