Graphene-Based Periodic Gate Field Effect Transistor Structures for Terahertz Applications (original) (raw)
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Graphene-based field-effect transistor structures for terahertz applications
SPIE Proceedings, 2012
We propose Terahertz (THz) plasmonic devices based on linearly integrated FETs (LFETs) on Graphene. LFET structures are advantageous for (THz) detection since the coupling between the THz radiation and the plasma wave is strongly enhanced over the single gate devices and accordingly higher-order plasma resonances become possible. AlGaN/GaN heterostructure LFETs with their high sheet carrier concentration and high electron mobility are promising for plasmonic THz detection. Nevertheless, our numerical studies show that room temperature resonant absorption of THz radiation by the plasmons in AlGaN/GaN LFETs is very weak even if the integration density is sufficiently large. Our simulations also demonstrate that similar LFETs on Graphene, which has very large electron mobility, can resonantly absorb THz radiation up to 5th harmonic at room temperature. Additionally, we investigated LFETs with integrated cavities on Graphene. Such Periodic Cavity LFETs substantially enhance the quality factor of the resonant modes.
Paving the Way for Tunable Graphene Plasmonic THz Amplifiers
Frontiers in Physics, 2021
This study reviews recent advances in room-temperature coherent amplification of terahertz (THz) radiation in graphene, electrically driven by a dry cell battery. Our study explores THz light-plasmon coupling, light absorption, and amplification using a currentdriven graphene-based system because of its excellent room temperature electrical and optical properties. An efficient method to exploit graphene Dirac plasmons (GDPs) for light generation and amplification is introduced. This approach is based on current-driven excitation of the GDPs in a dual-grating-gate high-mobility graphene channel field-effect transistor (DGG-GFET) structure. The temporal response of the DGG-GFETs to the polarization-managed incident THz pulsation is experimentally observed by using THz time-domain spectroscopy. Their Fourier spectra of the transmitted temporal waveform through the GDPs reveals the device functions 1) resonant absorption at low drain bias voltages below the first threshold level, 2) perfect transparency between the first and the second threshold drain bias levels, and 3) resonant amplification beyond the second threshold drain bias voltage. The maximal gain of 9% is obtained by a monolayer graphene at room temperatures, which is four times higher than the quantum limit that is given when THz photons directly interact with electrons. The results pave the way toward tunable graphene plasmonic THz amplifiers.
Simulation of terahertz plasmons in graphene with grating-gate structures
Frequency dispersion and damping mechanisms of two-dimensional plasmons in graphene in the terahert (THz) range are studied by a numerical simulation based on the Boltzmann equation. The fundamental plasmon mode in a singlegrating-gate structure is studied, and the coupling effect of plasmons in the gated and ungated regions are revealed. It is shown that the plasmon frequency as well as its gate-voltage tunability depend strongly on the coupling. It is also demonstrated that damping rates due to the acoustic-phonon scattering at room temperature and short-and finite-range disorder scattering can be on the order of 10 11 s −1 , depending on the level of disorders.
Graphene plasmonic devices for terahertz optoelectronics
Nanophotonics
Plasmonic excitations, consisting of collective oscillations of the electron gas in a conductive film or nanostructure coupled to electromagnetic fields, play a prominent role in photonics and optoelectronics. While traditional plasmonic systems are based on noble metals, recent work has established graphene as a uniquely suited materials platform for plasmonic science and applications due to several distinctive properties. Graphene plasmonic oscillations exhibit particularly strong sub-wavelength confinement, can be tuned dynamically through the application of a gate voltage, and span a portion of the infrared spectrum (including mid-infrared and terahertz (THz) wavelengths) that is not directly accessible with noble metals. These properties have been studied in extensive theoretical and experimental work over the past decade, and more recently various device applications are also beginning to be explored. This review article is focused on graphene plasmonic nanostructures designed...
Observation of Gate-Tunable Coherent Perfect Absorption of Terahertz Radiation in Graphene
ACS Photonics, 2016
We report experimental observation of electrically tunable coherent perfect absorption (CPA) of terahertz (THz) radiation in graphene. We develop a reflection-type tunable THz cavity formed by a large-area graphene layer, a metallic reflective electrode, and an electrolytic medium in between. Ionic gating in the THz cavity allows us to tune the Fermi energy of graphene up to 1 eV and to achieve a critical coupling condition at 2.8 THz with absorption of 99%. With the enhanced THz absorption, we were able to measure the Fermi energy dependence of the transport scattering time of highly doped graphene. Furthermore, we demonstrate flexible active THz surfaces that yield large modulation in the THz reflectivity with low insertion losses. We anticipate that the gate-tunable CPA will lead to efficient active THz optoelectronics applications.
Terahertz Amplifiers based on Multiple Graphene Layer with Field-Enhancement Effect
Japanese Journal of Applied Physics, 2011
Terahertz (THz) devices have been developed over the last decade to utilize THz waves for non-destructive sensing and high-speed wireless communications. Ryzhii et al. theoretically demonstrated the feasibility of THz lasing in optically pumped multiple graphene layer (MGL) structures and proposed THz laser structures [V. Ryzhii et al.: J. Appl. Phys. 106 (2009) 084507]. In addition, metallic sheets perforated with a periodic array of holes (metal mesh) have been used for band-pass filters with resonant transmittance of unity. In these periodic structures, induced surface plasmon polaritons (SPPs) enhance the electric field near the holes. We investigated THz amplifiers composed of MGL and metal mesh structures using finite difference time domain (FDTD) electromagnetic simulation. A remarkable increase in the transmittance for the metal mesh structure with MGL was observed.
Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications IX, 2016
We report the characterization of centimeter sized graphene field-effect transistors with ionic gating which enables active frequency and amplitude modulation of terahertz (THz) radiation. Chemical vapour deposited graphene with different grain sizes were studied using THz time-domain spectroscopy. We demonstrate that the plasmonic resonances intrinsic to graphene can be tuned over a wide range of THz frequencies by engineering the grain size of the graphene. Further frequency tuning of the resonance, up to ~65 GHz, is achieved by electrostatic doping via ionic gating. These results present the first demonstration of tuning the intrinsic plasmonic resonances in graphene.
Efficient terahertz electro-absorption modulation employing graphene plasmonic structures
Applied Physics Letters, 2012
We propose and discuss terahertz electro-absorption modulators based on graphene plasmonic structures. The active device consists of a self-gated pair of graphene layers, which are patterned to structures supporting THz plasmonic resonances. These structures allow for efficient control of the effective THz optical conductivity, thus absorption, even at frequencies much higher than the Drude roll-off in graphene where most previously proposed graphene-based devices become inefficient. Our analysis shows that reflectance-based device configurations, engineered so that the electric field is enhanced in the active graphene pair, could achieve very high modulation-depth, even ~100%, at any frequency up to tens of THz.
Plasmonic and bolometric terahertz detection by graphene field-effect transistor
Applied Physics Letters, 2013
Polarization dependence analysis of back-gated graphene field-effect transistor terahertz responsivity at frequencies ranging from 1.63 to 3.11 THz reveals two independent mechanisms of THz detection by graphene transistor: plasmonic, associated with the transistor nonlinearity, and bolometric, caused by graphene sheet temperature increase due to THz radiation absorption. In the bolometric regime, electron and hole branches demonstrate a very different response to THz radiation, which we link to the asymmetry of the current-voltage characteristics temperature dependence with respect to the Dirac point. Obtained results are important for development of high-efficiency graphene THz detectors. V