image: Optical and spectral characteristics of QDs, MoS2 monolayer and mixed-dimensional vdWHs. view more
Credit: OEA
In a new publication from Opto-Electronic Advances; DOI 10.29026/oea.2021.210017, researchers led by Professor Anlian Pan and Professor Ziwei Li, Hunan University, Hunan, China discuss light-triggered interfacial charge transfer and enhanced photodetection in 0D/2D mixed-dimensional phototransistors.
Low-dimensional heterostructures are extremely important components of various semiconductor devices, including photodetectors, phototransistors and light-emitting devices. Recently proposed van der Waals heterostructures (vdWHs) based on 2D transition metal dichalcogenides (TMDs) have attracted world-wide attention for application in next-generation optoelectronic integrations beyond traditional silicon-based integrated circuits. Such 2D/2D vdWHs show unique properties, such as high carrier mobility, atomic-scale depletion region and tunable light-matter interactions, which stem from the designed energy band alignment and the ultrafast interfacial charge transfer. However, the interlayer coulomb interactions and the carrier scatterings are dominant in such atomically-thin layers, which have great influence on the performance of optical behaviors and optoelectronic devices. These kinds of devices still suffer from performance limitations due to their weak light absorption and natural atom defects.
The authors of this paper designed a 0D/2D mix-dimensional vdWHs (ZnS/CdSe QD/MoS2) to investigate the light-controlled charge transfer processes at the interface and fabricate high-performance photodetectors working in both weak and strong light environment. The steady-state and transient-state optical measurements of colloidal QDs, MoS2 monolayers and heterostructures are systematically investigated, showing tunable PL spectra and ultrafast charge transfer stemmed from a type-II band alignment.
These power-sensitive charge transfer processes at the interface help to improve the performance of optoelectronic devices based on TMDs with large responsivity and detectivity at both low and high light powers. The difference of device performance of MoS2 and 0D/2D heterostructure has been systematically compared, and the deep discussion of device performance on the effect of interfacial charge doping has been provided. The hybrid phototransistor exhibits typical N-type behaviors in the dark environment. The photocurrent intensity (Iph) of heterostructure device is 2.3 times larger than that of MoS2 device, which is arising from the strong absorption characteristics of quantum dots and effective charge separation. The photoresponsivity (R) of the heterostructure device reaches up to 4.35 times larger than that of MoS2 device (856 AW-1 vs 3.72×103 AW-1), which exhibits outstanding performances compared with other TMD-based photodetectors. The highest detectivity of (D*) heterostructure device gets improved up to 28 times (6.95×1010 Jones vs 1.95×1012 Jones). The heterostructure photodetector exhibits stable and reproducible on-off photoelectric switching characteristics with an average rise time of 0.49 s and a fall time of 0.6 s, respectively.
These results are expected to soon provide the fundamental understanding of light-controlled charge transfer in 0D/2D mix-dimensional vdWHs, which contributes to the design of high-performance smart optoelectronic devices.
Article reference: Li ZW, Yang W, Huang M, Yang X, Zhu CG et al. Light-triggered interfacial charge transfer and enhanced photodetection in CdSe/ZnS quantum dots/MoS2 mixed-dimensional phototransistors. Opto-Electron Adv 4, 210017 (2021). doi: 10.29026/oea.2021.210017
Keywords: heterostructure; phototransistor; MoS2; quantum dots
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Professor Anlian Pan is President, College of Materials Science and Engineering of Hunan University, owner of China National Funds for Distinguished Young Scientists, President of Hunan Institute of Optoelectronic Integration and director of Sino-German Joint laboratory of "Low-dimensional semiconductor Integrated Photonics". Professor Pan received his PhD in Condensed Mater Physics from the Institute of Physics of Chinese Academy of Sciences in 2006. Afterwards, he worked as a Humboldt Research Fellow with Professor Ulrich Goseleand and Professor Margit Zacharias at the Max Planck Institute. In 2008, he joined Arizona State University as an Assistant Professor. At the beginning of 2010, he joined Hunan University as a full-time Professor of Hunan Province with the honor of "Furong Scholar". He is mainly engaged in the research of new semiconductor materials, integrated optoelectronics technology and new Micro LED, and strives to solve core components and photonic chip technology. He has published more than 200 research literatures in international journals such as Science, Nature Nanotechnology, Nature Materials and others. His research achievements have had important academic influence. He has twice won the first prize of Natural Science in Hunan Province. In 2019, he successfully won the second prize of National Natural Science Award.
Professor Ziwei Li is a doctoral supervisor with the honour of “Yuelu scholar”. He works in the College of Materials Science and Engineering of Hunan University. He graduated from Peking University with a PhD in condensed matter physics in 2018 and joined Hunan University. He focuses on 2D materials, nanophotonics and novel opto-electronic devices. He majors in nanofabrication and spectroscopic technology, and develops steady-state, transient spectral detection technology to investigate the light-physics of 2D materials. As first author and corresponding author, he has published more than 30 SCI literatures, such as Adv. Mater., ACS Nano, Research, etc. Some works have been reported and highlighted in the special issue of 'ACS Nano', Wiley Materials Views China and other news media. He hosted the Major Program of National Natural Science Foundation of China (NSFC), the Youth Fund of NSFC, and the Outstanding Youth Fund of the Natural Science Foundation of Hunan Province.
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