Synthesis of nanocrystalline aluminum–gallium nitride (AlxGa1− xN; x = 0.1 to 0.5) with oxide precursors via ammonolysis

Oxygen-containing precursor systems for the synthesis of mixed aluminum-gallium nitride (AlxGa1-xN with x = 0.1 to 0.5) through ammonolysis (heat treatment under ammonia) were evaluated. Three different precursor systems were studied: (i) aluminum isopropoxide (aluminum sec-butoxide)/gallium isopropoxide hydrolyzed with excess water and cross-linked with 1,6-hexanediol, (ii) aluminum-gallium hydroxide coprecipitated from aluminum-gallium nitrate solution, and (iii) spray-dried aluminum-gallium nitrate solutions. The specimens were heat-treated between 700 degreesC and 1100 degreesC and were characterized mainly by x-ray diffraction, nuclear magnetic resonance (NMR), and transmission electron microscopy (TEM). NMR was used to follow the conversion of oxygen to nitrogen bonds. TEM in combination with energy-dispersive x-ray spectroscopy was used to determine the solid-solution composition for separated particles. It is possible to synthesize a mixed hexagonal (AI,Ga)N with crystallite sizes in the range of similar to10 nm from all three precursor systems, but all products contained larger GaN crystals ranging from 20 nm (alkoxide-derived) to 200 nm (hydroxide-detived) and a fraction of untransformed Al-O bonds; e.g., (amorphous or gamma-phase) Al2O3