本論文研究旨在利用水熱法(Hydrothermal Method)成長氧化鋅奈米錐(ZnO-nanotapers)於氮化鎵發光二極體(LED)表面，提供表面粗化及折射係數漸變結構，提升氮化鎵LED之發光效率。
本論文研究架構主要分為兩個部分，第一部分偏重於理論模擬分析，係透過光學模擬軟體(TracePro)以分析氧化鋅奈米錐於總長度及直徑對發光二極體表面之光析出效率影響。由模擬光學顯示，氧化鋅奈米錐於長度0.5 m及直徑為100 nm 的結構，與傳統奈米線結構相比，可獲得光析出效率較大幅改之改善。第二部分中則集中於實驗研究，我們利用水熱法製備氧化鋅奈米錐於GaN-基LED表面。此一製程技術與傳統者最大差別在於成長氧化鋅奈米錐的製程溫度為200 oC，提高製程溫度可大幅降低成長氧化鋅奈米錐結構之時間。於物性分析方面，氧化鋅奈米錐結構的表面、晶體結構、成分及於GaN-基LED光電特性分析係分別利用掃描式電子顯微鏡(SEM)、穿透式電子顯微鏡(TEM)、能量散射光譜儀(EDS)與積分球進行。
實驗結果顯示，具有氧化鋅奈米錐表面粗化及折射係數漸變結構之GaN-基LED結構於注入電流350 mA時，與傳統GaN-基LED結構相較，其光析出效率增加36.15%。此證實本研究結構如所預期，確實可藉由氧化鋅奈米錐之表面粗化、折射係數調變與更進一步提升光析出效率。

In this thesis, the improvement in light output power of light emitting diodes (LEDs) is studied. The preparation of the ZnO nanotapers (ZnO-NTs) using hydrothermal growth method and their applications in LED is demonstrated. Effects of ZnO-NTs on light output improvement of GaN-LEDs are investigated theoretically and experimentally. Experimental results of light output improvement of GaN-LEDs are reported and discussed.
There are two parts comprised in the present thesis. The first part focuses on the simulation and design of ZnO-NTs for GaN-LEDs. An optical simulation software, TracePro, is used to simulate the size effects of ZnO-NTs (with different lengths, diameters, and densities) on the light output efficiency of GaN-LEDs. An optimum design for ZnO-NT’s with a length of 0.5μm and a diameter of 100 nm has been obtained.
The second part of the present study aims at the preparation of ZnO-NTs atop GaN-LEDs using of the hydrothermal growth (HTG) method. In the study, a much higher temperature of about 200 oC was used for the HTG process to reduce the processing time. Material analysis including surface morphology of ZnO-NTs, crystal structure and composition, and photoelectrical properties of the prepared LEDs are examined and results are presented and discussed. In this study, the fabrication and effectiveness of ZnO-NTs arrays atop LEDs to improve Lop has been demonstrated. The prepared ZnO-NTs show an average transmittance above 88% in the 454-466 nm wavelength range. Through the use of ZnO-NTs, a considerable improvement in Lop of LED by 36.15% at 350 mA as compared to regular VLED has been obtained.

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