Y. M. Meziani

• PhD in Physics
• Professor at University of Salamanca

A comprehensive study on the enhancement of terahertz (THz) detection through the terajet effect is performed using mesoscale dielectric lenses of different shapes and sizes. Polytetrafluoroethylene (PTFE) lenses, including spherical, aspherical, and cubic geometries, are fabricated and evaluated at frequencies of 0.15 and 0.3 THz. The lenses show...

In recent years, graphene Field-Effect-Transistors (GFETs) have demonstrated an outstanding potential for Terahertz (THz) photodetection due to their fast response and high-sensitivity. Such features are essential to enable emerging THz applications, including 6G wireless communications, quantum information, bioimaging and security. However, the ov...

It has recently been shown that Terahertz sensors can effectively detect the spin resonances of Dirac fermions in graphene. The associated photovoltaic measurement technique allows for the investigation of the intrinsic spin-orbit coupling in graphene as well as its topological properties from microwave to Terahertz frequencies. In this work, using...

In recent years, graphene field-effect-transistors (GFETs) have demonstrated an outstanding potential for terahertz (THz) photodetection due to their fast response and high-sensitivity. Such features are essential to enable emerging THz applications, including 6G wireless communications, quantum information, bioimaging and security. However, the ov...

An asymmetric dual-grating gate bilayer graphene-based field effect transistor (ADGG-GFET) with an integrated bowtie antenna was fabricated and its response as a Terahertz (THz) detector was experimentally investigated. The device was cooled down to 4.5 K, and excited at different frequencies (0.15, 0.3 and 0.6 THz) using a THz solid-state source....

Graphene is a quantum spin Hall insulator, with a nontrivial topological gap induced by the spin-orbit coupling. Such splitting is weak (∼45μ eV) in the absence of external magnetic field. However, due to rather long spin-relaxation time, graphene is an attractive candidate for applications in quantum technologies. When it is encapsulated in hexago...

We report on resolution enhancement of sub-terahertz (THz) images by using the terajet effect. A mesoscale cuboid dielectric particle, used to establish the terajet, was placed in front of an object located at the focus of the THz beam. The object under study was based on a printed circuit board (PCB) perforated with different holes with diameters...

Graphene is a quantum spin Hall insulator with a 45μeV-wide nontrivial topological gap induced by the intrinsic spin-orbit coupling. Even though this zero-field spin splitting is weak, it makes graphene an attractive candidate for applications in quantum technologies, given the resulting long spin-relaxation time. On the other side, the staggered s...

Graphene is a quantum spin Hall insulator with a 45 $\mu$eV wide non-trivial topological gap induced by the intrinsic spin-orbit coupling. Even though this zero-field spin splitting is weak, it makes graphene an attractive candidate for applications in quantum technologies, given the resulting long spin relaxation time. On the other side, the stagg...

This paper reports on optimization of the parameters, by mean of electromagnetic simulations to obtain the values of the parameters that permit optimal conditions for terahertz (THz) radiation detection using the terajet effect generated by inserting a cuboid-shaped mesoscopic dielectric particle in the optical path at in the front of the rectifier...

The nature of the low-frequency 1/f noise in electronic materials and devices is one of the oldest unsolved physical problems (f is the frequency). The fundamental question of the noise source-fluctuations in the mobility vs. number of charge carriers-is still debated. While there are several pieces of evidence to prove that the 1/f noise in semico...

Nanoflakes ultra-thin quantum dots are theoretically studied as innovative nanomaterials delivering outstanding results in various high fields. In this work, we investigated the surface properties of an electron confined in spherical ultra-thin quantum dots in the presence of an on-center or off-center donor impurity. Thus, we have developed a nove...

Terahertz (THz) waves have revealed a great potential for use in various fields and for a wide range of challenging applications. High-performance detectors are, however, vital for exploitation of THz technology. Graphene plasmonic THz detectors have proven to be promising optoelectronic devices, but improving their performance is still necessary....

The nature of the low-frequency current fluctuations, i.e. carrier number vs. mobility, defines the strategies for noise reduction in electronic devices. While the 1/f noise in metals has been attributed to the electron mobility fluctuations, the direct evidence is lacking (f is the frequency). Here we measured noise in h-BN encapsulated graphene t...

