Jeremie Torres | Université Montpellier (original) (raw)

Papers by Jeremie Torres

Effect of AlN growth temperature on trap densities of in-situ metal-organic chemical vapor deposi... more Effect of AlN growth temperature on trap densities of in-situ metal-organic chemical vapor deposition grown AlN/AlGaN/GaN metal-insulator-semiconductor heterostructure field-effect transistors AIP Advances 2, 022134 Ultra-low resistance ohmic contacts in graphene field effect transistors Appl. Phys. Lett. 100, 203512 (2012) Three-dimensional distribution of Al in high-k metal gate: Impact on transistor voltage threshold Appl. Phys. Lett. 100, 201909 Electric field effect in graphite crystallites Appl. Phys. Lett. 100, 203116 (2012) Efficient terahertz generation by optical rectification in Si-LiNbO3-air-metal sandwich structure with variable air gap Appl.

Recently, a new class of materials, so-called topological insulators, has emerged. These are syst... more Recently, a new class of materials, so-called topological insulators, has emerged. These are systems characterized by the inversion of the electronic band structure and also by a certain strength of the spin-orbit interaction. HgTe/Cd x Hg 1−x Te quantum wells represent a prominent example. They can change to the topological insulator phase from the conventional insulator phase when the thickness of the quantum well is increased over the critical thickness d c = 6.3 nm. Here, we report on a far-infrared magnetospectroscopy study of a set of HgTe/Cd x Hg 1−x Te quantum wells with different thicknesses from below to above the critical value d c. In quantizing magnetic fields up to 16 T, both intraband and interband transitions have been clearly observed. In the widest quantum well with inverted band structure, we confirm the avoided crossing of the zero-mode Landau levels observed earlier in similar structures. In both noninverted quantum wells close to the critical thickness, we report unambiguously on the square root dependence of the transition energy on the magnetic field, as expected in the single-particle model of massless Dirac fermions. The obtained results are compared with the allowed transition energies between Landau levels in the valence and conduction bands calculated using the 8 × 8 Kane model.

The potentialities of AlGaN/GaN nanochannels with broken symmetry (also called self-switching dio... more The potentialities of AlGaN/GaN nanochannels with broken symmetry (also called self-switching diodes) as direct and heterodyne THz detectors are analyzed. The operation of the devices in the free space heterodyne detection scheme have been measured at room temperature with RF up to 0.32 THz and explained as a result of high-frequency nonlinearities using Monte Carlo simulations. Intermediate-frequency bandwidth of 40 GHz is obtained.

to the low-frequency microwave noise. It is shown that there takes place a sharp growth of the ex... more to the low-frequency microwave noise. It is shown that there takes place a sharp growth of the excess low-frequency noise near the threshold of the development of the instability originated by the uncontrollable process of the impact ionization. It is found that the spectrum of the excess low-frequency noise in the prethreshold region manifests the 1/ behavior in the frequency region 0.1 ÷ 1 .

We investigate the relative transmission and the effective gain of a two-dimensional electron gas... more We investigate the relative transmission and the effective gain of a two-dimensional electron gas (2DEG) in the terahertz (THz) frequency domain. The position of THz source, device, and detector is numerically simulated in order to obtain an optimized experimental configuration. The effect of variation of polarization of incident beam, and geometries of devices is investigated. The inter-digitated finger (IDF) structures of the device under investigation show maximum transmission in direct polarization configuration which is attributed to the metallic polarizing nature of IDFs, and to the effective interaction of the incident THz radiations and the device. This technique should be helpful to measure THz transmission of electronic devices with 2DEG.

We report on terahertz wireless communication experiments at 0.2 THz, using a commercial GaAs fie... more We report on terahertz wireless communication experiments at 0.2 THz, using a commercial GaAs field-effecttransistor as detector. For the first time, we will present the transmission of pseudo-random bit sequence at 0.2 THz using this commercial transistor and demonstrate open eye-patterns up to 1.5 Gbps. This transistor is integrated into a machined horn, so that its sensitivity is improved to 1 V/W, and has a 10 GHz cut-off frequency. We will discuss signal-to-noise ratio in the terahertz wireless data transmission.

