Research ArticleMATERIALS SCIENCE

High-speed black phosphorus field-effect transistors approaching ballistic limit

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Science Advances  21 Jun 2019:
Vol. 5, no. 6, eaau3194
DOI: 10.1126/sciadv.aau3194
  • Fig. 1 Characterization of the device structure.

    (A) Schematic of a back-gated BP on an HfLaO substrate with top Ni/Au source and drain electrodes. (B) BP flake with a measured thickness of 12.5 nm by AFM. Inset of (B), AFM image of the few-layer BP devices. Scale bar, 2 μm. (C) Polarization-resolved Raman spectrum of the BP flake. The left image shows three spectra obtained from an individual flake in different orientations. The right image shows the orientation-dependent A2g/A1g peak intensities. (D) Representative false-colored SEM image of the BP transistors. AC and ZZ stand for the armchair and zigzag directions, respectively. Scale bar, 1 μm. a.u., arbitrary units.

  • Fig. 2 Transport properties of a BP transistor at low temperature.

    (A) Output characteristics of the BP device with a channel length of 100 nm at 300 K. (B) Output characteristics of the same device at 20 K. (C) Transfer characteristics of the 100-nm device for BP on HfLaO at different temperatures. (D) Hysteresis values of the 100-nm device for BP on HfLaO as a function of temperature.

  • Fig. 3 Saturation velocity of BP FETs.

    (A) Drift velocity as a function of transverse electric field in the channel for the 100-nm channel length BP device at 300 and 20 K. Scatters are experimental data; solid lines are fits to and extrapolation from Eq. 4. (B) Extracted saturation velocity versus temperature at various hole densities. (C) Comparison of hole saturation velocity as a function of bandgap for different materials at room temperature.

  • Fig. 4 Ballistic simulation of BP FETs.

    Comparison of the (lines) MVS model fit and (symbols) measured data for the Id-Vd characteristics in Fig. 2. (A) 300 K. (B) 20 K. (C) Benchmark of ballistic efficiency in this work with Si planar MOSFETs.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/6/eaau3194/DC1

    Additional supporting information

    Fig. S1. C-V characteristics of HfLaO films.

    Fig. S2. X-ray photoelectron spectroscopy characteristics of HfLaO films.

    Fig. S3. J-V characteristics of thin HfLaO films.

    Fig. S4. Temperature-dependent transport in BP transistors.

    Fig. S5. Gate-tunable contact resistance and Schottky barrier.

    Table S1. Comparison of saturation velocity for holes at room temperature.

    References (2831)

  • Supplementary Materials

    This PDF file includes:

    • Additional supporting information
    • Fig. S1. C-V characteristics of HfLaO films.
    • Fig. S2. X-ray photoelectron spectroscopy characteristics of HfLaO films.
    • Fig. S3. J-V characteristics of thin HfLaO films.
    • Fig. S4. Temperature-dependent transport in BP transistors.
    • Fig. S5. Gate-tunable contact resistance and Schottky barrier.
    • Table S1. Comparison of saturation velocity for holes at room temperature.
    • References (2831)

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