石墨烯透明電流擴散層應用於深紫外光發光二極體

Abstract

石墨烯(graphene)為碳原子以六角型晶格所排列而成之二維材料，其具有低電阻率、高載子遷移率、良好之熱特性與機械特性等多項優點，其中於紫外光波段之高穿透率更被看好應用於深紫外光發光二極體(UVCLED)做為透明電流擴散層(TCE)之材料。然而，石墨烯與深紫外光發光二極體頂層材料之高接觸電阻率則為應用之最大障礙。 本實驗中提出以原子層化學氣相沉積法(ALD)之氧化鎳做為緩衝層降低蕭特基位障以改善接觸性不良之問題。於石墨烯製程方面，本實驗使用電漿輔助化學氣相沉積法直接成長石墨烯於目標基板之技術，改善傳統低壓化學氣相沉積法之高溫製程與轉印製程之不利要素，使大面積量產石墨烯為可行。最終直接於頂層之p型氮化鋁鎵層成長出約五層厚度之石墨烯，並輔以氧化鎳做為緩衝層可達到低接觸電阻ρc = (4.29 ± 0.46) × 10-1Ω-cm2，於280 nm之透光性仍有50%穿透率，為有潛力取代銦錫氧化物(ITO)做為電流擴散層之材料。

Graphene is a two-dimensional material in which the carbon atoms are arranged in a hexagonal lattice. It has many advantages such as low resistivity, high carrier mobility, good thermal properties and mechanical properties, among which the high transmittance in the UV region is more promising for use in deep ultraviolet light emitting diodes as the material of the transparent conductive electrode. However, the high contact resistivity of graphene and the top material of deep ultraviolet light-emitting diode is the largest obstacle to the application. In this experiment, we propose a method to reduce the Schottky barrier by using nickel oxide which is made by atomic layer chemical vapor deposition as a buffer layer to improve the poor contact. In the graphene process, this experiment usess the plasma-enhanced chemical vapor deposition to directly grow graphene on the substrate. The system improves the high-temperature process and transfer process of conventional low-pressure chemical vapor deposition, so that makes large area production of graphene be feasible. Finally, we directly grow about five layer graphene on the top of the the p-AlGaN layer. With the use of NiO as the buffer layer, we get the contact resistance is equal to (4.29 ± 0.46) × 10-1Ω-cm2 and have transmittance about 50% at 280 nm. This material has the potential to replace indium tin oxide (ITO) as a transparent conductive electrode.