Room temperature photovoltaic non-resonant detection by large area double-grating-gate InGaP/InGaAs/GaAs heterostructures was investigated in sub-THz range (0.24 THz). Semi-quantitative estimation of the characteristic detection length combined with self-consistent calculations of the electric fields excited in the structure by incoming terahertz radiation allowed us to interpret quantitatively the results and conclude that this detection takes place mainly in the regions of strong oscillating electric field excited in depleted portions of the channel.

GaAs nanometric field effect-transistors are used for room temperature single-pixel imaging using radiation frequencies above 1 THz. Images obtained in transmission mode at 1.63 THz are recorded using transistors operating in a photovoltaic mode with spatial resolution of 300 mu m and voltage sensitivity of about 8 mV/W. A reduction in response with increasing frequency was observed and mitigated by the application of a source-drain current, leading to the demonstration of imaging at up to 2.54 THz.

Experiments on terahertz radiation detection with InGaAs/InAlAs field-effect transistor in quantizing magnetic field are reported. We observed oscillations of the photovoltaic signal analogous to Shubnikov-de Haas oscillations, as well as their strong enhancement at the cyclotron resonance conditions. The results are described quantitatively within the frame of a theory which takes into account a new source of nonlinearity related to the Landau quantization of the conduction band. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Because of their competitive Noise Equivalent Power (NEP) at room temperature and their fast modulation frequency, Field Effect Transistors (FETs) are one of the most promising devices for room temperature multipixel THz detection and imaging. We report here on an experimental study of the sub-THz detection as a function of the gate length in Silicon FETs and discuss the physical basis of their optimisation.

We observed a photovoltaic non-resonant terahertz photoresponse in a InGaAs/GaAs heterostructure with a large area double-grating-gate at room temperature. Semi-quantitative estimation of the characteristic detection length combined with self-consistent calculations of the electric fields exited in the structure by incoming terahertz radiation allowed us to interpret this detection as coming from the depleted regions of the channel.

Two experiments demonstrate that high electron mobility transistors (HEMTs) are well suited for terahertz (THz) imaging. We have shown that HEMTs can be effectively used as plasma wave detectors in a THz imaging system at frequencies higher than 1 THz at room temperature and this device are sensitive to the polarization direction of THz radiation.

The experiments on radiation coupling to field effect transistors working as terahertz radiation detectors are reported. Two types of high electron mobility transistors: InGaAs/InAlAs and GaAs/AlGaAs, with different layout geometries are studied. We show that terahertz radiation coupling efficiency is related to the layout of contact electrodes that play a role of an antenna. Our results show that the antenna coupling efficiency is one of the most important parameter to optimize in future field effect transistor based terahertz detectors.