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Development of a novel chip structure for high-power light emitting diodes with heat-dissipation mirror substrates
|關鍵字:||AlGaInP;磷化鋁銦鎵;GaN;LED;metal substrate;laser lift-off;electroplating;氮化鎵;發光二極體;金屬基板;雷射剝離;電鍍線性增加||出版社:||電機工程學系||摘要:||
在氮化鎵發光二極體應用方面，本研究發現氮化鎵/鏡面/銅基板結構之發光二極體其電流-電壓特性與原始氮化鎵/藍寶石基板結構之氮化鎵發光二極體非常類似，此意味著經過雷射剝離製程及電鍍製程的元件，並不會因為製程上的改變而使得其歐姆接觸受影響。在光強度上，氮化鎵/鏡面/銅基板結構之發光二極體在注入電流20 mA時，呈現出52 mcd之發光亮度，此值約是氮化鎵/藍寶石結構 (35 mcd @ 20 mA) 的1.5倍。而在光輸出功率方面，氮化鎵/鏡面/銅基板結構之發光二極體，其光輸出功率隨著注入電流增加呈線性增加直到180 mA才達飽和，而氮化鎵/藍寶石結構之發光二極體在注入電流增加至70 mA時即發生光輸出功率提早飽和的現象，意即說明此結構受熱效應的影響較大，反之氮化鎵/鏡面/銅基板結構則因為有熱傳導性佳的銅基板提供熱的散逸。
High-efficiency light-emitting diodes (LEDs) are desired for many applications such as outdoor displays, automobile signals, and traffic indicators. It is well known that the AlGaInP LEDs lattice-matched GaAs substrates have the highest luminous efficiency in the yellow-to-red spectral region, and the GaN-based LEDs have the spectral region from green-to-blue. On the other hand, high power LEDs are usually driven on high current, the huge joule heating could contribute the early saturation trends of light output. Hence, in this thesis, the main purpose is to develop a novel chip structure for high-power light emitting diodes with heat dissipation mirror substrates. The LED device has not only the high reflective mirror but the high thermal dissipated metal substrate. Furthermore, the problem which was induced by metal dicing has also been avoided.
The AlGaInP/mirror/Cu LEDs provide higher light output than original AlGaInP/GaAs LEDs due to the high reflective rate metal mirror. In the heat sink characteristic, It was found that the wavelength of the AlGaInP LED with Cu substrate exhibited only about 4 nm shift at 400 mA, corresponding to a ~40C rising in the junction temperature. However, the junction temperature raised to 110 oC easily as the injection current at 400 mA for the AlGaInP/GaAs LED sample. This indicates that the device heating is more pronounced for the conventional AlGaInP LED with a GaAs substrate. Obviously, the metallic substrate provides a good thermal management.
On the other hand, the GaN/mirror/Cu LEDs was developed by a combination of laser lift-off (LLO) and electroplating techniques. In particular, the I-V curves of the GaN/mirror/Cu and original GaN/sapphire LED samples are nearly the same. This suggests that the LLO and electroplating processes do not adversely affect the LED performance. The luminance intensity of the GaN/mirror/Cu LED is about 50% higher than that of the original GaN/sapphire sample. The output power of the GaN/mirror/Cu LED increases linearly with injection current up to 180 mA, while early saturation of the GaN/sapphire device occurs at 70 mA. These indicate that the joule heating is less pronounced for the GaN/mirror/Cu LED sample where the metallic substrate provides a good heat sink.
|Appears in Collections:||電機工程學系所|
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