We report on detection of terahertz radiation by using asymmetric dual-grating gates graphene-based FET. The graphene sheet was sandwiched between two layers of hexagonal Boron Nitride (h-BN) to avoid interaction with the substrate and... more
We report on detection of terahertz radiation by using asymmetric dual-grating gates graphene-based FET. The graphene sheet was sandwiched between two layers of hexagonal Boron Nitride (h-BN) to avoid interaction with the substrate and enhance carrier mobility. Asymmetric dual metal gates were processed on the top of the upper h-BN layer. The devices were excited with terahertz radiation at frequencies of 0.15 and 0.3 THz and a clear photocurrent was observed from 4K up to room temperature.
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We report on the proposal and modeling of a heterostructure device similar to a field-effect transistor using optical excitation of electron plasma oscillations and intended for generation of terahertz signals
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Summary: An ultra-fast optoelectronic decision circuit using resonant tunneling diodes (RTD's) and a uni-traveling-carrier photodiode (UTC-PD) is proposed. The circuit employs two cascaded RTD's for ultra-fast logic operation... more
Summary: An ultra-fast optoelectronic decision circuit using resonant tunneling diodes (RTD's) and a uni-traveling-carrier photodiode (UTC-PD) is proposed. The circuit employs two cascaded RTD's for ultra-fast logic operation and one UTC-PD that offers a direct optical ...
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Research Interests: Materials Science, Mirror Symmetry, Plasmonics, Optoelectronics, Fabrication, and 14 moreHigh Electron Mobility Transistors, Ultrashort Pulse, Schottky diodes, Schottky diode, Gallium Arsenide, Optoelectronic Devices, Grating, Detector, Schottky barriers, Responsivity, Plasmon, Terahertz radiation, Indium Gallium Arsenide, and High electron mobility transistor
Summary: The authors report ultra-high-speed digital IC modules that use 0.1-µm InAlAs/InGaAs/InP HEMTs for broadband optical fiber communication systems. The multiplexer IC module operated at up to 70 Gbit/s, and error-free operation of... more
Summary: The authors report ultra-high-speed digital IC modules that use 0.1-µm InAlAs/InGaAs/InP HEMTs for broadband optical fiber communication systems. The multiplexer IC module operated at up to 70 Gbit/s, and error-free operation of the decision IC module ...
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This paper describes recent advances in high-speed digital IC design technologies based on GaAs MESFETs for future high-speed optical communications systems. We devised new types of a data selector and flip-flops, which are key elements... more
This paper describes recent advances in high-speed digital IC design technologies based on GaAs MESFETs for future high-speed optical communications systems. We devised new types of a data selector and flip-flops, which are key elements in performing high-speed digital functions (signal multiplexing, decision, demultiplexing, and frequency conversion) in front-end transmitter/receiver systems. Incorporating these circuit design technologies with state-of-the-art 0.12 μm gate-length GaAs MESFET process, we developed a DC-to-44-Gbit/s 2:1 data multiplexer IC, a DC-to 22-Gbit/s static decision IC, and a 20-to-40-Gbit/s dynamic decision IC. The fabricated ICs demonstrated record speed performances for GaAs MESFETs. Although further operating speed margin is still required, the GaAs MESFET is a potential candidate for 20- to 40-Gbit/s class applications.
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We propose a novel technology for fabricating plasmonic photoconductive antennas (PCAs) based on superlattice (SL) with increased height of the plasmonic gratings up to 100 nm. We passivate the surface of the SL by Si3N4, etch there... more
We propose a novel technology for fabricating plasmonic photoconductive antennas (PCAs) based on superlattice (SL) with increased height of the plasmonic gratings up to 100 nm. We passivate the surface of the SL by Si3N4, etch there windows and deposit Ti/Au antenna metallization. The plasmonic gratings are formed by electron-beam lithography with Ti/Au metallization followed by lift-off. Then an Al2O3 anti-reflection coating layer for reduction of the Fresnel reflection losses is used on the top of the plasmonic gratings, which also serves for maintaining its mechanical stability and providing the excitation of guided modes at the resonant wavelengths of the subwavelength slab waveguide formed by the metal gratings. Current-voltage measurements under femtosecond laser illumination reveal strong increase of the transient photocurrent generated by the fabricated plasmonic PCA which is 15 times higher than for conventional one (i.e. without the plasmonic gratings). The obtained terahertz (THz) power spectra demonstrate 100-times increase of the THz power in the plasmonic PCA. The results might be of interest to the needs of THz spectroscopy and imaging systems, in particular, operating with low-power lasers.
