Chao Tang

• Doctor of Engineering
• Professor (Assistant) at Tohoku University

The lateral interdigital array of the graphene microribbons (GMRs) on the h-BN substrate connected by narrow graphene nanoribbon (GNR) bridges serves as an efficient detector of terahertz (THz) radiation. The detection is enabled by the nonlinear GNR elements providing the rectification of the THz signals. The excitation of plasmonic waves along th...

The lateral interdigital array of the graphene microribbons (GMRs) on the h-BN substrate connected by narrow graphene nanoribbon (GNR) bridges serves as an efficient detector of terahertz (THz) radiation. The detection is enabled by the nonlinear GNR elements providing the rectification of the THz signals. The excitation of plasmonic waves along th...

We analyze the operation of the hot-electron FET bolometers with the graphene channels (GCs) and the gate barrier layers. Such bolometers use the thermionic emission of the hot electrons heated by incident-modulated THz radiation. The hot electrons transfer from the GC into the metal gate. As the THz detectors, these bolometers can operate at room...

In this paper, we analyze the modulation characteristics and the ultimate modulation frequency of the terahertz (THz) hot-electron FET bolometers with the graphene channels (GCs), metal gate (MG), and gate barrier layers (BLs) in a wide temperature range. Our results predict that the responsivity of GC-FET bolometers decreases with decreasing opera...

In this paper, we propose and analyze the terahertz (THz) bolometric vector detectors based on the graphene-channel field-effect transistors (GC-FET) with the black-P gate barrier layer or with the composite b-BN/black-P/b-BN gate layer. The phase difference between the signal received by the FET source and drain substantially affects the plasmonic...

We analyze the generation of the terahertz (THz) radiation in photomixers using the interdigital graphene micro-nanoribbon (GMNR) array excited by modulated light or ultrashort radiation pulses. Replacing the standard metal electrodes by the GMNR array enables in the twofold advantages: an increase in the carrier generation efficiency due to the GM...

We analyze plasmonic oscillations in the coplanar graphene nanoribbon (GNR) structures induced by the applied terahertz (THz) signals and calculate the GNR impedance. The plasmonic oscillations in the GNR structures are associated with the electron and hole inductances and the lateral inter-GNR capacitance. A relatively low inter-GNR capacitance en...

We developed terahertz (THz) detectors based on a high-quality epitaxial graphene-channel transistor. The bias dependencies of the responsivity indicate the primary contributions of plasmonic and photothermoelectric rectification mechanisms and suggest a distinctive signature of the third rectification mechanism called the 3D-rectification.

In this study, we developed a fast and sensitive terahertz (THz) detector using a Bi 2 Se 3 /h-BN heterostructure rectenna that enables detection without a cathode-anode bias. The fabrication process involved synthesizing β-Bi 2 Se 3 via vapor-controlled liquid phase growth and h-BN via chemical vapor deposition [1]. The Bi 2 Se 3 flake were cleave...

We experimentally investigated the asymmetric dual-grating-gate plasmonic terahertz (THz) detector based on an InGaAs-channel high-electron-mobility transistor (HEMT) in the gate-readout configuration. Throughout the THz pulse detection measurement on the fabricated device, we discovered a new detection mechanism called the “3D rectification effect...

We propose and analyze the performance of terahertz (THz) room-temperature bolometric detectors based on the graphene channel field-effect transistors (GC-FET). These detectors comprise the gate barrier layer (BL) composed of the lateral hexagonal-boron nitride black-phosphorus/hexagonal-boron nitride (h-BN/b-P/h-BN) structure. The main part of the...

We investigate the response of the micromechanical field-effect transistors (MMFETs) to the impinging terahertz (THz) signals. The MMFET uses the microcantilevers (MC) as a mechanically floating gate and the movable mirror of the Michelson optical interferometer. The MC mechanical oscillations are transformed into optical signals and the MMFET oper...

We investigate the response of the micromechanical field-effect transistors (MMFETs) to the impinging terahertz (THz) signals. The MMFET uses the microcantilevers MC as a mechanically floating gate and the movable mirror of the Michelson optical interferometer. The MC mechanical oscillations are transformed into optical signals and the MMFET operat...

We propose the terahertz (THz) detectors based on field-effect transistors (FETs) with the graphene channel (GC) and the black-Arsenic (b-As) black-Phosphorus (b-P), or black-Arsenic-Phosphorus (b-As $$_x$$ x P $$_{1-x}$$ 1 - x ) gate barrier layer. The operation of the GC-FET detectors is associated with the carrier heating in the GC by the THz el...

We analyze the operation of terahertz (THz) bolometric detectors based on field-effect transistor (FET) structures with graphene channels (GCs) and black-phosphorus and black-arsenic gate barrier layers (BLs). Such GC FETs use two-dimensional electron gas (2DEG) heating by the incident THz radiation leading to the thermionic emission of hot electro...

We propose and analyze the performance of terahertz (THz) room-temperature bolometric detectors based on the graphene channel field-effect transistors (GC-FET). These detectors comprise the gate barrier layer (BL) composed of the lateral hexagonal-Boron Nitride black-Phosphorus/ hexagonal-Boron Nitride (h-BN/b-P/h-BN) structure. The main part of th...

We evaluate the terahertz (THz) detectors based on field-effect transistor (FET) with the graphene channel (GC) and a floating metal gate (MG) separated from the GC by a black-phosphorus (b-P) or black-arsenic (b-As) barrier layer. The operation of these GC-FETs is associated with the heating of the two-dimensional electron gas in the GC by impingi...

