Luminescence properties of hexagonal boron nitride: Cathodoluminescence and photoluminescence spectroscopy measurements

Cathodoluminescence and photoluminescence spectroscopies have been performed on hexagonal boron nitride powders. The combination of these techniques allows us to analyze the two observed luminescence bands. A deep-level UV emission at about 4 eV is attributed to defects or impurities, and a near-band-gap UV emission is observed at about 5.5 eV. The deep-level band is composed of four peaks, which are attributed to phonon replica due to localized vibrations. In the near-band-gap region, six components are observed between 5.2 and 5.96 eV, in agreement with the recent experiments performed on h-BN single crystals by Watanabe [Nat. Mater. 3, 404 (2004)], but they are assigned here to Frenkel excitons.