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 similar to 2.25 and similar to 2.9eV, 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 (V-Ga-O-N)(2-), (V-Ga-O2N)(1-) and surface defects. (C) 2008 Elsevier B.V. All rights reserved.