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Article

Dependence of Photoresponsivity and On/Off Ratio on Quantum Dot Density in Quantum Dot Sensitized MoS2 Photodetector

by
Yung-Yu Lai
1,
Yen-Wei Yeh
2,3,
An-Jye Tzou
4,
Yi-Yuan Chen
3,
YewChung Sermon Wu
1,
Yuh-Jen Cheng
2,* and
Hao-Chung Kuo
3,*
1
Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan
2
Research Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan
3
Department of Photonics and Institute of Electro-Optical Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan
4
Taiwan Semiconductor Research Institute, National Applied Research Laboratories, Hsinchu 30078, Taiwan
*
Authors to whom correspondence should be addressed.
Nanomaterials 2020, 10(9), 1828; https://doi.org/10.3390/nano10091828
Submission received: 18 August 2020 / Revised: 1 September 2020 / Accepted: 11 September 2020 / Published: 14 September 2020
(This article belongs to the Special Issue Quantum Dots and Micro-LED Display)
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Abstract

Non-radiative energy transfer (NRET) from quantum dots (QDs) to monolayer MoS2 has been shown to greatly enhance the photoresponsivity of the MoS2 photodetector, lifting the limitations imposed by monolayer absorption thickness. Studies were often performed on a photodetector with a channel length of only a few μm and an active area of a few μm2. Here, we demonstrate a QD sensitized monolayer MoS2 photodetector with a large channel length of 40 μm and an active area of 0.13 mm2. The QD sensitizing coating greatly enhances photoresponsivity by 14-fold at 1.3 μW illumination power, as compared with a plain monolayer MoS2 photodetector without QD coating. The photoresponsivity enhancement increases as QD coating density increases. However, QD coating also causes dark current to increase due to charge doping from QD on MoS2. At low QD density, the increase of photocurrent is much larger than the increase of dark current, resulting in a significant enhancement of the signal on/off ratio. As QD density increases, the increase of photocurrent becomes slower than the increase of dark current. As a result, photoresponsivity increases, but the on/off ratio decreases. This inverse dependence on QD density is an important factor to consider in the QD sensitized photodetector design.
Keywords: molybdenum disulfide; quantum dots; photodetectors; non-radiative energy transfer molybdenum disulfide; quantum dots; photodetectors; non-radiative energy transfer

Share and Cite

MDPI and ACS Style

Lai, Y.-Y.; Yeh, Y.-W.; Tzou, A.-J.; Chen, Y.-Y.; Wu, Y.S.; Cheng, Y.-J.; Kuo, H.-C. Dependence of Photoresponsivity and On/Off Ratio on Quantum Dot Density in Quantum Dot Sensitized MoS2 Photodetector. Nanomaterials 2020, 10, 1828. https://doi.org/10.3390/nano10091828

AMA Style

Lai Y-Y, Yeh Y-W, Tzou A-J, Chen Y-Y, Wu YS, Cheng Y-J, Kuo H-C. Dependence of Photoresponsivity and On/Off Ratio on Quantum Dot Density in Quantum Dot Sensitized MoS2 Photodetector. Nanomaterials. 2020; 10(9):1828. https://doi.org/10.3390/nano10091828

Chicago/Turabian Style

Lai, Yung-Yu, Yen-Wei Yeh, An-Jye Tzou, Yi-Yuan Chen, YewChung Sermon Wu, Yuh-Jen Cheng, and Hao-Chung Kuo. 2020. "Dependence of Photoresponsivity and On/Off Ratio on Quantum Dot Density in Quantum Dot Sensitized MoS2 Photodetector" Nanomaterials 10, no. 9: 1828. https://doi.org/10.3390/nano10091828

APA Style

Lai, Y.-Y., Yeh, Y.-W., Tzou, A.-J., Chen, Y.-Y., Wu, Y. S., Cheng, Y.-J., & Kuo, H.-C. (2020). Dependence of Photoresponsivity and On/Off Ratio on Quantum Dot Density in Quantum Dot Sensitized MoS2 Photodetector. Nanomaterials, 10(9), 1828. https://doi.org/10.3390/nano10091828

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