| Nano structures have been serving as fundamental components in contemporary optoelectronic devices. Upon interactions with electromagnetic field, nano structures on metal-dielectric interface in semiconductor devices particularly demonstrate new physical properties, in aspects like localized electromagnetic field, surface Raman enhancement, extraordinary optical transmission and coupling process related to surface plasmon. Thus intensive studies on the local coupling effect and corresponding fundamental physical problems, by means of computer numerical simulations, have great values in science and for potential applications. This not only provides new approaches to modulate the optoelectronic process and increase the electro-optical conversion efficiency in LEDs, but also enlightens a new way of energy saving and emission reduction.Focusing on metal-dielectric nano structures and electro-optical device GaN based LED, this dissertation investigates the fundamental physical problems such as local coupling, energy transmission and conversion within metal-dielectric nano structures by computer simulation and theoretical analysis, to get a profound understanding concerning the physical mechanisms responsible for electromagnetic wave propagation, localization and coupling on metal-dielectric nano structures. It contributes in providing theoretical guidance to increase the efficiency of LEDs through local coupling effect.Especially, this dissertation opens new paths to fabricate high efficiency LEDs. For this purpose, it studies how to increase the light emission of LED with adjusting and controlling the electic-optic conversion, near field localization, far field emission, extraordinary optical transmission by metal-dielectric nano structures. Then the adjusted mechanism, the coupling law between SPPs and semiconductor QWs are obtained.Around the above scientific topics, for the purpose to improve light emission efficiency, by using computer simulation and theoretical analysis, this dissertation studies on the related characteristics on metal-dielectric nano structures and GaN blue LED, and covers the following aspects:1) Computer simulation of LED containing metal-dielectric nano structures by using FDTD method and metal dispersion model;2) Exploration of approaches to increase the efficiency of LEDs by investigating the light emitting mechanism and electro-optical conversion processes in LEDs;3) Deriving from Maxwell's equations the physical characteristics of surface plasmon on infinitely and finitely thick metal-dielectric nano structures inside a electromagnetic field;4) Verification of the enhancement of electric dipole light emission through metal-dielectric nano structures by the surface plasmon local coupling effects on metal nano particles, and the validity of the numerical methods in the study of electric dipole emission enhancement;5) Introduction of easy-to-make silver film in GaN based LED to enhance light emission after investigation of the physical process of electric dipole emission enhancement by surface plasmon local coupling effect on metallic thin film surface and the dependence of enhancement factor on material and structural parameters.6) Optimization of structural parameters after combination of obtained simulation results with theory as well as based on the fact of better enhancement effect with silver thin film in GaN LEDs than with metallic reflectors.The main purpose of this dissertation is to numerically investigate the local coupling effect in metal-dielectric nano structures and its applications to the enhancement of electro-optical conversion efficiency. In close combination with key technologies in energy saving and emission reduction, environment protection in national economy and social developments, by introducing metal-dielectric nano structures and field coupling effect in LEDs and investigating the mechanism and controlling law of electric dipole light emission interacting with surface plasmon, this dissertation explores new approaches to increase the internal quantum efficiency of blue LEDs, and serves as the guidelines for experiments and manufacture. According to the above research objects and purposes, this dissertation is organized into the following innovation parts:â… . The 3D FDTD simulation of metal-dielectric nano structures in LED is realized with modified Drude model. A numerical simulation model is established to study the light emission and the characteristics of flip-chip GaN based LEDs containing metal nano thin film, and the validity of the method is verified.â…¡. According to the working principles and characteristics of LEDs, the approaches to increase lighting efficiency are analyzed. In order to increase internal quantum efficiency, based on the theoretical derivation of Purcell's effect and the characteristics of the electromagnetic field of metal surface plasmon, the theoretical foundation is established to increase the internal quantum efficiency of LEDs by metal surface plasmon enhanced electric dipole light emission.â…¢. With metal nano particles, the emission of electric dipole is enhanced by nearly a thousand times. According to the simulation results, the relation between the enhancement factor and the material and structural parameters of metal nano particles is concluded. It is well established that the localized field of surface plasmon on metal nano particles can enhance the emission of electric dipole by Purcell's effect.â…£. Based on the analysis of dispersion relation of surface plasmon from a infinitely thick metal, the dispersion characteristics of finitely thick metal films sandwiched between dielectrics of the same type and/or different types are analyzed and modified. Metallic film is introduced into GaN based LEDs, and the theoretical derivation of the electromagnetic characteristics of the infinitely thick metal and finitely thick metal film is verified according to the simulation results. The dependence of light emission enhancement on the material and structural parameters of metallic film and LED is concluded. After optimization,17 fold enhancement of light emission is obtained in blue light region.The work in this dissertation is supported by National Fundamental Program of China. Through numerical simulation research on local coupling effect in LEDs based on metal-dielectric nanostructures, this work has deepened the knowledge and understanding on the interactions between visible light and metals. It also sheds light on development of high brightness blue/white LEDs with new technology, new engineering, and new process, and provides theoretical background to enhance light emission of LEDs with metal-dielectric nano structures.
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