A generalization of the approach which describes the emission capabilities of micron and submicro... more A generalization of the approach which describes the emission capabilities of micron and submicron semiconductor structures in terms of the spectrum of thermally non-equilibrium noise/emission temperature is considered for the case of threeterminals FET/HEMT structures. By using, in the framework of hydrodynamic approach, a direct numerical modeling of the frequency dependence of the components of the small-signal impedance/admittance and spectral densities of voltage/current fluctuations at FET/HEMT terminals, it is shown that: (i) in contrast with two-terminal devices (diodes) the emission capabilities of FET/HEMT cannot be characterized by a single spectrum of the noise/emission temperature, and (ii) the character of the noise/emission temperature spectrum depends on both the choice of the FET/HEMT loading circuit which contains the emitting antenna (source-to-drain or source-to-gate) and the operation mode (constant current or constant voltage) of the accompanying non-emitting external circuit. ICNF2013 978-1-4799-0671-0/13/$31.00 c ⃝2013 IEEE

Single hole transport in a silicon metal-oxide-semiconductor quantum dot

In this paper, we perform, by means of Monte Carlo simulations and experimental measurements, a g... more In this paper, we perform, by means of Monte Carlo simulations and experimental measurements, a geometry optimization of GaN-based nano-diodes for broadband Terahertz direct detection (in terms of responsivity) and mixing (in terms of output power). The capabilities of the so-called self-switching diode (SSD) are analyzed for different dimensions of the channel at room temperature. Signal detection up to the 690 GHz limit of the experimental set-up has been achieved at zero bias. The reduction of the channel width increases the detection responsivity, while the reduction in length reduces the responsivity but increases the cut-off frequency. In the case of heterodyne detection an intrinsic bandwidth of at least 100 GHz has been found. The intermediate frequency (IF) power increases for short SSDs, while the optimization in terms of the channel width is a trade-off between a higher non-linearity (obtained for narrow SSDs) and a large current level (obtained for wide SSDs). Moreover, the RF performance can be improved by biasing, with optimum performances reached, as expected, when the DC non-linearity is maximum.

We report on room temperature electrically-induced terahertz emission from interdigitated GaN qua... more We report on room temperature electrically-induced terahertz emission from interdigitated GaN quantum well structures. The emission spectrum has been analysed in a Michelson interferometer using a 4K-Si bolometer as a terahertz detector. A resonant peak at the frequency of around 3 THz was observed in emission spectra. A threshold behaviour of the resonance with respect to applied voltage takes place. By using the proposed analytical model the measured/observed experimentally resonant behaviour of emission spectra is interpreted as a result of ungated stream-plasma instability in the channel.

The dynamical properties and diffusive behavior of a collection of mutually interacting particles... more The dynamical properties and diffusive behavior of a collection of mutually interacting particles are numerically investigated for two types of long-range interparticle interactions: Coulomb-electrostatic and dipole-electrodynamic. It is shown that when the particles are uniformly distributed throughout the accessible space, the self-diffusion coefficient is always lowered by the considered interparticle interactions, irrespective of their attractive or repulsive character. Transitional phenomena are observed for Coulomb-electrostatic (repulsive) and dipole-electrodynamic (attractive) interactions considered both separately and in competition. The outcomes reported in this paper clearly indicate a feasible experimental method to probe the activation of resonant electrodynamic interactions among biomolecules.

Electron transport and drain current noise in wurtzite GaN MOSFET have been studied by Monte Carl... more Electron transport and drain current noise in wurtzite GaN MOSFET have been studied by Monte Carlo particle simulation that simultaneously solves the Boltzmann transport and pseudo-2D Poisson equations. It is shown that at positive gate voltages giving excess electron concentration in the n-region of the channel, drain current self-oscillations in the THz frequency range up to 6 THz are possible. These self-oscillations are driven by an electron plasma instability. Additionally a step-like drain current dependence on drain bias is demonstrated.

GaN-based asymmetric nanodiodes have been used as heterodyne detectors up to 0.69 THz in free-spa... more GaN-based asymmetric nanodiodes have been used as heterodyne detectors up to 0.69 THz in free-space configuration where Intermediate Frequency bandwidth has been measured up 13 GHz. Monte Carlo simulations, used to estimate nano-device intrinsic conversion losses of 27 dB have confirmed these results.

An experimental demonstration of GaN-based asymmetric nanodiodes as direct and heterodyne detecto... more An experimental demonstration of GaN-based asymmetric nanodiodes as direct and heterodyne detectors up to 0.69 THz has been performed at room temperature. Responsivities of 2 and 0.3 V/W in a free-space configuration were obtained at 0.30 and 0.69 THz, respectively. An intermediate frequency (IF) signal has been measured up to 40 and 13 GHz in the same frequency ranges. The characterization of the nanodiodes as mixers did not show any deviation from linearity between the RF input power and the IF output. Monte Carlo simulations, used to estimate nanodevice intrinsic conversion losses of 27 dB at 0.69 THz, have confirmed these results.

