PHOTOLUMINESCENCE PROPERTIES OF NANOCRYSTALLINE, WIDE-BAND GAP NITRIDES (C3N4, BN, ALN, GAN)

Nanocrystalline layers of C3N4, BN, AlN and GaN were grown by Impulse Plasma Assisted Chemical Vapor Deposition method on silicon substrates kept at 300K. Optical absorption studies of the layers revealed broad bands below the fundamental absorption edge, which were ascribed to t ransitions involving defect levels. When excited by a 3 mW He-Cd laser (325 nm line) all samples showed a wide photoluminescence spectrum (2 .0 to 3.5 eV), but the disordered crystalline structure quenched the e xcitonic photoluminescence observed in monocrystals. The efficient vis ible luminescence of nanocrystalline AlN layers in the 2-3 eV region o bserved under non optimal excitation conditions (energy bandgap of AlN is twice the excitation energy) is promising for optoelectronic use o f this material as a visible light source. (C) 1998 Acta Metallurgica Inc.