Extrinsic Origin of Persistent Photoconductivity in Monolayer MoS2 Field Effect Transistors

Wu, Yueh Chun; Liu, Cheng-Hua; Chen, Shao Yu; Shih, Fu Yu; Ho, Po Hsun; Chen, Chun-Wei; Liang, Chi‐Te; Wang, Wei Hua

doi:10.1038/srep11472

Cited by 116 publications

(115 citation statements)

References 67 publications

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“…However, the photo-excited holes in MoTe 2 get trapped mostly at the MoTe 2 -SiO 2 interface as well as at the defect states inside the MoTe 2 closer to its valence band, which are mostly immobile (reflected in poor mobility <1 cm and hence do not participate in conduction. [32][33][34][35] This also explains why it takes almost a day to come back to its initial value after the light is off (Fig. 3c).…”

Section: Discussionmentioning

confidence: 82%

Photo-tunable transfer characteristics in MoTe2–MoS2 vertical heterostructure

et al. 2017

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Fabrication of the out-of-plane atomically sharp p-n junction by stacking two dissimilar two-dimensional materials could lead to new and exciting physical phenomena. The control and tunability of the interlayer carrier transport in these p-n junctions have a potential to exhibit new kind of electronic and optoelectronic devices. In this article, we present the fabrication, electrical, and optoelectrical characterization of vertically stacked few-layers MoTe 2 (p)-single-layer MoS 2 (n) heterojunction. Over and above the antiambipolar transfer characteristics observed similar to other hetero p-n junction, our experiments reveal a unique feature as a dip in transconductance near the maximum. We further observe that the modulation of the dip in the transconductance depends on the doping concentration of the two-dimensional flakes and also on the power density of the incident light. We also demonstrate high photo-responsivity of~10 5 A/W at room temperature for a forward bias of 1.5 V. We explain these new findings based on interlayer recombination rate-dependent semi-classical transport model. We further develop first principles-based atomistic model to explore the charge carrier transport through MoTe 2 -MoS 2 heterojunction. The similar dip is also observed in the transmission spectrum when calculated using density functional theory-non-equilibrium Green's function formalism. Our findings may pave the way for better understanding of atomically thin interface physics and device applications.

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Section: Discussionmentioning

confidence: 82%

Photo-tunable transfer characteristics in MoTe2–MoS2 vertical heterostructure

et al. 2017

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“…For a disordered system, it is common to use the stretched exponential decay to describe the PPC relaxation. [30][31][32] Here, we can analyze the photocurrent relaxation by a single stretched exponential decay 33…”

Section: Resultsmentioning

confidence: 99%

Environment-insensitive and gate-controllable photocurrent enabled by bandgap engineering of MoS2 junctions

Shih

et al. 2017

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Two-dimensional (2D) materials are composed of atomically thin crystals with an enormous surface-to-volume ratio, and their physical properties can be easily subjected to the change of the chemical environment. Encapsulation with other layered materials, such as hexagonal boron nitride, is a common practice; however, this approach often requires inextricable fabrication processes. Alternatively, it is intriguing to explore methods to control transport properties in the circumstance of no encapsulated layer. This is very challenging because of the ubiquitous presence of adsorbents, which can lead to charged-impurity scattering sites, charge traps, and recombination centers. Here, we show that the short-circuit photocurrent originated from the built-in electric field at the MoS2 junction is surprisingly insensitive to the gaseous environment over the range from a vacuum of 1 × 10−6 Torr to ambient condition. The environmental insensitivity of the short-circuit photocurrent is attributed to the characteristic of the diffusion current that is associated with the gradient of carrier density. Conversely, the photocurrent with bias exhibits typical persistent photoconductivity and greatly depends on the gaseous environment. The observation of environment-insensitive short-circuit photocurrent demonstrates an alternative method to design device structure for 2D-material-based optoelectronic applications.

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“…The former is exacerbated by the high surface-to-volume ratio in 2D materials and oxide surface treatments have been used to modify this effect. Also, a considerable contribution from extrinsic effects, such as charge transfer into surface bound water molecules or other adsorbates, has been observed [146] which leads to a conductivity change upon light exposure that persists for a long time after the light is switched off [147]. This phenomenon, called persistent photoconductivity, limits the practical usability of such devices because of the extremely slow response time and the sensitivity to the environment.…”

Section: Photovoltaic Solar Cellsmentioning

confidence: 99%

Exciton physics and device application of two-dimensional transition metal dichalcogenide semiconductors

2018

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Two-dimensional group-VI transition metal dichalcogenide semiconductors, such as MoS2, WSe2 and others, exhibit strong light-matter coupling and possess direct band gaps in the infrared and visible spectral regimes, making them potentially interesting candidates for various applications in optics and optoelectronics. Here, we review their optical and optoelectronic properties with emphasis on exciton physics and devices. As excitons are tightly bound in these materials and dominate the optical response even at room-temperature, their properties are examined in depth in the first part of this article.We discuss the remarkably versatile excitonic landscape, including bright, dark, localized and interlayer excitons. In the second part, we provide an overview on the progress in optoelectronic device applications, such as electrically driven light emitters, photovoltaic solar cells, photodetectors and opto-valleytronic devices, again bearing in mind the prominent role of excitonic effects. We conclude with a brief discussion on challenges that remain to be addressed to exploit the full potential of transition metal dichalcogenide semiconductors in possible exciton-based applications.

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Extrinsic Origin of Persistent Photoconductivity in Monolayer MoS2 Field Effect Transistors

Cited by 116 publications

References 67 publications

Photo-tunable transfer characteristics in MoTe2–MoS2 vertical heterostructure

Photo-tunable transfer characteristics in MoTe2–MoS2 vertical heterostructure

Environment-insensitive and gate-controllable photocurrent enabled by bandgap engineering of MoS2 junctions

Exciton physics and device application of two-dimensional transition metal dichalcogenide semiconductors

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