近年來，隨著有機金屬化學氣相磊晶(MOCVD)技術的快速發展，磷化鋁鎵銦發光二極體(AlGaInP light emitting diodes)的內部量子效率(internal quantum efficiency)幾乎可以達到100%。然而，其外部量子效率(external quantum efficiency)卻仍有很大的改善空間。本論文的主要研究目的即為研究數種不同的製程方法來改善發光二極體的外部量子效率以期製作更高亮度的發光二極體。
　　首先，我們利用氯氣和氬氣的混和氣體以電感耦合電漿蝕刻(ICP)對磷化鎵窗口層(GaP window layer)進行乾式蝕刻，而後以電漿化學氣相沉積法(PECVD)成長二氧化矽當電流阻障層(current blocking layer)。藉由電流阻障層的加入，可以有效的改善注入電流聚集在正電極下方的情形，使注入電流可以擴散至發光二極體的邊緣而提高發光效率。在20mA驅動電流下，9mil及16mil尺寸的發光二極體晶粒可分別提高17.61%及22.17%的發光效率。此外，元件的可靠度測試結果亦在標準範圍內。
其次，我們加入氮化矽抗反射層於發光二極體表面來降低Fresnel loss 以增加光取出。我們先以TFcalc軟體模擬氮化矽和其他材料的穿透率。結果顯示四分之一波長(quarter wavelength)光學厚度(optical thickness)的氮化矽具有最佳的穿透率。實驗結果亦顯示此種條件下的光激發光譜(PL)最高，發光效率可提升28.23%。
　　根據司乃耳定律，磷化鎵和空氣的臨界角約等於17.1o以致於大部分的光無法透射出來。利用濕蝕刻方法在磷化鎵窗口層上形成許多梯形島(trapezoid islands)可以減低臨界角的限制。32.15o的梯形斜邊可以增加光透射的機會，有8.21%的亮度提昇。
最後，我們混合電流阻障層與抗反射層的雙重效果。在20mA驅動電流下，9mil及16mil尺寸發光二極體晶粒的發光效率可分別提高至59.72%及63.08%。

Recently, with the quick development technique of metal organic chemical vapor deposition (MOCVD), the internal quantum efficiency of AlGaInP light emitting diodes (LEDs) can achieve near 100%. However, there is still a lot of hard work needed to improve the external quantum efficiency. The main purpose of this thesis is to improve external quantum efficiency of LEDs by investigating several different fabrication methods, which can help increase the brightness of LEDs.
The first method proposed is the application of current blocking layer to LED structure. The fabrication process was dry etching on GaP window layer, which is implemented by inductively coupled plasma (ICP) employing the mixture of Cl2 and Ar gases, followed by the deposition of SiO2 film by plasma enhanced CVD (PECVD). By means of inserting current blocking layer, current crowding under positive electrode can be prevented effectively, and the injection current can spread out to the edge of light-emitting diodes to further heighten efficiency. Efficiency was raised by 17.61% and 22.17% at an operation current of 20mA for light-emitting diodes chips with 9mil and 16mil sizes, respectively. In addition, the testing results of the devices reliability were within the standard.
Next, we added SiNx antireflection layer (AR) on LEDs surface to reduce Fressnel loss and increase light extraction. We simulated the transmittance of Si3N4 and other materials by TFcalc. The simulation results showed that we can obtain the best transmittance when the optical thickness of Si3N4 AR layer equaled quarter wavelength of incident light. Under this condition, the PL intensity was the maximum and efficiency was increased by 28.38%.
From Snell’s law, the critical angle between GaP and air is about 17.1o and makes a great fraction of light unable to emit into air. We fabricated many trapezoid islands on GaP window layer by wet etching technology to reduce the low critical angle limitation. By 32.15o bevel edge angle, luminous intensity was raised by 8.21%.
Last, we combined the functions of both current blocking and AR. Under a driving current of 20mA, efficiency was increased up to 59.72% and 63.08% for light-emitting diodes with 9mil and 16mil sizes, respectively.

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