We demonstrate two different THz rectification mechanisms by graphene field effect transistors: a mesoscopic rectification due to the existence of 2nd-order conductance fluctuations and a rectification mechanism where THz radiation modulates simultaneously carrier velocity and carrier density.

L'invention concerne un dispositif (1) de mesure de l'état de polarisation d'une onde incidente de fréquence de 10 GHz à 30 THz , comportant un transistor à effet de champ (2), une antenne (3) de réception. Suivant l'invention, les parties (31, 33) d'antenne détectent une composante de polarisation de l'onde, colinéaire à une direction (X) provoquant dans le transistor (2) une tension alternative (Us) de détection, les parties (32, 33) détectent une composante de polarisation de l'onde, colinéaire à une direction (Y) provoquant l'apparition dans le transistor (2) d'une tension alternative (Ud) de détection, le transistor (2) étant agencé pour générer, comme signal électrique (ΔU) de détection entre la borne (21) de source et la borne (22) de drain, une tension continue (ΔU) de détection dont une partie est déterminée par l'état de polarisation elliptique de l'onde par interférence dans le transistor (2) entre les tensions alternatives (Us, Ud).

The concept of THz detection based on excitation of plasma waves in two-dimensional electron gas in Si FETs is one of the most attractive ones, as it makes possible the development of the large-scale integrated devices based on a conventional microelectronic technology including on-chip antennas and readout devices integration. In this work we report on investigations of Terahertz detectors based on low-cost silicon technology field effect transistors and asymmetric unit cell double grating gate field effect transistor. Double-grating-gate field-effect transistors have a great potential as terahertz detectors. This is because the double grating gate serves not only for carrier density tuning but also as an efficient THz radiation coupler. In this paper, we present characterization of these transistors using high magnetic fields. Low and high magnetic field data are used to determine the electron mobility and electron concentration, respectively, in different parts of the transistor channel. We show that detectors, consisting of a coupling antenna and a n-MOS field effect transistor as rectifying element, are efficient for THz detection and imaging. We demonstrate that in the atmospheric window around 300 GHz, these detectors can achieve a record noise equivalent power below 10 pW/Hz(0.5) and responsivity above 90 kV/W once integrated with on-chip amplifier. We show also that they can be used in a very wide frequency range: from similar to 0.2 THz up to 1.1 THz. THz detection by Si FETs paves the way towards high sensitivity silicon technology based focal plane arrays for THz imaging

Double-grating-gate field-effect transistors have a great potential as terahertz detectors. This is because the double grating gate serves not only for carrier density tuning but also as an efficient THz radiation coupler. In this paper, we present characterization of these transistors using high magnetic fields. Low and high magnetic field data are used to determine the electron mobility and electron concentration, respectively, in different parts of the transistor channel.

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 terahertz electromagnetic wave conversion device has an HEMT structure having a substrate (201), an electron transit layer (202), an electron supply layer (203), a source (204) and a drain (205), and comprises a first group of gates (G1) and a second group of gates (G2). The gate length (L1) of each finger of the first group of gates (G1) is narrower than the gate length (L2) of each finger of the second group of gates (G2), and each finger of each group of gates is disposed between the source (204) and the drain (205) on the same cycle (W). A first distance (D1) and a second distance (D2) from each finger of the first group of gates (G1) to two fingers of the second group of gates (G2) adjoining that finger are set to unequal lengths

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/CdxHg1−xTe 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 dc = 6.3 nm. Here, we report on a far-infrared magnetospectroscopy study of a set of HgTe/CdxHg1−xTe quantum wells with different thicknesses from below to above the critical value dc. 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.

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 of magnitude higher than any earlier reported one. Also, linear polarization sensitive photoresponse was registered by the same transistors. The results provide the basis for a new sensitive, all-electric, room-temperature, and fast (better than 1 ns) characterisation of all polarization parameters (Stokes parameters) of terahertz radiation. It paves the way towards terahertz ellipsometry and polarization sensitive imaging based on plasma effects in field-effect-transistors.