Abstract- Terahertz plasmon-emitting graphene-channel transistor

A.A. Dubinov, V. Ya Aleshkin, S.V. Morozov, V. Ryzhii, T. Otsuji,



https://www.sciencedirect.com/science/article/abs/pii/S1230340218301550

In this work we propose and analyze the possibility of creating terahertz plasmon-emitting graphene-channel transistor. It is shown that at electric pumping the damping of the terahertz plasmons can give way to their amplification, when the real part of the dynamic conductivity of graphene becomes negative in the terahertz range of frequencies due to the interband population inversion.

Abstract-Negative terahertz conductivity and amplification of surface plasmons in graphene–black phosphorus injection laser heterostructures

V. Ryzhii, T. Otsuji, M. Ryzhii, A. A. Dubinov, V. Ya. Aleshkin, V. E. Karasik, and M. S. Shur

https://journals.aps.org/prb/accepted/9b078O08Pf81783789dd94946bdb6e0d63736de90

We propose and evaluate the heterostructure based on the graphene-layer (GL) with the lateral electron injection from the side contacts and the hole vertical injection via the black phosphorus layer (PL) (p${}^{+}$P-PL-GL heterostructure). Due to a relatively small energy of the holes injected from the PL into the GL (about 100 meV, smaller than the energy of optical phonons in the GL which is about 200 meV), the hole injection can effectively cool down the two-dimensional electron-hole plasma in the GL. This simplifies the realization of the interband population inversion and the achievement of the negative dynamic conductivity in the terahertz (THz) frequency range enabling the amplification of the surface plasmon modes. The later can lead to the plasmon lasing. The conversion of the plasmons into the output radiation can be used for a new types of the THz sources.

Abstract-Negative photoconductivity and hot-carrier bolometric detection of terahertz radiation in graphene-phosphorene hybrid structures

Journal of Applied Physics

V. Ryzhii, M. Ryzhii, D. S. Ponomarev, V. G. Leiman,  V. Mitin,  M. S. Shur,  T. Otsuji,

The structures of (a) the GP-LD and (b) the GP-FET (b), their asymmetric with respect to the Dirac point (Δe>Δh${\mathrm{\Delta }}^e>{\mathrm{\Delta }}^h$) energy band diagrams with the G-Dirac cones and the parabolic extrema corresponding to the P-layer at (c) T=T0$T=T_0$ and (d) T>T0$T>T_0$ (T$T$ and T0$T_0$ are the carrier effective temperature and the lattice temperature, respectively), and (e) the energy dependence of the density of state (DoS). Open circles correspond to the holes in the valence bands of G- and P-layers.

https://aip.scitation.org/doi/abs/10.1063/1.5054142

We consider the effect of terahertz (THz) radiation on the conductivity of the ungated and gated graphene (G)-phosphorene (P) hybrid structures and propose and evaluate the hot-carrier uncooled bolometric photodetectors based on the GP-lateral diodes (GP-LDs) and GP-field-effect transistors (GP-FETs) with the GP-channel. The operation of the GP-LDs and GP-FET photodetectors is associated with the carrier heating by the incident radiation absorbed in the G-layer due to the intraband transitions. The carrier heating leads to the relocation of a significant fraction of the carriers into the P-layer. Due to a relatively low mobility of the carriers in the P-layer, their main role is associated with a substantial reinforcement of the scattering of the carriers. The GP-FET bolometric photodetector characteristics are effectively controlled by the gate voltage. A strong negative conductivity of the GP-channel can provide much higher responsivity of the THz hot-carriers GP-LD and GP-FET bolometric photodetectors in comparison with the bolometers with solely the G-channels.

Abstract-Plasmonic terahertz emitters with high-aspect ratio metal gratings

D. V. Lavrukhin, A. E. Yachmenev, I. A. Glinskiy, R. A. Khabibullin, M. Ryzhii, T. Otsuji, M. Shur, K. I. Zaytsev, D. S. Ponomarev

https://www.spiedigitallibrary.org/conference-proceedings-of-spie/11022/1102203/Plasmonic-terahertz-emitters-with-high-aspect-ratio-metal-gratings/10.1117/12.2521290.short

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.

