利用石墨烯改善氮化鎵歐姆接觸之研究;Improved Ohmic Contact on Gallium Nitride by Graphene Layer

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題名:	利用石墨烯改善氮化鎵歐姆接觸之研究;Improved Ohmic Contact on Gallium Nitride by Graphene Layer
作者:	陳逸弘;Chen, Yi-Hong
貢獻者:	電機工程學系
關鍵詞:	氮化鎵;石墨烯;GaN;Graphene
日期:	2023-08-16
上傳時間:	2023-10-04 16:13:12 (UTC+8)
出版者:	國立中央大學
摘要:	本論文主要針對氮化鋁鎵歐姆接觸進行研究，分別對石墨烯特性及挖槽式歐姆接觸進行討論。研究包含，石墨烯轉印流程，並以拉曼光譜分析在不同表面處裡及退火溫度，對石墨烯所造成的影響，並利用傳輸線模型分析加入石墨烯後，接面等效能障的變化。最後綜合石墨烯及挖槽式歐姆接觸氮化鋁鎵/氮化鎵之高電子遷移率電晶體元件，分析其直流電性及接觸電阻的改善。石墨烯表面經氧電漿處理後，有助於提升後續金屬電極的附著度，實驗觀察到，在短暫的氧電漿處理後，石墨烯的親水度有著明顯的上升，但在拉曼光譜分析中，也觀察到氧電漿處理後，石墨烯缺陷的增加。本研究也探討了300 ℃至850 ℃退火溫度對石墨烯所帶來的衝擊，經由拉曼光譜分析，在氮氣環境下，因為溫度所導致的缺陷增加，發生在400 ℃至500 ℃之間。傳統氮化鋁鎵/氮化鎵之高電子遷移率電晶體，多使用高溫退火，來形成較好的歐姆接觸，而傳統式特徵歐姆接電阻(Specific contact resistivity, ρc)為7.3×10-5 Ω·cm2，在歐姆接觸區域引入石墨烯插入層，可有效使其特徵歐姆接觸電阻下降至8.1×10-6 Ω·cm2。經傳輸線模型分析、擬合後觀察，電子在熱離子場發射(Thermionic field emission, TFE)模型中，接面等效能障由傳統式歐姆接觸的1.02 eV，下降至有石墨烯插入層歐姆接觸的0.83 eV，解釋了其接觸電阻下降的成因。挖槽式歐姆接觸也是一個已被實證，有效降低歐姆接觸電阻的方式，本研究加入並聯的長方形挖槽(2×48 μm2)，並在引入石墨烯插入層，有效的降低了接觸電阻至1.36 Ω·mm，相較傳統式歐姆接觸的4.13 Ω·mm，有著67.1 %的下降。並在製程中加入氧電漿處理，有效的去除了石墨烯所導致的額外電流路徑，使得元件能夠達到良好的開關特性。 ;This thesis primarily focuses on the study of gallium nitride ohmic contacts, discussing the characteristics of graphene and recessed ohmic contacts. The research includes the graphene transfer process and analyzes the effects of different surface treatments and annealing temperatures on graphene using Raman spectroscopy. Additionally, the changes in interface barrier height are examined by employing a transfer length method after inserting a graphene layer. Finally, the combined graphene and recessed ohmic contact AlGaN/GaN HEMT are analyzed for their DC electrical properties and contact resistance improvement. After oxygen plasma treatment on the graphene surface, the adhesion of metal electrodes is enhanced. Experimental observations reveal a significant increase in graphene′s hydrophilicity after a brief oxygen plasma treatment. However, the Raman spectroscopy analysis shows increased defects following the oxygen plasma treatment. This study also investigates the impact of annealing temperatures ranging from 300 °C to 850 °C on graphene. Through Raman spectroscopy analysis in a nitrogen environment, the temperature-induced defect increase is observed to occur between 400 °C and 500 °C. Conventional high-electron-mobility transistors based on gallium nitride typically undergo high-temperature annealing to form better ohmic contacts. The specific contact resistivity (ρc) of the conventional specific ohmic contact is 7.3×10-5 Ω·cm2. Introducing graphene into the ohmic contact region can effectively reduce its specific contact resistivity to 8.1×10-6 Ω·cm2. Through transfer length method analysis and fitting observations, the interface barrier height in the thermionic field emission (TFE) model is reduced from 1.02 eV for the traditional ohmic contact to 0.83 eV for graphene insert layer ohmic contacts, explaining the decrease in contact resistance. Recessed ohmic contacts have also been proven to be an effective method for reducing ohmic contact resistance. In this study, 2×48 μm2 rectangular recesses are introduced, and graphene insert layer, effectively reducing the contact resistance to 1.36 Ω·mm. Compared to the traditional ohmic contact resistance of 4.13 Ω·mm, this represents a 67.1% reduction. Furthermore, introducing oxygen plasma treatment during fabrication effectively removes the additional current paths caused by graphene, allowing the device to achieve good on/off characteristics.
顯示於類別:	[電機工程研究所] 博碩士論文

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