目前LED基板使用為藍寶石基板，而氮化鎵與藍寶石基板間存在著高晶格不匹配度，致使氮化鎵薄膜內部產生 109~1010 cm2 之貫穿型差排缺陷，嚴重影響到後續 LED 元件光電性能。圖案藍寶石基板之使用能有效降低差差排密度，然而圖案間之c面區域依舊存在高密度貫穿型差排。
本研究嘗試在圖案化藍寶石基板與氮化鎵薄膜間插入石墨烯介面層，再降低氮化鎵薄膜於圖案化藍寶石基板c面差排密度。利用八吋低壓化學氣相沉積系統(LPCVD)在四吋圖案化藍寶石基板上石墨烯薄膜。分別在圖案化藍寶石基板上鍍上一層銅膜與鎳膜，透過調整金屬膜的厚度、反應氣體比例、製程溫度、不同加熱方式進行石墨烯薄膜的優化。在銅製程方面，由於銅的熔點較低，使製程過程中會產生大量的銅蒸氣，進而影響石墨烯的成長，造成石墨烯薄膜於圖案化藍寶石基板不均勻的現象，因此我們選擇熔點較高的金屬-鎳來當作金屬催化層。在鎳製程方面，經拉曼分析圖可以發現，增加在製程前退火的氫氣流量，可以大幅得提升石墨烯薄膜的品質，透過調整不同鎳薄膜的厚度，在鎳薄膜厚度為200 nm，退火氣體氬氣/氫氣比為100/100 sccm，製程反應氣體甲烷/氫氣比為50/100 sccm，製程壓力0.85 torr，製程溫度1000 °C成長30分鐘下，透過拉曼光譜分析可以得到D/G比為0.14，層數約為3層的高品質石墨烯薄膜。

Currently, LEDs are using sapphire substrate; however, high lattice mismatch are existed between Gallium Nitride and sapphire substrates, causing 109~1010 cm2 of threading dislocation inside Gallium Nitride thin film, which seriously impacts the photoelectric performance of LED components. The application of patterned sapphire substrate(PSS) can effectively reduce dislocation density; yet, the c-plane area between the pattern still exists high density threading dislocation.
In this study, we attempts to insert a graphene interlayer between the patterned sapphire substrate and the GaN film to further reduce the c-face dislocation density of the gallium nitride film on the patterned sapphire substrate..We use 8 inch low pressure chemical vapor deposition system (LPCVD)to grow graphene thin film on 4 inch PSS. Coat a layer of copper and nickel on PSS respectively, through adjusting the thickness of metal thin film, the proportion of reaction gas, the process temperature and different heating method to improve the quality of graphene thin film.In terms of copper process, due to low melting point of copper, large amount of copper steam will be produced through the process, caussing graphene thin film to be uneven on PSS. Thus we choose metal with a higher melting point; that is, nickel, to be the metal catalyst layer. In terms of nickel process, through Raman spectroscopy we can discover that increasing the flow of Argon before annealing can significantly improve the quality of graphene thin film. By adjusting different thickness of nickel thin film, with thickness at 200nm, annealing gas Argon/Hydrogen ratio is 100/100 sccm, Process reaction gas methane/hydrogen ratio is 50/100 sccm，process pressure 0.85 torr，process tempreture 1000°C with 10 minutes growth time, through raman spectroscopy we can observe high quality graphene thin film with D/G ratio of 0.14 with thickness of about 3 layers.

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