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Terahertz (THz) response spectra of GaN-based field-effect transistor (FET) arrays are calculated in a self-consistent electromagmetic approach. Two types of FET arrays are considered: (i) FET array with a common channel and a large-area grating gate, and (ii) array of FET units with separate channels and combined intrinsic source and drain contacts. It is shown that the coupling between plasmons and THz radiation in the FET array can be strongly enhanced as compared to a single-unit FET. The computer simulations show that the higher-order plasmon modes can be excited much more effectively in the array of FET units with separate channels and combined source and drain contacts then in FET array with a common channel and a large-area grating gate.

Using a rigorous electrodynamic approach, the spectra of the terahertz response of periodically ordered arrays of field-effect transistors with two-dimensional electron channel were calculated. It was shown that the higher-order plasmon resonances can be excited in such structures at frequencies above 10 THz.

We study theoretically the terahertz (THz) response of a bilayer of density-modulated two-dimensional electron gases, which we employ to model the actual double-quantum-well electron channel of a grid-gated field-effect transistor in which strong THz photoresponse was recently observed. We have shown that such a system can be driven into the anticrossing regime between gated and ungated plasma resonances by tuning the gate voltage. The amplitude of the interlayer THz electric field in the ungated (double-layered) portions of the channel increases dramatically in the anticrossing regime. This strong interlayer THz electric field may strongly affect interlayer electron tunneling which, in turn, may contribute to the physical mechanism underlying the strong THz photoresponse observed in recent experiments.

Polariton excitations associated with magnetoplasma and cyclotron oscillations in a two-dimensional (2D) electron plasma are studied. In contrast to previous works by other authors, it is concluded that there exists a low-frequency nontransmission band in the spectrum of 2D surface magnetoplasma polaritons. Radiative polariton excitations associated with nonuniform cyclotron oscillations of electrons in a 2D system are investigated.

We model resonant terahertz photoconductance recently observed in field-effect transistors with a double-quantum-well (DQW) channel. Comparison of the measured THz resonant photoresponse to the calculated THz absorption spectrum establishes that the resonances are determined by standing plasma waves in the DQW channel under metallic portions of the grating gate. It is found theoretically that the DQW asymmetry mixes the acoustic and optical plasmons resulting in a rather intense ac electric field between the QWs.

New equations are proposed for classical relativistic field theory, which insure a finite value for the intrinsic energy of a point charge.

We show that the strong amplification of terahertz radiation takes place in an array of field-effect transistors at small DC drain currents due to hydrodynamic plasmon instability of the collective plasmon mode. Planar designs compatible with standard integrated circuit fabrication processes and strong coupling of terahertz radiation to plasmon modes in FET arrays make such arrays very attractive for potential applications in solid-state terahertz amplifiers and emitters.

We study theoretically the terahertz (THz) response of a bilayer of two-dimensional electron strips modeling the double-quantum-well electron channel of a grid-gated field-effect transistor, in which strong THz photoresponse was recently observed. We have shown that the mixing between optical and acoustic plasmons hugely increases at the anticrossing of optical-like and acoustic-like plasma resonances excited by incoming THz radiation in such a bilayer. As a result, the amplitude of interlayer THz electric field also increases dramatically in the anticrossing regime. This strong interlayer THz electric field must strongly enhance the interlayer electron tunneling which, in turn, may contribute to the physical mechanism underlying the strong THz photoresponse observed in recent experiments.

High-frequency response of field-effect transistors and diodes with two-dimensional electron channels is strongly affected by plasma oscillations in the channel. This phenomenon in its various manifestations can be used for the detection, frequency multiplication and generation of terahertz radiation. One of the main parameters of a device, which determines its high-frequency properties, is the device impedance. We calculate here the impedance of a slot diode with conductively contacted two-dimensional electron channel using the full system of the Maxwell equations. In this way, we account for the radiation resistance and inter-contact capacitance from first principles.