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We show that the ballistic electron injection from the n+ source region through the i-region into the gated n-region of the n+-i-n-n+ graphene field-effect transistor (GFET) leads to the effective drag of quasi-equilibrium electrons... more
We show that the ballistic electron injection from the n+ source region through the i-region into the gated n-region of the n+-i-n-n+ graphene field-effect transistor (GFET) leads to the effective drag of quasi-equilibrium electrons toward the drain. The drag results in the positive feedback between the ballistic injection and the reverse injection from the n+ drain region and can lead to the negative real part of the GFET source-drain impedance accompanied with the change of the impedance imaginary part sign. As a result, the steady-state current flow along the GFET channel can be unstable giving rise to the current driven self-excitation of the electron density high-frequency oscillations (plasma instability). The related oscillations of the current feeding an antenna can be used for the terahertz radiation emission.
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We report on amplified spontaneous broadband terahertz emission in 1–7.6 THz range at 100 K via current injection in a distributed-feedback dual-gate graphene-channel field effect transistor (DFB-DG GFET). The device exhibited a nonlinear... more
We report on amplified spontaneous broadband terahertz emission in 1–7.6 THz range at 100 K via current injection in a distributed-feedback dual-gate graphene-channel field effect transistor (DFB-DG GFET). The device exhibited a nonlinear threshold-like behavior with respect to the current-injection level. A precise DFB cavity design is expected to transcend the observed spontaneous broadband emission to single-mode THz lasing.
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We study instability of plasmons in a dual-grating-gate graphene field-effect transistor induced by dc current injection using self-consistent simulations with the Boltzmann equation. With ultimately high-quality graphene where the... more
We study instability of plasmons in a dual-grating-gate graphene field-effect transistor induced by dc current injection using self-consistent simulations with the Boltzmann equation. With ultimately high-quality graphene where the electron scattering is only limited by acoustic phonons, it is demonstrated that a total growth rate of the plasmon instability, with the terahertz/mid-infrared range of the frequency, can exceed 4 X 1012 s-1 at room temperature, which is an order of magnitude larger than in two-dimensional electron gases based on usual semiconductors. We show that the giant total growth rate originates from cooperative promotion of the so-called Dyakonov-Shur and Ryzhii-Satou-Shur instabilities.
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We evaluate the operation of vertical hot-electron graphene-base transistors (HET-GBTs) as detectors of terahertz (THz) radiation using the developed device model. The model accounts for the carrier statistics, tunneling injection from... more
We evaluate the operation of vertical hot-electron graphene-base transistors (HET-GBTs) as detectors of terahertz (THz) radiation using the developed device model. The model accounts for the carrier statistics, tunneling injection from the emitter, electron propagation across the barrier layer with partial capture into the graphene-layer (GL) base, and the self-consistent plasma oscillations of the electric potential and the hole density in the GL-base. The calculated responsivity of the HET-GBT THz detectors as a function of the signal frequency exhibits sharp resonant maxima in the THz range of frequencies associated with the excitation of plasma oscillations. The positions of these maxima are controlled by the applied bias voltages. The HET-GBTs can compete with and even surpass other plasmonic THz detectors.
