本論文主要研究將光致電化學反應(Photoelectrochemica; PEC Oxidation )與壓印(Imprint Technique)技術結合，進而應用於網狀發光二極體並提升氮化鎵發光二極體之外部量子效率。在氮化鎵表面成長出區域性的氮化鎵氧化物(GaxOy)，利用其相對於氮化鎵有著較低的折射(n=1.8~1.9)以及較高的介電常數之特性，來減少內部全反射角以及增加元件出光效率。並在本論文裡針對此結構作一系列歐姆接觸特性，以及不同氧化條件下對於發光二極體之光電特性的影響之研究與探討。
在本論文裡，利用Transmission Line Model (TLM)探討經過PEC Oxidation與熱處理之後Ni/Au 透明導電膜與半導體的接觸電特性，實驗發現在550℃得到最佳的特徵接觸電阻值(ρc)，為7.85×10-2 (Ω-cm2)，沒有氧化的ρc 為1.68×10-3 (Ω-cm2)。在發光二極體光電特性方面，首先比較不同氧化速率成長相同厚度(40nm)的GaxOy，在20 mA電流注入下，順向導通電壓比未氧化的LED增加約0.11 V~0.22 V，光輸出功率約為3.0~3.14 mW，增加17.2~22.7%。在網狀氧化物LEDs中發現有壓抑漏電流的現象，其原因為減少TCL Ni/Au的接觸面積，而氧化物也有效的覆蓋元表面的漏電路徑。
實驗結果顯示，利用“PEC壓印氧化法”在LED元件表面產生特定圖形的GaxOy，電流在表面傳播時能經由網狀的TCL結構達到均勻散佈的效果。並利用折射率與表面結構的改變，減少LED元件光輸出時的內部全反射機率，以增加光取出效率。

In this work,we developed a novel and low-cost oxidation process for growing gallium oxide on GaN in water. This process combines alternating (AC) bias-assisted photoelectrochemical (PEC) oxidation with imprint technique, which can grow and pattern gallium thin film by an ITO-coated molds. Because of the low refractive index (n=1.8-1.9) and high dielectric constant contrast to GaN, gallium oxide is suggested to reduce the internal reflection and to increase light escape from the surface of the GaN-based LEDs. Here, we performed mesh-oxide LEDs by the novel process and investigated their optoelectrical characteristics.
The Ni-Au contact characteristic of p-type GaN with and without PEC oxidation was studied in this work. After thermal annealing in 550 OC for 5min in O2 ambient in furnace, both of the two samples have specific contact resistances of 1.68×10-3 and 7.85×10-2 Ω-cm2,respectively. In the optoelectrical characteristics of LEDs, we performed the oxide LEDs with the same oxide thickness of 40nm to study further. The forward voltage (Vf) was increased by 0.11~0.22 V in the oxide LEDs, and the light output power of LEDs at 20mA were between 3.0 mW and 3.14 mW which were 17.2%~22.7% higher than the conventional LED. The decrease of leakage current was also observed in the mesh-oxide LEDs. Because of decrease the area for Ni/Au TCL as compared to the conventional LEDs, and the oxidized region tends to effectively cover or suppress threading dislocation located at the top surface of the mesh-oxide LEDs.
The improvement on light output power can be attributed to the PEC grown convex oxide layer with nano-rough morphology, resulting in uniform current spreading by mesh TCL. The change in the intermediate refractive index of the oxide film can reduces the total internal reflection at the GaN surface, then make light escape out of the surface of LED more efficiently.

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