應用於光電邏輯閘之光致量子隧穿二硫化鉬元件

Photo induced quantum tunneling MoS2 device for optoelectronic logic gate applications

李昭穎(Chao-Ying Li)

指導教授 ： 管傑雄

共同指導教授 ： 藍彥文(Yann-Wen Lan)

國立臺灣大學/電機資訊學院/電子工程學研究所/碩士(2022年)

https://doi.org/10.6342/NTU202202735

摘要

近年來電子邏輯門控在準確和快速計算方面開始面臨限制，難以支撐未來對廣泛數據處理的爆炸性需求，為了因應速度的需求於是光子傳輸訊號的方式成了討論話題，雖然全光邏輯門控看來是有利候選者之一，然而不論是聚光或是收光都需要複雜的光學組件來構建，實務上不易於實踐，因此近期一種光電邏輯門控受到關注，不僅不需像全光邏輯閘複雜的組件問題，也具備了光子在速度上的優勢，因而備受矚目，近期相關研究由於材料多屬於單向傳輸運行，研究大都僅展現了AND 或 OR 邏輯閘功能，但這樣遠遠不夠，因此如何實現多功能的光電邏輯閘是目前較為迫切的問題。
二硫化鉬由於其具備的半導體性質以及原子級厚度為現今討論度最高的二維材料之一，且具備可見光波段的發光能力適合作為光偵測器，然而傳統以橫向傳輸為主的二硫化鉬電晶體易受水氣分子極性以及介面陷阱影響，容易在電子傳輸時發生持續光傳導(Persistent Photo Conductive, PPC) 效應，導致光響應時間非常慢(約45.7s)。
在此，本研究探討一種垂直傳輸的單層二硫化鉬元件，避開了傳統橫向傳輸面臨的持續光傳導(PPC)的影響，我們利用薄約30nm厚度之二氧化矽作為絕緣層，使熱電子發射機制主導的暗電流藉由可見光的激發能夠引起FN穿隧的光電流，不僅極大的減少了其光響應時間(上升時間約3.52ms以及下降時間約1.54ms)，還達到了光響應度約0.3 A/W 以及偵測度約7.4 x 109 Jones，更有趣的是，藉由結構中二硫化鉬的載子受光激發後產生的穿隧電流展現了雙向光響應性質，根據此特性我們將元件組合成4種基本光邏輯閘(OR、AND、NOR、NAND)，得以利用二硫化鉬元件實現多功能的光電邏輯閘。

關鍵字

單層二硫化鉬光感測器 ； FN穿隧電流 ； 光響應 ； 光偵測度 ； 光電邏輯閘

並列摘要

In recent years, electronic logic gate begins to face limitations in accurate and fast computation, and it is difficult to support the explosive demand for extensive data processing in the future. In order to meet the demand for speed, photon transmission has become a topic of discussion, although all-optical logic gate seems to be a great candidate, however, both concentrating and receiving light require complex optical components to construct, which is not easy to implement. Therefore, a photoelectric logic gate has recently attracted lots of attention, which not only does not need to face the complex components of all-optical logic gate, and it also has the advantage of photons in speed, so it has attracted much attention. Since most of the recent related researches are unidirectional transmission operation, most of the researches only show the function of AND or OR logic gate, but this is far from enough, so how to realize multifunctional photoelectric logic gate is a more urgent problem at present.
Molybdenum disulfide (MoS2) is one of the most discussed two-dimensional materials due to its semiconducting properties and atomic thickness, and its luminescence in the visible light band is suitable for use as a photodetector. However, the traditional lateral transmission-based MoS2 photodetector are easily affected by the polarity of water vapor molecules and interface traps, and are prone to persistent photoconductive (PPC) effect during electron transport, resulting in a very slow photo response time (about 45.7s).
Here, this study investigates a vertically transported single-layer MoS2 device, which avoids the influence of PPC. We use a thin SiO2 with a thickness of about 30 nm as an insulating layer, so that the dark current dominated by the thermionic emission mechanism is transmitted by the excitation of visible light can induce the photocurrent of FN tunneling, which not only greatly reduces its photo response time (rise time is about 3.52ms and fall time is about 1.54ms), but also achieves responsivity of about 0.3 A/W and detectivity of about 7.4 x 109 Jones. What is more interesting is that the tunneling current which is induced by photo shows bidirectional photo response properties. Finally, we successfully combine the three MoS2 device to implement four basic optical logic gates (OR, AND, NOR, NAND).

並列關鍵字

Monolayer molybdenum disulfide photodetector ； Fowler-Nordheim Tunneling ； Optoelectronic logic gate ； Responsivity ； Detectivity

參考文獻

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