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This paper reviews recent advances in the double-graphene-layer (DGL) active plasmonic heterostructures for the terahertz (THz) device applications. The DGL consists of a core shell in which a thin tunnel barrier layer is sandwiched by... more
This paper reviews recent advances in the double-graphene-layer (DGL) active plasmonic heterostructures for the terahertz (THz) device applications. The DGL consists of a core shell in which a thin tunnel barrier layer is sandwiched by the two GLs being independently connected with the side contacts and outer gate stack layers at both sides. The DGL core shell works as a nano-capacitor, exhibiting inter-GL resonant tunneling (RT) when the band offset between the two GLs is aligned. The RT produces a strong nonlinearity with a negative differential conductance in the DGL current-voltage characteristics. The excitation of the graphene plasmons by the THz radiation resonantly modulates the tunneling currentvoltage characteristics. When the band offset is aligned to the THz photon energy, the DGL structure can mediate photonassisted RT, resulting in resonant emission or detection of the THz radiation. The cooperative double-resonant excitation with structure-sensitive graphene plasmons gives rise to various functionalities such as rectification (detection), photomixing, higher harmonic generation, and self-oscillation, in the THz device implementations.
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We report on amplified spontaneous broadband terahertz emission in 1–7.6 THz range at 100 K via current injection in a distributed-feedback (DFB) dual-gate graphene-channel transistor. The device exhibited a nonlinear threshold-like... more
We report on amplified spontaneous broadband terahertz emission in 1–7.6 THz range at 100 K via current injection in a distributed-feedback (DFB) dual-gate graphene-channel transistor. The device exhibited a nonlinear threshold-like behavior with respect to the current-injection level. A precise DFB cavity design is expected to transcend the observed spontaneous broadband emission to single-mode THz lasing.
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We report on detection of terahertz radiation by using bilayer graphene-based FET with asymmetric grating gates. The device was fabricated with a stack of h-BN/Graphene/h-BN with a back gate as well as an asymmetric dual grating top... more
We report on detection of terahertz radiation by using bilayer graphene-based FET with asymmetric grating gates. The device was fabricated with a stack of h-BN/Graphene/h-BN with a back gate as well as an asymmetric dual grating top gates. It was subjected to terahertz radiation at frequencies of 150 and 300 GHz at 4K and a clear photocurrent was obtained.
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Terahertz emission by the photon-assisted resonant radiative transitions between graphene layers (GLs) in double-GL structures is theoretically and experimental demonstrated. Devices such as terahertz/infrared lasers base on this... more
Terahertz emission by the photon-assisted resonant radiative transitions between graphene layers (GLs) in double-GL structures is theoretically and experimental demonstrated. Devices such as terahertz/infrared lasers base on this technology are very promising for terahertz optoelectronics.
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We evaluate the optical pumping efficiency of the graphene-layer (GL) heterostructures intended for the terahertz (THz) lasing using the interband transitions in the GL. The pumping of such by near- or mid-infrared (NIR or MIR) radiation... more
We evaluate the optical pumping efficiency of the graphene-layer (GL) heterostructures intended for the terahertz (THz) lasing using the interband transitions in the GL. The pumping of such by near- or mid-infrared (NIR or MIR) radiation leads to the creation of a substantially hot two-dimensional electron-hole plasma (2D-EHP) in the GL. This hampers the interband population inversion in the 2D-EHP and can suppress the THz lasing. To prevent the 2D-EHP overheating, we propose to use the NIR/MIR radiation pumping of the GL through a sufficiently thick layer absorbing this radiation. This layer with sufficiently small energy gap enables an increase in the quantum efficiency of the pumping accompanied by strong cooling of the electron-hole pairs injected into the GL. As shown, the absorbing-cooling layers made of black-arsenic-phosphorus can be fairly efficient if their energy gap is smaller than the optical phonon energy in the GL.
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Electrons and holes in graphene behave as relativistic charged massless Dirac fermions due to the graphene unique gapless electronic band structure with a linear dispersion law. Dirac plasmons - the quanta of the plasma oscillation of the... more
Electrons and holes in graphene behave as relativistic charged massless Dirac fermions due to the graphene unique gapless electronic band structure with a linear dispersion law. Dirac plasmons - the quanta of the plasma oscillation of the Dirac electrons - can dramatically enhance the interaction of terahertz (THz) photons with graphene. We have proposed an original current-injection graphene THz laser transistor, demonstrated single-mode THz laser oscillation at low temperatures [1-3], and discovered and demonstrated the THz giant gain enhancement effect by the graphene Dirac plasmons [4-8]. However, further breakthroughs are needed to realize room-temperature high-intensity THz lasing and ultrafast modulation operation for the next generation wireless 6G and 7G communications. In this paper, we will present new ideas on the operating principle and device structures of the THz graphene plasmonic laser transistors with a high radiation intensity and ultrafast modulation capability o...
