Plasmonic Field Effect Transistors Research Articles

Compact Spice Models for Terafets

Field effect transistors (FETs) in plasmonic regimes of operation could detect terahertz (THz) radiation and operate as THz interferometers, spectrometers, frequency-to-digital converters and THz modulators and sources. We report on the development of compact models for Si MOS (Metal-Oxide-semiconductor) and heterostructure-based plasmonic FETs (or TeraFETs) suitable for circuit design in the THz range and based on the multi-segment unified charge control model. This model accounts for the electron inertia effect (by incorporating segmented Drude inductances), for the ballistic field effect mobility, which is proportional to the channel length, for parasitic resistances and capacitances and for the leakage current. It is validated by comparison with experimental data and TCAD simulation results. The model can be used for simulation and optimization of sub-THz and THz detectors. Our simulations use up to 200 segments in the device channel. The results are also in good qualitative agreement with the hydrodynamic simulations. Applications of our model could dramatically reduce astronomical design costs of nanoscale VLSI reaching US$1.5 billion for the 3 nm technological node.

A Roadmap toward the Thematic Design of Plasmonic Field Effect Transistors: Crossing the Milestones

AbstractRecently, nano‐optics have attracted immense interest among researchers for the design of all‐optical devices to fulfill the ongoing demands of sustainable energy. Plasmonics of nanoscale materials can be employed to manipulate, guide, and convert ambient electromagnetic radiation to elevate the present state‐of‐the‐art in energy technology. To meet the clean energy challenges that lie ahead, it is indispensable to imbue preconceived notions of the electromagnetic configurations emerging from a set of physical observables that define the plasmonic states of the nanosystem. In this work, a set of hypothetical two‐dimensional plasmonic lattices formed with periodically interdigitated gold nanorods having different geometries and orientations is used as a top layer to simulate the carrier densities of field effect transistors (FETs) as a function of their near‐field potentials within the limit of classical electromagnetism. Based on these considerations, theoretically, a set of principles for the strategic design of different symmetric motifs is illustrated that can increase the effective path length of carriers through strong electromagnetic field confinement to achieve the desired enhancement of the photocurrent of a FET. In essence, the work demonstrates a protocol to design a plasmonic top layer for the maximization of gain voltage of an FET by manipulating the on‐chip local field through plasmonic coupling, giving a new pathway to designing plasmonic FETs.

THz detection and amplification using plasmonic field effect transistors driven by DC drain currents

We report on the numerical and theoretical results of sub-THz and THz detection by a current-driven InGaAs/GaAs plasmonic field-effect transistor (TeraFET). New equations are developed to account for the channel length dependence of the drain voltage and saturation current. Numerical simulation results demonstrate that the effect of drain bias current on the source-to-drain response voltage (dU) varies with the device channel length. In a long-channel TeraFET where plasmonic oscillations cannot reach the drain, dU is always positive and rises rapidly with increasing drain current. For a short device in which plasmonic oscillations reach the drain, the current-induced nonuniform electric field leads to a negative response, agreeing with previous observations. At negative dU, the amplitude of the small-signal voltage at the drain side becomes larger than that at the source side. Thus, the device effectively serves as a THz amplifier in this condition. Under the resonant mode, the negative response can be further amplified near the resonant peaks. A new expression of dU is proposed to account for this resonant effect. Based on those expressions, a current-driven TeraFET spectrometer is proposed. The ease of implementation and simplified calibration procedures make it competitive or superior compared with other TeraFET-based spectrometers.

Frequency to digital conversion using Si TeraFETs

Our simulations using the validated multisegment simulation program with integrated circuit emphasis (SPICE) model show that the terahertz (THz) spectrometers using plasmonic field effect transistors could be used for the frequency to digital conversion. The THz SPICE unified charge control model that uses the distributed channel resistances, capacitances, and Drude inductances is validated by technology computer-aided design simulations. The THz spectrometers using Si plasmonic field effect transistors (or TeraFETs) determine the frequency of the impinging radiation by measuring the gate bias where the responsivity changes sign. This crossover frequency is sensitive to the channel length and nearly insensitive to the gate bias in the weak and moderate inversion regions. This unique feature allows the use of multiple THz spectrometers with different channel lengths to implement the frequency-to-digital converters in the sub-THz and THz frequency range. The simulations predict the operation frequency from 110 GHz up to 4 THz for the frequency-to-digital converters using Si TeraFETs with feature sizes from 20 to 130 nm.

