Abstract-Tunnel field-effect transistors for sensitive terahertz detection

 

I. Gayduchenko, S. G. Xu, G. Alymov, M. Moskotin, I. Tretyakov, T. Taniguchi, K. Watanabe, G. Goltsman, A. K. Geim, G. Fedorov, D. Svintsov,  D. A. Bandurin, 

 https://www.nature.com/articles/s41467-020-20721-z

The rectification of electromagnetic waves to direct currents is a crucial process for energy harvesting, beyond-5G wireless communications, ultra-fast science, and observational astronomy. As the radiation frequency is raised to the sub-terahertz (THz) domain, ac-to-dc conversion by conventional electronics becomes challenging and requires alternative rectification protocols. Here, we address this challenge by tunnel field-effect transistors made of bilayer graphene (BLG). Taking advantage of BLG’s electrically tunable band structure, we create a lateral tunnel junction and couple it to an antenna exposed to THz radiation. The incoming radiation is then down-converted by the tunnel junction nonlinearity, resulting in high responsivity (>4 kV/W) and low-noise (0.2 pW/Hz−−−√$\sqrt{\mathrm{H}\mathrm{z}}$) detection. We demonstrate how switching from intraband Ohmic to interband tunneling regime can raise detectors’ responsivity by few orders of magnitude, in agreement with the developed theory. Our work demonstrates a potential application of tunnel transistors for THz detection and reveals BLG as a promising platform therefor.

Abstract-Effective detection of weak terahertz pulses in electro-optic sampling at kilohertz repetition rate

Philipp Krauspe, Natalie Banerji, and Julien Réhault

https://www.osapublishing.org/josab/abstract.cfm?uri=josab-37-1-127

The standard terahertz (THz) detection mechanism known as electro-optic sampling can be improved in sensitivity by biasing the polarization of the sampling field. In this work, we show theoretically and experimentally how weak signals can be amplified without inducing distortions. Our study identifies the influence of THz field strength, the polarization quality, and biasing amplitude on signal amplification and distortion. Here we present a distortion-free amplification of a factor of 28 while at the same time reducing the measurement time significantly.

© 2019 Optical Society of America

Abstract-Terahertz detection with an antenna-coupled highly-doped silicon quantum dot

Takuya Okamoto, Naoki Fujimura, Luca Crespi, Tetsuo Kodera, Yukio Kawano,

https://www.nature.com/articles/s41598-019-54130-0

Nanostructured dopant-based silicon (Si) transistors are promising candidates for high-performance photodetectors and quantum information devices. For highly doped Si with donor bands, the energy depth of donor levels and the energy required for tunneling processes between donor levels are typically on the order of millielectron volts, corresponding to terahertz (THz) photon energy. Owing to these properties, highly doped Si quantum dots (QDs) are highly attractive as THz photoconductive detectors. Here, we demonstrate THz detection with a lithographically defined and highly phosphorus-doped Si QD. We integrate a 40 nm-diameter QD with a micrometer-scale broadband logarithmic spiral antenna for the detection of THz photocurrent in a wide frequency range from 0.58 to 3.11 THz. Furthermore, we confirm that the detection sensitivity is enhanced by a factor of ~880 compared to a QD detector without an antenna. These results demonstrate the ability of a highly doped-Si QD coupled with an antenna to detect broadband THz waves. By optimizing the dopant distribution and levels, further performance improvements are feasible.

Abstract-Fast and sensitive bolometric terahertz detection at room temperature through thermomechanical transduction

Journal of Applied Physics

 Ya Zhang, Suguru Hosono, Naomi Nagai, Sang-Hun Song,  Kazuhiko Hirakawa

(a) Wafer structure used to fabricate the doubly clamped GaAs beam resonator. (b) Schematic illustration of the GaAs beam resonator fabricated by selective etching. (c) Microscope image of a fabricated GaAs MEMS beam resonator (100 × 30 × 1.2 μm3). The 2DEG layer and the top gates on both ends of the beam form two piezoelectric capacitors, C1 and C2. A 15-nm-thick NiCr THz absorbing layer was deposited on the beam. This metal film was also used as a heater to calibrate the thermal responsivity of the resonator. (d) The resonance spectra measured by sweeping the driving frequency at various input heating powers, Pin, from 0 μW to ∼1100 μW. The red curve is the resonance spectrum at Pin = 0. (e) Normalized frequency shift as a function of Pin.

