Terahertz (THz) detection by plasma wave mechanism in InGaAs field effect transistors is studied in high/quantizing magnetic fields regime. The correlation between the photovoltaic response and magnetoresistance is revealed. It allows explaining the dominant physical mechanism responsible for strong oscillations observed in the transistor THz photoresponse. The results indicate also a serious discrepancy between experimental data and existing theoretical model. (C) 2010 American Institute of Physics.

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

In this work, we report on room temperature terahertz radiation from sub-micron size GaN/AlGaN based high electron mobility transistors (HEMTs). They could successfully replace the standard Fourier Transform spectrometer source and were investigated with a standard Si-bolometer as a detector. The relatively broad (~1THz) emission line was observed. The maxima were found to be tunable by the gate voltage between 0.75 and 2.1 THz. The observed emission was interpreted as due to the current driven plasma waves instability in the two-dimensional electron gas. The emitted power from a single device reached 150 nW, showing possible application of these transistors as compact sources for terahertz spectroscopy and imaging.

We report on a broadband terahertz emission from a doubly interdigitated grating gates high electron mobility transistor. The observed emission was explained as due to the excitation of multi mode of plasmons: thermally excited incoherent modes and instability-driven coherent modes. The experiment was performed using Fourier spectrometer system coupled with high sensitive 4K Silicon bolometer under the vacuum. To enhance the efficiency, the device was subjected, from the backside, to a CW 1.5 μm laser beam. Dependence of the emission on the gate bias was observed and interpreted as due to the self-oscillation of the plasma waves.

We present experimental results of THz detection signal dependence on the magnetic field. THz radiation was detected with AlGaAs/GaAs high electron mobility transistor where 2D plasma excitations are responsible for the detection signal appearance. We observe both Shubnikov - de Haas oscillations and cyclotron resonance in the detection signal. Fourier transform analysis of the oscillations allowed us to observe two parts of the 2D electron gas: gated and ungated. This allows us to conclude that 2D electrons in the transistor channel are necessary for detection process and both gated and ungated parts takes part in that process.

High electron mobility transistors can work as room-temperature direct detectors of radiation at frequency much higher than their cutoff frequency. One open issue is how the radiation couples to the sub-wavelength transistor channel. Here, we studied the coupling of radiation to an AlGaN/GaN transistor with cut-off frequency of 30 GEL Local irradiation with a Free Electron Laser source at 0.15 THz allowed us to selectively couple the signal to the channel through one transistor terminal at a time. Far-field experiments at 0.15 - 0.94 THz were also performed in order to study the nonlinear properties of the transistor channel.