Compact and fast detectors, for imaging and wireless communication applications, require efficient rectification of electromagnetic radiation with frequencies approaching 1 THz and modulation bandwidth up to a few tens of GHz. This can be obtained only by using a mature technology allowing monolithic integration of detectors with low-noise amplifiers. One of the best candidates is indium phosphide bipolar transistor (InP HBT) technology. In this work, we report on room temperature high sensitivity terahertz detection by InP double-heterojunction bipolar transistors (DHBTs) operating in a large frequency range (0.25–3.1 THz). The performances of the DHBTs as terahertz sensors for communications were evaluated showing the modulation bandwidth of investigated DHBTs close to 10 GHz.

This paper presents terahertz detectors based on high performance 0.7-μm InP double heterojunction bipolar transistor (DHBT) technology and reports on the analysis of their voltage responsivity over a wide frequency range of the incoming terahertz radiation. The detectors operated without any spatial antennas to couple terahertz radiation to the device and have been characterized in the 0.25 - 3.1 THz range with the responsivities (normalized to 1 W radiant power) of 5 V/W and 200 μV/W measured at 0.35 THz and 3.11 THz, respectively. The InP DHBTs also performed as the imaging single-pixels at room temperature in the raster scanned transmission mode. A set of the sub-terahertz images of plant leaves suggest potential utility of InP DHBT detectors for terahertz imaging dedicated to non-invasive testing of plants.

We evaluate the optical performance of the InP heterojunction bipolar transistors (DHBTs) designed for 100 Gbit/s circuit applications as a room temperature detector operating above 1 THz. They can operate far above the frequencies at which they have gain and can still rectify THz current and voltage.

The terahertz SPICE PET model has been experimentally validated in Si CMOS and InGaAs HEMTs up to 4.5 THz and updated to account for parasitic gate fringing capacitance and parasitic source and drain resistance. The model is in good agreement with experimental data at low and high THz field intensities. We also show that introducing additional capacitances linking the drain and gate electrodes may lead to enhancement of the THz plasmonic detector response at lower THz frequencies. The simulation results of the plasmonic detector response to a single terahertz pulse are in good agreement with our measured data. (C) 2014 Elsevier Ltd. All rights reserved.

Terahertz power dependence of the photoresponse of field effect transistors, operating at frequencies from 0.1 to 3 THz for incident radiation power density up to 100 kW/cm(2) was studied for Si metal-oxide-semiconductor field-effect transistors and InGaAs high electron mobility transistors. The photoresponse increased linearly with increasing radiation intensity up to the kW/cm(2) range. Nonlinearity followed by saturation of the photoresponse was observed for all investigated field effect transistors for intensities above several kW/cm(2). The observed photoresponse nonlinearity is explained by nonlinearity and saturation of the transistor channel current. A theoretical model of terahertz field effect transistor photoresponse at high intensity was developed. The model explains quantitative experimental data both in linear and nonlinear regions. Our results show that dynamic range of field effect transistors is very high and can extend over more than six orders of magnitudes of power densities (from similar to 0.5 mW/cm(2) to similar to 5 kW/cm(2)). (C) 2014 AIP Publishing LLC.

Terahertz power dependence of the photoresponse of field effect transistors, operating at frequencies from 0.1 to 3 THz for incident radiation power density up to 100 kW/cm^2 was studied for Si metal-oxide-semiconductor field-effect transistors and InGaAs high electron mobility transistors. The photoresponse increased linearly with increasing radiation power up to kW/cm^2 range. The saturation of the photoresponse was observed for all investigated field effect transistors for intensities above several kW/cm^2. The observed signal saturation is explained by drain photocurrent saturation similar to saturation in direct currents output characteristics. The theoretical model of terahertz field effect transistor photoresponse at high intensity was developed. The model explains quantitatively experimental data both in linear and nonlinear (saturation) range. Our results show that dynamic range of field effect transistors is very high and can extend over more than six orderd of magnitudes of power densities (from 0.5 mW/cm^2 to 5 kW/cm^2).

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.

