Graphene Klein tunnel transistors for high speed analog RF applications

Tan, Yaohua; Elahi, Mirza M.; Tsao, Han-Yu; Habib, K. M. Masum; Barker, N. Scott; Ghosh, Avik W.

doi:10.1038/s41598-017-10248-7

Cited by 18 publications

(23 citation statements)

References 45 publications

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“…There may be ways to mitigate this problem with split gates that can align and misalign different parts of the Dirac cones independently. The application of this split-gate approach to graphene led to the design of a so-called Klein tunnel transistor [6,7], providphysics.aps.org c 2020 American Physical Society ing a way to modulate graphene's ultrahigh mobilities with modest voltages (∼ 1-2 V), with potential applications in high-speed analog devices [8]. Split-gate schemes may also be used to apply bi-directional torques to efficiently write information onto magnetic memory bits, as shown recently for 3D topological insulators [9].…”

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confidence: 99%

Spin Control with a Topological Semimetal

Ghosh

2020

Physics

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T opological materials, from graphene to topological insulators, owe their remarkable properties to their two-dimensional surface states, which are protected from disorder and defects by topology and symmetry. A recently discovered class of materials, known as topological semimetals, often exhibit even richer and more robust topological effects. These materials include Dirac semimetals (DSMs) and Weyl semimetals (WSMs) [1,2], which host electronic excitations behaving like Dirac and Weyl fermions, respectively. One of their intriguing properties is that the spins and momenta of their surface Figure 1: The band structure of a topological semimetal. Two pairs of cones meet at Dirac points with a vanishing gap between them. (Bottom right) With no applied voltage, Fermi surfaces are at the Dirac points and are connected by ''Fermi-arcs''-electronic states whose spin and momentum are locked. (Top right) With a sufficiently large voltage, Fermi surfaces expand from the Dirac points until they merge, and the material becomes a conventional conductor. (APS

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confidence: 99%

Spin Control with a Topological Semimetal

Ghosh

2020

Physics

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“…Sajjad et al have shown that such a GKT transistor would show a clean transport gap in the off state leading to a nearly ideal transfer characteristic consisting of low off current, high on-off ratio (I on /I of f =R of f /R on =10 4 ) and steep subthreshold swing (SS) lower than the Boltzmann limit of 60 mV/decade [2,4]. Beyond a desirable gate transfer characteristic, the GKT transistor was also shown to have an excellent output characteristic with a high saturating on current retaining a high mobility in the on state [7,15]. In these calculations [2,4,15] however, non-idealities such as momentum scattering, in particular at the edges were not considered.…”

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confidence: 99%

“…The output characteristic, however, bears more promise. At high drain bias (V DS ), a small transport gap (n + -n-n + , on state) at energies far from the equilibrium Fermi level is predicted to produce a strongly saturating I D -V D that is robust against edge roughness [7]. Even cases with an on-off ratio ∼10 can result in an order of magnitude increment in r out (output resistance) without hurting the mobility.…”

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confidence: 99%

“…We further showed that an angle of 45 • between collimator and re-flector gives the best performance even in the presence of edge roughness. Our analysis shows that even with geometry optimization the on-off ratio may not be enough for scaled digital switching, but may still offer advantages for high frequency RF analog applications [7]. This work was supported by Semiconductor Research Corporation's (SRC) NRI-INDEX center.…”

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confidence: 99%

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Impact of geometry and non-idealities on electron “optics” based graphene p-n junction devices

Elahi

Habib

Wang

et al. 2019

Applied Physics Letters

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We articulate the challenges and opportunities of unconventional devices using the photon like flow of electrons in graphene, such as Graphene Klein Tunnel (GKT) transistors. The underlying physics is the employment of momentum rather than energy filtering to engineer a gate tunable transport gap in a 2D Dirac cone bandstructure. In the ballistic limit, we get a clean tunable gap that implies subthermal switching voltages below the Boltzmann limit, while maintaining a high saturating current in the output characteristic. In realistic structures, detailed numerical simulations and experiments show that momentum scattering, especially from the edges, bleeds leakage paths into the transport gap and turns it into a pseudogap. We quantify the importance of reducing edge roughness and overall geometry on the low-bias transfer characteristics of GKT transistors and benchmark against experimental data. We find that geometry plays a critical role in determining the performance of electron optics based devices that utilize angular resolution of electrons. *

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“…fig. 3.5c) for analog high frequency applications and predict a 10-fold increase in the maximum operating frequency f max compared to a conventional graphene FET [196].…”

Section: Tilted Junctions and Electronic Switchesmentioning

confidence: 96%

Dirac fermion optics and plasmonics in graphene microwave devices

Graef

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This thesis addresses the physics of non-interacting and interacting Dirac fermions in ballistic graphene. Three main phenomena are investigated: Dirac fermion optics in electronic prisms defined by p-n junctions, GHz plasmonics in plasma resonance capacitors, and the breakdown of the integer quantum Hall effect (QHBD) by a magnetoexciton instability. Our technology relies on h-BN encapsulated graphene devices characterized by DC to GHz electronic transport and noise.We first study the total internal reflection of electrons in a gate-defined corner reflector. Both geometric and coherent electron optics effects are demonstrated and the device is shown to be sensitive to minute phonon scattering rates. It is then used as a proof-of-concept for GHz electron optics experiments in graphene.We introduce top-gated graphene field-effect capacitors as a platform to study ultralong wavelength plasmons characterized with a vector network analyzer. We simultaneously measure resistivity, capacitance and kinetic inductance. We observe a resonance at 40 GHz with a quality factor of two, corresponding to a plasmon of 100 µm wavelength. This result sets a milestone for the realization of resonant plasmonic devices.We finally move our attention to the QHBD in a bilayer graphene sample. DC transport and GHz noise measurements show that the elusive intrinsic breakdown field can be reached in graphene. Its signature is an abrupt increase of noise, with a super-Poissonian Fano factor. We propose a magnetoexciton instability scenario as the origin of breakdown.These results show how progress in sample fabrication has enabled us to study new classes of ballistic devices, to explore new fundamental phenomena and to envision more complex experiments like: time-of-flight measurements of acoustic phonons, characterization of plasmon propagation in bipolar superlattices, or breakdown in single layer graphene. In terms of applications, this thesis paves the way for room-temperature electron optics devices, plasma-resonance-based THz detectors, and improvement of quantum Hall resistance standards.

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Graphene Klein tunnel transistors for high speed analog RF applications

Cited by 18 publications

References 45 publications

Spin Control with a Topological Semimetal

Spin Control with a Topological Semimetal

Impact of geometry and non-idealities on electron “optics” based graphene p-n junction devices

Dirac fermion optics and plasmonics in graphene microwave devices

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