Ohmic contact engineering in few–layer black phosphorus: approaching the quantum limit

Telesio, Francesca; Gal, G. Le; Serrano‐Ruiz, Manuel; Prescimone, Federico; Toffanin, Stefano; Peruzzini, Margherita; Heun, S.

doi:10.1088/1361-6528/ab8cf4

Cited by 25 publications

(27 citation statements)

References 76 publications

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“…By extrapolating the results for wide nanoribbons to large-area 2D material devices, our results indicate that micro-scale phosphorene devices should have a significantly higher R C than graphene devices. This finding agrees with the literature that reports the best R C of 400 Ω µm [21] to 310 Ω µm [22] for phosphorene FETs, whereas the best reported R C for graphene FETs is ~80 Ω µm [35]. On the other hand, R C is very low in narrowest PNRs which means that patterning phosphorene into nanoribbons offers a promising avenue for R C minimization in ultra-scaled devices that enable high-density integration.…”

Section: Resultssupporting

confidence: 91%

“…While 2D materials and their nanostructures seem promising for nanodevices, they suffer from high contact resistance (R C ), which limits their performance and conceals their exceptional transport properties. For micro-scale BP FETs, R C was measured in the range from ≈1750 Ω µm [19] and ≈1100 Ω µm [9], over ≈700 Ω µm [20], down to ≈400 Ω µm [21] and 310 Ω µm [22]. Even the best reported R C values are unacceptably high for transistors in future high-density integrated circuits and, additionally, very little is known about R C levels and its behavior in PNR-based devices [23].…”

Section: Introductionmentioning

confidence: 99%

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Lower Limits of Contact Resistance in Phosphorene Nanodevices with Edge Contacts

et al. 2022

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Edge contacts are promising for improving carrier injection and contact resistance in devices based on two-dimensional (2D) materials, among which monolayer black phosphorus (BP), or phosphorene, is especially attractive for device applications. Cutting BP into phosphorene nanoribbons (PNRs) widens the design space for BP devices and enables high-density device integration. However, little is known about contact resistance (RC) in PNRs with edge contacts, although RC is the main performance limiter for 2D material devices. Atomistic quantum transport simulations are employed to explore the impact of attaching metal edge contacts (MECs) on the electronic and transport properties and contact resistance of PNRs. We demonstrate that PNR length downscaling increases RC to 192 Ω µm in 5.2 nm-long PNRs due to strong metallization effects, while width downscaling decreases the RC to 19 Ω µm in 0.5 nm-wide PNRs. These findings illustrate the limitations on PNR downscaling and reveal opportunities in the minimization of RC by device sizing. Moreover, we prove the existence of optimum metals for edge contacts in terms of minimum metallization effects that further decrease RC by ~30%, resulting in lower intrinsic quantum limits to RC of ~90 Ω µm in phosphorene and ~14 Ω µm in ultra-narrow PNRs.

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Section: Resultssupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Lower Limits of Contact Resistance in Phosphorene Nanodevices with Edge Contacts

et al. 2022

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“…Finally, we inspect the behavior of the junction at elevated bias, to look for any subharmonic gap features. V bg = 0 V. Also in the n-type regime, as shown in the Supplementary Information, the quality of the contacts does not improve, consistent with previous observations, 59 and the metal-semiconductor contacts are still dominated by the Schottky barrier, which prevents observation of a bipolar signal in supercurrent amplitude. Thus, in the following we will focus on the accumulation region.…”

supporting

confidence: 86%

Evidence of Josephson coupling in a few-layer black phosphorus planar Josephson junction

Telesio,

Carrega,

Cappelli

et al. 2021

Preprint

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Setting up strong Josephson coupling in van der Waals materials in close proximity to superconductors offers several opportunities both to inspect fundamental physics and to develop novel cryogenic quantum technologies. Here we show evidence of Josephson coupling in a planar few-layer black Phosphorus junction. The planar geometry allows us to probe the junction behavior by means of external gates, at different carrier concentrations. Clear signatures of Josephson coupling are demonstrated by measuring supercurrent flow through the junction at milli Kelvin temperatures. Manifestation of Fraunhofer pattern with a transverse magnetic field is also reported, confirming the Josephson coupling. These findings represent the first evidence of proximity Josephson coupling in a planar junction based on a van der Waals material beyond graphene and open the way to new studies, exploiting the peculiar properties of exfoliated black phosphorus thin flakes.

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“…[ 40 , 41 ]. Moreover, we neglect contact resistance in this study although it is a severe performance limiter in all 2D material-based FETs [ 42 , 43 ], including monolayer BP [ 4 , 44 , 45 ] and nanoribbon-based FET structures [ 22 , 33 , 46 , 47 ]. Nevertheless, our work illustrated the importance of using a proper Hamiltonian in the simulation of PNR nanodevices, quantified the magnitude of size-scaling and bandstructure effects, and demonstrated a considerable improvement of PNR FET figures-of-merit in comparison to the simpler TBL model.…”

Section: Discussionmentioning

confidence: 99%

Bandstructure and Size-Scaling Effects in the Performance of Monolayer Black Phosphorus Nanodevices

Poljak

Matić

2021

Materials

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Nanodevices based on monolayer black phosphorus or phosphorene are promising for future electron devices in high density integrated circuits. We investigate bandstructure and size-scaling effects in the electronic and transport properties of phosphorene nanoribbons (PNRs) and the performance of ultra-scaled PNR field-effect transistors (FETs) using advanced theoretical and computational approaches. Material and device properties are obtained by non-equilibrium Green’s function (NEGF) formalism combined with a novel tight-binding (TB) model fitted on ab initio density-functional theory (DFT) calculations. We report significant changes in the dispersion, number, and configuration of electronic subbands, density of states, and transmission of PNRs with nanoribbon width (W) downscaling. In addition, the performance of PNR FETs with 15 nm-long channels are self-consistently assessed by exploring the behavior of charge density, quantum capacitance, and average charge velocity in the channel. The dominant consequence of W downscaling is the decrease of charge velocity, which in turn deteriorates the ON-state current in PNR FETs with narrower nanoribbon channels. Nevertheless, we find optimum nanodevices with W > 1.4 nm that meet the requirements set by the semiconductor industry for the “3 nm” technology generation, which illustrates the importance of properly accounting bandstructure effects that occur in sub-5 nm-wide PNRs.

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Ohmic contact engineering in few–layer black phosphorus: approaching the quantum limit

Cited by 25 publications

References 76 publications

Lower Limits of Contact Resistance in Phosphorene Nanodevices with Edge Contacts

Lower Limits of Contact Resistance in Phosphorene Nanodevices with Edge Contacts

Evidence of Josephson coupling in a few-layer black phosphorus planar Josephson junction

Bandstructure and Size-Scaling Effects in the Performance of Monolayer Black Phosphorus Nanodevices

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