Enhanced Light Emission by Exciton-Surface Plasmon Coupling
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1055-GG05-03
Enhanced Light Emission by Exciton-Surface Plasmon Coupling Koichi Okamoto1,2, Axel Scherer3, and Yoichi kawakami1 1 Department of Electronic Science and Engineering, Kyoto University, Katsura Campus, Nishikyo-ku, Kyoto, 615-8510, Japan 2 PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho Kawaguchi, Saitama, 3320012, Japan 3 Department of Physics, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA, 91125 ABSTRACT Surface plasmon coupling technique was performed to enhanced green light emissions from InGaN/GaN quantum well. We found that photoluminescence intensities were increased by fabricated nano-grating structures on the gold layers and enhancement ratios depend on the grating periods. We also simulated the localized SP modes by 3D-finite difference time domain (FDTD) calculation. The experimental results were well correlated to the calculated results, and we found that the both exciton-SP coupling and light extraction process can be controlled by the nano-structures of the interfaces. This suggests that even more efficient emission should be obtainable by optimizing the nanostructure geometries. INTRODUCTION We have an earnest desire to enhance a green emission of InGaN-based single quantum well (QW) structures. Recently, high efficient blue InGaN emission has already been achieved and commercialized, but it is very difficult to get similar high efficiency at other wavelength regions. We propose exciton-SP coupling method as one solution to dramatically increase the efficiencies of light emitting materials and devices. The idea of SP enhanced light emission had been previously described [1-2], and for the first time, we directly measured significant enhancement of internal quantum efficiency of visible light emission due to spontaneous recombination rate increases for InGaN-QWs [3-4], CdSe-QDs [5], and organic light emitters [67]. The SP coupling technique can enhance light emission at any wavelength region by choosing a metal layer. High efficient InGaN emission with RGB colors should be applicable to a white light LED without a yellow phosphor. In order to understand more detail mechanism of exciton-SP coupling and design even more efficient device structures, we perfume both experimental approach and theoretical calculations. Recently we report the photoluminescence (PL) measurements for several nanograting structures on the metal layers [8]. Here we compare the experimental results with the simulation of the localized SP modes by three-dimension finite difference time domain (3DFDTD) calculation. EXPERIMENT A GaN(10 nm)/InGaN(3nm)/GaN(4 µm) QW was grown on a sapphire substrate by a metal-organic chemical vapour deposition (MOCVD). A 50nm thick gold film was evaporated
on top of the surface of wafers. After polishing the bottom surface of the samples, we photoexcite and detect emission from the backside of the samples through the transparent substrate. Such back side access to the QWs permit us the rapidly compare the PL from QWs with and without the influence o
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