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We experimentally demonstrate terahertz light amplification by instability-driven stimulated emission of graphene plasmon polaritons in an asymmetric dual-grating-gate transistor structure. D.C. channel current driven by the drain bias... more
We experimentally demonstrate terahertz light amplification by instability-driven stimulated emission of graphene plasmon polaritons in an asymmetric dual-grating-gate transistor structure. D.C. channel current driven by the drain bias voltage induces plasmon instability, alternating the electromagnetic response from the resonant absorption to the resonant amplification (up to ~ 9 % gain) beyond the threshold drain bias voltage at room temperature.
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We review the performance of terahertz and infrared graphene photodetectors using heterostructures enabled by van der Waals bonding and the application of these devices for up-conversion to visible or UV range.
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The operation of the graphene n+–i–n–n+ field‐effect transistors (GFETs) and lateral diodes (GLDs) with the injection of ballistic electrons into the n‐region is analyzed. The momentum transfer of the injected ballistic electrons can lead... more
The operation of the graphene n+–i–n–n+ field‐effect transistors (GFETs) and lateral diodes (GLDs) with the injection of ballistic electrons into the n‐region is analyzed. The momentum transfer of the injected ballistic electrons can lead to an effective Coulomb drag of the quasiequilibrium electrons in the n‐region and the plasma instability in the GFETs and GLDs. The instability enables the generation of terahertz radiation. The obtained results can be used for the optimization of the structures under consideration for different devices, in particular, terahertz emitters.
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We develop the device models for the far-infrared interband photodetectors (IPs) with the graphene-layer (GL) sensitive elements and the black Phosphorus (b-P) or black-Arsenic (b-As) barrier layers (BLs). These far-infrared GL/BL-based... more
We develop the device models for the far-infrared interband photodetectors (IPs) with the graphene-layer (GL) sensitive elements and the black Phosphorus (b-P) or black-Arsenic (b-As) barrier layers (BLs). These far-infrared GL/BL-based IPs (GBIPs) can operate at the photon energies ℏ Ω smaller than the energy gap, Δ G , of the b-P or b-As or their compounds, namely, at ℏ Ω ≲ 2 Δ G / 3 corresponding to the wavelength range λ ≳ ( 6 − 12 ) μ m. The GBIP operation spectrum can be shifted to the terahertz range by increasing the bias voltage. The BLs made of the compounds b-As x B1−x with different x, enable the GBIPs with desirable spectral characteristics. The GL doping level substantially affects the GBIP characteristics and is important for their optimization. A remarkable feature of the GBIPs under consideration is a substantial (over an order of magnitude) lowering of the dark current due to a partial suppression of the dark-current gain accompanied by a fairly high photoconduct...
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We study theoretically the carrier transport and the plasmonic phenomena in the gated structures with dense lateral carbon nanotube (CNT) networks (CNT “felt”) placed between the highly-conducting slot line electrodes. The CNT networks... more
We study theoretically the carrier transport and the plasmonic phenomena in the gated structures with dense lateral carbon nanotube (CNT) networks (CNT “felt”) placed between the highly-conducting slot line electrodes. The CNT networks under consideration consist of a mixture of semiconducting and metallic CNTs. We find the dispersion relations for the two-dimensional plasmons, associated with the collective self-consisted motion of electrons in the individual CNTs, propagating along the electrodes as functions of the net electron density (gate voltage), relative fraction of the semiconducting and metallic CNTs, and the spacing between the electrodes. In a wide range of parameters, the characteristic plasmonic frequencies can fall in the terahertz (THz) range. The structures with lateral CNT networks can used in different THz devices.