Effect of AlN growth temperature on trap densities of in-situ metal-organic chemical vapor deposi... more Effect of AlN growth temperature on trap densities of in-situ metal-organic chemical vapor deposition grown AlN/AlGaN/GaN metal-insulator-semiconductor heterostructure field-effect transistors AIP Advances 2, 022134 Ultra-low resistance ohmic contacts in graphene field effect transistors Appl. Phys. Lett. 100, 203512 (2012) Three-dimensional distribution of Al in high-k metal gate: Impact on transistor voltage threshold Appl. Phys. Lett. 100, 201909 Electric field effect in graphite crystallites Appl. Phys. Lett. 100, 203116 (2012) Efficient terahertz generation by optical rectification in Si-LiNbO3-air-metal sandwich structure with variable air gap Appl.

Recently, a new class of materials, so-called topological insulators, has emerged. These are syst... more Recently, a new class of materials, so-called topological insulators, has emerged. These are systems characterized by the inversion of the electronic band structure and also by a certain strength of the spin-orbit interaction. HgTe/Cd x Hg 1−x Te quantum wells represent a prominent example. They can change to the topological insulator phase from the conventional insulator phase when the thickness of the quantum well is increased over the critical thickness d c = 6.3 nm. Here, we report on a far-infrared magnetospectroscopy study of a set of HgTe/Cd x Hg 1−x Te quantum wells with different thicknesses from below to above the critical value d c. In quantizing magnetic fields up to 16 T, both intraband and interband transitions have been clearly observed. In the widest quantum well with inverted band structure, we confirm the avoided crossing of the zero-mode Landau levels observed earlier in similar structures. In both noninverted quantum wells close to the critical thickness, we report unambiguously on the square root dependence of the transition energy on the magnetic field, as expected in the single-particle model of massless Dirac fermions. The obtained results are compared with the allowed transition energies between Landau levels in the valence and conduction bands calculated using the 8 × 8 Kane model.

The potentialities of AlGaN/GaN nanochannels with broken symmetry (also called self-switching dio... more The potentialities of AlGaN/GaN nanochannels with broken symmetry (also called self-switching diodes) as direct and heterodyne THz detectors are analyzed. The operation of the devices in the free space heterodyne detection scheme have been measured at room temperature with RF up to 0.32 THz and explained as a result of high-frequency nonlinearities using Monte Carlo simulations. Intermediate-frequency bandwidth of 40 GHz is obtained.

to the low-frequency microwave noise. It is shown that there takes place a sharp growth of the ex... more to the low-frequency microwave noise. It is shown that there takes place a sharp growth of the excess low-frequency noise near the threshold of the development of the instability originated by the uncontrollable process of the impact ionization. It is found that the spectrum of the excess low-frequency noise in the prethreshold region manifests the 1/ behavior in the frequency region 0.1 ÷ 1 .

We investigate the relative transmission and the effective gain of a two-dimensional electron gas... more We investigate the relative transmission and the effective gain of a two-dimensional electron gas (2DEG) in the terahertz (THz) frequency domain. The position of THz source, device, and detector is numerically simulated in order to obtain an optimized experimental configuration. The effect of variation of polarization of incident beam, and geometries of devices is investigated. The inter-digitated finger (IDF) structures of the device under investigation show maximum transmission in direct polarization configuration which is attributed to the metallic polarizing nature of IDFs, and to the effective interaction of the incident THz radiations and the device. This technique should be helpful to measure THz transmission of electronic devices with 2DEG.

We report on terahertz wireless communication experiments at 0.2 THz, using a commercial GaAs fie... more We report on terahertz wireless communication experiments at 0.2 THz, using a commercial GaAs field-effecttransistor as detector. For the first time, we will present the transmission of pseudo-random bit sequence at 0.2 THz using this commercial transistor and demonstrate open eye-patterns up to 1.5 Gbps. This transistor is integrated into a machined horn, so that its sensitivity is improved to 1 V/W, and has a 10 GHz cut-off frequency. We will discuss signal-to-noise ratio in the terahertz wireless data transmission.

