氮化鎵系列的發光二極體都會有效率下降的問題，所以會導致藍光發光二極體在發展上受到限制，而一般來說效率下降的機制可被分為兩大類型。一是內部損耗(Internal Losses)，像是歐傑複合(Auger Recombination)、作用區體積減少(Reduced Effective Volume)以及載子離域(Carrier Delocalization)。二是載子溢漏(Carrier Leakage)，而其中又包含了極化效應(Polarization Charge)、非對稱的載子傳輸特性(Asymmetry)、電流壅塞(Current Crowding)、少量電洞注入(Poor hole injection)……等。而本實驗針對後面三個效率下降的因素想要透過實驗製程上的改善來減緩效率下降的問題，像是鎳金電流擴散層利用不同退火條件、溫度以及時間上的改變進而提升電流擴散的特性；而沉積鈷鎵共摻氧化鋅層是想要改善非對稱載子的傳輸特性，減緩電子電洞的載子濃度不對稱，以提升元件的電性及發光亮度。

The development of high-efficiency InGaN light-emitting diodes (LEDs) is considered one of the most important topics in the area of solid-state lighting. However, the efficiency of LEDs is limited by several factors including the high resistivity of p-GaN; hence, the severe current crowding occurs under the p electrode. For this reason, a thin Ni/Au layer with transparency below 70% in the visible region has been extensively investigated to serve as the transparent contact layer (TCL). Transparent conductive oxides (TCO), such as indium oxide (ITO), have high transparency in the visible region, allowing it to serve as the TCL in LEDs. Moreover, the effect of the asymmetry in carrier concentration and mobility is studied in InGaN pn-junction light-emitting diodes. To overcome this problem of efficiency droop, we deposit the ZnO:CoGa layer on n-GaN. This method can reduce the difference between the hole concentration and the electron concentration.

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