氧化銦錫擴散電流層厚度對氮化鎵發光二極體光電特性的影響

Abstract

近年來，隨著氮化鎵發光二極體的發展，高透明度且電阻率小的氧化銦錫已經被廣泛的用作為透明電流擴散層。在此篇研究中，於P型氮化鎵上蒸鍍了不同厚度的氧化銦錫薄膜，並且製造成傳統的發光二極體，用以研究氧化銦錫薄膜和發光二極體元件的光電特性。我們發現氧化銦錫薄膜的片電阻值會隨著其厚度增加而降低，並影響到電流擴散能力和動態串接電阻值，氧化銦錫晶粒尺寸也和其厚度有關。另外，接觸電阻係數也受到在氧化銦錫和氮化鎵界面間氧含量的支配。然而，電流擴散長度或氧化銦錫厚度似乎都和量測到的元件亮度沒有關連，我們嘗試找出造成此種不一致的可能原因。

With the development of nitride-based light-emitting diodes (LEDs) in the past year, indium-tin-oxide (ITO) has been widely applied as a transparent current spreading layer due to its high transparency and low electrical resistivity. In this research, ITO films with different thicknesses are evaporated on p-type GaN, and then the conventional GaN-based LEDs are fabricated. Optical and electrical characteristics of these ITO films and LED devices have been analyzed. We find that sheet resistance has an obviously decrease with adding the thickness of ITO film, which has effect on the current spreading ability and dynamic series resistance. The grain size of ITO is also corresponding to its thickness. In addition, the specific contact resistance is dominated by the oxygen proportion in the ITO/p-GaN interface. However, the measured light luminance of devices seems no relationship with the current spreading length, or ITO film thickness. We tend to find the possible reason for the discrepancy.