本論文的主要目標為應用奈米結構來發展高效率的氮化鎵與磷化鋁鎵銦系列發光二極體，此研究所使用的奈米結構包括電子發射多重量子井、奈米圖案化藍寶石基板、二氧化矽微米柱陣列、光子晶體與奈米網狀氧化鋅。
電子發射多重量子井結構在氮化鎵發光二極體中除了可以作為電子發射層外，也能作為預應變層。當電子發射多重量子井的週期從0對增加到8對時，順向偏壓隨之降低，同時，多重量子井的應力也跟著減少，使得漏電流減少與人體放電模式下的抗靜電能力增強，因此光輸出強度提升32%，除此之外，波長紅移與電流誘致波長藍移現象也能獲得改善。當電子發射多重量子井維持在8對的條件下，量子位障層的厚度為18.5 nm時可獲得最佳的消耗功率和光輸出特性。
我們成功地利用奈米球微影術搭配乾蝕刻技術製作出奈米圖案化藍寶石基板。相較於使用微米圖案化藍寶石基板來成長氮化鎵發光二極體，藉由使用奈米圖案化藍寶石基板可提升8%的光輸出功率，同時，磊晶品質、電特性、接面溫度和光輸出特性都能有效地改善，然而奈米圖案化藍寶石基板結構的深寬比大小將會影響這些元件特性。
相較於使用微米圖案化藍寶石基板來成長氮化鎵發光二極體，藉由使用二氧化矽微米柱陣列可增強磊晶層的側向成長，有效提升磊晶品質和光輸出特性，除此之外，可以進一步地利用氧化物緩衝蝕刻液移除二氧化矽微米柱陣列，而形成空氣微米孔洞陣列，因此光輸出功率可提升5%，接著再利用氫氧化鈉溶液將空氣微米孔洞陣列蝕刻成倒金字塔的形狀後，光輸出功率可提升8%。
在此利用具量產能力的奈米球微影術成功地製作出光子晶體氮化鎵發光二極體。相較於傳統發光二極體，光子晶體可使發光二極體的光輸出功率提升15%，然而發光二極體的波長是否位於光子能隙將會影響發光二極體的光輸出特性。
藉由使用奈米球微影術，我們製作出奈米網狀氧化鋅於磷化鋁鎵銦發光二極體上，並可使光輸出功率提升15%，此改善原因來自於奈米網狀氧化鋅可有效散射被侷限於晶片內部的光到外界，除此之外，由於奈米網狀氧化鋅的折射率位於p型磷化鎵窗戶層和空氣之間，可有效抑制Fresnel反射損失。

The main purpose of this dissertation is to develop high efficiencies of GaN- and AlGaInP-based light-emitting diodes (LEDs) by applying nanostructures, including electron emitter multiple-quantum well (EE-MQW) structures, nano-patterned sapphire substrates (NPSS), SiO2 microrod array on sapphire substrate, photonic crystal (PhC) structures, and nano-mesh ZnO layers.
The function of EE-MQW structures could be not only an electron emitter but also a prestrain layer for GaN-based LEDs. With the period of EE-MQW structure increases from 0 to 8 periods, the forward voltage reduces. Besides, the strain of MQW reduces, and it results in the reduced leakage current and the enhanced electrostatic discharge (ESD) endurance ability. Thus, the luminance intensity of LED with 8-period EE-MQW structure increases by 32% compared with the conventional LED at the injection current of 20 mA. The other optical properties, including the spectral redshift and current-induced blueshift range, could be more improved with the period of EE-MQW structure increases. Then, when the period of EE-MQW structure was kept at 8 periods, both the power consumption and light-output characteristic were optimal at 18.5 nm quantum barrier (QB) thickness of EE-MQW structure.
NPSS was successfully demonstrated by using a combination of nanosphere lithography and dry etching technique. By introducing NPSS, the output power of GaN-based LED grown on patterned sapphire substrate (PSS) could increase by 8% when the pattern size of PSS reduces from micro- to nano-scale. For the detailed investigation of NPSS, the crystalline quality, electrical properties, junction temperature, and light-output characteristics of LED could be effectively improved by using NPSS technique, but depended on the aspect ratio of NPSS.
The single growth technique by using SiO2 microrod array directly deposited on sapphire substrate provides the epitaxial lateral overgrowth (ELOG) of the epitaxial GaN films. Compared with LED grown on PSS, the crystalline quality and light-output characteristic could be more effectively improved by using SiO2 microrod array. For the further improvement in light extraction, SiO2 microrod array was first removed by buffer oxide etching (BOE) to form the air microhole array. Then, NaOH was used to etch the air microhole array again to form the inverted pyramid shape. Compared LED grown with SiO2 microrod array, the output power of LED increases 5% and 8.5% after BOE and NaOH wet-etching process at the injection current of 20 mA, respectively.
Nanosphere lithography as a simple and economic method was utilized to fabricate PhC structures on the p-GaN layers of GaN-based LEDs. The output power of PhC LED was 15% higher than that of the conventional LED at the injection current of 20 mA. The optical properties of PhC LEDs were related to the fact that the PhC effect was only performed when the emitting wavelength of PhC LED was located inside the photonic bandgap (PBG).
Nano-mesh ZnO layers were fabricated on the top of the p-GaP window layers of AlGaInP-based LEDs by using nanosphere lithography. Compared with the conventional LED, a 15% enhancement in the output power of LED with nano-mesh ZnO layer could be attributed to the fact that the nano-mesh ZnO layer effectively scatters or redirects the guided light inside an LED chip to find escape cones. Besides, the nano-mesh ZnO layer serves as an intermediate refractive index layer between the p-GaP window layer and air could effectively suppress Fresnel reflection loss.

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