We propose the terahertz (THz) detectors based on field-effect transistors (FETs) with the graphene channel (GC) and the black-Arsenic (b-As) black-Phosphorus (b-P), or black-Arsenic-Phosphorus (b-As$_x$P$_{1-x}$) gate barrier layer. The operation of the GC-FET detectors is associated with the carrier heating in the GC by the THz electric field res...

We evaluate the terahertz (THz) detectors based on field effect transistor (FET) with the graphene channel {GC} and a floating metal gate (MG) separated from the GC by a black-phosphorus (b-P) or black-arsenic (b-As) barrier layer (BL). The operation of these GC-FETs is associated with the heating of the two-dimensional electron gas in the GC by im...

We analyze the two-dimensional electron gas (2DEG) heating by the incident terahertz (THz) radiation in the field-effect transistor (FET) structures with the graphene channels (GCs) and the black-phosphorus and black-arsenic gate barrier layers (BLs). Such GC-FETs can operate as bolometric THz detectors using the thermionic emission of the hot elec...

We experimentally investigate an epitaxial-graphene-channel FET THz detector demonstrated a 10-ps-order fast response time and a high responsivity of 0.3 mA/W at room temperature. We also identify coexisting of both plasmonic and photothermoelectric rectification effects.

In this study, we propose a novel approach to THz wave detection using an asymmetrically gated graphene field-effect transistor (GFET). By utilizing two sets of gates arranged in an asymmetric manner, we achieve periodic modulation of the carrier density along the channel. Previous re-search has explored various mechanisms for THz detection, includ...

We designed and fabricated an epitaxial-graphene-channel field-effect transistor (EG-FET) featuring an asymmetric dual-grating-gate (ADGG) structure working as a current-driven terahertz detector and experimentally demonstrated a 10 ps-order fast response time and a high responsivity of 0.3 mA/W to 0.95 Terahertz (THz) radiation incidence at room t...

We designed and fabricated an epitaxial-graphene-channel field-effect transistor (EG-FET) featured by the asymmetric dual-grating-gate (ADGG) structure working for a current-driven terahertz detector, and experimentally demonstrated a 10-ps order fast response time and a high responsivity of 0.3 mA/W to the 0.95-THz radiation incidence at room temp...

Indium selenide compounds are promising materials for energy conversion, spintronic applications, and chemical sensing. However, it is difficult to grow stoichiometric indium selenide crystals due to the high equilibrium selenium vapor pressure and the complicated phase equilibrium system of indium selenide compounds. In this paper, we apply a nove...

Indium selenide compounds are promising materials for energy conversion, spintronic applications, and chemical sensing. However, it is difficult to grow stoichiometric indium selenide crystals due to the high equilibrium selenium vapor pressure and the complicated phase equilibrium system of indium selenide compounds. In this paper, we apply a nove...

InxGa1−xSe mixed crystals have been successfully grown from an indium flux by the traveling heater method at three growth temperatures. The thickness of the grown InxGa1−xSe mixed crystal perpendicular to (001) was more than 3 mm. The lattice constant, and optical and electrical properties of the InxGa1−xSe mixed crystals and undoped GaSe crystals...

We have demonstrated enhancement of the spin-charge current interconversion by oxidation of rhenium (Re). Although amorphous rhenium oxide (ReOX) is electrically conductive, the spin-orbit torque efficiency measured by spin-torque ferromagnetic resonance is 0.074, and 37 times larger than the pure Re case whose amplitude is 0.002. Furthermore, we h...

Terahertz (THz) waves at 9.7, 10.1 and 10.6 THz were generated via difference frequency generation in high-quality InxG1-xaSe mixed crystals with a relatively high indium compositions (x = 0.040, 0.048, 0.074) grown from an indium flux. The phase-matching angle for THz wave generation was measured for each indium content. As a result, it is confirm...

The growth rate of crystalline GaSe from solution was increased by using indium as a solvent. The solubility and concentration gradient of Se were measured using differential scanning calorimetry (DSC). The Se solubility and the temperature coefficient of the solubility were respectively 15 times and 2.2 times greater in crystals grown from an In f...

We demonstrate the generation of THz waves (frequency 9.7 THz) using difference frequency generation in an InxGa1-xSe mixed crystal grown from In flux. The amount of indium and the lattice constant of the crystal were evaluated using electron micro probe analysis and X-ray diffraction, respectively. We believe that the Ga sites were substituted by...

The structures of fiber, including the distance between fibers and the arrangement direction of fibers, were quantitatively investigated using coherent terahertz (THz) wave. Composite fibers with periodically arranged 57% silk and 43% nylon are measured, then the specific absorption spectra due to intermolecular vibration and interference effect ar...

Creating oxide interfaces with precise chemical specificity at the atomic layer level is desired for the engineering of quantum phases and electronic applications, but highly challenging, owing partially to the lack of in situ tools to monitor the chemical composition and completeness of the surface layer during growth. Here we report the in situ o...

The interlayer van der Waals bonding force in crystalline InSe was directly measured using a mechanical test equipment. The bulk γ-InSe crystal was grown by the temperature difference method under controlled vapor pressure, a unique liquid phase solution crystal growth method with a low and fixed growth temperature. The measured bonding force in th...

Indium selenide (InSe), which is one of the most promising layered III-chalcogenide compounds, is an attractive material for applications in infrared detection, solar energy conversion and high mobility transfer devices etc. In this work, InSe crystals were grown from the liquid phase using the temperature difference method under controlled vapor p...

W e focus on crystal growth and evaluation of 2D-layered compounds. For crystal growth, liquid phase growth with temperature difference method under controlled vapour pressure (TDM-CVP) has been studied GaSe and InSe are grown by this method. GaSe can generate wide frequency tunable terahertz (THz) wave. Due to the superior characteristic features...