本論文主要探討高效能氮化鎵系列覆晶式發光二極體之研究。
首先，我們採用具備透明歐姆層與反射鏡面層的組合作為覆晶式發光二極體的主體結構。而研究中發現較適用於這兩層結構的材料為鎳與銀。以此材料設計搭配快速回火製程之長360微米、寬280微米尺寸的發光二極體在20毫安培電流操作時，操作電壓約為3.15伏特，輸出必v相對於一般傳統上非覆晶式發光二極體可提升75%而達16毫瓦。而此種結構的覆晶式發光二極體在可靠度方面的測試亦優於非覆晶式的發光二極體。
進一步為增強發光二極體的輸出發光強度，我們也針對以氧化銦錫搭配鎳為材料的透明歐姆層之發光二極體加以研究。發現經設計的快速回火製程與適當厚度之氧化銦錫搭配鎳之透明歐姆層的發光二極體將可提升30%的亮度而達21毫瓦，並且可保持操作電壓不會升高。而相同的發光二極體在長時間可靠度測試上，也只衰減5%的亮度。
另外在1000微米見方之尺寸的高必v發光二極體應用方面，我們研究了以研磨技術在藍寶石基板背面製作具有高度落差的粗操表面，應用在覆晶式發光二極體將可提升35%的亮度並且亦提升發光二極體的可靠度。
另一方面，由於散熱一直是高必v發光二極體的關鍵問題，因此我們研究以高導熱的銅基板應用在覆晶式發光二極體可降低發光二極體在高電流操作時的電壓與降低發光二極體的接面溫度進而提升可靠度，使得發光二極體在長時間燒測後仍可維持九成以上的發光強度。
更深入地，我們研製將抗靜電元件製作在銅基板上應用於覆晶式發光二極體除了可避免一般將元件製作在發光二極體晶粒上因而降低發光面積的缺點外亦可大幅提高發光二極體的承受靜電壓值，約傳統非覆晶式發光二極體的九倍，且將不會影響發光二極體其他的光電特性與穩定度。

In this dissertation, high performance nitride-based flip-chip (FC) light-emitting diodes (LEDs) were investigated and fabricated.
Firstly, the structure of FC LEDs with transparent ohmic contact and reflective mirror was designed and Ni and Ag were proper materials for them. It was found voltages measured from rapid thermal annealed (RTA) FC LEDs (280 μm X 360 μm) with Ni and Ag layers were 3.15 V at a 20-mA forward current while output powers were improved about 75% and were 16 mW, compared with the traditional non-flip-chip (NFC) LEDs. The same structure was also found making lifetimes longer for FC LEDs as compared with NFC LEDs.
To enhance output intensity furthermore, indium-tin-oxide (ITO)/Ni films as transparent ohmic contacts of FC LEDs were studied. It was observed RTA ITO/Ni films could provide good electrical and optical properties to improve powers about 30%, which were 21mW and keep voltages stable for FC LEDs applications. Output intensity only decayed by 5% after long-time reliability test.
For power FC LEDs (1000 μm X 1000 μm) in addition, we reported the fabrication with roughened surface of sapphire backside prepared by grinding process could increase output power by about 35%. And the surface was rough with a typical peak-to-valley distance. Reliability of the proposed FC LEDs with rough surfaces was also better, as compared to that with conventional flat surfaces.
On the other hand, heat dissipation is a key issue for power chip LEDs. In our research, Cu sub-mounts were studied to replace conventional ones. With a much higher thermal conductivity, we could achieve a lower operation voltage under high current injections and a lower junction temperature from the power FC LEDs with Cu sub-mounts. Compared with the power FC LEDs with Si sub-mount, the reliability of the proposed LEDs was much better. And the EL intensity remained above 90% after operated during long time.
Further, we found the internal ESD protection devices fabricated in Cu sub-mounts could not only avoid lighting area losses for FC LEDs, compared to those fabricated in LED chips but also provide good ESD protection function. It was achieved that negative ESD thresholds could be notably increased. And the values were about 9 times larger than those of traditional NFC LEDs. It also suggested the ESD protection devices in Cu sub-mounts would not affect electro-optical and reliability properties for FC LEDs.

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