Preparation of Gallium Nitride Powders and Nanowires from a Gallium(III) Nitrate Salt in Flowing Ammonia

Gallium nitride (GaN) powders were prepared by calcining a gallium(III) nitrate salt in flowing ammonia in the temperature ranging from 500 to 1050 .deg. C. The process of conversion of the salt to GaN was monitored by X-ray diffraction and 71Ga MAS (magic-angle spinning) NMR spectroscopy. The salt decomposed to γ-Ga2O3 and then converted to GaN without γ-β Ga2O3 phase transition. It is most likely that the conversion of γ-Ga2O3 to GaN does not proceed through Ga2O but stepwise via amorphous gallium oxynitride (GaOxNy) as intermediates. The GaN nanowires and microcrystals were obtained by calcining the pellet containing a mixture of γ-Ga2O3 and carbon in flowing ammonia at 900 .deg. C for 15 h. The growth of the nanowire might be explained by the vapor-solid (VS) mechanism in a confined reactor. Room-temperature photoluminescence spectra of as-synthesized GaN powders obtained showed the emission peak at 363 nm