On the ammonolysis of Ga2O3: An XRD, neutron diffraction and XAS investigation of the oxygen-rich part of the system Ga2O3–GaN

We investigated the ammonolysis of β-Ga2O3 at elevated temperatures by means of ex situ X-ray diffraction, ex situ neutron diffraction and in situ X-ray absorption spectroscopy. Within the detection limits of these methods, we can rule out the existence of a crystalline or amorphous oxynitride phase that is not derived from wurtzite-type GaN. No evidence for a β-Ga2O3 related oxynitride phase was found, and the nitrogen solubility in β-Ga2O3 was found to be below the detection limit of about 2–3 at% in the anionic sublattice. These findings were obtained by monitoring the anionic occupancy factors and the lattice parameters of the β-Ga2O3 phase obtained from total diffraction pattern refinement with the Rietveld method and by linear combination fitting of the X-ray absorption spectra that were recorded during the ammonolysis.