石墨烯(graphene)為一種二維材料，由碳原子排列形成六角晶格結構，其具備多種特性，如低片電阻、高載子遷移率、良好之熱導性、機械性與高光穿透度等，其中於紫外光波段具高穿透度，因此為一相當具潛力之材料，可應用於深紫外光發光二極體上之電流擴散層。然而，石墨烯與深紫外光發光二極體最上層之p型磊晶材料之功函數差太大，此介面間存在蕭特基位障之高接觸電阻率，為石墨烯應用於深紫外光發光二極體上之一大障礙。
為降低石墨烯與發光二極體介面間之接觸電阻率，本實驗中提出藉由原子層氣相沉積法(Atomic Layer Deposition；ALD)，沉積功函數介於石墨烯與深紫外光發光二極體最上層之p型磊晶材料中間之氧化鎳作為石墨烯與發光二極體間之緩衝層，以降低此介面間之蕭特基位障，減少接觸電阻率之問題。本實驗中成長石墨烯製程之部分，乃藉由電漿輔助式化學氣相沉積法，以鎳薄膜作為金屬催化劑，直接生長大面積石墨烯於目標基板，其與傳統化學氣相沉積法成長石墨烯相比，可大幅降低製程溫度與省去轉印之步驟，增添量產之可能性。最後，於深紫外光發光二極體之p型氮化鎵磊晶層，生長約十五層厚度之石墨烯，且因加入氧化鎳作為緩衝層之結構，測得接觸電阻ρc為1.8×10-2 Ω-cm2，且於280 nm波段之透光率仍有約50%。

Graphene is a two-dimensional material that is arranged by carbon atoms to form a hexagonal lattice structure with various properties such as low sheet resistance, high carrier mobility, good thermal conductivity, mechanical properties and high transmittance etc., which has high transmittance in the ultraviolet region, is therefore a potential material apply on UVCLED as the transparent conductivity electrode. However, the work function difference between the graphene and the p-type epitaxial material of the uppermost layer of the deep ultraviolet light emitting diode is too large, and there is a high contact resistivity of the Schottky barrier between the interfaces. This high contact resistivity between graphene and p-type layer of the UVCLED, which is a major obstacle for graphene to be applied to the UVCLED.
In order to reduce the contact resistivity between the graphene and the light-emitting diode interface, this experiment proposes that NiO thin film which the work function is between graphene and deep ultraviolet light emitting diode acts as a buffer layer by Atomic Layer Deposition (ALD). Nickel oxide acts as a buffer layer between graphene and the light-emitting diode to reduce the Schottky barrier between the interfaces and reduce the contact resistivity. In this experiment, the part of the growing graphene process is a plasma-enhanced chemical vapor deposition method using a nickel film as a metal catalyst to directly grow large-area graphene on a target substrate. Compared with the conventional process of chemical vapor deposition method, significantly reducing the process temperature and the step of eliminating the need for a transfer, increase the possibility of mass production. Finally, in the deep ultraviolet light emitting diode p-type gallium nitride epitaxial layer, about fifteen layers of graphene are grown, and nickel oxide is added as a buffer layer structure, and the contact resistance ρc is 1.8×10-2 Ω-cm2, and the transmittance at 280 nm is still about 50%.

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