O. Klimenko

Helicity sensitive terahertz radiation detection by field effect transistors

Terahertz light helicity sensitive photoresponse in GaAs/AlGaAs high electron mobility transistors. The helicity dependent detection mechanism is interpreted as an interference of plasma oscillations in the channel of the field-effect-transistors (generalized Dyakonov-Shur model). The observed helicity dependent photoresponse is by several orders of magnitude higher than any earlier reported one. Also, linear polarization sensitive photoresponse was registered by the same transistors. The results provide the basis for a new sensitive, all-electric, room-temperature, and fast (better than 1 ns) characterisation of all polarization parameters (Stokes parameters) of terahertz radiation. It paves the way towards terahertz ellipsometry and polarization sensitive imaging based on plasma effects in field-effect-transistors.

Temperature enhancement of terahertz responsivity of plasma field effect transistors

Temperature dependence of THz detection by field effect transistors was investigated in a wide range of temperatures from 275 K down to 5 K. The important increase of the photoresponse following 1/T functional dependence was observed when cooling from room temperature down to 30 K. At the temperatures below ∼30 K, the THz response saturated and stayed temperature independent. Similar behavior was observed for GaAs, GaN, and Si based field effect transistors. The high temperature data were successfully interpreted using recent theory of overdamped plasma excitation in field effect transistors. The low temperature saturation of the photoresponse was tentatively explained by the change of the transport regime from diffusive to ballistic or traps governed one. Our results clearly show that THz detectors based on field effect transistors may improve their responsivity with lowering temperature but in the lowest temperatures (below ∼30 K) further improvement is hindered by the physics of the electron transport ...

Terahertz wide range tunable cyclotron resonance p-Ge laser

We present a Terahertz (THz) p-Ge laser operating in a cyclotron resonance (CR) mode. Thanks to the use of the optimum crystallographic orientation of p-Ge with respect to crossed E⊥B fields, the laser line frequency is continuously tunable in the range 1.2–2.8 THz (40–90 cm−1) with the linewidth being 6 GHz (0.2 cm−1). We also show that due to such a wide CR radiation range, the laser can serve as a base for a THz spectrometer.

Terahertz detection and emission by field effect transistors: Influence of high magnetic fields and channel geometry

We review a few recent results concerning the physics and applications of FETs as Terahertz detectors and emitters. Particulary we stress results concerning dependance of THz detection and emission on high/quantizing magnetic fields and the geometry of the FETs channel.

Recent Results on Broadband Nanotransistor Based THz Detectors

Nanometer size field effect transistors can operate as efficient detectors of terahertz radiation that means far beyond their fundamental cut-of frequency. This work is an overview of some recent results concerning the low temperatures operation, linearity, circular polarization studies and double grating gate structures of nanometer scale field effect transistors working as terahertz detectors.

High-frequency response and the possibility of detecting the quantum amplification mode in resonant-tunneling diode structures

The conditions of the implementation of the quantum mode of microwave generation in semiconductor resonant-tunneling diode (RTD) structures were theoretically analyzed. Based on the constructed analytical model of the steady-state current and high-frequency response in symmetric RTD structures with finite barrier widths, high-frequency properties of RTDs in an external ac electric field were analyzed by numerical simulation methods. It was shown that the quantum amplification mode can appear not only in the high-frequency region of the terahertz range, but also at relatively low frequencies due to deformation of frequency dependences in a dc electric field.

Plasma nonlinearities and terahertz detection by Field Effect Transistors

On overview of recent results concerning the plasma excitations in Field Effect Transistor is presented. We report on high magnetic field studies and we show evidences that the plasma waves are indeed propagating in the transistor channel. We show also how FET based THz detectors parameters can be determined using the static current voltage characteristics. The role of loading effects and temperature to enhance the THz responsivity is also demonstrated.