A bilayer-graphene-based field-effect-transistor with asymmetric dual-grating gates was fabricated and characterized under excitation of 0.3 THz where a clear gatebias- dependent photocurrent was measured at 4 K. The photocurrent was measured versus both top gates bias voltages and shows a maximum attributed to the creation of p-n regions along the...

Two-dimensional transition metal dichalcogenide (TMD) phototransistors have been the object of intensive research during the last years due to their potential for photodetection. Photoresponse in these devices is typically caused by a combination of two physical mechanisms: the photoconductive effect (PCE) and photogating effect (PGE). In earlier l...

In the present work, we report on resolution enhancement of a terahertz imaging system using the terajet effect. A wavelength-scaled particle (a Teflon cube for simplicity) was used to localize incident radiation to a subwavelength volume and focus it directly onto the objects under imaging. A strained-silicon modulation �field effect transistor wa...

An infrared (IR) pyroelectric detector was investigated for terahertz (THz) detection using the principle of the terajet effect, which focuses the beam beyond the diffraction limit. The terahertz beam was coupled to the detector’s optical window through a two-wavelength-dimension dielectric cubic particle-lens based on the terajet effect. We experi...

Natural killer (NK) cells (lymphocytes) control and limit the spread of several types of tumors and microbial infections and corresponding tissue damage. The NK cells are activated by Type I IFN, IL-15, IL-12, IL-18 cytokines sent by virus affected cells. Later, the NK cells release IFN-ϒ and TNF cell surface receptors/cytokines to control/regulate...

We report on the enhancement of responsivity by more than one order of magnitude of a silicon-based sub-terahertz detector when a mesoscopic dielectric particle was used to localize incident radiation to a sub-wavelength volume and focus it directly onto the detector. A strained-silicon modulation field-effect transistor was used as a direct detect...

This paper reports on a study of the response of a T-gate strained-Si MODFETs (modulation-doped field-effect transistor) under continuous-wave sub-THz excitation. The sub-THz response was measured using a two-tones solid-state source at 0.15 and 0.30 THz. The device response in the photovoltaic mode was non-resonant, in agreement with the Dyakonov...

The temperature, hydrostatic pressure, and external electric field effects on the confined exciton in cylindrical quantum dots by considering a parabolic confining potential are investigated. The effects of these external perturbations on the binding energy and interband emission energy are calculated numerically by adopting the variational method...

Two-dimensional transition metal dichalcogenide phototransistors have been object of intensive research during the last years due to their potential for photodetection. Photoconductivity in these devices is typically caused by a combination of two physical mechanisms: photoconductive effect (PCE) and photovoltaic effect (PVE; also known as photogat...

A simple millimeter wave and terahertz (THz) receiver scheme that uses subwave- length focusing of electromagnetic beam on the point-contact detector area with waveguide dimensions is studied. A detection system with such an optical coupling scheme is implemented, where the signal to be detected is coupled to a detector through a mesoscale dielectr...

Exciton physics in two-dimensional semiconductors are typically studied by photoluminescence spectroscopy. However, this technique does not allow for direct observation of non-radiating excitonic transitions. Here, we use low-temperature photocurrent spectroscopy as an alternative technique to investigate excitonic transitions in a high-quality mon...

A simple millimeter wave and terahertz (THz) receiver scheme that uses subwavelength focusing of electromagnetic beam on the point-contact detector area with waveguide dimensions is studied. A detection system with such an optical coupling scheme is implemented, where the signal to be detected is coupled to a detector through a mesoscale dielectric...

Plasma waves in semiconductor gated 2-D systems can be used to efficiently detect Terahertz (THz) electromagnetic radiation. This work reports on the response of a strained-Si Modulation-doped Field-Effect Transistor (MODFET) under front and back sub-THz illumination. The response of the MODFET has been characterized using a two-tones solid-state c...

The recent progress of intelligent electronic devices makes computer science, electronic and information technology, highly related to teaching and learning physics. The main question is how education can integrate this knowledge. Methods and components of new technology are applicable for education also; teachers and learners used the parts and to...

A graphene-based field-effect-transistor with asymmetric dual-grating gates was fabricated and characterized under excitation of terahertz radiation at two frequencies: 0.15 THz and 0.3 THz. The graphene sheet was encapsulated between two flakes of h-BN and placed on a highly doped SiO2/Si substrate. An asymmetric dual-grating gate was implemented...

