Blue and yellow luminescence of GaN nanocrystals-doped SiO2 matrix

GaN–SiO2 nanocomposite and GaN-free nanopowder are studied. X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence (PL) and photoluminescence electron excitation (PLE) techniques are used to investigate their structural and optical properties. Microstructural study reveals flattened sphere-like crystallites with a mean size of around 150 nm in the GaN–SiO2 sample, and multimodal size distributions in the raw GaN powder. A strong yellow and blue luminescence centred at ∼2.25 and ∼2.9 eV, respectively, is observed in the room-temperature PL spectra of the nanocomposite with the one of the powder. Ambient PLE measurements reveal several zero-phonon lines of the YL line, which lead to several type defects. The optical measurements are correlated with structural defects such as (VGa–ON)2−, (VGa–O2N)1− and surface defects.