為進一步提升垂直結構氮化鎵系列發光二極體(LED)之發光效率，採用水熱法(Hydrothermal Method)成長氧化鋅奈米線(ZnO-nanowires)於元件表面來達到粗化的目的。實驗結果顯示，利用此一技術40 mil垂直結構LED之光輸出功率(Light Output Power, LOP)於注入電流350 mA下可獲得20.3%之提升。此外，本研究亦提出製作結合了氧化鋅奈米線(ZnO-NWs)與準分子雷射粗化n-GaN表面之12 mil垂直結構LED。在先前實驗室已成功研製出元件表面具有準分子雷射粗化過之垂直結構GaN-based LED，在光電特性上都有一定程度的改善，為了更進一步提升發光效率，本研究在準分子雷射粗化過的元件表面上再成長氧化鋅奈米線，以減少光受到元件內部全反射的機會。實驗結果顯示，元件表面已先經過準分子雷射粗化過後再成長氧化鋅奈米線(ZnO-NWs)之VM-LEDs與標準垂直結構LED (Regular VM-LEDs)相比，在注入電流20 mA下，光輸出功率增加32%。

Devices with a vertical structure would allow a much large power handling capability due to the immune of current crowding effect. In this study, Vertical-conducting Metal-substrate GaN-based Light-Emitting Diodes (VM-LEDs) were fabricated by using of nickel electroplating substrate transformation in conjunction with laser lift-off (LLO) technique. To further improve light output power of VM-LEDs, a cost-effective and efficient surface roughening technology using hydrothermal method to grow ZnO-nanowires was proposed and demonstrated. Experimental results revealed that the proposed structure could effectively enhance light extraction efficiency for VM-LEDs. Compared with the regular VM-LEDs, 20.3% in average improvement in the light output power at 350 mA has been obtained from the ones with ZnO-NWs.
To further improve light output power of VM-LEDs, additional surface roughness by KrF excimer laser together with ZnO-nanowires was also proposed and demonstrated. As compare to regular VM-LEDs, typical improvement in light output power under an injection current of 20 mA by about 32% has been obtained.

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