Collision dominated, ballistic, and viscous regimes of terahertz plasmonic detection by graphene

The terahertz detection performance and operating regimes of graphene plasmonic field-effect transistors (FETs) were investigated by a hydrodynamic model. Continuous wave detection simulations showed that the graphene response sensitivity is similar to that of other materials including Si, InGaAs, GaN, and diamond-based FETs. However, the pulse detection results indicated a very short response time, which favors rapid/high-sensitively detection. The analysis on the mobility dependence of the response time revealed the same detection regimes as the traditional semiconductor materials, i.e., the non-resonant (collision dominated) regime, the resonant ballistic regime, and the viscous regime. When the kinematic viscosity (ν) is above a certain critical viscosity value, νNR, the plasmonic FETs always operates in the viscous non-resonant regime, regardless of channel length (L). In this regime, the response time rises monotonically with the increase of L. When ν < νNR, the plasmonic resonance can be reached in a certain range of L (i.e., the resonant window). Within this window, the carrier transport is ballistic. For a sufficiently short channel, the graphene devices would always operate in the non-resonant regime, regardless of the field-effect mobility, corresponding to another viscous regime. The above work mapped the operating regimes of graphene plasmonic FETs and demonstrated the significance of the viscous effects for the graphene plasmonic detection. These results could be used for the extraction of the temperature dependences of viscosity in graphene.

TCAD Model for TeraFET Detectors Operating in a Large Dynamic Range

We present technology computer-aided design (TCAD) models for AlGaAs/InGaAs and AlGaN/GaN and silicon TeraFETs, plasmonic field effect transistors (FETs), for terahertz (THz) detection validated over a wide dynamic range. The modeling results are in good agreement with the experimental data for the AlGaAs/InGaAs heterostructure FETs (HFETs) and, to the low end of the dynamic range, with the analytical theory of the TeraFET detectors. The models incorporate the response saturation effect at high intensities of the THz radiation observed in experiments and reveal the physics of the response saturation associated with different mechanisms for different material systems. These mechanisms include the gate leakage, the velocity saturation and the avalanche effect.

Field-effect transistor based on surface plasmon polaritons.

We investigate the working mechanism of a plasmon field-effect transistor (FET) based on the modulation of surface plasmon polariton (SPP) flow by varying an external electric field. SPP flow propagates at the surface of a metal strip waveguide embedded in a dielectric medium. The external electric field is applied to the metal electrode located under the isolated metal nanoplate placed in the middle of the strip waveguide. In this case, a signal on the control electrode changes the permittivity of the near-surface layer of the nanoplate. Thus, the control signal modulates the intensity of the SPP signal transmitted at the surface of the strip waveguide.

Exact Solution for Driven Oscillations in Plasmonic Field-Effect Transistors

High-mobility field effect transistors can serve as resonant detectors of terahertz radiation due to excitation of plasmons in the channel. The modeling of these devices previously relied either on approximate techniques, or complex full-wave simulations. In this paper, we obtain an exact solution for driven electrical oscillations in plasmonic field-effect transistor with realistic contact geometry. The obtained solution highlights the importance of evanescent plasma waves excited near the contacts, which qualitatively modify the detector responsivity spectra. We derive the boundary condition on the ac floating electrodes of plasmonic FET which interpolates between open-circuit (Dyakonov-Shur) and short-circuit (clamped voltage) boundary conditions. In both limits, the FET photovoltage possesses resonant fringes, however, the absolute value of voltage is greater in the open-circuit regime.

Efficient broadband energy detection from the visible to near-infrared using a plasmon FET

Plasmon based field effect transistors (FETs) can be used to convert energy induced by incident optical radiation to electrical energy. Plasmonic FETs can efficiently detect incident light and amplify it by coupling to resonant plasmonic modes thus improving selectivity and signal to noise ratio. The spectral responses can be tailored both through optimization of nanostructure geometry as well as constitutive materials. In this paper, we studied various plasmonic nanostructures using gold for a wideband spectral response from visible to near-infrared. We show, using empirical data and simulation results, that detection loss exponentially increases as the volume of metal nanostructure increases and also a limited spectral response is possible using gold nanostructures in a plasmon to electric conversion device. Finally, we demonstrate a plasmon FET that offers a broadband spectral response from visible to telecommunication wavelengths.

