Plasmonic Terahertz Detectors Research Articles

InP- and GaAs-Based Plasmonic High-Electron-Mobility Transistors for Room-Temperature Ultrahigh-Sensitive Terahertz Sensing and Imaging

This paper reviews recent advances in the design and performance of our original InP- and GaAs-based plasmonic high-electron-mobility transistors (HEMTs) for ultrahighly-sensitive terahertz (THz) sensing and imaging. First, the fundamental theory of plasmonic THz detection is briefly described. Second, single-gate HEMTs with parasitic antennae are introduced as a basic core device structure, and their detection characteristics and sub-THz imaging potentialities are investigated. Third, dual-grating-gate (DGG)-HEMT structures are investigated for broadband highly sensitive detection of THz radiations, and the record sensitivity and the highly-sensitive THz imaging are demonstrated using the InP-based asymmetric DGG-HEMTs. Finally, the obtained results are summarized and future trends are addressed.

Plasmonic terahertz detector response at high intensities

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.

Ultrahigh sensitive plasmonic terahertz detector based on an asymmetric dual-grating gate HEMT structure

We report on ultrahigh sensitive, broadband terahertz (THz) detectors based on asymmetric dual-grating-gate (A-DGG) high electron mobility transistors, demonstrating a record responsivity of 2.2kV/W at 1THz with a superior low noise equivalent power of 15pW/√Hz using InGaAs/InAlAs/InP material systems. When THz radiation is absorbed strong THz photocurrent is first generated by the nonlinearity of the plasmon modes resonantly excited in undepleted portions of the 2D electron channel under the high-biased sub-grating of the A-DGG (as a quadratic nature of the product of local carrier density and velocity perturbations), then the THz photovoltaic response is read out at high-impedance parts of 2D channel under the other sub-grating biased at the level close to the threshold. Extraordinary enhancement by more than two orders of magnitude of the responsivity is verified with respect to that for a symmetric DGG structure.

Design and Characterization of Plasmonic Terahertz Wave Detectors Based on Silicon Field-Effect Transistors

We report the first implementation of a modeling and simulation environment for the plasmonic terahertz (THz) detector based on the silicon (Si) field-effect transistor (FET) with a technology computer-aided-design (TCAD) platform. The nonresonant plasmonic behavior has been modeled by introducing a quasi-plasma electron box as a two-dimensional electron gas (2DEG) in the channel region. The alternate-current (AC) signal as an incoming THz wave radiation successfully induced a direct-current (DC) drain-to-source voltage as a detection signal in the broadband sub-THz frequency regime. The simulated dependences of photoinduced DC detection signals on structural parameters such as gate length and dielectric thickness confirmed the operation principle of the nonresonant plasmonic THz detector in the Si FET structure. We evaluated the design specifications of THz detectors considering both responsivity and noise equivalent power (NEP) as the typical performance metrics. The proposed methodologies provide the physical design platform for developing novel plasmonic THz detectors operating in the nonresonant detection mode.

Plasmonic terahertz detection by a double-grating-gate field-effect transistor structure with an asymmetric unit cell

Plasmonic terahertz detection by a double-grating gate field-effect transistor structure with an asymmetric unit cell is studied theoretically. Detection responsivity exceeding 8 kV/W at room temperature in the photovoltaic response mode is predicted for strong asymmetry of the structure unit cell. This value of the responsivity is an order of magnitude greater than reported previously for the other types of uncooled plasmonic terahertz detectors. Such enormous responsivity can be obtained without using any supplementary antenna elements because the double-grating gate acts as an aerial matched antenna that effectively couples the incoming terahertz radiation to plasma oscillations in the structure channel.

A plasmonic terahertz detector with a monolithic hot electron bolometer

A plasmonic terahertz detector that integrates a voltage-controlled planarbarrier into a grating gated GaAs/AlGaAs high electron mobility transistor hasbeen fabricated and experimentally characterized. The plasmonic response atfixed grating gate voltage has a full width at half-maximum of 40 GHz at∼405 GHz. Substantially increased responsivity is achieved by introducing an independentlybiased narrow gate that produces a lateral potential barrier electrically in series with theresonant grating gated region. DC electrical characterization in conjunction withbias-dependent terahertz responsivity and time constant measurements indicate thata hot electron bolometric effect is the dominant response mechanism at 20 K.

Plasmonic terahertz detectors for biodetection

A report is presented on the biodetection capabilities of plasmonic terahertz detectors. Large changes in the terahertz response of plasmonic detectors loaded with solutions of globulin-free bovine serum albumin, arginine and heparin were measured for concentrations that did affect the device transfer characteristics. The consistent change of the response characteristics with specimen type and concentration can be used to identify and quantify biological and chemical substances. The device structure makes it suitable for use as a building block of a biochip with integrated processing capabilities.

Enhanced responsivity in membrane isolated split-grating-gate plasmonic terahertz detectors

A 50-fold increase in responsivity of plasmon resonant detectors is achieved by thermally isolating the detector on a thin membrane. Terahertz radiation is resonantly absorbed in the grating-gated channel while temperature modulation is sensed by the resistance of a narrow center region biased to pinch off. Thermal isolation enhances the temperature rise on absorption. Detectors with and without the additional thermal isolation demonstrate a linear power dependence.