Spinel-structured gallium oxynitride (Ga ₃O ₃N) synthesis and characterization: An experimental and theoretical study

Recently the new family of spinel-structured nitrides and oxynitrides of group 14 elements (Si, Ge, Sn) has been explored using high-pressure synthesis techniques. The solid-state compounds have high hardness, and they are semiconducting materials that are predicted to have a wide direct band gap. Here we have prepared the corresponding gallium oxynitride spinel with ideal formula G ₃O ₃N. The synthesis conditions and stability of the new phase were predicted using first-principles calculations, and the experimental study was realized using a combination of laser-heated diamond anvil cell and multianvil high-pressure, high-temperature synthesis techniques. Chemical analysis and X-ray structure refinement indicate that the new phase contains vacancies on the octahedrally coordinated Ga sites, to give an experimental stoichiometry of Ga _2.8N _0.64O _3.24. The Raman spectrum consists of broad bands and resembles the phonon density of states, due to N/O disorder on the anion sites. Optical excitation of the sample with 325 nm laser light at room temperature results in strong photoluminescence between 400 and 750 nm.