© (2019) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Abstract-Negative photoconductivity and hot-carrier bolometric detection of terahertz radiation in graphene-phosphorene hybrid structures

V. Ryzhii, M. Ryzhii, D. S. Ponomarev, V. G. Leiman, V. Mitin, M. S. Shur, T. Otsuji

https://arxiv.org/abs/1808.09083

We consider the effect of terahertz (THz) radiation on the conductivity of the ungated and gated graphene (G)-phosphorene (P) hybrid structures and propose and evaluated the hot-carrier uncooled bolometric photodetectors based on the GP-lateral diodes (GP-LDs) and GP-field-effect transistors (GP-FETs) with the GP channel.
The operation of the GP-LDs and GP-FET photodetectors is associated with the carrier heating by the incident radiation absorbed in the G-layer due to the intraband transitions. The carrier heating leads to the relocation of a significant fraction of the carriers into the P-layer. Due to a relatively low mobility of the carriers in the P-layer, their main role is associated with a substantial reinforcement of the scattering of the carriers. The GP-FET bolometric photodetector characteristics are effectively controlled by the gate voltage. A strong negative conductivity of the GP-channel can provide much higher responsivity of the THz hot-carriers GP-LD and GP-FET bolometric photodetectors in comparison with the bolometers with solely the G-channels.

Abstract- Near-Field nanoscopy of current-induced excess noise in graphene

K.-T. Lin,  Q. Weng, H. Nema,  S. Kim,   K. Sugawara,  T. Otsuji,  S. Komiyama,   Y. Kajihara

http://ieeexplore.ieee.org/document/8067243/

We describe a near-field nanoimaging method employed to spatially map the current-induced excess noise occurring in a bilayer graphene constriction with passive scanning near-field microscope (s-SNOM). We find that the excess noise, manifesting itself as fluctuating electromagnetic evanescent fields generated on the sample surface, is discernible only in the constricted region and increases linearly with increasing current. The passive s-SNOM thus proves to be a unique non-invasive experimental tool for investigating the electron transport mechanism via noise mapping in graphene device at the nanometer scale

Abstract-Current-injection terahertz lasing in a distributed-feedback dual-gate graphene-channel transistor

G. Tamamushi,  T. Watanabe,  J. Mitsushio,  A. A. Dubinov,  A. Satou, T. Suemitsu,  M. Ryzhii,  V. Ryzhii,  T. Otsuji

https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10111/1011126/Current-injection-terahertz-lasing-in-a-distributed-feedback-dual-gate/10.1117/12.2249983.pdf?SSO=1

This paper reviews recent advancement on the research toward graphene-based terahertz (THz) lasers. Optical and/or injection pumping of graphene can enable negative-dynamic conductivity in the THz spectral range, which may lead to new types of THz lasers. A forward-biased graphene structure with a lateral p-i-n junction was implemented in a distributed-feedback (DFB) dual-gate graphene-channel FET and observed a single mode emission at 5.2 THz at 100K. The observed spectral linewidth fairly agrees with the modal gain analysis based on DFB-Fabry-Perrot hybrid-cavitymode modeling. Although the results obtained are still preliminary level, the observed emission could be interpreted as THz lasing in population-inverted graphene by carrier-injection.

© (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Abstract-Two-dimensional plasmons in lateral carbon nanotube network structures and their effect on the terahertz radiation detection

V. Ryzhii, T. Otsuji, M. Ryzhii, V. G. Leiman, G. Fedorov, G. N. Goltzman, I. A. Gayduchenko, N. Titova, D. Coquillat, D. But, W. Knap, V. Mitin, M. S. Shur

(Submitted on 17 Feb 2016)

http://arxiv.org/abs/1602.05306

We consider the carrier transport and plasmonic phenomena in the lateral carbon nanotube (CNT) networks forming the device channel with asymmetric electrodes. One electrode is the Ohmic contact to the CNT network and the another contact is the Schottky contact. These structures can serve as detectors of the terahertz (THz) radiation. We develop the device model for response of the lateral CNT networks which comprise a mixture of randomly oriented semiconductor CNTs (s-CNTs) and quasi-metal CNTs (m-CNTs). The proposed model includes the concept of the two-dimensional plasmons in relatively dense networks of randomly oriented CNTs (CNT "felt") and predicts the detector responsivity spectral characteristics. The detection mechanism is the rectification of the ac current due the nonlinearity of the Schottky contact current-voltage characteristics under the conditions of a strong enhancement of the potential drop at this contact associated with the plasmon excitation. We demonstrate that the excitation of the two-dimensional plasmons by incoming THz radiation the detector responsivity can induce sharp resonant peaks of the detector responsivity at the signal frequencies corresponding to the plasmonic resonances. The detector responsivity depends on the fractions of the s- and m-CNTs. The burning of the near-contact regions of the m-CNTs or destruction of these CNTs leads to a marked increase in the responsivity in agreement with our experimental data. The resonant THz detectors with sufficiently dense lateral CNT networks can compete and surpass other THz detectors using plasmonic effects at room temperatures.

