WSe<sub>2</sub> Light-Emitting Tunneling Transistors with Enhanced Brightness at Room Temperature

Withers, Freddie; Pozo-Zamudio, Osvaldo Del; Schwarz, Stefan; Dufferwiel, S.; Walker, P. M.; Godde, Tillmann; Rooney, Aidan; Gholinia, Ali; Woods, Colin R.; Blake, P.; Haigh, Sarah J.; Watanabe, Kenji; Taniguchi, Takashi; Aleǐner, I. L.; Geǐm, A. K.; Falko, Vladimir; Tartakovskii, A. I.; Новоселов, К. С.

doi:10.1021/acs.nanolett.5b03740

Cited by 242 publications

(313 citation statements)

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“…In recent years, van der Waals (vdW) heterostructures based on transition metal dichalcogenides (TMDs) are being studied extensively, due to their excellent electronic and opto-electronic properties [1][2][3][4] with potential applications such as transistor, 5 photo detector, 6,7 light-emitting diode (LED), [8][9][10] and solar cells. 11,12 Atomically sharp interfaces with intralayer high carrier mobility and lack of dangling bonds result in unique spatial charge separation 13 between the layers, as well as produce long-lived interlayer excitons 14 under light exposure.…”

Section: Introductionmentioning

confidence: 99%

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: Introductionmentioning

confidence: 99%

Photo-tunable transfer characteristics in MoTe2–MoS2 vertical heterostructure

et al. 2017

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“…S1 in SI), approaching the quality of exfoliated WSe 2 embedded in boron nitride (FWHM ∼ 10 meV). 44 The free exciton emission overlaps with a weak broad background emission from the sapphire substrate (the narrow peak just below 1.8 eV corresponds to the emission from a color center in sapphire). The highest energy peak in the reflectivity contrast spectrum of the trilayer (see Fig.…”

mentioning

confidence: 99%

Defect Healing and Charge Transfer-Mediated Valley Polarization in MoS₂/MoSe₂/MoS₂ Trilayer van der Waals Heterostructures

et al. 2017

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Monolayer transition metal dichalcogenides (TMDC) grown by chemical vapor deposition (CVD) are plagued by a significantly lower optical quality compared to exfoliated TMDC. In this work we show that the optical quality of CVD-grown MoSe 2 is completely recovered if the material is sandwiched in MoS 2 /MoSe 2 /MoS 2 trilayer van der Waals heterostructures. We show by means of density-functional theory that this 1 arXiv:1703.00806v2 [cond-mat.mes-hall] 14 Jun 2017 remarkable and unexpected result is due to defect healing: S atoms of the more reactive MoS 2 layers are donated to heal Se vacancy defects in the middle MoSe 2 layer. In addition, the trilayer structure exhibits a considerable charge-transfer mediated valley polarization of MoSe 2 without the need for resonant excitation. Our fabrication approach, relying solely on simple flake transfer technique, paves the way for the scalable production of large-area TMDC materials with excellent optical quality. KeywordsChemical Vapor Deposition, transition metal dichalcogenides, van der Waals heterostructures, defect healing, charge transfer mediated valley polarization Monolayer transition metal dichalcogenides (TMDC) have a direct bandgap situated in the visible range, which makes them ideal building blocks for novel electronic and optoelectronic devices. [1][2][3][4][5][6][7][8][9][10] The bandgap of monolayer TMDCs occurs at the inequivalent (but degenerate) K and K' points of the hexagonal Brillouin zone. The broken inversion symmetry of a TMDC monolayer combined with the time reversal symmetry imposes opposite magnetic moments at the K and K' valleys. This in turn determines the characteristic circular dichroism exhibited by these materials, wherein each valley can be addressed separately with circularly polarized light of a given helicity. 11-13 Additionally, optical spectra are influenced by the strong spin-orbit coupling, which lifts the degeneracy of band states at the valence band edges, resulting in well-resolved A and B resonances, as observed in reflectivity or absorption spectra. 2,14-16 The interplay of spin-orbit coupling with broken inversion symmetry and time reversal symmetry locks the valley and spin degrees of freedom, making TMDC attractive candidates for valleytronics. 17 The spin-valley index locking along with the large 2 distance in the momentum space between K and K' valleys preserves the valley polarization observed in the degree of circular polarization (DCP) in helicity resolved photoluminescence emission. [18][19][20][21][22] Applications require a scalable fabrication platform providing high-quality large-area monolayer TMDC. Unfortunately, the most promising approach today, namely chemical vapor deposition (CVD) growth 23-27 struggles to compete with exfoliated TMDC in terms of sample quality. Low temperature PL spectroscopy of CVD-grown MoS 2 and MoSe 2 reveals broad emission from defect bound excitons, which is significantly more intense than the free exciton peak [28][29][30] and is related to chalcogen vacancies induced...

