本研究聚焦於過渡金屬硫屬化物（TMDs）異質結之接觸工程與光電調控。本徵二碲化鉬（MoTe₂）常因晶格內天然存在之碲（Te）空缺，於中能隙誘發缺陷態，將費米能階強烈釘紮於導帶底附近，導致高昂的電洞注入肖特基障壁並限制其 p 型調控能力。為克服此瓶頸，本文引入低壓通氧快速熱退火（O₂-RTA）製程，利用氧原子插層填補 Te 空缺以根除缺陷能階，成功解除費米能階釘紮，使導電最小值點（CMP）顯著向正壓方向移動，大幅提升 p 型載流子調控效率與遷移率。
在元件構築上，本文創新結合機械剝離之薄層 MoTe2 與化學氣相沉積（CVD）生長之大面積二硫化鉬（MoS₂）薄膜，構築垂直凡得瓦異質結構。製程中引入標準微影與精確蝕刻技術裁剪MoS₂ 通道，有效消除因材料幾何尺寸隨機性所導致的實驗變因，實現了結構標準化。電性量測顯示，經 O2-RTA 調控後，異質結場效電晶體之遷移率、轉導、閾值電壓及次閾值擺幅（SS）均獲得本質性優化。此外，奠基於 MoTe₂（1.2 eV）與 MoS₂（1.7 eV）所建構之 Type-II 能帶對齊與強大內建電場，該元件成功克服了二維材料外側接觸之傳輸限制，在順向偏壓下激發出巨額的光電導增益。多波長（600~750 nm）與不同後閘極偏壓（VBG）之光響應量測進一步證實，該元件不僅精確對應了材料的截止波長特性，更顯著拓寬了光偵測器的響應譜帶並大幅調升光響應度（Responsivity），在低功耗電子學與寬頻光電偵測領域展現出巨大的工業應用潛力。

In this study, we investigate the contact engineering and optoelectronic modulation of transition metal dichalcogenide (TMD) heterojunctions. Intrinsic molybdenum ditelluride (MoTe₂) often suffers from naturally occurring tellurium (Te) vacancies, which induce mid-gap defect states and cause severe Fermi-level pinning, thereby restricting its p-type modulation capability. To overcome this bottleneck, a low-pressure oxygen rapid thermal annealing (O₂-RTA) process was introduced. The oxygen intercalation effectively filled the Te vacancies, eliminated the defect states, and successfully unpinned the Fermi level. This significantly shifted the charge neutrality point and substantially enhanced the p-type carrier mobility and modulation efficiency of MoTe₂.
Furthermore, we innovatively combined mechanically exfoliated MoTe₂ flakes with large-area chemical vapor deposition (CVD) grown molybdenum disulfide (MoS₂) films to construct a vertical van der Waals heterostructure. Standard photolithography and dry etching techniques were utilized to pattern the MoS₂ channel, effectively eliminating experimental variables caused by random material geometries. Electrical measurements revealed that, following the O₂-RTA modulation, the heterostructure field-effect transistors (FETs) exhibited fundamental optimizations in mobility, transconductance, threshold voltage, and subthreshold swing.
Optically, the Type-II band alignment and strong built-in electric field between MoTe₂ (1.2 eV) and MoS₂ (1.7 eV) effectively accelerated the separation of photogenerated electron-hole pairs, overcoming the transport limitations of outer contacts on 2D materials and generating massive photoconductive gain under forward bias. Multi-wavelength photoresponse measurements (600~750 nm) under various back-gate biases confirmed that the device accurately matched the cutoff wavelength characteristics of the materials, significantly broadened the photoresponse spectrum, and drastically elevated the responsivity, demonstrating enormous industrial application potential in low-power electronics and broadband optoelectronic detection.

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