https://aip.scitation.org/doi/abs/10.1063/1.5045256

Terahertz (THz) electromagnetic spectrum draws wide attention for nondestructive and/or biocompatible sensing. In order to be widely applicable to the THz sensing, it is of prime importance to develop THz sensors that can be operated at room temperature and have high sensitivity and fast operation speed. However, conventional room-temperature THz thermal sensors fall short of expectations in these characteristics required in various applications of THz sensing, including THz cameras. Utilizing a thermomechanical transduction scheme, we have developed an uncooled, sensitive, and fast THz bolometer by using a doubly clamped GaAs microelectromechanical system (MEMS) beam resonator as a sensitive thermistor. Owing to its ultrahigh temperature sensitivity (the noise equivalent temperature difference of ∼1 μK/√Hz), the present bolometer achieves not only high sensitivity but also an operation bandwidth of several kHz, which is more than 100 times faster than other uncooled THz thermal sensors. The obtained electrical noise equivalent power is as low as ∼90 pW/√Hz, which is close to the limit set by the thermal fluctuation noise. The MEMS bolometers are fabricated by the standard semiconductor fabrication processes and are well suited for making detector arrays for realizing THz cameras.

Abstract-Terahertz Detection in MOS-FET: A new model by the self-mixing

Fabrizio Palma, Rosario Rao,

https://ieeexplore.ieee.org/document/8510162

High frequency detection based on MOS-FET technology was long justified using a mechanism described by the plasma wave detection theory. In this paper we propose a new model based on the self-mixing process, taking place not in the channel, but in the depleted portion of the transistor body. Hydrodynamic semiconductor equations are solved in the small signal approximation. As a result, we present the dependence of the rectified voltage on the bias gate voltage, which fits carefully several experimental literature results.

Abstract-The detection of sub-terahertz radiation using graphene-layer and graphene-nanoribbon FETs with asymmetric contacts

Igor A. Maxim, V.Moskotin, Yakov E. Matyushkin, Maxim G. Rybin,  Elena D. Obraztsova, Victor I.Ryzhii, Gregory N. Goltsman, Georgy E. Fedorov, 

https://www.sciencedirect.com/science/article/pii/S2214785318321321

We report on the detection of sub-terahertz radiation using single layer graphene and graphene-nanoribbon FETs with asymmetric contacts (one is the Schottky contact and one – the Ohmic contact). We found that cutting graphene into ribbons a hundred nanometers wide leads to a decrease of the response to sub-THz radiation. We show that suppression of the response in the graphene nanoribbons devices can be explained by unusual properties of the Schottky barrier on graphene-vanadium interface

Abstract-Performance evaluation of tunneling field effect transistor on Terahertz detection

Q. Yang, J. Zhang,  C. Zhu,  X. Lin, F. Yan, X. Ji

https://ieeexplore.ieee.org/document/8369195

Tunneling field-effect transistor (TFET) with integrated circuit manufacture process is capable of rectifying high frequency radiations in THz region. As an efficient device to detect Terahertz signal. In this paper, we demonstrate a Si-based TFET device for THz imaging. The static characteristics and THz performance are presented by using technology computer-aided design simulation. For an optimally designed TFETs with SS of 40.3mV/dec, it has a high responsivity of 4300V/W to a 1THz radiation. Compared to the traditional CMOS Terahertz detector, TFET-based one has faster response rate and higher detect efficiency, suggesting TFET a promising device for the low-power Terahertz imagin

Abstract-Plasmon ratchet effect with electrons and holes simultaneously existing in the graphene channel: a promising effect for the terahertz detection

