Effect Of Silver Nanostructure On The Luminous Efficiency Of GaN-LED

With the advantages of saving energy,high reliability,long life etc.,GaN based light emitting diode?GaN-LED?can be used in illumination,display and communication.The narrow modulation band-width and the Efficiency Droop are the two key limitations in development of GaN-LED.With the development of nanotechnology,improved the luminous efficiency and the modulation bandwidth by localized surface plasmon?LSP?is a hot research.In this paper,a model for embedding silver nanosphere array above the GaN substrate is designed by using FDTD Solution.The LSP properties of the silver nanosphere array with different size of silver nanospheres and distance between silver nanospheres are investigated.The results show that with the distance between silver nanospheres decreasing,two LSP resonant peaks of silver nanosphere array are presented and the longer resonant wavelength is red-shifted.The enhanced scattering efficiency of LSP and red-shift of the resonant peaks can be obtained by increasing the size of silver nanosphere.The LSP formed by the coupling between the silver nanosphere array and the incident light is dipolar plasmon.A silver nanocylindrical model is established.The LSP properties of the silver nanocylindrical with different size are analyzed.The results show that with the radius increasing,the LSP resonant wavelength is red-shifted.A secondary resonance peak appeared with excitation wavelength of 350 nm and the longer resonant wavelength is blue-shifted with the increasing of height.Then a Ag/Al₂O₃ nanocylindrical core-shell model is designed.The red-shift of the resonant peaks can be obtained by increasing the thickness of Al₂O₃ shell.The Near-field of two kinds of silver nanostructures under the LSP resonant wavelength are calculated.When the luminous wavelength of the GaN-LED is equal or similar to that of the silver nanostructure's LSP,the radiation luminescence and the LSP of the silver nanostructures are coupled with the energy transfer,which results in the near field enhancement of the LSP,hence the spontaneous emission rate of Ga N-LED improved.The coupled energy between the radiation luminescence and the LSP could be scattered or absorbed by the silver nanostructures.When the scattering coefficients of the silver nanostructures are larger than the internal quantum efficiency of the GaN-LED without silver nanostructures,the coupled energy will be scattered and the luminous efficiency of GaN-LED will be improved.