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

Abstract

Gallium nitride (GaN) powders were prepared by calcining a gallium(III) nitrate salt in flowing ammonia in the temperature ranging from 500 to 1050 <TEX>$^{\circ}C$</TEX>. The process of conversion of the salt to GaN was monitored by X-ray diffraction and <TEX>$^{71}Ga$</TEX> MAS (magic-angle spinning) NMR spectroscopy. The salt decomposed to <TEX>${\gamma}-Ga_2O_3$</TEX> and then converted to GaN without <TEX>${\gamma}-{\beta}Ga_2O_3$</TEX> phase transition. It is most likely that the conversion of <TEX>${\gamma}-Ga_2O_3$</TEX> to GaN does not proceed through <TEX>$Ga_2O$</TEX> but stepwise via amorphous gallium oxynitride (<TEX>$GaO_xN_y$</TEX>) as intermediates. The GaN nanowires and microcrystals were obtained by calcining the pellet containing a mixture of <TEX>${\gamma}-Ga_2O_3$</TEX> and carbon in flowing ammonia at 900 <TEX>$^{\circ}C$</TEX> 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.