A dielectric cube, with dimensions of wavelength, was placed at the length of terajet in front of a terahertz detector. Enhancement of the detector responsivity by 4.3 dB with a decrease of noise equivalent power was experimentally demonstrated under excitation of 0.3 THz (see article number 1900700 by Yahya Moubarak Meziani and co‐workers). This o...

We investigate excitonic transitions in a h-BN encapsulated monolayer $\textrm{MoS}_2$ phototransistor by photocurrent spectroscopy at cryogenic temperature (T = 5 K). The spectra presents excitonic peaks with linewidths as low as 8 meV, one order of magnitude lower than in earlier photocurrent spectroscopy measurements. We observe four spectral fe...

Here, we propose a simple THz receiver that uses subwavelength focusing of the THz beam on the detector area. As a proof of concept, we implemented a THz detection system with an original optical coupling scheme where the signal to be detected is coupled to a terahertz detector through a mesoscale dielectric particle-lens. Coherent detection is suc...

We report on a novel implementation of the cryo-etching method, which enabled us to fabricate low-roughness hBN-encapsulated graphene nanoconstrictions with unprecedented control of the structure edges; the typical edge roughness is on the order of a few nanometers. We characterized the system by atomic force microscopy and used the measured parame...

More than a decade after the discovery of graphene, ballistic transport in nanostructures based on this intriguing material still represents a challenging field of research in two-dimensional electronics. The presence of rough edges in nanostructures based on this material prevents the appearance of truly ballistic electron transport as theo\-re\-t...

This letter reports on room temperature sub-THz detection using self-switching diodes based on an AlGaN/GaN heterostructure on a Si substrate. By means of free-space measurements at 300 GHz, we demonstrate that the responsivity and noise equivalent power (NEP) of sub-THz detectors based on planar asymmetric nanochannels can be improved and voltage...

We report here our recent electron transport results in spatially separated two-dimensional electron and hole gases with nominally degenerate energy subbands, realized in an InAs(10 nm)/GaSb(5 nm) coupled quantum well. We observe a narrow and intense maximum (~500 kΩ) in the four-terminal resistivity in the charge neutrality region, separating the...

A commercial GaN high electron mobility transistor (HEMT) is investigated as efficient detector of terahertz radiations. Enhancement of the photoresponse in excess of one order of magnitude (up to 1 kV W−1) is obtained when a constant drain‐to‐source current is applied. The photoresponse remains unchanged with chopping frequency up to 5 kHz demonst...

Plasma waves in gated 2-D systems can be used to efficiently detect THz electromagnetic radiation. Solid-state plasma wave-based sensors can be used as detectors in THz imaging systems. An experimental study of the sub-THz response of II-gate strained-Si Schottky-gated MODFETs (Modulation-doped Field-Effect Transistor) was performed. The response o...

We report on experimental and theoretical studies of nanoscale gate-lengths strained Silicon MODFETs as room temperature non resonant detectors. Devices were excited at room temperature by an electronic source at 150 and 300 GHz to characterize their sub-THz response. The maximum of the photovoltaic response was obtained when the FET gate was biase...

Plasma waves in gated 2-D systems can be used to detect THz electromagnetic radiation. This work reports on a two-dimensional hydrodynamic-model (HDM) applied to investigate the sub-THz photovoltaic response of Schottky-gated strained-Si MODFETs. TCAD simulation results are validated through comparison with measurements on the transistors. Simulati...

We report on room temperature non-resonant detection of terahertz radiation using strained Silicon MODFETs with nanoscale gate lengths. The devices were excited at room temperature by an electronic source at 150 and 300 GHz. A maximum intensity of the photoresponse signal was observed around the threshold voltage. Results from numerical simulations...

Many-body interactions can produce novel ground states in a condensed-matter system. For example, interacting electrons and holes can spontaneously form excitons, a neutral bound state, provided that the exciton binding energy exceeds the energy separation between the single particle states. Here we report on electrical transport measurements on sp...

Graphene Characterization by THz-TDS spectroscopy @ NANOLITO 2017, Salamanca (Spain)

We report on room temperature non-resonant detection of terahertz radiation using strained Silicon MODFETs with nanoscale gate lengths. The devices were excited at room temperature by an electronic source at 150 and 300 GHz. A maximum intensity of the photoresponse signal was observed around the threshold voltage. Results from numerical simulations...

