Single layer back gate graphene filed effect transistors exhibit strong physical magnetoresistance. We measured the maximum magnetoresistance at B=14T within the range R/R=1.5-2, depending on temperature and gate voltage. These values significantly exceed the possible geometrical magnetoresistance estimated for used transistor configuration. The noise measurements at 80 K and 285 K indicated a complex and non-monotonic dependence of 1/f noise on the magnetic field and gate voltage that has never been observed before. In relatively low magnetic fields, B<2 T, the noise decreased with the increasing magnetic field at both temperatures. At high fields B>2 T, the measured spectral noise density increased significantly with increasing magnetic field. The noise amplitude at B=14 T was at least one order of magnitude higher than that at B=0. These dependences cannot be explained by the geometrical effect and, therefore, we conclude that physical (not geometrical) mechanisms are responsible for the observed noise dependence on the magnetic field. Non-monotonic dependence on the magnetic field and a strong increase of noise in high magnetic fields in graphene are very different from what is observed in conventional semiconductors. In particular, GaAs and GaN/AlGaN samples exhibit only a weak dependence of noise on the magnetic field, consistent with the number of carriers fluctuations as the origin of noise in these materials. The reported magnetic field dependence of noise in graphene confirms unconventional nature of noise in graphene.

We report on room-temperature plasmonic detection of sub-terahertz radiation by InAlAs/InGaAs/InP high electron mobility transistors with an asymmetric dual-grating-gate structure. Maximum normalized responsivities of 22.7 kV/W at 200 GHz and 21.5 kV/W at 292 GHz were achieved under unbiased drain-to-source condition.

Nanometer size field effect transistors can operate as efficient resonant or broadband terahertz detectors, mixers, phase shifters and frequency multipliers at frequencies far beyond their fundamental cut-of frequency. This work is an overview of some recent results concerning the THz detection by Si MOS transistors with back-gate, low temperatures operation, and circular polarization studies of nanometer scale field effect transistors for the detection of terahertz radiation. Also first results on graphene transistors are discussed.

We report on the first error-free terahertz (THz) wireless communication at 0.310 THz for data rates up to 8.2 Gbps using a 18-GHz-bandwidth GaAs/AlGaAs field-effect transistor as a detector. This result demonstrates that low-cost commercially-available plasma-wave transistors whose cut-off frequency is far below THz frequencies can be employed in THz communication. Wireless communication over 50 cm is presented at 1.4 Gbps using a uni-travelling-carrier photodiode as a source. Transistor integration is detailed, as it is essential to avoid any deleterious signals that would prevent successful communication. We observed an improvement of the bit error rate with increasing input THz power, followed by a degradation at high input power. Such a degradation appears at lower powers if the photodiode bias is smaller. Higher-datarate communication is demonstrated using a frequency-multiplied source thanks to higher output power. Bit-error-rate-measurements at data rates up to 10 Gbps are performed for different input THz powers. As expected, bit error rates degrade as data rate increases. However, degraded communication is observed at some specific data rates. This effect is probably due to deleterious cavity effects and/or impedance mismatches. Using such a system, real-time uncompressed high-definition video signal is successfully and robustly transmitted.

This paper reviews recent advances in ultrafast and ultrahigh sensitive broadband terahertz detection utilizsing asymmetric double-grating-gate InP-based high-electron-mobility transistors, demonstrating a record responsivity of 2.2 kV/W at 1 THz under drain-unbiased conditions with a superior low noise equivalent power of 15 pW/root Hz and 6.4 kV/W even at 1.5 THz under drain-biased conditions.

We report on terahertz wireless communication experiments at 0.2 THz, using a commercial GaAs field-effect-transistor as detector. For the first time, we will present the transmission of pseudo-random bit sequence at 0.2 THz using this commercial transistor and demonstrate open eye-patterns up to 1.5 Gbps. This transistor is integrated into a machined horn, so that its sensitivity is improved to 1 V/W, and has a 10 GHz cut-off frequency. We will discuss signal-to-noise ratio in the terahertz wireless data transmission.