Abstract
Due to the recent commercial interest in nitride-based optoelectronics and rare-earth emission in nitride materials, the structural and optical characteristics of powders and thin films have been investigated in this work. The powder samples were made using a three-step solution method. Pulsed laser deposition (PLD) and metallorganic vapor phase epitaxy (MOVPE) methods were utilized for depositing films on sapphire substrates. The GaN powders with activator concentrations up to 8 atom % exhibited luminescence due to the transitions under cathodoluminescence (CL) as well as under photon excitation. Both near-band-edge emission and activator emission have been observed in PLD thin films made from the corresponding powders. X-ray diffraction revealed polycrystalline PLD thin films with a preferred growth direction along the axis, while scanning electron micrographs showed rough film morphology with submicrometer particles. CL emission from accompanied by near-band-edge emission and defect emissions from the GaN host was observed for the MOVPE films made using tris(2,2,6,6-tetramethyl-3,5-heptanedionato)terbium but not films made with tris(isopropylcyclopentadienyl)terbium. Despite visible luminescence from in GaN powders and thin films, no energy transfer from the host to activator ions was observed. This suggests that is unlikely to fluoresce if used in a GaN-based optoelectronic device.
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