Accumulation-Mode Two-Dimensional Field-Effect Transistor: Operation Mechanism and Thickness Scaling Rule

Fang, Nan; Nagashio, Kosuke

doi:10.1021/acsami.8b10687

Cited by 33 publications

(69 citation statements)

References 66 publications

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“…S.S . extracted at the current range of ≈ 10 −12 to 10 −10 A is mainly discussed in this paper and can be expressed as

S . S . = \ln 10 \frac{k_{normalB} T}{e} \frac{C_{ox} + C_{it}}{C_{ox}}

where k B , T , and e are defined as the Boltzmann constant, temperature, and elementary charge, respectively. C ox is the oxide capacitance, and C it is the interface states capacitance ( C it = e 2 D it ).…”

Section: Resultsmentioning

confidence: 99%

“…Therefore, the transverse axis for the D it –energy distribution is shown as the energy from the CB/VB edge. For the high‐ k /bulk n ‐MoS 2 interface, D it is extracted from frequency dispersion‐free C–V curves by the Terman method . The bulk MoS 2 thickness is ≈ 58 nm, which is larger than W Dm , supporting the availability of the C–V measurement.…”

Section: Introductionmentioning

confidence: 92%

“…Here, the recent demonstration of a natural thin‐body MoS 2 FET with an effective channel length of ≈ 3.9 nm has facilitated research on 2D layered channels due to overcoming the scaling limit of ≈ 5 nm for Si gate length . Although the dangling‐bond‐free surface of the layered channel is expected to ideally provide an electrically inert interface, there are many reports on the wide range of interface state densities ( D it ) from 10 11 to 10 13 eV −1 cm −2 for high‐ k top‐gate n ‐MoS 2 FET in reality, which must be reduced to improve the device performance. To date, several physical origins for D it have been proposed, which are summarized in Figure a.…”

Section: Introductionmentioning

confidence: 99%

“…One of the interesting properties of 2D materials is that they can be scaled down to atomic thickness. Strain is easily induced in a thin MoS 2 channel by both substrate surface roughness and/or the high‐ k deposition process, resulting in MoS bond bending . Since the conduction and valence bands of MoS 2 are mainly composed of the energy splitting of the Mo d orbital, the band tail states will be easily introduced, as schematically illustrated in Figure b.…”

Section: Introductionmentioning

confidence: 99%

“…Although the energy distribution of D it is critical to reveal its origin from the comparison with the DFT calculation, a recent study indicated that the conventional C – V method for the D it —energy relation developed for Si systems cannot be simply applied to the FET structure of 2D channels because the channel charging process due to the high channel resistance is more dominant than the electron capture/emission process by the interface trap . In this study, in order to obtain the energy distribution of D it , we performed the modeling of I D – V TG characteristics by considering the MoS 2 channel carrier statistics through the quantum capacitance ( C Q ) and its transport through the Drude model . Based on the systematic investigation of over 100 devices for both n ‐ and p ‐ MoS 2 with a wide thickness range of 1 layer (L) to bulk and various gate stack structures including a 2D heterostructure with h ‐BN as well as typical high‐ k top gate structure, the whole picture of high‐ k /MoS 2 interface is discussed.…”

Section: Introductionmentioning

confidence: 99%

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Full Energy Spectra of Interface State Densities for n‐ and p‐type MoS₂ Field‐Effect Transistors

Fang

Toyoda

Taniguchi

et al. 2019

Adv Funct Materials

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2D materials are promising to overcome the scaling limit of Si field-effect transistors (FETs). However, the insulator/2D channel interface severely degrades the performance of 2D FETs, and the origin of the degradation remains largely unexplored. Here, the full energy spectra of the interface state densities (D it ) are presented for both n-and p-MoS 2 FETs, based on the comprehensive and systematic studies, i.e., full rage of channel thickness and various gate stack structures with h-BN as well as high-k oxides. For n-MoS 2 , D it around the mid-gap is drastically reduced to 5 × 10 11 cm −2 eV −1 for the heterostructure FET with h-BN from 5 × 10 12 cm −2 eV −1 for the high-k top-gate. On the other hand, D it remains high, ≈10 13 cm −2 eV −1 , even for the heterostructure FET for p-MoS 2 . The systematic study elucidates that the strain induced externally through the substrate surface roughness and high-k deposition process is the origin for the interface degradation on conduction band side, while sulfur-vacancy-induced defect states dominate the interface degradation on valance band side. The present understanding of the interface properties provides the key to further improving the performance of 2D FETs.