Results of a theoretical investigation of the polarization conversion of the electromagnetic wave (EW) in a density- modulated two-dimensional (2D) electron system are presented. A giant enhancement of the polarization conversion efficiency is found to merge under plasma oscillation resonance in the periodic 2D electron system. The cases of the normal and an oblique incidence of the external EW are considered. It is shown that in the total internal reflection regime the total polarization conversion can be reached if the electron scattering in the 2D electron system vanishes. Numerical calculations are performed with the characteristic parameters of an actual 2D electron system in the electron inversion layer on p-Si at the far- infrared frequencies. A solid angle in which the wavevector of the incident EW should reside in order to produce the greatest polarization conversion efficiency is calculated for different aspect fraction values of the periodic 2D electron system.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

International audience; We observed a photovoltaic non-resonant terahertz photoresponse in a InGaAs/GaAs heterostructure with a large area double-grating-gate at room temperature. Semi-quantitative estimation of the characteristic detection length combined with self-consistent calculations of the electric fields exited in the structure by incoming terahertz radiation allowed us to interpret this detection as coming from the depleted regions of the channel.

We investigated the emission of terahertz radiation from a doubly interdigitated grating gates high electron mobility transistor. The experiment was performed using Fourier spectrometer system coupled with high sensitive 4 K Silicon bolometer under the vacuum. The observed emission was explained as due to the excitation of the plasma waves by means of hot 2D plasmons. We also investigated the optical stimulation of the plasma waves by subjecting the device to a CW 1.5 µm laser beam. Dependence of the emission on the gate bias (i.e. on electron density) was observed and interpreted as due to the self oscillation of the plasma waves.

Room temperature terahertz (far infrared) radiation emission from double grating coupled GaInAs∕AlGaAs∕GaAs heterojunctions is reported. Theoretical calculations of plasmon absorption spectrum are performed using a first principles electromagnetic approach. They correctly reproduce the frequency range and overall shape of the main (broad-band) part of the experimental spectra. The results clearly indicate that important part of the observed room temperature terahertz emission spectra can be due to the radiative decay of hot two-dimensional plasmons in the grating structure.

We present a theory of dc photoresponse, change in device conductance, at the plasmon resonance in the density modulated two-dimensional electron channel of the grating-gated GaAs∕AlGaAs field-effect transistor irradiated by an electromagnetic wave of terahertz frequency. An equilibrium density modulation is shown to give rise to a specific mechanism of photoresponse due to a plasma electrostriction effect. In strongly modulated systems, this effect dominates the photoresponse and results in a strong increase of the resonant peak amplitudes and photoresponse sign reversal dependent on the modulation depth and the equilibrium density profile. These results are in good qualitative agreement with recent experiments.

A strict electrodynamic approach is used to analyze the excitation of oscillations of a two-dimensional electron plasma by an external plane electromagnetic wave in a semiconductor heterostructure with a grating coupling element. An analysis is made of the influence of the substrate thickness on the resonance magnitude and the profile of the resonance curve.

The authors computer simulations show that plasmon modes excited in an array of field-effect transistors with two-dimensional electron channel strongly couple to terahertz radiation due to the synchronization of plasma oscillations in different unit cells of the array. It is shown that in such a device the higher-order plasmon modes are excited much more effectively than in a large area two-dimensional electron channel coupled to terahertz radiation by a slit-grating gate. Effective excitation of the higher-order plasmon modes makes it possible to design terahertz plasmonic devices with operating frequencies up to 15THz or even higher.

We carry out a theoretical analysis of the terahertz response of an asymmetric bilayer of two-dimensional electron strips, modeling the double-quantum-well electron channel of a grid-gated field-effect transistor in which strong terahertz photoresponse was recently observed. We have shown that mixing between optical and acoustic plasmons hugely increases at the anticrossing of optical-like and acousticlike plasma resonances excited by incoming terahertz radiation in such a bilayer. As a result, the amplitude of the interlayer terahertz electric field also increases dramatically in the anticrossing regime, becoming two and a half orders of magnitude greater than the amplitude of electric field of incoming terahertz wave.

Two methods are proposed for solving the equations of radiative-conductive heat exchange — analytic and computational. The efficiency of both methods is illustrated by specific examples of a calculation of the temperature fields and radiation fluxes at the cathode.

The temperature distribution for thin filaments heated by an electric current in vacuo is found, and simple analytical expressions are derived for calculations of the fundamental variables characterizing the thermal mode of the heater. The results of calculations according to these expressions are compared with the experimental data.

Electromagnetic theory of plasma oscillations in field-effect transistor with two-dimensional electron channel is presented. Two different key electromagnetic problems are considered. They are the problems of diffraction of the plane electromagnetic wave (i) on the slot in infinite perfectly conductive plane, which is bridged by 2D electron channel and (ii) on the perfectly conductive strip, which screens partially an infinite 2D electron sheet located at a given distance from the strip. New physics inherent in these problems is revealed.