Anqi Yu

http://iopscience.iop.org/article/10.1088/1361-6463/aad942

In this work, the plasmon drag effect in the grating gated graphene with symmetric unit cell, the plasmon ratchet effect and the photo-thermoelectric effect in the grating gated graphene with asymmetric unit cell are studied. The correlation between the total responsivity of the plasmon drag effect and the source-drain bias is calculated numerically through the hydrodynamic approach under small source-drain bias approximation. The total responsivity of the plasmon drag effect under small source-drain bias is found to be much smaller than the responsivity of the unidirectional travelling plasmons. The responsivity of the plasmon ratchet effect is calculated by fixing the lengths of the longer gated region and ungated region and changing the lengths of the shorter gated region and ungated region. The results show that non-zero plasmon ratchet responsivity can be obtained by only assuming one kind of charge carrier in the whole channel. By assuming holes in the shorter gated region and electrons in the other regions, the maximum responsivity is much higher than the former and can be as high as that reported in the reference. The responsivity of the photo-thermoelectric effect can be higher than that of the plasmon ratchet effect for currently available graphene. For ideal graphene with ultrahigh mobility, however, the responsivity of the photo-thermoelectric effect is orders of magnitude smaller than that of the plasmon ratchet effect.

Abstract-Terahertz detection of alcohol using a photonic crystal fiber sensor

Jakeya Sultana, Md. Saiful Islam, Kawsar Ahmed, Alex Dinovitser, Brian W.-H. Ng, and Derek Abbott

http://65.202.222.105/ao/abstract.cfm?uri=ao-57-10-2426

Ethanol is widely used in chemical industrial processes as well as in the food and beverage industry. Therefore, methods of detecting alcohol must be accurate, precise, and reliable. In this content, a novel Zeonex-based photonic crystal fiber (PCF) has been modeled and analyzed for ethanol detection in terahertz frequency range. A finite-element-method-based simulation of the PCF sensor shows a high relative sensitivity of 68.87% with negligible confinement loss of 7.79×10−12  cm−1$7.79\times {10}^{-12}{\mathrm{cm}}^{-1}$ at 1 THz frequency and 𝑥$x$-polarization mode. Moreover, the core power fraction, birefringence, effective material loss, dispersion, and numerical aperture are also determined in the terahertz frequency range. Owing to the simple fiber structure, existing fabrication methods are feasible. With the outstanding waveguiding properties, the proposed sensor can potentially be used in ethanol detection, as well as polarization-preserving applications of terahertz waves.

© 2018 Optical Society of America

Abstract-Optical and electrical properties of vanadium-doped ZnTe crystals grown by the temperature gradient solution method

Bao Xiao, Mengqin Zhu, Binbin Zhang, Jiangpeng Dong, Leilei Ji, Hui Yu, Xiaoyan Sun, Wanqi Jie, and Yadong Xu

https://www.osapublishing.org/ome/abstract.cfm?uri=ome-8-2-431&origin=search

Vanadium-doped ZnTe (ZnTe:V) crystals 30 mm in diameter and 45 mm in length were grown by the temperature gradient solution growth method. The band gap of as-grown ZnTe:V crystals was estimated to be about 2.22 eV. Infrared spectra exhibit a mean transmittance of 50%-60% in the wavenumber range from 500 cm−1 to 4000 cm−1. Compared with the intrinsic ZnTe crystal, the resistivity of ZnTe:V is increased 6-7 orders of magnitude up to 109 Ω·cm and the carrier concentration reduced from 1014 to 108 cm−3. Accordingly, the THz detection sensitivity is also enhanced by 20%-30%. The improvements on the optical and electrical properties were attributed to the compensation of Zn vacancies by the vanadium element.

© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Efficient Terahertz detection in black-phosphorus nano-transistors with selective and controllable plasma-wave, bolometric and thermoelectric response

http://www.laboratorionest.it/efficient-terahertz-detection-in-black-phosphorus-nano-transistors-with-selective-and-controllable-plasma-wave-bolometric-and-thermoelectric-response/


