Gallium Nitride Powders from Ammonolysis: Influence of Reaction Parameters on Structure and Properties

Gallium nitride (GaN) has been prepared by the reaction of ammonia with three different gallium precursors: Gallium oxide, a mixture of gallium oxide and elemental gallium, and elemental gallium. X-ray diffraction indicates that all three starting materials yield highly crystalline wurtzite GaN particles. Solid-state 1H NMR has been employed to ascertain the presence of hydrogen in the samples. The technique allows a clear distinction between structural protons and protons bound to the surface of the crystals. In addition, solid-state 71Ga NMR and energy-dispersive X-ray analysis display significant differences in the material. Depending on the starting material, the GaN product consists of up to three different phases. The optical properties of the product GaN powders could be correlated to the NMR data. By converting nonluminescing GaN prepared from gallium oxide into GaN, with a bright emission at room temperature around 370 nm when excited by a 325 nm He -Cd laser, further insight was gained on the correlation of structural and optical properties of GaN.