石墨烯與氟化石墨烯對氮化鎵電晶體歐姆接觸電阻與閘極控制特性之影響;Impact of Graphene and Fluorinated Graphene on the Contact Resistance and Gate Control Performance of GaN Transistors

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题名:	石墨烯與氟化石墨烯對氮化鎵電晶體歐姆接觸電阻與閘極控制特性之影響;Impact of Graphene and Fluorinated Graphene on the Contact Resistance and Gate Control Performance of GaN Transistors
作者:	惠中;黃
贡献者:	電機工程學系
关键词:	氮化鎵;石墨烯;GaN;Graphene
日期:	2025-08-25
上传时间:	2025-10-17 12:55:33 (UTC+8)
出版者:	國立中央大學
摘要:	氮化鋁鎵/氮化鎵高電子遷移率電晶體通常由Ti/Al/Ni/Au在高溫熱退火下形成歐姆接觸，但如此高溫會造成如熱預算(Thermal budget)及表面粗糙度較高。因此，本研究透過將退火溫度降低至700 ℃，將金歐姆屬改為Ti/Al/Ti，並在歐姆接觸下方插入一層石墨烯，與傳統元件進行比較。得到有無石墨烯插入層的特徵歐姆接觸電阻(Specific contact resistivity, ρc)分別為5.09 × 10-6 Ω·cm2及5.12 × 10-5 Ω·cm2，足足減少了一個數量極。後續透過TEM分析其歐姆接觸成分，並於AlGaN層附近透過晶向分析發現TiC結構，該結構被認為是降低特徵歐姆接觸電阻的關鍵。氟化石墨烯已在多篇論文中被證實其作為鈍化層優異的特性，但同時其本身也是具有約2.9 eV能隙的材料，因此本研究將其加入閘極下方，發現閘極到源極的蕭特基二極體(Schottky barrier diode)，蕭特基能障有明顯提升，且理想因子無明顯增加，推論其接面的缺陷不會受到影響。 ;Ohmic contacts in AlGaN/GaN high-electron-mobility transistors (HEMTs) are conventionally formed using Ti/Al/Ni/Au metal stacks under high-temperature rapid thermal annealing (RTA). However, such elevated temperatures lead to concerns such as thermal budget constraints and increased surface roughness. In this study, the RTA temperature was reduced to 700 °C by modifying the metal stack to Ti/Al/Ti and inserting a graphene interlayer beneath the contact. Compared with conventional devices, the proposed structure achieved a specific contact resistivity (ρc) of 5.09×10-6 Ω·cm², significantly lower than 5.12×10-5 Ω·cm² in the reference sample, representing an order-of-magnitude improvement. Further transmission electron microscopy (TEM) and phase analysis near the AlGaN layer revealed the formation of a TiC phase, which is believed to be the key contributor to the improved contact performance. Fluorinated graphene (FG) has been reported as an effective passivation material due to its chemical stability and wide bandgap (~2.9 eV). In this work, FG was inserted beneath the gate electrode. Schottky barrier diode (SBD) measurements between gate and source revealed an increase in Schottky barrier height and a similar ideality factor, indicating good interface quality with a FG layer.
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