氮化鎵擁有高能隙、高電子飽和速度及高崩潰電場等優越特性，成為第三代
高頻、高功率應用元件之寬能隙半導體熱門材料。然而高功率操作下，元件產生
高溫，傳統金屬電極特性衰退，致使元件性能產生熱退化問題。因此開發溫度穩
定性更優異之電極材料，對於高功率元件熱穩定性至關重要。石墨烯具有高熱傳
導率及高電子遷移率特性，適合使用在高溫操作之元件電極材料。本研究首先使
用氫/甲烷氣態碳源配合金屬鎳催化層在氮化鎵源元件上製備石墨烯，然而鎳與
鎵原子在700 度以上互熔情況嚴重，氮化鎵表面粗糙，無法製備石墨烯。有鑑於
此，本研究嘗試使用類鑽石碳固態碳源，期望隔絕金屬鎳與鎵原子擴散。然而，
礙於電漿系統成長之類鑽石碳薄膜硬度偏軟，加上熱穩定性不佳在超過400 度即
有結碳球現象，無法阻止鎳鎵原子擴散，致使氮化鎵表面粗糙，亦無法成長出高
材料品質石墨烯。最後，研究回到使用轉貼法，將銅箔上石墨烯轉移至氮化鎵薄
膜，並透過氧電漿製程形成蕭特基電極結構。傳統金屬蕭特基電極在室溫下的理
想因子為1.65，蕭特基能障為0.88 eV；而石墨烯蕭特基電極在室溫下的理想因
子為5.2，蕭特基能障為0.74 eV。值得一提，與傳統金屬蕭特基電極相較，石墨
烯蕭特基電極之理想因子隨量測溫度增加卻呈現下降趨勢，且蕭特基能障幾乎不
隨溫度變化，此實驗結果驗證石墨烯電極具有優異溫度穩定性，為發展高功率元
件極具潛力之電極材料。

GaN has many excellent advantages such as high bandgap, high saturation velocity and high breakdown field that already become a promising material for the development of third-generation high-power semiconductor devices. However, the devices operated in a high power condition would generate huge heat, resulted in a degeneration of devices’ performances. The GaN based devices using a conventional electrode operated over 300 oC will generate a non-ideal phenomenon that called metal atoms interdiffusion. The increasing contact resistance degenerate device’s performance significantly. Thus, finding a high thermal stability electrode is a crucial target for a high-power GaN-based device. It is well known, graphene has high thermal conductivity and high electron mobility that is a promising electrode material for high-power GaN based devices. In this study, two kinds of methods using gas precursors (i.e. methane/hydrogen) and solid-state carbon source (i.e. diamond-like carbon thin-film) which combined metal nickel catalyst were used for growth a graphene layer on GaN thin films. Unfortunately, the experimental results showed a poor materials quality of graphene layer on the rough surface GaN thin films due to the interdiffusion behavior of metal Ni and Ga atoms. Finally, the graphene from copper foil was transferred on the GaN thin films. The graphene Schottky contact was obtained using an oxygen plasma etching process. The ideality factor and Schottky barrier of the traditional metal electrode at room temperature are 1.65 and 0.88 eV, respectively. In addition, the ideality factor and Schottky barrier height of the graphene Schottky contact are 5.2 and 0.74 eV, respectively. It is worth noted that ideality factor decreased with increasing measuring temperature. In addition, the Schottky barrier height shows a temperature independent behavior in the temperature range of 30 – 220 oC. The experimental results indicated that the grapheme electrode exhibits an excellent thermal stability that is a promising electrode material for high-power GaN-based devices.

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