單層二硒化鎢合成研究與 二維P型電晶體元件之接觸工程

Abstract

本研究利用化學氣相沉積（Chemical Vapor Deposition, CVD）方法成功合成大面積單層 WSe₂ 薄膜，並針對 WO₃ 及 Se 區溫度、壓力與載氣流速等參數進行優化。Raman 與 PL 量測證實所得薄膜具有單層結構，其 E₂g 與 A₁g 峰分別位於約 250 與 260 cm⁻¹，且 PL 峰位約 1.63–1.64 eV，符合直接能隙材料特徵。XPS 分析顯示 Se/W 原子比穩定接近 2.0，證明材料具良好化學計量性。 進一步製作背閘極場效電晶體後，長通道元件展現載子遷移率 20–30 cm²/V·s 及 10⁷–10⁸ 等級之開關電流比，顯示其優異的半導體表現。為抑制曝光過程造成之DIGS，本研究於接觸製程引入原子層沉積（ALD）形成之 AlOx 作為保護層，元件顯示明顯 n 型摻雜行為與電性提升。另一方面，於 WSe₂ 與 Pd 之間導入 Te–TeOx 作為接觸緩衝層以降低 MIGS，並改善能帶彎曲與接觸電阻。最後再結合紫外臭氧（Ultraviolet Ozone, UVO）處理形成薄 WOₓ 層，引入可控制 p 型摻雜，使元件閾值電壓正向位移並改善飽和電流與次臨界特性。接觸電阻則分別以 Y-function 與 TLM 進行交叉驗證，最終最低可達約 2 kΩ·μm；兩方法雖有微小差異，但趨勢一致，顯示多層次介面工程之有效性。 綜言之，本研究成功建立以 AlOx 保護層、Te–TeOx 緩衝層與 UVO 摻雜調控 為核心之接觸工程策略，能同時緩解 MIGS 與 DIGS 並調控能帶排列，顯著提升 WSe₂ 電晶體電性表現。本成果顯示二維半導體若能兼顧材料品質與介面設計，將可望於未來低功耗與高效能電子元件中展現高度應用潛力。

Monolayer WSe₂ films were synthesized via chemical vapor deposition (CVD), and the influences of WO₃ and Se source temperatures, chamber pressure, and carrier gas flow rate were systematically optimized. Raman spectroscopy revealed characteristic E₂g and A₁g phonon modes at ~250 and ~260 cm⁻¹, respectively, while photoluminescence (PL) exhibited a strong direct bandgap emission near 1.63–1.64 eV. X-ray photoelectron spectroscopy (XPS) confirmed a stable Se/W atomic ratio close to 2.0, indicating good chemical stoichiometry and process reproducibility. Back-gated WSe₂ FETs fabricated using wet transfer exhibited field-effect mobility values of ~20–30 cm²/V·s and on/off current ratios exceeding 10⁷, demonstrating excellent semiconducting behavior. To mitigate DIGS generated during lithography, an AlOx protective layer was introduced, effectively reducing interface trap density and inducing an n-type doping effect. In addition, an ultrathin Te–TeOx interlayer was inserted between Pd and WSe₂ to suppress MIGS and smooth the band-bending profile, thereby lowering the contact resistance. Subsequent ultraviolet-ozone (UVO) treatment generated a thin WOₓ surface layer that provided controllable p-type doping, shifting the threshold voltage toward the positive direction and further improving the device switching behavior. Contact resistance was extracted using both the Y-function and transfer-length method (TLM), with the optimized structure achieving a minimum value of ~2 kΩ·μm. Slight deviations between the two extraction methods were attributed to modeling assumptions in the Y-function approach, while both showed consistent trends. In conclusion, this work establishes an integrated contact-interface engineering strategy combining AlOx encapsulation, Te–TeOx buffer layers, and UVO-induced doping control, effectively suppressing both MIGS and DIGS while optimizing band alignment and reducing contact resistance. These results demonstrate that high-quality WSe₂, when coupled with well-designed contact engineering, holds strong potential for future low-power and high-performance electronic applications.