Abstract-Resonant plasmonic terahertz detection in vertical graphene-base hot-electron transistors

V. Ryzhii, T. Otsuji, M. Ryzhii, V. Mitin, M. S. Shur

(Submitted on 11 Sep 2015)

http://arxiv.org/abs/1509.03375#

We analyze dynamic properties of vertical graphene-base hot-electron transistors (GB-HETs) and consider their operation as detectors of terahertz (THz) radiation using the developed device model. The GB-HET model accounts for the tunneling electron injection from the emitter, electron propagation across the barrier layers with the partial capture into the GB, and the self-consistent oscillations of the electric potential and the hole density in the GB (plasma oscillations), as well as the quantum capacitance and the electron transit-time effects. Using the proposed device model, we calculate the responsivity of GB-HETs operating as THz detectors as a function of the signal frequency, applied bias voltages, and the structural parameters. The inclusion of the plasmonic effect leads to the possibility of the HET-GBT operation at the frequencies significantly exceeding those limited by the characteristic RC-time. It is found that the responsivity of GB-HETs with a sufficiently perfect GB 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 GB-HETs can compete with and even surpass other plasmonic THz detectors.

Abstract-Helicity sensitive terahertz radiation detection by dual-grating-gate high electron mobility transistors

P. Faltermeier¹, P. Olbrich¹, W. Probst¹, L. Schell¹, T. Watanabe², S. A. Boubanga-Tombet², T. Otsuji² and S. D. Ganichev¹
http://scitation.aip.org/content/aip/journal/jap/118/8/10.1063/1.4928969
1 Terahertz Center, University of Regensburg, 93040 Regensburg, Germany
2 Research Institute of Electrical Communication, Tohoku University, 980-8577 Sendai, Japan
J. Appl. Phys. 118, 084301 (2015); http://dx.doi.org/10.1063/1.4928969

We report on the observation of a radiation helicity sensitive photocurrent excited by terahertz (THz) radiation in dual-grating-gate (DGG) InAlAs/InGaAs/InAlAs/InP high electron mobility transistors (HEMT). For a circular polarization, the current measured between source and drain contacts changes its sign with the inversion of the radiation helicity. For elliptically polarizedradiation, the total current is described by superposition of the Stokes parameters with different weights. Moreover, by variation of gate voltages applied to individual gratings, the photocurrentcan be defined either by the Stokes parameter defining the radiation helicity or those for linearpolarization. We show that artificial non-centrosymmetric microperiodic structures with a two-dimensional electron system excited by THz radiation exhibit a dc photocurrent caused by the combined action of a spatially periodic in-plane potential and spatially modulated light. The results provide a proof of principle for the application of DGG HEMT for all-electric detection of the radiation's polarization state.

Abstract-Negative terahertz conductivity in remotely doped graphene bilayer heterostructures

V. Ryzhii, M. Ryzhii, V. Mitin, M. S. Shur, T. Otsuji

(Submitted on 20 Aug 2015)

http://lib-arxiv-008.serverfarm.cornell.edu/abs/1508.04931

Injection or optical generation of electrons and holes in graphene bilayers (GBLs) can result in the interband population inversion enabling the terahertz (THz) radiation lasing. The intraband radiative processes compete with the interband transitions. We demonstrate that remote doping enhances the indirect interband generation of photons in the proposed GBL heterostructures. Therefore such remote doping helps surpassing the intraband (Drude) absorption and results in large absolute values of the negative dynamic THz conductivity in a wide range of frequencies at elevated (including room) temperatures. The remotely doped GBL heterostructure THz lasers are expected to achieve higher THz gain compared to previously proposed GBL-based THz lasers.

Abstract-Negative terahertz conductivity in disordered graphene bilayers with population inversion

D. Svintsov¹, T. Otsuji², V. Mitin^2,3, M. S. Shur⁴ and V. Ryzhii^2,a)
http://scitation.aip.org/content/aip/journal/apl/106/11/10.1063/1.4915314?TRACK=RSS
a) Electronic mail: v-ryzhii@riec.tohoku.ac.jp
Appl. Phys. Lett. 106, 113501 (2015); http://dx.doi.org/10.1063/1.4915314

The gapless energy band spectra make the structures based on graphene and graphenebilayer with the population inversion to be promising media for the interband terahertz (THz) lasing. However, a strong intraband absorption at THz frequencies still poses a challenge for efficient THz lasing. In this paper, we show that in the pumped graphene bilayer, the indirect interband radiative transitions accompanied by scattering of carriers by disorder can provide a substantial negative contribution to the THz conductivity (together with the direct interbandtransitions). In the graphene bilayer on high-κ substrates with point charged defects, thesetransitions substantially compensate the losses due to the intraband (Drude) absorption. We also demonstrate that the indirect interband contribution to the THz conductivity in a graphenebilayer with the extended defects (such as the charged impurity clusters) can surpass by several times the fundamental limit associated with the direct interband transitions, and the Drude conductivity as well. These predictions can affect the strategy of the graphene-based THz laser implementation.

