本論文主要針對具有微米導光柱、反射式電極(Ag/Cr/Au)以及透明導電層氧化銦錫(ITO)/氧化鋅鎵(GZO)表面網狀粗化結構應用於氮化鎵發光二極體之製作與研究。
在電極部分，我們利用未經合金處理之傳統電極(鉻/金)以及反射式電極(銀/鉻/金)作為LEDs之金屬電極，首先探討金屬接觸於N型氮化鎵上之歐姆接觸特性研究。由實驗可知，傳統電極(Cr/Au)以及反射式電極(Ag/Cr/Au) 在N型氮化鎵上皆具有良好的歐姆接觸特性，特徵接觸電阻值(ρ_c)皆能達到～10^(-4)Ω-cm^2。而在光特性部分，由於傳統電極通常由不透光或低反射率的金屬構成，其電極面積會遮蔽或吸收來自多重量子井(MQW)的光源，所以我們利用反射式電極的高反射率特性，避免光子被電極遮蔽或吸收，進而提升光萃取效率。接著，為了進一步提升光萃取效率，透過黃光微影的方式，經過乾蝕刻及濕蝕刻，分別在發光二極體的周圍形成微米導光柱以及在ITO/GZO薄膜表面形成網狀粗化結構。
為了能夠顯著的提升光萃取效率，我們將上述方法應用於LEDs。首先我們利用ITO/GZO當作透明導電層，在GZO薄膜表面作網狀粗化結構，由實驗可知，在20mA電流注入下，ITO/mesh GZO LED其光輸出功率相較於傳統ITO/Planar GZO LED增加20.6%，進一步的加入反射式電極取代傳統電極，更可將光輸出功率增加至32.9%。
接著我們利用同樣的實驗方式，將這兩種結構應用於尺寸大小為575×250μm^2的LED上，在20mA電流注入下，ITO/mesh GZO LED其光輸出功率相較於傳統ITO/Planar GZO LED增加20.9%，進一步的加入反射式電極取代傳統電極，可將光輸出功率增加至29.4%。
為了要更進一提升光輸出功率，在元件周圍加入微米導光柱，與ITO/GZO薄膜表面網狀粗化結構及反射式電極結合，在20mA電流注入下，將光輸出功率增加百分比由29.4%提升至38.6%。
　　綜合上述，具有微米導光柱、反射式電極及ITO/GZO表面網狀粗化結構應用於發光二極體上，其光輸出功率相較於傳統LED增加了38.6%，能夠有效的提升外部量子效率，而操作電壓只有些微上升0.1~0.15V。

In this study, we demonstrated GaN-based light-emitting diodes(LEDs) with non-alloyed metal contacts on n-GaN and transparent contact layer(TCL), which was indium tin oxide and/or gallium-doped zinc oxide, to serve as the n-type electrode and the p-type electrode, respectively. The TCLs had rough surface with mesh structure. Besides, photolithography process was applied to form micro-pillar waveguide at the periphery of LEDs to enhance the light extraction efficiency. The result will be discussed in detail in this thesis.

In this study, the non-alloyed metal contacts including Cr/Au and Ag/Cr/Au were used to serves as electrodes and reflectors at the same time. The conventional electrode pad (Cr/Au) and the reflective electrode pad (Ag/Cr/Au) deposited on n-GaN layer can exhibit Ohmic characteristics on n-GaN. The specific contact resistance(ρ_c) was as low as ~10^(-4)Ω-cm^2. The non-alloyed metal contacts(Ag/Cr/Au) used in the present experimental blue LEDs also play the role of reflector to prevent the emitted light from absorption by the opaque electrode pads(Cr/Au) with low reflectivity.

The experiments implemented by the above-mentioned schemes exhibited a marked enhancement in light-extraction efficiency, and their electrical properties were comparable with the conventional LEDs. With an injection current of 20mA, the light output power of the ITO/mesh GZO LEDs can be markedly improved by 20.6% of magnitude as compared to the conventional ITO/planar GZO LEDs. Furthermore, the enhancement can be boosted to 32.9% if the Cr/Au electrode pads were replace by the reflective Ag/Cr/Au electrode pads.

The same experiment were also performed to GaN-based LEDs with different sizes which chip size was 575×250 μm^2. With an injection current of 20mA, the light output power of the ITO/mesh GZO LEDs can be markedly improved by 20.9% of magnitude as compared to the conventional ITO/planar GZO LEDs. Similarly, the enhancement can be further boosted like the technique was used in the LEDs with chip size of 300×300 μm^2. The enhancement in light output power was as high as 29.4% of magnitude if the Cr/Au electrode pads were replace by the reflective Ag/Cr/Au electrode pads.

In order to further increase the light output power, micro-pillar waveguides at the periphery of LEDs were implemented. As a result, the light output power is boosted to 38.6%.

In summary, we had demonstrated GaN-based LEDs with micro-pillar waveguides, reflective pads and roughed TCL. The light output power of the LEDs could be enhanced about 38.6% of magnitude, and the operation voltage of the LEDs had just a slightly increase of 0.1~0.15v as compared to the conventional LEDs.

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