A generalization of the approach which describes the emission capabilities of micron and submicro... more A generalization of the approach which describes the emission capabilities of micron and submicron semiconductor structures in terms of the spectrum of thermally non-equilibrium noise/emission temperature is considered for the case of threeterminals FET/HEMT structures. By using, in the framework of hydrodynamic approach, a direct numerical modeling of the frequency dependence of the components of the small-signal impedance/admittance and spectral densities of voltage/current fluctuations at FET/HEMT terminals, it is shown that: (i) in contrast with two-terminal devices (diodes) the emission capabilities of FET/HEMT cannot be characterized by a single spectrum of the noise/emission temperature, and (ii) the character of the noise/emission temperature spectrum depends on both the choice of the FET/HEMT loading circuit which contains the emitting antenna (source-to-drain or source-to-gate) and the operation mode (constant current or constant voltage) of the accompanying non-emitting external circuit. ICNF2013 978-1-4799-0671-0/13/$31.00 c ⃝2013 IEEE

Single hole transport in a silicon metal-oxide-semiconductor quantum dot

In this paper, we perform, by means of Monte Carlo simulations and experimental measurements, a g... more In this paper, we perform, by means of Monte Carlo simulations and experimental measurements, a geometry optimization of GaN-based nano-diodes for broadband Terahertz direct detection (in terms of responsivity) and mixing (in terms of output power). The capabilities of the so-called self-switching diode (SSD) are analyzed for different dimensions of the channel at room temperature. Signal detection up to the 690 GHz limit of the experimental set-up has been achieved at zero bias. The reduction of the channel width increases the detection responsivity, while the reduction in length reduces the responsivity but increases the cut-off frequency. In the case of heterodyne detection an intrinsic bandwidth of at least 100 GHz has been found. The intermediate frequency (IF) power increases for short SSDs, while the optimization in terms of the channel width is a trade-off between a higher non-linearity (obtained for narrow SSDs) and a large current level (obtained for wide SSDs). Moreover, the RF performance can be improved by biasing, with optimum performances reached, as expected, when the DC non-linearity is maximum.

We report on room temperature electrically-induced terahertz emission from interdigitated GaN qua... more We report on room temperature electrically-induced terahertz emission from interdigitated GaN quantum well structures. The emission spectrum has been analysed in a Michelson interferometer using a 4K-Si bolometer as a terahertz detector. A resonant peak at the frequency of around 3 THz was observed in emission spectra. A threshold behaviour of the resonance with respect to applied voltage takes place. By using the proposed analytical model the measured/observed experimentally resonant behaviour of emission spectra is interpreted as a result of ungated stream-plasma instability in the channel.

The dynamical properties and diffusive behavior of a collection of mutually interacting particles... more The dynamical properties and diffusive behavior of a collection of mutually interacting particles are numerically investigated for two types of long-range interparticle interactions: Coulomb-electrostatic and dipole-electrodynamic. It is shown that when the particles are uniformly distributed throughout the accessible space, the self-diffusion coefficient is always lowered by the considered interparticle interactions, irrespective of their attractive or repulsive character. Transitional phenomena are observed for Coulomb-electrostatic (repulsive) and dipole-electrodynamic (attractive) interactions considered both separately and in competition. The outcomes reported in this paper clearly indicate a feasible experimental method to probe the activation of resonant electrodynamic interactions among biomolecules.

Electron transport and drain current noise in wurtzite GaN MOSFET have been studied by Monte Carl... more Electron transport and drain current noise in wurtzite GaN MOSFET have been studied by Monte Carlo particle simulation that simultaneously solves the Boltzmann transport and pseudo-2D Poisson equations. It is shown that at positive gate voltages giving excess electron concentration in the n-region of the channel, drain current self-oscillations in the THz frequency range up to 6 THz are possible. These self-oscillations are driven by an electron plasma instability. Additionally a step-like drain current dependence on drain bias is demonstrated.

GaN-based asymmetric nanodiodes have been used as heterodyne detectors up to 0.69 THz in free-spa... more GaN-based asymmetric nanodiodes have been used as heterodyne detectors up to 0.69 THz in free-space configuration where Intermediate Frequency bandwidth has been measured up 13 GHz. Monte Carlo simulations, used to estimate nano-device intrinsic conversion losses of 27 dB have confirmed these results.

An experimental demonstration of GaN-based asymmetric nanodiodes as direct and heterodyne detecto... more An experimental demonstration of GaN-based asymmetric nanodiodes as direct and heterodyne detectors up to 0.69 THz has been performed at room temperature. Responsivities of 2 and 0.3 V/W in a free-space configuration were obtained at 0.30 and 0.69 THz, respectively. An intermediate frequency (IF) signal has been measured up to 40 and 13 GHz in the same frequency ranges. The characterization of the nanodiodes as mixers did not show any deviation from linearity between the RF input power and the IF output. Monte Carlo simulations, used to estimate nanodevice intrinsic conversion losses of 27 dB at 0.69 THz, have confirmed these results.