適用於發光二極體導電擴散層之石墨烯材料特性研究

Abstract

石墨烯是一種由碳原子六角形陣列的二維碳材料，其具有卓越的特性，如低片電阻、高穿透度、機械與熱特性等，被認為是未來優良之透明導電電極能夠運用於許多光電子元件上。 本實驗中，吾等將化學氣相沉積生產之石墨烯運用於發光二極體元件之p-GaN上作為透明導電電流擴散層。化學氣相沉積5 sccm甲烷、10 sccm氫氣與100 ~ 500 sccm氬氣濃度混和於攝氏900 ℃沉積石墨烯薄膜，接續運用奈米轉印技術將石墨稀轉印至發光二極體元件之p-GaN上。為了減少石墨烯與p-GaN界面之間蕭特基位能障，在p-GaN表面先沉積厚度為3奈米之鎳奈米層(Ni thin film)，緊接著將樣品放置於含氧氣體中以攝氏400℃進行熱退火3分鐘，使其鎳奈米層轉換成氧化鎳(NiO)，後續將石墨烯轉印於氧化鎳上再做一次熱退火使石墨烯與NiO/ p-GaN緊密接合，以降低石墨烯與p-GaN之間之蕭特基位能障進而形成歐姆接觸。最後使用圓形傳輸線模型(CTLM)進行電性量測。Graphene is a two-dimensional carbon material which consists of hexagonal array of carbon atoms, and offers exceptional characteristics such as high transparency, low sheet resistance, suppleness, etc. In this study, we show that chemical vapor deposition grown graphene on copper foil and transfer it on p-GaN as light-emitting-devices transparent conducting electrode. To decrease Schottky barrier between graphene and p-GaN interface, we deposit Ni nanolayeron p-GaN substract as a buffer layer between graphene and p-GaN. After deposited 3 nm thickness nickel (Ni thin film) on p-GaN surface, followed by placing the sample in an oxygen-containing gas to 400°C thermal annealing for 3 minutes, so that the nickel layer is converted into nano nickel oxide (NiOx) dots. NiOx dots haave high transparency at blue light and UV light region. Follow the graphene transferred to do a thermal anneal make graphene with NiO / p-GaN close contact, in order to reduce the Schottky barrier between graphene and the p-GaN thus forming an ohmic contact on nickel oxide. Finally, using a circular transmission line model (CTLM) for electrical resistance measurements.