Polarity dependence of AlN {0 0 0 1} decomposition in flowing H2

The thermal stabilities of Al- and N-polarity AlN layers grown on (0 0 0 1) sapphire substrates were investigated at temperatures ranging from 1100 to 1400 °C in various gas flows (He, H2 and H2+NH3). Decomposition of AlN occurred in flowing H2, while it did not occur in He or H2+NH3 flow. The decomposition rate in H2 increased with an increase in the temperature over 1200 °C, and the decomposition rate of the Al-polarity AlN layer was found to be lower than that of the N-polarity AlN layer at each temperature. The decomposition reaction of AlN and the relationship between the polarities of the AlN layers and their different decomposition rates are discussed.