Terahertz Time Domain Spectroscopy (THz-TDS) technique has been used to characterize two graphene based samples produced by exfoliation and CVD methods. In both cases, we find two interesting bands, in both CVD and exfoliated graphene, in the 0.2-2 THz range. Quality information can be extracted with this non-destructive technique. The obtained val...

This paper reports on a bi-dimensional TCAD study of the sub-THz response of strained-Si MODFETs. A charge boundary condition for the floating drain contact was implemented to obtain the photovoltaic (PV) response of the device. A non-resonant THz PV response was obtained in agreement with theoretical and experimental works. A main result of this s...

We report on non resonant detection of sub-terahertz radiation (148-353 GHz) using strained silicon modulation field effect transistor with different gate lengths. The devices were excited at room temperature by a Backward Wave Oscillator (BWO) source. Enhancement of the photoresponse signal by drain-to-source bias was observed. Increasing drain-to...

This paper reports on the study of strained-Si n-channel MODFETs as detectors of sub-THz radiation. Simulations based on a bi-dimensional hydrodynamic model for the charge transport coupled to a Poisson equation solver were performed. A charge boundary condition for the floating drain contact was implemented to obtain the photovoltaic response of t...

We report on the intrinsic responsivity of an asymmetric dual-grating-gate plasmonic detector over 100 kV/W at 200 GHz and 50 kV/W at 300 GHz measured at room temperature with zero source-drain bias. We demonstrate that broadband characteristics of the responsivity depend much on the geometrical parameters of the detectors.

Terahertz Time Domain Spectroscopy (THz-TDS) technique has been used to characterize two graphene based samples produced by exfoliation and CVD methods. In both cases, we find two interesting bands, in both CVD and exfoliated graphene, in the 0.2-2 THz range. Quality information can be extracted with this non-destructive technique. The obtained val...

We study theoretically and experimentally the plasmonic THz detection by the asymmetric dual-grating-gate HEMT at room temperature without source-to-drain bias. We derive the analytical expressions of photocurrents due to the plasmonic drag and ratchet effects, and we discuss about their frequency dependences. We also compare the theory to the expe...

We report on room-temperature plasmonic detection of sub-terahertz radiation by InAlAs/InGaAs/InP high electron mobility transistors with an asymmetric dual-grating-gate structure. Maximum responsivities of 22.7 kV/W at 200 GHz and 21.5 kV/W at 292 GHz were achieved under unbiased drain-to-source condition. The minimum noise equivalent power was es...

We report on an extremely-high sensitive terahertz (THz) detector based on our original asymmetric dual-grating gate high electron mobility transistors (A-DGG HEMTs) designed and fabricated using InAlAs/InGaAs/InP material systems. The obtained responsivity is 22.7 kV/W at 200 GHz. To the best of our knowledge, this value is the record responsivity...

In this paper, we performed time domain terahertz spectroscopy (THz-TDS) of two drugs (Paracetamol and Ibuprofen). The THz-TDS is based on a Ti:Sapphire femtosecond laser and a two low-temperature grown GaAs photoconductive antennas for emission and detection of terahertz radiation. A working window from 0.2 to 2.5 THz was obtained. First, spectral...

We report on resonant and non-resonant (broad-band) detection of terahertz (THz) radiation using Strained-Si MODFETs. The devices were excited at room temperature by two types of THz sources at 0.292 THz and at 1.5 THz. Non-resonant response with maxima around the threshold voltage was observed. Shubnikov-de Haas along with photoresponse measuremen...

This paper reviews recent advances in the design and performance of our original InP- and GaAs-based plasmonic high-electron-mobility transistors (HEMTs) for ultrahighly- sensitive terahertz (THz) sensing and imaging. First, the fundamental theory of plasmonic THz detection is briefly described. Second, single-gate HEMTs with parasitic antennae are...

Terahertz (THz) light helicity sensitive photoresponse in GaAs/AlGaAs high electron mobility transistors and silicon metal oxide semiconductor field effect transistors is reported. The helicity dependent detection mechanism is interpreted as an interference of plasma oscillations in the channel of the field-effect-transistors (generalized Dyakonov-...

Terahertz light helicity sensitive photoresponse in GaAs/AlGaAs high electron mobility transistors. The helicity dependent detection mechanism is interpreted as an interference of plasma oscillations in the channel of the field-effect-transistors (generalized Dyakonov-Shur model). The observed helicity dependent photoresponse is by several orders o...

