在本研究論文中，為了改善氮化鎵系發光二極體之電流散佈能力(current spreading ability)與光取出效率(light extraction efficiency)，吾人成功研製具有金屬薄膜修飾結構之氮化鎵系發光二極體。分別提出了元件製程技術與奈米材料應用，其中包含複合式鋁金屬薄膜/氧化鋁鋅透明導電層、一維條紋狀銀金屬導電薄膜以及複合式氧化鋅奈米結構與一維條紋狀銀金屬導電薄膜之結構，有效改善氮化鎵系發光二極體的光電特性，提升氮化鎵系發光二極體之性能與可靠度。本文對氮化鎵系發光二極體之光電特性與電流散佈能力，以及透明導電層與金屬薄膜結構之製程皆有深入之研究與探討。
首先吾人研製鋁金屬薄膜沉積於氧化鋁鋅透明導電層表面之氮化鎵系發光二極體，同時改善發光二極體元件的電流擁擠效應(current crowding effect)與導通電壓過高的缺點。具有高導電率之鋁金屬薄膜可有效改善電流擁擠效應，增加電流散佈能力，大幅增加電流分佈之面積，使得電流不會只侷限在電極附近，進而提升光輸出功率18.6%。不僅如此，複合式鋁金屬薄膜/氧化鋁鋅透明導電層之氮化鎵系發光二極體亦能有效降低特徵接觸電阻，根據傳輸線模型(transmission line model, TLM)量測，此研發元件之特徵電阻值降低至8.4 x 10-4 Ω-cm2，導通電壓降低0.3伏特 。
其次，探討一維條紋狀銀金屬導電薄膜之氮化鎵系發光二極體，藉由條紋狀銀金屬導電薄膜增加電流散佈的能力並減少光被半透明的銀金屬導電薄膜所吸收。雖然此研發元件之光輸出功率僅提升約5%，但元件導通電壓大幅降低0.6伏特。不僅如此，相較於傳統氮化鎵系發光二極體，此研發元件在電流對光輸出功率之關係圖中，電流飽和點右移約150毫安培，這是因為一維條紋狀銀金屬導電薄膜能有效減緩電流擁擠效應以及焦耳熱效應(Joule heating effect)，使電流不會只侷限在元件之電極附近，因而讓元件對溫度的影響減弱，可有效改善光電轉換效率以及降低消耗功率。
最後，探討成長氧化鋅奈米結構與一維條紋狀銀金屬導電薄膜之氮化鎵系發光二極體，改善第三章中一維條紋狀銀金屬導電薄膜穿透率過低的問題，藉由氧化鋅奈米結構降低內部全反射之效應，將由主動區發散之光重新導正向上，並增加光散射至元件之外的機會，提升光輸出功率與外部量子效率達15.1%以及10.0%。本研究論文所研製的具有金屬薄膜修飾結構之氮化鎵系發光二極體，皆可有效提升光電轉換效率以及降低消耗功率，可用於實際上的應用。

In this dissertation, for purposes of improving the current spreading ability and light extraction efficiency (LEE), GaN-based light-emitting diodes (LEDs) with decorated metal thin film structures were fabricated and studied. The device fabrication processes and nanomaterials applications, including a hybrid Al metal thin film/AZO transparent conductive layer, an one-dimension (1-D) stripe Ag metal thin film, hybrid ZnO nanostructure and stripe Ag metal thin film, were introduced to improve wall-plug efficiency (WPE) of GaN-based LEDs. Therefore, enhanced performance and reliability of GaN-based LEDs could be obtained. In addition, optical properties and current spreading ability of the GaN-based LEDs were studied and discussed. The fabrication processes of transparent contact layer (TCL) and metal thin film structures are also discussed in detail.
First, GaN-based LEDs with a high-current spreading ability based on a hybrid Al metal thin film/AZO transparent conductive layer was fabricated and studied. The use of a hybrid Al metal thin film structures improve the current crowding effect and high forward voltage problem. A hybrid Al metal thin film structures substantially increases the current distribution area rather than the current crowding near the electrodes. As compared with conventional GaN-based LEDs at 20 mA, the studied device exhibits a 18.6% improvement in light output power. In addition, GaN-based LEDs with a high-current spreading ability based on a hybrid Al metal thin film/AZO transparent conductive layer could efficiently reduce specific contact resistance. According to transmission line model measurement, the specific contact resistance of the studied device is reduced to 8.4 x 10-4 Ω-cm2. As compared with conventional GaN-based LEDs at 20 mA, the studied device can reduce 0.3 V.
Second, an one-dimension (1-D) stripe Ag metal thin film was successfully fabricated. A stripe Ag metal thin film could efficiently enhance current spreading ability and reduce the absorption of photos by semi-transparent only Ag metal thin film. Although the studied device only 5% improvement in light output power, the forward voltage of device substantially reduced 0.6 V. In addition, As DC forward current is increased from 10 to 100 mA, the increased junction temperature also reduced from 53.3 to 3.3oC of the studied device. The saturation point of the light output power increased from 350 to 500 mA. It is attributed to an 1-D stripe Ag metal thin film could effectively abate current crowding effect and joule heating effect. Due to the current distribution more uniform, the performances and power consumption of GaN-based LEDs are significantly improved.
Finally, GaN-based LEDs with a hybrid ZnO nanostructures and stripe Ag metal thin film is fabricated and studied. A stripe Ag metal thin film was used to enhance current spreading ability and abate thermal effect. The forward voltage was reduced from 3.54 to 3.12 V of studied devices. The use of ZnO nanorods effectively reflect photons and redirect the light path rather than total internal reflection effect. As compared with conventional GaN-based LEDs at 20 mA, studied device exhibits 15.1% (14.9%) improvements in light output power as well as EQE. Optical and electrical properties could be improved by the employment of a hybrid ZnO nanostructure and stripe Ag metal thin film. Moreover, due to the lattice constant approximation of AZO and ZnO, ZnO nanordos could directly grow in the AZO surface by low-temperature hydrothermal. It is a low cost and simple process for GaN-based LEDs.
In conclusion, all of these specific approaches in this dissertation could effectively improve performances and power consumption of GaN-based LEDs. Thus, GaN-based LEDs have high potential actual applications.

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