本研究探討銦鎵錫氧化物（Indium Gallium Tin Oxide, IGTO）薄膜之材料特性及其於紫外光偵測器、薄膜電晶體與光電晶體之應用。IGTO薄膜係利用射頻磁控濺鍍系統於不同氧流量條件下製備，並藉由X光光電子能譜儀（XPS）、紫外光光電子能譜儀（UPS）、低能量反向光電子能譜儀（LEIPS）、原子力顯微鏡（AFM）及X光繞射儀（XRD）分析其化學組成、能帶結構、表面形貌及結晶特性。
材料分析結果顯示，隨氧流量增加，薄膜中的氧空缺濃度逐漸降低，使能帶結構產生明顯變化。由UPS與LEIPS分析結果可知，IGTO薄膜之能隙由0%氧流量時的3.697 eV增加至10%氧流量時的4.328 eV。AFM量測結果顯示，4%氧流量樣品具有最低表面粗糙度（Rq = 0.526 nm），顯示適量氧氣供應有助於提升薄膜均勻性。XRD分析則顯示所有樣品皆維持非晶質結構，未觀察到明顯繞射峰，表示氧流量調控與200°C退火處理並未造成顯著結晶化。
在紫外光偵測器方面，本研究製備IGTO紫外光偵測器，探討氧流量與退火條件對元件特性的影響。結果顯示，低氧流量元件具有較高光電流與響應度，但同時伴隨較高暗電流及持續性光導效應。經200°C退火後，元件之光響應穩定性與恢復特性皆獲得改善。
在薄膜電晶體方面，本研究系統性探討氧流量調控、熱退火、雙主動層結構及高介電常數閘極氧化層對元件特性的影響。結果顯示，4%氧流量單層IGTO薄膜電晶體具有最佳初始開關特性，其開關比達6.34 × 10⁴。經200°C退火後，0%氧流量元件之場效遷移率提升至13.0 cm²/V·s，開關比提升至6.04 × 10⁵。雙主動層結構可進一步改善載子傳輸特性，其中8 nm IGTO / 12 nm IGO結構展現最佳整體表現。當以氧化鋁取代傳統二氧化矽作為閘極氧化層後，元件場效遷移率進一步提升至43.7 cm²/V·s，開關比達1.19 × 10⁹，次臨界擺幅降低至148.37 mV/decade。
此外，本研究進一步探討IGTO光電晶體之光響應特性。結果顯示元件於紫外光波段具有良好波長選擇性，且氧化鋁閘極氧化層可顯著提升光響應能力。其中氧化鋁光電晶體於260 nm光照及閘極電壓10 V條件下之響應度可達1.46 × 10² A/W。整體而言，本研究證實氧空缺調控、熱退火、雙主動層結構及介電層工程皆能有效提升IGTO元件之電性與光電特性，並展現其於紫外光感測及光電記憶體元件之應用潛力。

This study investigates the material characteristics of indium gallium tin oxide (IGTO) thin films and their applications in ultraviolet photodetectors, thin-film transistors (TFTs), and phototransistors. IGTO thin films were deposited under different oxygen flow ratios by RF magnetron sputtering. Their chemical composition, electronic structure, surface morphology, and crystallographic properties were characterized using X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), low-energy inverse photoemission spectroscopy (LEIPS), atomic force microscopy (AFM), and X-ray diffraction (XRD).
The material characterization results revealed that increasing the oxygen flow ratio reduced the concentration of oxygen vacancies and significantly modified the electronic structure of the IGTO films. UPS and LEIPS analyses showed that the optical bandgap increased from 3.697 eV at 0% oxygen flow ratio to 4.328 eV at 10% oxygen flow ratio. AFM measurements indicated that the 4% oxygen-flow sample exhibited the lowest surface roughness (Rq = 0.526 nm), suggesting improved film uniformity under moderate oxygen incorporation. XRD analysis confirmed that all films remained amorphous without distinct diffraction peaks, indicating that oxygen-flow modulation and annealing at 200°C did not induce significant crystallization.
For ultraviolet photodetectors, metal-semiconductor-metal (MSM) structured IGTO photodetectors were fabricated to investigate the effects of oxygen flow ratio and thermal annealing on device performance. The results showed that low-oxygen-flow devices exhibited higher photocurrent and responsivity due to the higher oxygen-vacancy concentration but also suffered from increased dark current and persistent photoconductivity behavior. Thermal annealing at 200°C improved the photoresponse stability and recovery characteristics of the devices.
For TFT applications, the effects of oxygen-flow engineering, thermal annealing, dual-active-layer structures, and high-k gate dielectric engineering were systematically investigated. The 4% oxygen-flow single-layer IGTO TFT exhibited the best switching characteristics among the as-deposited devices, with an on/off current ratio of 6.34 × 10⁴. After annealing at 200°C, the 0% oxygen-flow TFT demonstrated significantly improved electrical performance, achieving a field-effect mobility of 13.0 cm²/V·s and an on/off current ratio of 6.04 × 10⁵. The dual-active-layer structure further enhanced carrier transport, and the 8 nm IGTO / 12 nm IGO configuration exhibited the best overall performance. By replacing the conventional SiO₂ gate dielectric with Al₂O₃, the field-effect mobility further increased to 43.7 cm²/V·s, the on/off current ratio reached 1.19 × 10⁹, and the subthreshold swing decreased to 148.37 mV/decade.
Furthermore, the photoresponse characteristics of IGTO phototransistors were investigated. The devices exhibited excellent wavelength selectivity in the ultraviolet region, and the Al₂O₃-gate-dielectric phototransistor demonstrated significantly enhanced photoresponse performance. A maximum responsivity of 1.46 × 10² A/W was achieved at 260 nm under a gate bias of 10 V. Overall, the results demonstrate that oxygen-vacancy engineering, thermal annealing, dual-active-layer channel design, and dielectric engineering are effective approaches for improving the electrical and optoelectrical properties of IGTO-based devices, showing strong potential for ultraviolet sensing and optoelectronic memory applications.

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