Test chips with Si MOSFETs integrating bow tie antennas are investigated to check the polarization and frequency dependence of THz sensitivity. The azimuthal angle corresponding to the maximum sensitivity changes with the pixel position on the chip. This means that the surrounding pixels affect the bow tie radiation pattern and possibly contribute to the antenna coupling. The frequency dependence suggests the presence of surface modes phenomena in the silicon substrate.

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.

We report about fabrication and characterization of semiconductor nanowire-based field effect transistor devices which can act as detectors for electromagnetic radiation in the THz frequency range. The detection mechanism is based on the nonlinear transfer characteristic of the transistor, which is used to realize signal rectification; the small capacitance related to the nanowire small cross section is beneficial in allowing a good device sensitivity up to 1.5 THz at room temperature. Due to the extreme flexibility with which semiconductor nanowires can be grown, we discuss how the basic, homogeneous InAs or InSb nanowire FETs can be improved to realize smarter devices and functionalities.

Ultrahigh Sensitive Plasmonic Terahertz Detection Using Asymmetric Dual-Grating Gate HEMT Structures

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