Structure and optical properties of cubic gallium oxynitride synthesized by solvothermal route

Cubic gallium oxynitride was synthesized using a solvothermal processing route. Crystal structure, chemical composition, optical properties and the influence of heat treatment in either reactive or inert atmospheres have been investigated. Despite a strongly distorted lattice revealed using X-ray diffraction, the Raman active modes of a cubic gallium oxynitride structure could be observed. With diffusive reflectance UV–Vis spectroscopy a band gap at around 4.8 eV has been observed. Additionally, cathodoluminescence spectroscopy exhibited observable luminescence caused by defect-related transitions within the optical gap. Cathodoluminescence and photoluminescence spectra collected after heat treatments showed significant changes in the defect structure. In particular, for annealing in ammonia the main spectral modifications were related to the substitution of oxygen by nitrogen on anion sites.

CL spectra of gallium oxynitride: As-prepared and heat-treated at temperatures of 500 °C in different atmospheres.Figure optionsDownload as PowerPoint slideHighlights
► Raman spectrum of cubic gallium oxynitride.
► Experimental determination of optical band gap.
► Shift of band gap energy due to heat treatment.
► Nitrogen incorporation leads to deep level acceptor states.
► Red shifted luminescence spectrum.