| With the rapid development of GaN based light-emitting diodes(LEDs), LED is gradually replacing the traditional lighting device and widely used in various fields due to its superior and excellent performance, such as high luminous efficiency, short response time, wide adjustable range spectrum, long service life, a material non-polluting, energy saving, and many other advantages. Although LED commercial application has been more common, the price is cheap, but it still up against the problem of low external quantum efficiency, the key lies in how to solve low light extraction efficiency problem caused by the total internal reflection in the interface between air and GaN material. Many methods have been approved, such as photonic crystals, flip chip, a transparent substrate, surface roughening, surface plasmons etc. This article mainly through the semiconductor surface preparation of micro-nano structure enhanced GaN LED light efficiency, started with the deposited metal film, metal particles and etching three parts. And the performance of several kinds of micro-nano LED structures was analyzed by photoluminescence system. Research has made the following main results and conclusions:1. Light extraction enhancement induced by metallic nanoparticles(NPs) for GaN ultraviolet light emitting diodes is investigated by Finite difference time domain method(FDTD). The systems under study consist of different size's Al nanoparticles(NPs) with varying diameter separated by a nano-gap, and the symmetrical dimer NPs with different geometrical parameters are studied. We have demonstrated that spectral response can be controlled by varying the size of the nanoparticles and nano-gaps. It is found that the enhancement of the electric field and the peak position are subject to geometrical characteristics of the nanoparticle(NP) components in different manners for symmetrical and asymmetrical systems respectively. High enhancement ratio for UV wavelength can be obtained by tuning parameters of asymmetrical system, which is potential for improving the performance of deep-UV LEDs.2. Ag films were desposed on the surface of GaN-based LED epitaxial wafers by magnetron sputtering with different thickness. In addition, the influence of the Ag films in LED has been investigated by photoluminescence(PL) measurement. FDTD simulation results further verified that the metal could enhance electrical field.3. Metal nanoparticles were obtained by annealing treatment carried out on the metal film, experimental research on the three different diameter of Ag nanoparticles effect on the light efficiency of GaN-based LED, at the same time the extinction spectrum of the three different diameter Ag nanoparticles was calculated by FDTD software, which are consistent with our experimental results. The electric field also enhanced largely around the Ag nanoparticles in line with expectations. The highest enhancement of PL intensity is increased by 219% for the sample with NPs.4. The p-type layers of GaN LED were etched by ICP system, the peak position of spectrum of PL were enhanced markedly. Then the Ag film was deposited on the surface of the nanowire after etching. The experimental results have compared with others. The highest enhancement of PL intensity is increased by 224% for the sample with NPs embedded in etched p-GaN near the MQWs as compared with the bare MQWs, also is about 1.24 times higher than the MQW sample covered Ag NPs on the surface, indicating strong surface scattering and SP coupling between Ag NPs and NUV-MQWs. |
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