氮化鎵高電子遷移率電晶體(GaN HEMTs)在高功率操作下，傳統金屬電極與元件結構層間之電致遷移現象變得更為嚴重，電致遷移現象除了使電晶體源極與汲極之歐姆接觸電阻上升；也導致閘極產生漏電路徑，使電晶體開關須更大閘偏壓，使消耗功率增加。有鑑於此，本論文提出利用石墨烯/氮摻雜超奈米晶鑽石薄膜複合電極結構，配合金屬調控功函數，製備溫度穩定度更高之電極。具體作法為使用氮摻雜超奈米晶鑽石薄膜(N-UNCD)作為固態碳源，並以鎳金屬為催化層於高溫腔體中製備複合薄膜。後續藉由熱蒸鍍機製備源、汲極之歐姆接點與閘極之蕭特基接點。研究初期通過調整氮摻雜超奈米晶鑽石薄膜的成長參數，在 GaN HEMTs 上成長厚度 80 奈米且均勻連續之多層石墨烯薄膜。
本研究開發之複合電極經由 TLM 量測其與 GaN HEMTs 之特徵接觸電阻最低可達 4.210-4 Ω-cm2。配合遮罩的設計，我們也成功製備出具閘極截止功能的電晶體。而在 350 度下進行長時熱燒實驗中，傳統金屬電極 GaN HEMTs 隨著熱燒時間增加，源汲極間歐姆接觸電阻明顯增加；反之複合電極 GaN HEMTs 源汲極間歐姆接觸電阻值幾乎不隨熱燒時間變化。實驗結果表明本研究開發之石墨烯/氮摻雜超奈米晶鑽石複合電極較傳統金屬電極具有更高的溫度穩定性。

Gallium Nitride-based High Electron Mobility Transistors (GaN HEMTs) exhibit amplified electromigration problems between traditional metal electrodes and the device structural layer, under high power operational conditions. The contact resistance between the transistor's source and drain is increased by electromigration, which enhances power consumption. Consequently elevated gate biases are required to switch the transistor, which creates leakage channel in the gate. To address this challenge, this research proposes a novel approach involving a composite electrode structure. This structure combines an ultrananocrystalline diamond film doped with nitrogen and a graphene layer, accompanied by metal-controlled work function modulation, with the aim of producing electrodes possessing enhanced thermal stability.The specific approach involves using nitrogen-doped ultrananocrystalline diamond films (N-UNCD) as a solid carbon source, with a nickel metal catalyst layer, to prepare the composite film in a high-temperature chamber. Subsequently, the source and drain ohmic contacts and the gate schottky contacts are deposited using a thermal evaporation system. In the preliminary stages of the study, the growth parameters of the nitrogen-doped ultrananocrystalline diamond film were adjusted to achieve the growth of a uniform continuous, multilayer of approximately 80 nm thick, on GaN HEMTs. The composite electrode developed in this study exhibited a minimum specific contact resistance with GaN HEMTs of 4.2 × 10-4 Ω-cm2, as determined by transmission line measurement (TLM). We were able to successfully fabricate transistors with gate cutoff capabilities via mask design. During prolonged thermal burning experiments at 350 oC, the contact resistance between the source and drain of GaN HEMTs with conventional metal electrodes increased significantly with burning time. Conversely, the contact resistance of GaN HEMTs with composite electrodes remained almost unchanged throughout the annealing process. These experimental findings indicate that the graphene/nitrogen-doped ultrananocrystalline diamond composite electrode developed in this study exhibits its potential exhibiting higher thermal stability compared to traditional metal electrodes.

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