Development of new terahertz (THz) direct sensors based on the oscillation of the plasma waves in the channel of sub-micron FETs is increasing in interest due to its great potential in imaging and spectroscopy. FETs based in the heterosystem Si/SiGe is wafer-compatible with mainstream CMOS closely follow both noise and gain performances of III-V fa...

We report on ultrahigh sensitive, broadband terahertz (THz) detectors based on asymmetric double-grating-gate (ADGG) high electron mobility transistors, demonstrating a record responsivity of 2.2 kV/W at 1 THz with a superior low noise equivalent power of 15 pW/v Hz using InGaAs/InAlAs/InP material systems. When THz radiation is absorbed strong THz...

Abstract: The purpose of the present invention is to improve the efficiency of conversion between terahertz electromagnetic wave energy and direct current energy via plasma waves in a terahertz electromagnetic wave conversion device with a field effect transistor ...

Plasmonic Terahertz Ratchet Effect in a Periodically Gated 2D Electron System

Plasmonic terahertz detection by a double-grating gate field-effect transistor structure with an asymmetric unit cell is studied theoretically. Detection responsivity exceeding 8 kV/W at room temperature in the photovoltaic response mode is predicted for strong asymmetry of the structure unit cell. This value of the responsivity is an order of magn...

The current flowing in two-dimensional channel of field effect transistors can generate different types of charge density perturbations. They can have a form of uncorrelated hot plasmons or plasma waves. The mechanism of plasma wave generation depends on the parameter omega t and on boundary conditions of the channel. At omega t << 1 only hot plasm...

In this paper, we report on room temperature detection of terahertz radiation from strained-Si modulation-doped field-effect transistors. A non-resonant signal was observed with a maximum around the threshold voltage. The signal was interpreted due to the plasma wave nonlinearities in the channel. The intensity of the signal increases for the highe...

The purpose of the present invention is to improve the efficiency of conversion between terahertz electromagnetic wave energy and direct current energy via plasma waves in a terahertz electromagnetic wave conversion device with a field effect transistor structure. This invention has an HEMT structure having a substrate, an electron transit layer, a...

Non-resonant terahertz detection in strained-Si modulation doped field effect transistors: first terahertz imaging

Strained-Si modulation doped · eld effect transistors have been studied as a photomixer within terahertz range. It was subjected to two CW lasers where Δf=|f1-f2|=4 THz. A clear signal was observed with maximum located at around Vg=-0.15V and interpreted as due to the oscillation of the plasma waves under the gate bias.

We present experimental results on the Terahertz radiation from high electron mobility transistors at room temperature, which clearly show the tunability of the emission frequency by the gate voltage.

We report on the observation of photocurrents in GaAs High Electron Mobility and Si Field Effect Transistors. We show that illuminating the samples with high power terahertz laser radiation causes electric currents. These currents are driven by plasmonic effects in two dimensional electron gases.

Resonant frequencies of the two-dimensional plasma in field effect transistors (FETs) increase with the reduction of the channel dimensions and can reach the Terahertz (THz) range. Nonlinear properties of the plasma/electron gas in the transistor channel can be used for the rectification and detection of THz radiation. The excitation of plasma wave...

Room temperature photovoltaic non-resonant detection by large area double-grating-gate InGaP/InGaAs/GaAs heterostructures was investigated in sub-THz range (0.24 THz). Semi-quantitative estimation of the characteristic detection length combined with self-consistent calculations of the electric fields excited in the structure by incoming terahertz r...

We report on room temperature terahertz generation by a submicron size AlGaN/GaN-based high electron mobility transistors. The emission peak is found to be tunable by the gate voltage between 0.75 and 2.1 THz. Radiation frequencies correspond to the lowest fundamental plasma mode in the gated region of the transistor channel. Emission appears at a...

We have investigated experimentally and theoretically the effect of repulsive and attractive ionized impurities on the resistivity components (ρxx and ρxy) in the quantum Hall effect regime. GaAs/GaAlAs asymmetric modulation-doped quantum wells with additional delta doping (by Si donor atoms or Be acceptor atoms) in the GaAs channel or at the AlGaA...

In this work, we report on room temperature terahertz radiation from sub-micron size GaN/AlGaN based high electron mobility transistors (HEMTs). They could successfully replace the standard Fourier Transform spectrometer source and were investigated with a standard Si-bolometer as a detector. The relatively broad (~1THz) emission line was observed....