在LED(Light Emitting Diode)的製作程序上，有關p-GaN的歐姆接觸(ohmic contact)已經被廣泛的研究及發表。本篇論文除了符合歐姆接觸的特性外，也因應Thin-GaN LED結構所需之高反射率的特性，我們提出具有高功函數(work function)的Pt以及高反射率的Ag應用在p-GaN的製程。 首先利用兩種不同厚度的Pt(5 nm和10 nm)在氮氣環境下，分別做500 ℃~800 ℃的熱處理，加熱時間為5分鐘，從中可發現特徵接觸電阻(specific contact resistance)及穿透率都隨溫度上升而上升。接著鍍上Ag後，置入氮氣環境下做500 ℃的熱處理，加熱時間為5分鐘，發現原先變差的特徵接觸電阻又下降至一穩定值，最低可得之值約為4.5x10-3 Ω-cm2。因為Pt的穿透率會隨熱處理溫度上升而上升，所以Pt / Ag的反射率亦可得到相同趨勢。在470 nm下，可得到Pt / Ag最高反射率約為83%。 The electrical and optical properties of metal scheme contacts on p-GaN were investigated widely. In this paper, firstly, we studied the transmittance of Pt ohmic layer on p-GaN. Then, the contact resistance and reflectivity of Pt / Ag was evaluated. Pt p-contact with two different thickness 5 and 10 nm were studied on p-GaN. Pt / p-GaN samples were annealed at N2 ambient for 5 minutes and annealing temperatures were 500℃~800℃. We find the specific contact resistance and transmittance of Pt raise with increasing annealing temperatures. After specific contact resistance and transmittance measurement, 150 nm Ag layer was deposited on the annealed Pt contact pads. Finally, the metal scheme of Pt/Ag/p-GaN was investigated by annealing together at at N2 ambient for 5 minutes and annealing temperature was 500℃. The lowest specific contact resistance of Pt / Ag we can get is about 4.5x10-3 Ω-cm2。 At 470 nm, the highest reflectivity of Pt / Ag is about 83%.