The ability to convert light into an electrical signal with high efficiencies and controllable dynamics, is a major need in photonics and optoelectronics. In the Terahertz (THz) frequency range, with its exceptional application possibilities in high data rate wireless communications, security, nightvision, biomedical or video-imaging and gas sensing, detection technologies providing efficiency and sensitivity performances that can be “engineered” from scratch, remain elusive. In the publication on Nature-Scientific Report journal, researchers Leonardo Viti, Miriam Vitiello and co-workers, Istituto Nanoscienze and Scuola Normale superiore at NEST Laboratory, by exploiting the inherent electrical and thermal in-plane anisotropy of a flexible thin flake of black-phosphorus (BP), devise plasma-wave, thermoelectric and bolometric nano-detectors with a selective, switchable and controllable operating mechanism. All devices operates at room-temperature and are integrated on-chip with planar nanoantennas, which provide remarkable efficiencies through light-harvesting in the strongly sub-wavelength device channel. The achieved selective detection (∼5–8 V/W responsivity) and sensitivity performances (signal-to-noise ratio of 500), are there exploited to demonstrate the first concrete application of a phosphorus-based active THz device, for pharmaceutical and quality control imaging of macroscopic samples, in real-time and in a realistic setting.
More details at the following LINK

Abstract-Efficient Terahertz detection in black-phosphorus nano-transistors with selective and controllable plasma-wave, bolometric and thermoelectric response

Leonardo Viti, Jin Hu, Dominique Coquillat, Antonio Politano, Wojciech Knap,  Miriam S. Vitiello,

http://www.nature.com/articles/srep20474

The ability to convert light into an electrical signal with high efficiencies and controllable dynamics, is a major need in photonics and optoelectronics. In the Terahertz (THz) frequency range, with its exceptional application possibilities in high data rate wireless communications, security, night-vision, biomedical or video-imaging and gas sensing, detection technologies providing efficiency and sensitivity performances that can be “engineered” from scratch, remain elusive. Here, by exploiting the inherent electrical and thermal in-plane anisotropy of a flexible thin flake of black-phosphorus (BP), we devise plasma-wave, thermoelectric and bolometric nano-detectors with a selective, switchable and controllable operating mechanism. All devices operates at room-temperature and are integrated on-chip with planar nanoantennas, which provide remarkable efficiencies through light-harvesting in the strongly sub-wavelength device channel. The achieved selective detection (∼5–8 V/W responsivity) and sensitivity performances (signal-to-noise ratio of 500), are here exploited to demonstrate the first concrete application of a phosphorus-based active THz device, for pharmaceutical and quality control imaging of macroscopic samples, in real-time and in a realistic setting.

Intrinsic photo-conductance triggered by the plasmonic effect in graphene for terahertz detection

http://iopscience.iop.org/0957-4484/labtalk-article/63646?labTalkTab=mostRead

Terahertz (THz) technology is becoming more prominent for applications including biomedical imaging, communication, security and astronomy. However, THz technology still possesses some challenges due to the lack of sources and detectors available. Although the terahertz wavelength ranges from 0.1~100 mm, this exceeds the dimensions of the nanoscale. Reporting in Nanotechnology, researchers Dr Lin Wang, Professor Xiaoshuang Chen, and colleagues at Shanghai Institute of Technical Physics explain an even stronger response of graphene with only a single carbon atomic layer at terahertz region. They find that the terahertz-induced potential wells or barriers trapping or detrapping carriers in graphene FET channel make it very promising for photo-detection. This property combined with its 2D nature offer a new route for future compact graphene-based integration and high performance flexible focal plane array in the field of terahertz imaging and security.

Schematic of the photo-doping process

“The stronger response is due to the carrier dynamics at the timescale around terahertz frequency in graphene,” says Dr. Wang, “The motion of electron bunch at this frequency behaves like a fluid or sound wave, which leads to plasmonic resonances when Dirac fermions are ac excited.” The researchers find that the near-field of the grating coupler leads to enhanced localised nonlinearity of Dirac fermions and change the conductance ultimately, which is obviously different from mechanisms discovered before including photothermoelectric (PTE) bolometric effects.

The researchers point out that controlling the distribution of the THz field enables the freedom of controlling the transport of carriers in any fantastic way, and leads to the appearance of more intriguing phenomena such as photogalvanic, helicity-sensitive and photovoltaic detections.

More information about this research can be found in the journal Nanotechnology 27 035205.