發光二極體是藉由電子-電洞對在活性層復合，再將其多餘的能量以光子的型式放出，因此在論文中，藉由電性和光性的量測，來更了解及改進其特性。
　　透過精密半導參數分析儀，所量得之電壓-電流特性曲線來分析其擴散電流及復合電流；再透過發光二極體元件測試機，所量得之發光強度-電流曲線來分析發光強度與電流之間的關係，還有以電激發光頻譜來研究其復合機制。
　　我們藉由電性之量測，發現藍光二極體在低電流區域，有一種別於傳統擴散電流以及復合電流的電流成分存在，根據研究是透過缺陷的一種穿隧機制(Tunneling mechanism)，在量測電激發光頻譜時，可以發現隨著電流的增加，放射波峰(Emission peak)會往短波長移動，這種現象是由於能帶填充(Band filling)，這是由於注入的電洞藉由穿隧到空的受體雜質能帶及空的價帶帶尾(Valence band tails)。

　　The main mechanism of LED is based on the electron-hole recombination in the active layer, and then the energy emitted by the form of photon. In this thesis we try to understand and improve the characteristics by both optical and electrical measurement.
　　By the I-V curve obtained by HP4156, we analyze the diffusion and recombination current. By the L-I curve obtained by led tester, we analyze the relation between light output intensity and current, research the mechanism of recombination by electroluminescence spectra.
　　By our experiment we can find that there is a current different from other conventional forms in low current injected blue light-emitting diodes, and it is believed as a tunneling mechanism due to defects. By electroluminescence spectra, the emission peak will shift to short wavelength with the increase of current. It is caused by the band filling, which means the holes tunnel to empty acceptor impurity band and valence band tails.

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