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“…1 and 2, whereas in ML WSe 2 , the discrete emitters can overlap with broad peaks linked to localized 2D excitons and/or their phonon replica. 30 (ii) The 2D neutral exciton states in ML MoSe 2 are optically bright, whereas the lowest energy transition in ML WSe 2 is optically dark, [30][31][32][33][34][35] which will impact carrier relaxation and recombination dynamics. The MoSe 2 ML flakes are obtained by micro-mechanical cleavage of a bulk crystal using viscoelastic stamping.…”

mentioning

confidence: 99%

Discrete quantum dot like emitters in monolayer MoSe2: Spatial mapping, magneto-optics, and charge tuning

Branny

Wang

Kumar

et al. 2016

Applied Physics Letters

118

110

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Transition metal dichalcogenide monolayers such as MoSe2,MoS2 and WSe2 are direct bandgap semiconductors with original optoelectronic and spin-valley properties. Here we report spectrally sharp, spatially localized emission in monolayer MoSe2. We find this quantum dot like emission in samples exfoliated onto gold substrates and also suspended flakes. Spatial mapping shows a correlation between the location of emitters and the existence of wrinkles (strained regions) in the flake. We tune the emission properties in magnetic and electric fields applied perpendicular to the monolayer plane. We extract an exciton g-factor of the discrete emitters close to -4, as for 2D excitons in this material. In a charge tunable sample we record discrete jumps on the meV scale as charges are added to the emitter when changing the applied voltage.

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WSe₂ Light-Emitting Tunneling Transistors with Enhanced Brightness at Room Temperature

Cited by 242 publications

References 44 publications

Photo-tunable transfer characteristics in MoTe2–MoS2 vertical heterostructure

Photo-tunable transfer characteristics in MoTe2–MoS2 vertical heterostructure

Defect Healing and Charge Transfer-Mediated Valley Polarization in MoS₂/MoSe₂/MoS₂ Trilayer van der Waals Heterostructures

Discrete quantum dot like emitters in monolayer MoSe2: Spatial mapping, magneto-optics, and charge tuning

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WSe2 Light-Emitting Tunneling Transistors with Enhanced Brightness at Room Temperature

Cited by 242 publications

References 44 publications

Photo-tunable transfer characteristics in MoTe2–MoS2 vertical heterostructure

Photo-tunable transfer characteristics in MoTe2–MoS2 vertical heterostructure

Defect Healing and Charge Transfer-Mediated Valley Polarization in MoS2/MoSe2/MoS2 Trilayer van der Waals Heterostructures

Discrete quantum dot like emitters in monolayer MoSe2: Spatial mapping, magneto-optics, and charge tuning

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Product

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WSe₂ Light-Emitting Tunneling Transistors with Enhanced Brightness at Room Temperature

Defect Healing and Charge Transfer-Mediated Valley Polarization in MoS₂/MoSe₂/MoS₂ Trilayer van der Waals Heterostructures