外部量子效率在LED的製作上是非常重要的，根據司乃耳定律，傳統LED的外部量子效率被LED內部所發生的全反射給侷限住，而會發生全反射的原因則是因為半導體和空氣間存在著很大的折射細數差異。也因為這樣才會造成內部量子效率和外部量子效率間如此大的差距。因此有許多人致力於提升外部量子效率的工作上，而其中一個方法就是將LED表面給粗化。此外，多孔氧化鋁的折射係數值為1.7，剛好藉於P型磷化鎵與空氣間，因此我們不僅可以利用多孔氧化鋁來當作中間層，更可以利用它的多孔性來粗化LED表面。

　　本論文分為兩部份，第一部份介紹多孔氧化鋁的製備以及特性：多孔氧化鋁是由鋁在酸性電解液中氧化而形成，我們可以藉由控制氧化的條件去調整孔洞的間距(由25-80奈米)與直徑(由20-45奈米)，進一步去利用這些特性來做不同的應用，像是沉積或是蝕刻光罩。在本文我們則是直接利用其多孔性來達成作粗化LED表面的目的；第二部份則是直在在紅光LED上生成多孔氧化鋁，並在LED製程後量測其電性以及光性，藉由上述的方法，我們使AlGaInP發光二極體的亮度提升了6%。

　As is well known, external quantum efficiency is very important in fabricating LEDs. Accordind to the Snell’s law, the external quantum efficiency of conventional LEDs is limited by the total internal reflection of the generated light due to the large difference in the refractive index between semiconductor and air. Thus a significant gap exists between the internal quantum efficiency and the external quantum efficiency. Therefore, much work has focused on improving the external quantum efficiency. One method is to roughen the upper surface of LEDs. The refractive index of porous alumina is between GaP and air. Not only we can use it as the intermedium but the porosity may microroughen the surface of LEDs.

　There are two parts in this thesis. One is the introduction of the properties and fabrication of porous alumina. The porous alumina is the anodization of aluminum in acid electrolyte. The diameter of the pores(25-80nm) and the interpore distance(20-45nm) can be modulated by changing the anodization parameters. Furthermore, using porous alumina as evaporation and etching mask would be successful by the properties. In this thesis, we directly utilize the alumina to microroughen the surface of LEDs. In the other part of this thesis, the porous alumina formd on the upper surface of red-light LEDs. The optical and electrical measurement can be obtaind after we complete all process. We have demonstrated that there was additional 6% improvement in the luminous intensity of GaAlInP LED by employing the above method.

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