Abstract-Terahertz Plasmonics: Good Results and Great Expectations

Otsuji, T. Shur, M.
Research Institute of Electrical Communication,, Tohoku University, Sendai, 980-8577, JAPAN 
http://ieeexplore.ieee.org/xpl/abstractAuthors.jsp?arnumber=6954554&sortType%3Dasc_p_Sequence%26filter%3DAND%28p_IS_Number%3A6954433%29

The terahertz (THz) range is the next frontier of electronics and optoelectronics with potential applications ranging from imaging, space communications, computing, quality control, and homeland security to biotechnology and medicine. At THz frequencies, the electron inertia becomes important, providing delay between the applied voltage and electron velocity and current. When the electron collisions with impurities and lattice vibrations are infrequent, this delay leads to oscillations of the electronic density (called plasma waves) with the transistor channels serving as resonant cavities for the plasma waves. In the collision-dominated regime, the plasma waves are overdamped but still play a role by dramatically changing the electron distribution in the device channels at THz frequencies. The resonant regime can be used to generate THz radiation. Both resonant and overdamped plasma waves enable other THz electronic devices, such as detectors, mixers, and phase shifters. Periodic (symmetrical and asymmetric) plasmonic structures are especially promising for generation and detection of THz radiation. In this article, we review the state of the art of the plasma-wave electronics for silicon, III-V, III-N, and graphene semiconductor devices and project future performance of plasma-wave THz devices.

Abstract-Graphene vertical hot-electron terahertz detectors

V. Ryzhii^1,2,a), A. Satou¹, T. Otsuji¹, M. Ryzhii³, V. Mitin⁴ and M. S. Shur⁵
http://scitation.aip.org/content/aip/journal/jap/116/11/10.1063/1.4895738
1 Research Institute for Electrical Communication, Tohoku University, Sendai 980-8577, Japan
2 Center for Photonics and Infrared Engineering, Bauman Moscow State Technical University and Institute of Ultra High Frequency Semiconductor Electronics, Russian Academy of Sciences, Moscow 111005, Russia
3 Department of Computer Science and Engineering, University of Aizu, Aizu-Wakamatsu 965-8580, Japan
4 Department of Electrical Engineering, University at Buffalo, Buffalo, New York 1460-1920, USA
5 Departments of Electrical, Electronics, and Systems Engineering and Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
a) Electronic mail: v-ryzhii@riec.tohoku.ac.jp
J. Appl. Phys. 116, 114504 (2014); http://dx.doi.org/10.1063/1.4895738

We propose and analyze the concept of the vertical hot-electron terahertz (THz) graphene-layerdetectors (GLDs) based on the double-GL and multiple-GL structures with the barrier layers made of materials with a moderate conduction band off-set (such as tungsten disulfide and related materials). The operation of these detectors is enabled by the thermionic emissions from the GLs enhanced by the electrons heated by incoming THz radiation. Hence, thesedetectors are the hot-electron bolometric detectors. The electron heating is primarily associated with the intraband absorption (the Drude absorption). In the frame of the developed model, we calculate the responsivity and detectivity as functions of the photon energy, GL doping, and the applied voltage for the GLDs with different number of GLs. The detectors based on the cascade multiple-GL structures can exhibit a substantial photoelectric gain resulting in the elevated responsivity and detectivity. The advantages of the THz detectors under consideration are associated with their high sensitivity to the normal incident radiation and efficient operation at room temperature at the low end of the THz frequency range. Such GLDs with a metal grating, supporting the excitation of plasma oscillations in the GL-structures by the incident THz radiation, can exhibit a strong resonant response at the frequencies of several THz (in the range, where the operation of the conventional detectors based on A3B5 materials, in particular, THz quantum-well detectors, is hindered due to a strong optical phonon radiation absorption in such materials). We also evaluate the characteristics of GLDs in the mid- and far-infrared ranges where the electron heating is due to the interband absorption in GLs.