Reflectivity of hexagonal Boron-Nitride in deep UV

Hexagonal boron nitride (hBN) is one of the most promising materials for light emitting devices in the deep UV. hBN-bulk was demonstrated as an indirect band-gap semiconductor with an excitonic emission at 5.95 eV and phonon replicas between 5.7 and 5.9 eV. At lower energies emission bands comes from extended defects or stacking faults while the optical properties for the energy range higher than the fundamental band-gap are still under debate.