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Register a new userTerahertz Response of Field-Effect Transistors in Saturation Regime
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We report on the broadband THz response of InGaAs/GaAs HEMTs operating at 1.63 THz and room temperature deep in the saturation regime. We demonstrate that responses show linear increase with drain-to-source voltage (or drain bias current) and reach very high values up to 170V/W. We also develop a phenomenological theory valid both in the ohmic and in the saturation regimes.
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This is a brief overview of the main physical ideas for application of field effect transistors for generation and detection of TeraHertz radiation. Resonant frequencies of the two-dimensional plasma oscillations in FETs increase with the reduction of the channel dimensions and reach the THz range for sub-micron gate lengths. When the mobility is high enough, the dynamics of a short channel FET at THz frequencies is dominated by plasma waves. This may result, on the one hand, in a spontaneous generation of plasma waves by a dc current and on the other hand, in a resonant response to the incoming radiation. In the opposite case, when plasma oscillations are overdamped, the FET can operate as an efficient broadband THz detector.
Magnetic skyrmions are of considerable interest for low-power memory and logic devices because of high speed at low current and high stability due to topological protection. We propose a skyrmion field-effect transistor based on a gate-controlled Dzyaloshinskii-Moriya interaction. A key working principle of the proposed skyrmion field-effect transistor is a large transverse motion of skyrmion, caused by an effective equilibrium damping-like spin-orbit torque due to spatially inhomogeneous Dzyaloshinskii-Moriya interaction. This large transverse motion can be categorized as the skyrmion Hall effect, but has been unrecognized previously. The propose device is capable of multi-bit operation and Boolean functions, and thus is expected to serve as a low-power logic device based on the magnetic solitons.
We report on Terahertz detection by inverted band structure HgTe-based Field Effect Transistor up to room temperature. At low temperature, we show that nonlinearities of the transistor channel allows for the observation of the quantum phase transition due to the avoided crossing of zero-mode Landau levels in HgTe 2D topological insulators. These results pave the way towards Terahertz topological Field Effect Transistors.
The advent of black phosphorus field-effect transistors (FETs) has brought new possibilities in the study of two-dimensional (2D) electron systems. In a black phosphorus FET, the gate induces highly anisotropic 2D electron and hole gases. Although the 2D hole gas in black phosphorus has reached high carrier mobilities that led to the observation of the integer quantum Hall effect, the improvement in the sample quality of the 2D electron gas (2DEG) has however been only moderate; quantum Hall effect remained elusive. Here, we obtain high quality black phosphorus 2DEG by defining the 2DEG region with a prepatterned graphite local gate. The graphite local gate screens the impurity potential in the 2DEG. More importantly, it electrostatically defines the edge of the 2DEG, which facilitates the formation of well-defined edge channels in the quantum Hall regime. The improvements enable us to observe precisely quantized Hall plateaus in electron-doped black phosphorus FET. Magneto-transport measurements under high magnetic fields further revealed a large effective mass and an enhanced Lande g-factor, which points to strong electron-electron interaction in black phosphorus 2DEG. Such strong interaction may lead to exotic many-body quantum states in the fractional quantum Hall regime.
Detectors of high-frequency radiation based on high-electron-mobility transistors benefit from low noise, room-temperature operation, and the possibility to perform radiation spectroscopy using gate-tunable plasmon resonance. Despite successful proof-of-concept demonstrations, the responsivity of transistor-based detectors of THz radiation, at present, remains fairly poor. To resolve this problem, we propose a class of devices supporting singular plasmon modes, i.e. modes with strong electric fields near keen electrodes. A large plasmon-enhanced electric field results in amplified non-linearities, and thus efficient ac-to-dc conversion. We analyze sub-terahertz detectors based on a two-dimensional electron system (2DES) in the Corbino geometry as a prototypical and exactly solvable model and show that the responsivity scales as $1/r_0^{2}$ with the radius of the inner contact $r_0$. This enables responsivities exceeding 10 kV/W at sub-THz frequencies for nanometer-scale contacts readily accessible by modern nanofabrication techniques.
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