D. B. But, C. Drexler, M. V. Sakhno, N. Dyakonova , O. Drachenko, F. F. Sizov, A. Gutin, S. D. Ganichev, W. Knap 1 UMR 5221 CNRS, Universite Montpellier 2, Montpellier 34095, France 2 V.E. Lashkaryov Inst Semicond Phys, Kiev, 03028, Ukraine 3 Terahertz Center, University of Regensburg, Regensburg, 93040, Germany 4 Helmholtz Zentrum Dresden Rossendorf, Inst Ion Beam Phys & Mat Res, Dresden, 01314, Germany and 5 Rensselaer Polytechnic Institute, Troy, New York, 12180, USA (Dated: February 4, 2014)

We demonstrate detection of individual pulses of terahertz radiation generated in femtosecond laser systems by InGaAs plasma-wave terahertz detectors. Nonlinearity of the detection mechanism is analyzed experimentally by comparison of saturation effects at femtosecond and nanosecond terahertz excitations. Good sensitivity and wide dynamic range make these detectors promising for short-pulsed terahertz applications.

Electron gas in the conduction channel of a Field Effect Transistor (FET) can support collective plasma oscillations tunable by the gate voltage. In the Dyakonov-Shur terahertz (THz) detector, nonlinearities in the plasma wave propagation in the gated channel of a FET lead to a constant source-to-drain voltage providing the detector output. We present the detector theory in the frame of the hydrodynamic model using the electron plasma Navier-Stokes and thermal transport equations, thus fully accounting for the hydrodynamic non-linearity, the viscosity, and pressure gradients in the detector response. Both resonant and broadband operations of the high electron mobility transistor (HEMT) based plasmonic detectors are described by this model. The relation between the electron channel density and gate voltage was modeled by the unified charge control model applicable both above and below the threshold voltage. The theoretical results are compared with the response measured in the short channel InGaAs HEMT and the analytical approximation. The THz source was operating at 1.63 THz, and the response was measured at varying signal intensities. The response of the detector operated in the open drain mode was measured above and below the threshold, and the theoretical and experimental results are shown to be in good agreement. (C) 2014 AIP Publishing LLC.

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 THz detection by Si MOS transistors with back-gate, low temperatures operation, and circular polarization studies of nanometer scale field effect transistors for the detection of terahertz radiation. Also first results on graphene transistors are discussed.

In the Dyakonov-Shur terahertz (THz) detector, nonlinearities in the plasma wave propagation in the conduction channel of a heterostructure High Electron Mobility Transistor (HEMT) lead to a constant source-to-drain voltage providing the detector output. For a small signal, the perturbation theory treatment shows that the response is proportional to the intensity of the radiation. The proportionality factor can have a resonant or a broad dependence on the signal frequency. For submicron HEMTs, the typical measured response falls within the range of 0.1 to 4.5 THz. The deviations from this relation have been studied and reported in the approximation of the local Ohm's law and transmission line model for the non-resonant response. Here we present the results obtained with the hydrodynamic model using the electron plasma Navier-Stokes equation, thus fully accounting for the hydrodynamic non-linearity, the viscosity and pressure gradients in the detector response. The model is applicable to both resonant and broadband operations of the HEMT based plasmonic detectors. The relation between the electron channel density and gate voltage was modeled by the unified charge control model applicable both above and below the threshold voltage. The theoretical results are compared with the response measured in the short channel InGaAs HEMT and the analytical approximation. The THz source was operating at 1.63 THz and the response was measured at varying signal intensities. The response of the detector operated in the open drain mode was measured above and below the threshold. The theoretical and experimental results are in good agreement.

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/cm(2). 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/cm(2) 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.

Recent work on plasmonic terahertz detection using field effect transistors (FETs) has yielded detectors with high responsivity. Therefore, deviation from small signal mode of operation, when the detector signal is simply proportional to the THz intensity, must be considered. This work presents a new analytical model to predict terahertz response in a FET at arbitrary intensity levels. The proposed analytical model was experimentally validated using a 0.13 μm InGaAs high electron mobility transistor and optically pumped CO2 gas laser operating at 1.63 THz of varying output intensities. The model is suitable for implementation in circuit simulators and might be used for device optimization and THz circuit design.