n型矽金氧半元件於光照下之電流特性研究

Abstract

本研究針對n型矽基金氧半電容元件（MOS(n)）在不同光照條件下的電流行為進行深入探討，特別聚焦於其在黑暗環境與紫外光（UV）照射下的導電特性與電流機制。元件的閘極氧化層是透過陽極氧化（Anodic Oxidation, ANO）技術製成，並比較ANO時有無白光輔助下對氧化層厚度的影響，實驗結果顯示，在ANO過程中加入白光可產生大量電子-電洞對，進而加速氧化反應、提高氧化效率並形成更厚的氧化層。透過IV與CV量測，本研究分析了不同閘極電壓區域下的暗電流與光電流行為，發現當閘極電壓小於平能帶電壓時，UV照射下的光電流明顯大於暗電流，且在飽和區域差異最大，光電流可達暗電流的數十倍甚至千倍以上，並具備20至45毫秒等級的快速響應特性，顯示其作為UV感測器的潛力。暗電流分析顯示其主要來自穿隧機制，與元件面積成正比，而光電流則根據操作區域不同，表現出與面積或周長相關的行為，反映出空間電場分佈與載子傳輸的複雜交互關係。此外，本研究亦探討不同氧化層厚度與元件幾何尺寸對光響應的影響，結果顯示較厚的氧化層會產生更強的界面電場，進一步吸引更多周圍區域的電洞參與導電過程，使飽和電流提升；而元件尺寸則與邊緣效應密切相關，小尺寸元件因周長與面積比例高，邊緣電場影響明顯，導致壓降分配與元件半徑呈現相關性。整體而言，本研究釐清了MOS(n)元件在不同操作區域下的導電機制，並指出其幾何設計與氧化層厚度對UV感測性能的影響，驗證其具備發展為CMOS相容、高靈敏度且具低成本潛力的紫外光感測器之可行性。未來建議可進一步研究不同區域中電子與電洞電流的相對貢獻、不同波長的UV光對元件的光譜響應、MOS(p)與MOS(n)元件在機制與應用上的異同，並針對長時間光照下的可靠性與環境穩定性進行評估，以期實現元件在穿戴式裝置、環境監測、智慧感測與航太科技等領域中的實際應用。

This study conducts an in-depth investigation into the current behavior of n-type silicon-based metal-oxide-semiconductor capacitors (MOS(n)) under various illumination conditions, with a particular focus on their conductive characteristics and operational mechanisms in both dark environments and under ultraviolet (UV) illumination. The gate oxide layers of the devices were formed using anodic oxidation (ANO), and the effect of white-light photon-assistance during the ANO process on oxide thickness was examined. Experimental results show that incorporating white light during ANO generates a large number of electron-hole pairs, which accelerates the oxidation reaction, enhances oxide growth efficiency, and leads to thicker oxide layers. Through current-voltage (I-V) and capacitance-voltage (C-V) measurements, this study analyzes the behavior of dark and photocurrents across different gate voltage regions. It was found that when the gate voltage is below the flat-band voltage, the photocurrent under UV illumination significantly exceeds the dark current, with the greatest difference observed in the saturation region. In these conditions, the photocurrent can be tens to nearly a thousand times larger than the dark current and demonstrates a rapid response time in the range of 20 to 45 milliseconds, indicating strong potential for UV sensing applications. Analysis of the dark current reveals that it primarily arises from tunneling mechanisms and is proportional to the device area, whereas the photocurrent exhibits behavior that correlates with either the area or the perimeter of the device, depending on the operating region. This reflects a complex interplay between spatial electric field distribution and carrier transport. Additionally, the study explores the influence of oxide thickness and device geometry on photo-response characteristics. Results indicate that thicker oxide layers produce stronger interfacial electric fields, which further attract holes from surrounding regions and enhance the saturation current. Meanwhile, device size is closely related to edge effects; smaller devices, due to a higher perimeter-to-area ratio, experience more pronounced lateral electric field influence, leading to a correlation between voltage drop distribution and device radius. Overall, this study elucidates the conduction mechanisms of MOS(n) devices across different operating regimes and identifies the impact of geometric design and oxide thickness on UV sensing performance, verifying the feasibility of developing CMOS-compatible, high-sensitivity, and low-cost UV photodetectors. Future work is suggested to include analysis of the relative contributions of electron and hole currents in various regions, spectral response studies under different UV wavelengths, comparison of MOS(p) and MOS(n) device mechanisms and applications, and evaluations of long-term stability and environmental robustness under sustained illumination, aiming toward practical implementations in wearable devices, environmental monitoring, smart sensing, and aerospace technologies.