Department: Grad. Program in Materials Science
Name: Jonathan H. Tao
Email: jtao @ ucsd.edu
Grad Year: 2008
The recent discovery of fluorescence from rare earth ions in nitride hosts opens up the possibility of creating a white light solid state source via the combination of different rare earth ions. By controlling the type of dopant and its concentration, the color of the emitted light upon e-h recombination in the active layer of a double heterostructure design of a GaN-based LED light source may be tuned. Using combustion synthesis as part of a two-step process, and a three-step wet-chemical synthesis process, we were able to synthesize nitride hosts doped with various rare-earth ions. Pure GaN powders have been synthesized with oxide precursors made by combustion synthesis, and AlN powders doped with Eu3+, Tm3+, and Tb3+ have been synthesized from fluoride precursors. X-ray diffraction (XRD) and energy dispersive spectrometry (EDS) have been used to characterize the phase and composition of the powders, respectively. Photoluminescence (PL) was measured on doped AlN powders and cathodoluminescence (CL) was measrued on pure GaN powders to characterize the emission of each sample at room temperature. Among the successful nitride samples, Eu3+, Tm3+, and Tb3+ doped AlN samples demonstrated strong dopant-related emission and reduced defect emission compared to the pure nitride host. The 3-step process has been extended to synthesize high purity GaN powders as well as GaAlN alloys, with as low as ~4 at% oxygen and an 8% oxygen- to-nitrogen ratio.
« Back to Posters or Search Results