We use two antenna model to develop a theory of the recently observed helicity-sensitive detection of terahertz radiation by FETs. The effect is due to the mixing of the ac signals produced in the channel by the two antennas. We obtain the helicity-dependent part of the photoresponse and its dependence on the antenna impedance, gate length, and gate voltage. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Cyclotron resonance (CR) study of HgCdTe-based quantum wells with both inverted and normal band structures in quantizing magnetic fields was performed. In normal-band sample in addition to electron CR transitions a strong absorption line presumably related to impurity transitions was discovered. Anticrossing of electron and hole Landau levels was observed in inverted-band sample. In semimetallic HgTe quantum wells with inverted band structure, a hole CR line was observed for the first The obtained results were interpreted within the Kane 8 × 8 model, the valence band offset of CdTe and HgTe, and the Kane parameter EP being adjusted.

Field effect transistors are promising detectors of THz radiation. They operate at room temperatures have high responsivity, low noise equivalent power, and fast response time. However, their linearity (dynamic range) and possibility of their application in the domain of high power radiation has not been yet sufficiently studied. We have investigated room temperature field effect transistors, detection at frequencies from 0.3 to 3 THz with power up to 100 kW/cm2. Several types of HEMTs and MOSFETs operating in the broadband non resonant detection regime, have been investigated. To provide a wide range of incident THz radiation intensities we used continuous-wave and pulsed sources: backward oscillators, CO2 pumped methanol laser, free electron laser, NH3, D2O, and CH3F lasers. We find that the photoresponse of HEMTs and MOSFETs is linear in radiation intensity up to a several kW/cm2 and then it saturates. The onset of the saturation depends on the radiation frequency and the transistor type. The observed saturation behavior can not be explained by the existing theoretical model which predict a square root like dependence of the photoresponse. We tentatively attribute the unusual features of the photoresponse saturation observed at high intensities considering high electric field transport phenomena, e.g., electron heating and electron velocity saturation. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

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 low temperatures operation, linearity, and circular polarization studies of nanometer scale field effect transistors for the detection of terahertz radiation. Also first results on graphene transistors are discussed. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Polarization dependence analysis of back-gated graphene field-effect transistor terahertz responsivity at frequencies ranging from 1.63 to 3.11 THz reveals two independent mechanisms of THz detection by graphene transistor: plasmonic, associated with the transistor nonlinearity, and bolometric, caused by graphene sheet temperature increase due to THz radiation absorption. In the bolometric regime, electron and hole branches demonstrate a very different response to THz radiation, which we link to the asymmetry of the current-voltage characteristics temperature dependence with respect to the Dirac point. Obtained results are important for development of high-efficiency graphene THz detectors.

Recent advances in emission and detection of terahertz radiation using two-dimensional (2D) electron systems in III-V semiconductors and graphene are described. First the 2D plasmon resonance is presented to demonstrate intense broadband terahertz emission and detection from InGaP/InGaAs/GaAs and InAlAs/InGaAs/InP material systems. The device structure is based on a high-electron mobility transistor and incorporates the author's original asymmetrically interdigitated dual-grating gates. Second topic focuses on graphene, a monolayer carbon-atomic honeycomb lattice crystal, exhibiting peculiar carrier transport and optical properties owing to massless and gapless energy spectrum. Theoretical and experimental studies toward the creation of graphene terahertz injection lasers are described.

The low frequency 1/f noise in graphene devices was studied in a transverse magnetic field of up to B = 14 T at temperatures T = 80 K and T = 285 K. The examined devices revealed a large physical magnetoresistance typical for graphene. At low magnetic fields (B < 2 T), the level of 1/f noise decreases with the magnetic field at both temperatures. The details of the 1/f noise response to the magnetic field depend on the gate voltage. However, in the high magnetic fields (B > 2 T), a strong increase of the noise level was observed for all gate biases.