Hydrodynamic modeling of optically excited terahertz plasma oscillations in nanometric field effect transistors

Abstract

We present a hydrodynamic model to simulate the excitation by optical beating of plasma waves in nanometric field effect transistors. The biasing conditions are whatever possible from Ohmic to saturation conditions. The model provides a direct calculation of the time-dependent voltage response of the transistors, which can be separated into an average and a harmonic component. These quantities are interpreted by generalizing the concepts of plasma transit time and wave increment to the case of nonuniform channels. The possibilities to tune and to optimize the plasma resonance at room temperature by varying the drain voltage are demonstrated.

THz Emission Induced by an Optical Beating in Nanometer-Length High-Electron-Mobility Transistors

“…As a consequence one can conclude that the observed resonant emission at T = 200 K is directly related to the induced excitation of 2D plasma waves, since: (i) the emission is absent with the absence of photoexcitation, and, (ii) the resonant frequency values coincide with those predicted by the analytical theory [9].…”

“…(ii) both techniques (based on emission and rectification spectra) allow us to detect photoexcited plasma waves in the HEMT channel with dispersion of 2D plasma waves predicted by the analytical approach [9], (iii) the direct radiation emission was measured only at 200 K while at 300 K it was absent, (iv) the detection by using rectification effects shows a photoexcitation of plasma waves at both 300 and 200 K with a resonance quality increase of about one order of magnitude.…”

Terahertz Detection of Quantum Cascade Laser Emission by Plasma Waves in Field Effect Transistors

“…(2) was derived assuming a constant velocity in the device channel and a constant momentum relaxation time. These assumptions are not valid in the transistor saturation region [11]. Moreover, the transistor channel region under the gate cannot be considered as separated from the other parts of the transistor.…”

Plasma Oscillations in Nanotransistors: Application to THz Radiations Detection and Generation

“…The model includes two external source terms: (i) a beating optical excitation through the term G + δG = G 0 [1 + cos(2πf t)] [12], and, (ii) an electric excitation on the gate, which, for example, can describe the coupling between a THz radiation and an antenna connected to the gate [11], δV g = ∆V g cos(2πf t). We will restrict our study to the cases of a harmonic excitation at f frequency.…”

“…As we shall demonstrate, such a model allows us to simulate nanometric FETs/HEMTs from ohmic to saturation conditions by taking into account nonequilibrium effects, presence of access regions, etc. [12]. The two different means -electrical and optical -to excite the plasma modes as well as the influence of the biasing conditions on the plasma effects will be discussed.…”