We present recent results on detection of terahertz radiation with nanometer size GaAs FETs and Si MOSFETs at room temperature. We demonstrate that the detection sensitivity and speed allows application of the transistors in terahertz imaging systems. At low temperatures the transistors can act as magnetic field tunable detectors.

Resonant frequencies of the two-dimensional plasma in field effect transistors (FETs) increase with the reduction of the channel dimensions and can reach the THz range for nanometer size devices. Nonlinear properties of the electron plasma in the transistor channel can lead to the detection and emission of THz radiation. The excitation of plasma waves by sub-THz and THz radiation was experimentally demonstrated at cryogenic as well as at room temperatures. We present an overview of experimental results on THz detection by FETs discussing possibilities of improvement of their performance and application for THz room temperature imaging. We present also recent results on THz emission from GaN/AlGaN-based FETs

We evaluate the optical performance of AlGaN/GaN MISFETs as a non-resonant sub-terahertz, room temperature detector. The single-pixel responsivity and the noise equivalent power are determined. The efficiency of the detection is demonstrated by the room temperature imaging of different solutions of acetone in cyclohexane..

We report on active imaging with CMOS transistors at 300 GHz and 1.05 THz. Two basic focal plane arrays consisting of nMOS transistors and wide-band bow-tie antennas have been implemented in a low-cost 130 nm CMOS technology. Raster scan imaging of objects concealed in a paper envelope has been achieved at 300 GHz with a commercial radiation source. The images clearly reveal the concealed objects with a dynamic range of 35 dB and a resolution of 3 mm. At 1.05 THz, the pixels achieve a responsivity of 50 V/W and a noise equivalent power of 900 pW/Hz0.5.

We demonstrate that a proper antenna and transistor design can provide high responsivity for Terahertz radiation and imaging capability even above the 1 THz limit with a low-cost 130 nm CMOS technology. This result opens the way to CMOS THz imagers working at high frequencies and therefore exhibiting high a spatial resolution - down to similar to 300 mu m.

GaAs field effect-transistors are used for single-pixel imaging using frequencies above 1 THz at 300 K. Images obtained in transmission mode at 1.63 THz are recorded with spatial resolution of 300 mu m. We demonstrate that, with applied drain to source current, the imaging at up to 2.5 THz is possible.

Resonant frequencies of the two-dimensional plasma in FETs reach the THz range for nanometer transistor channels. Non-linear properties of the electron plasma are responsible for detection of THz radiation with FETs. Resonant excitation of plasma waves with sub-THz and THz radiation was demonstrated for short gate transistors at cryogenic temperatures. At room temperature, plasma oscillations are usually over-damped, but the FETs can still operate as efficient broadband THz detectors. The paper presents the main theoretical and experimental results on detection with FETs stressing their possible THz imaging applications. We discuss advantages and disadvantages of application of III-V GaAs and GaN HEMTs and silicon MOSFETs.