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“…S.S . extracted at the current range of ≈ 10 −12 to 10 −10 A is mainly discussed in this paper and can be expressed as

S . S . = \ln 10 \frac{k_{normalB} T}{e} \frac{C_{ox} + C_{it}}{C_{ox}}

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Full Energy Spectra of Interface State Densities for n‐ and p‐type MoS₂ Field‐Effect Transistors

Fang

Toyoda

Taniguchi

et al. 2019

Adv Funct Materials

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Thickness Scaling Effects on the Complex Optical Conductivity of Few‐Layer WSe₂ Investigated by Spectroscopic Ellipsometry

Fang

Guo

et al. 2022

Advanced Photonics Research

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2D WSe2 have attracted widespread attentions as an ideal platform for new type optoelectronic and nanoelectronics applications. Understanding the intrinsic thickness scaling effects in complex optical conductivity of 2D, WSe2 is vital for WSe2‐based photonic and optoelectronic devices. Herein, complex optical conductivities of 1–5 layers in the energy range of 0.73–6.42 eV by spectroscopic ellipsometry with the classical slab model have been determined. Up to eight feature peaks (A–H) are observed in the optical conductivity spectra, and the central energies of these peaks are identified by the differential spectrum analysis method. These central energies exhibit interesting layer dependencies due to the thickness scaling effects. Specifically, for the low‐energy feature peaks A–E, their central energies decrease with the thickness increasing. But for the high‐energy feature peaks G and H, their central energies first show significant blueshifts and then redshifts as the thickness increases. These novel layer‐dependent evolvements are attributed in the optical conductivity of few‐layer WSe2 to the competition mechanism between the decreasing exciton binding energy and the band gap narrowing.

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Intrinsic Electronic Transport Properties and Carrier Densities in PtS₂ and SnSe₂: Exploration of n⁺‐Source for 2D Tunnel FETs

Sato

Nishimura

Duanfei

et al. 2021

Adv Elect Materials

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Boltzmann tails can be cut off in band-to-band tunneling (BTBT). However, despite intensive research on conventional semiconductor heterojunction TFETs, carrier generation at the p-n heterointerface degrades the SS due to the difficulty in reducing the active defect levels at the heterointerface. [4][5][6][7] Here, 2D materials provide an ideal platform for TFETs because the dangling-bond-free van der Waals (vdW) heterointerface minimizes carrier generation and the short tunnel distance at the vdW interface increases the on current. [8,9] To date, n-type 2D-TFETs have been mainly investigated because degenerately doped p + -2D materials, such as Nb-doped p + -MoS 2 , [10,11] intrinsic p + -black phosphorus (BP), [12][13][14][15] and externally doped p + -WSe 2 , [16,17] are available as source materials. Degenerately doped source materials are indispensable for TFETs because their high carrier densities afford sharp SS values as well as high on current by modulating the band alignment only in the channel region, not in the source region. However, contrary to n-type 2D-TFETs, degenerately doped n-type source materials in p-type 2D-TFETs have been very limited. Indeed, only intrinsic n + -SnSe 2 is utilized for the source. [18][19][20][21][22][23] Although there are some reports on p-type 2D-TFETs with nondegenerately doped source materials, [24][25][26][27] electrostatic doping by an additional local gate electrode has been applied to the sources, which causes other problems, such as a complicated device structure and an increase in the parasitic capacitance. Recently, the substitutional doping technique during 2D growth has been intensively investigated. [28][29][30][31][32] However, controlling the dopant concentration and crystallinity is still a major challenge.Other air-stable n + -2D crystals except n + -SnSe 2 are in high demand to extend our knowledge of p-type 2D-TFETs. In general, the source material with a narrow bandgap (E G ) is favorable to TFETs in combination with the wide E G channel material because it reduces the barrier height for BTBT. [2] From this perspective, PtS 2 , one of the noble metal dichalcogenides, is a reasonable candidate because of the narrow E G for bulk PtS 2 that has been reported (0.25 eV from experiments and 0.48 eV from density functional theory (DFT) calculations). [33]

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Accumulation-Mode Two-Dimensional Field-Effect Transistor: Operation Mechanism and Thickness Scaling Rule

Cited by 33 publications

References 66 publications

Full Energy Spectra of Interface State Densities for n‐ and p‐type MoS₂ Field‐Effect Transistors

Full Energy Spectra of Interface State Densities for n‐ and p‐type MoS₂ Field‐Effect Transistors

Thickness Scaling Effects on the Complex Optical Conductivity of Few‐Layer WSe₂ Investigated by Spectroscopic Ellipsometry

Intrinsic Electronic Transport Properties and Carrier Densities in PtS₂ and SnSe₂: Exploration of n⁺‐Source for 2D Tunnel FETs

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Accumulation-Mode Two-Dimensional Field-Effect Transistor: Operation Mechanism and Thickness Scaling Rule

Cited by 33 publications

References 66 publications

Full Energy Spectra of Interface State Densities for n‐ and p‐type MoS2 Field‐Effect Transistors

Full Energy Spectra of Interface State Densities for n‐ and p‐type MoS2 Field‐Effect Transistors

Thickness Scaling Effects on the Complex Optical Conductivity of Few‐Layer WSe2 Investigated by Spectroscopic Ellipsometry

Intrinsic Electronic Transport Properties and Carrier Densities in PtS2 and SnSe2: Exploration of n+‐Source for 2D Tunnel FETs

Contact Info

Product

Resources

About

Full Energy Spectra of Interface State Densities for n‐ and p‐type MoS₂ Field‐Effect Transistors

Full Energy Spectra of Interface State Densities for n‐ and p‐type MoS₂ Field‐Effect Transistors

Thickness Scaling Effects on the Complex Optical Conductivity of Few‐Layer WSe₂ Investigated by Spectroscopic Ellipsometry

Intrinsic Electronic Transport Properties and Carrier Densities in PtS₂ and SnSe₂: Exploration of n⁺‐Source for 2D Tunnel FETs