Reaction mechanism of the nitridation of α-gallium oxide to gallium nitride under a flow of ammonia

The reaction mechanism of nitridation of α-gallium oxide (α-Ga2O3) to gallium nitride (GaN) under a flow of ammonia was deduced by observing the change in morphology of α-Ga2O3 powder coated with silicon substrate at an increasing reaction temperature. Upon their complete nitridation to GaN below 1000 °C, the morphology of α-Ga2O3 powder was retained. This strongly indicates that the conversion of α-Ga2O3 to GaN does not proceed through any gaseous intermediate but solid-state intermediates of gallium oxynitrides (GaOxNy). The occurrence of the intermediates was also evidenced by the change in weights of products with increasing the reaction temperature and by comparison of XRD patterns and 71Ga magic-angle spinning (MAS) NMR spectra of incomplete nitrided samples before and after oxidation.