Utilization of surface plasmon resonance of Au/Pt nanoparticles for highly photosensitive ZnO nanorods network based plasmon field effect transistor

Hydrothermally processed highly photosensitive ZnO nanorods based plasmon field effect transistors (PFETs) have been demonstrated utilizing the surface plasmon resonance coupling of Au and Pt nanoparticles at Au/Pt and ZnO interface. A significantly enhanced photocurrent was observed due to the plasmonic effect of the metal nanoparticles (NPs). The Pt coated PFETs showed Ion/Ioff ratio more than 3 × 104 under the dark condition, with field-effect mobility of 26cm2V−1s−1 and threshold voltage of −2.7V. Moreover, under the illumination of UV light (λ = 350nm) the PFET revealed photocurrent gain of 105 under off-state (−5V) of operation. Additionally, the electrical performance of PFETs was investigated in detail on the basis of charge transfer at metal/ZnO interface. The ZnO nanorods growth temperature was preserved at 110°C which allowed a low temperature, economical and simple method to develop highly photosensitive ZnO nanorods network based PFETs for large scale production.

Efficient hot electron collection, detection, and amplification in plasmon field-effect transistor

Plasmon field-effect transistor is a hybrid device using nanostructures to detect the plasmonic energy. This device efficiently transfers plasmonic hot electrons from the metal nanostructures to the semiconductor. The transported hot electrons to the electron channel increases transistor drain current. We investigate the efficiency of plasmonic hot carrier harvesting between metal and semiconductor. We analyzed the effect of gold nanoparticle (NP) density and distribution on plasmon FET spectral response. Then, we studied electric field-assisted hot electron transfer and transport using different device structures. The position of plasmonic structures plays an important role in plasmonic energy detection efficiency because the gradient of electric field seen by induced hot electrons varies depending on the distance between drain and source. Both the experimental and simulation results confirm that by fabricating the gold NPs close to source the spectral response increases by 31% in comparison with having gold NPs close to the drain. Our simulation and experimental data suggest important design considerations to improve hot electron collection and conversion using metallic nanostructures for plasmonic energy harvesting.

Monitoring interfacial lectin binding with nanomolar sensitivity using a plasmon field effect transistor

By immobilizing glycopolymers onto the surface of the recently developed plasmonic field effect transistor (FET), the recognition between lectins and surface-immobilized glycopolymers can be detected over a wide dynamic range (10-10 to 10-4 M) in an environment that resembles the glycocalyx. The binding to the sensor surface by various lectins was tested, and the selectivities and relative binding affinity trends observed in solution were maintained on the sensor surface, and the significantly higher avidities are attributed to cluster-glycoside effects that occur on the surface. The combination of polymer surface chemistry and optoelectronic output in this device architecture produces amongst the highest reported detection sensitivity for ConA. This work demonstrates the benefits that arise from combining emerging device architectures and soft-matter systems to create cutting edge nanotechnologies that lend themselves to fundamental biological studies and integration into point-of-use diagnostics and sensors.

Plasmon Field Effect Transistor for Plasmon to Electric Conversion and Amplification.

Direct coupling of electronic excitations of optical energy via plasmon resonances opens the door to improving gain and selectivity in various optoelectronic applications. We report a new device structure and working mechanisms for plasmon resonance energy detection and electric conversion based on a thin film transistor device with a metal nanostructure incorporated in it. This plasmon field effect transistor collects the plasmonically induced hot electrons from the physically isolated metal nanostructures. These hot electrons contribute to the amplification of the drain current. The internal electric field and quantum tunneling effect at the metal-semiconductor junction enable highly efficient hot electron collection and amplification. Combined with the versatility of plasmonic nanostructures in wavelength tunability, this device architecture offers an ultrawide spectral range that can be used in various applications.

Terahertz Sensing Technology

Sensing applications of THz technology include applications for space exploration, detection of concealed objects, explosive identification, and THz cancer detection. This paper will review these and other emerging applications and existing and potential THz sources and detectors, including photonic and electronic THz devices, such as plasmonic field effect transistors capable of detecting and emitting THz radiation. Plasma wave electronics devices demonstrated THz detection using GaAs-based and GaN-based HEMTs, Si MOS, SOI, and FINFETs and FET arrays. This technology has potential to become a dominant THz electronics technology.

Tuning of plasmon propagation in two-dimensional electrons

It is shown theoretically that the propagation of plasmons can be tuned by an external electric field via spin-orbit interactions in a two-dimensional electron gas formed in a semiconductor heterostructure. This may provide a manageable way of transmitting quantum information in a quantum device. A possible plasmon field effect transistor is proposed.