Dual-gate Transistor Research Articles

Моделирование передаточных характеристик двухзатворных полевых графеновых транзисторов

Моделирование передаточных характеристик двухзатворных полевых графеновых транзисторов

Dual-gate organic phototransistor with high-gain and linear photoresponse

The conversion of light into electrical signal in a photodetector is a crucial process for a wide range of technological applications. Here we report a new device concept of dual-gate phototransistor that combines the operation of photodiodes and phototransistors to simultaneously enable high-gain and linear photoresponse without requiring external circuitry. In an oppositely biased, dual-gate transistor based on a solution-processed organic heterojunction layer, we find that the presence of both n- and p-type channels enables both photogenerated electrons and holes to efficiently separate and transport in the same semiconducting layer. This operation enables effective control of trap carrier density that leads to linear photoresponse with high photoconductive gain and a significant reduction of electrical noise. As we demonstrate using a large-area, 8 × 8 imaging array of dual-gate phototransistors, this device concept is promising for high-performance and scalable photodetectors with tunable dynamic range.

Vertical ITO/SiOX/a-Si:H Photodiode-Gated Low-Temperature Polycrystalline Silicon Thin-Film Transistor Intended for In-Display Fingerprint Imaging Applications

To embed an active pixel optical sensor in a display pixel for fingerprint imaging, an area-efficient and vertical ITO/SiOX/a-Si:H photodiode-gated low-temperature polycrystalline silicon dual-gate thin-film transistor with controllable photosensitivity is proposed and experimentally demonstrated. The device can be operated as a driving switch to the display pixel, and the driving current is insensitive to normal ambient light; the device can also be operated as an optical sensor, which provides 8 bits of effective data and reasonable detectable intensity range. The compact structure and dual-mode operation make it a promising solution to in-display, large-area fingerprint identification for smartphones.

(Invited) 3D Monolithic Integration in Flexible Organic Printed Transistors

Despite the significant enhancements in material properties such as carrier mobility, few attempts have been made to print organic integrated circuits (ICs). The relatively large size of printed features (typically 10 μm – 100 μm) have limited the implementation of organic ICs with reasonable transistor densities. To overcome the limitation, we introduce three-dimensional (3D) integration of inkjet-printed organic transistors and circuits. We fabricated a p-type organic field-effect transistor that is inkjet-printed on top of an n-type organic field-effect transistor with a shared gate joining the two transistors. Based on the common-gate transistor-on-transistor structure, a complementary inverter array is fabricated with a high static noise margin and reliable characteristics. We have further developed 3D integration of a dual-gate NAND technology fabricated by printing technique with a demonstration of flexible logic circuits. The vertical stacking of independent-gate controlled dual gate transistors offers enhanced on-current, lowered sub-threshold swing, increased device stability and density. The present study fulfills the essential requirements for the fabrication of organic printed complex ICs, and the findings can be applied to realize more complex digital/analogue ICs and intelligent devices

Dual-gate MoS2 transistors with sub-10 nm top-gate high-k dielectrics

High quality sub-10 nm high-k dielectrics are deposited on top of MoS2 and evaluated using a dual-gate field effect transistor configuration. Comparison between top-gate HfO2 and an Al2O3/HfO2 bilayer shows significant improvement in device performance due to the insertion of the thin Al2O3 layer. The results show that the Al2O3 buffer layer improves the interface quality by effectively reducing the net fixed positive oxide charge at the top-gate MoS2/high-k dielectric interface. Dual-gate sweeping, where both the top-gate and the back-gate are swept simultaneously, provides significant insight into the role of these oxide charges and improves overall device performance. Dual-gate transistors encapsulated in an Al2O3 dielectric demonstrate a near-ideal subthreshold swing of ∼60 mV/dec and a high field effect mobility of 100 cm2/V·s.

Dual-Gated Transistor Platform for On-Site Detection of Lead Ions at Trace Levels.

On-site monitoring of heavy metals in drinking water has become crucial because of several high profile instances of contamination. Presently, reliable techniques for trace level heavy metal detection are mostly laboratory based, while the detection limits of contemporary field-based methods are barely meeting the exposure limits set by regulatory bodies such as the World Health Organization (WHO). Here, we show an on-site deployable, Pb2+ sensor on a dual-gated transistor platform whose lower detection limit is 2 orders of magnitude better than the traditional sensor and 1 order of magnitude lower than the exposure limit set by WHO. The enhanced sensitivity of our design is verified by numerically solving PNP (Planck-Nernst-Poisson) model. We demonstrate that the enhanced sensitivity is due to the suppression of ionic flux. The simplicity and the robustness of the design make it applicable for on-site screening, thereby facilitating rapid response to contamination events.

A Wearable Piezoelectric Energy Harvester Rectified by a Dual-Gate Thin-Film Transistor

This paper addresses a wearable piezoelectric energy harvester that combines a PVDF piezoelectric charge generator with an a-Si:H dual-gate thin-film transistor as a rectifier. An analytical model and equivalent circuit elaborate their working principle and device physics. A preliminary experimental study proves the device concept and demonstrates that such a harvester is capable of generating microwatt-range power with a simple 90° finger bending action. Coupled with low-cost and large-area fabrication processes, a pixelated energy-harvesting array can be potentially achievable, making it a promising alternative to energy sources for wearable electronics.

3-D Dual-Gate Photosensitive Thin-Film Transistor Architectures Based on Amorphous Silicon

In contrast to the conventional planar p-i-n photodiode and a metal-semiconductor–metal photodetector, the 3-D dual-gate photosensitive thin-film transistor (TFT) architectures presented here attain excellent photoresponse characteristics. Operating the device in the subthreshold regime further boosts the photoconductive gain as a result of light-induced decrease in the threshold voltage. This paper presents design considerations along with a performance comparison between 3-D photosensitive TFTs that have $\pi $ - and FIN-shaped channels and conventional TFT with a planar channel. Our paper shows that the $\pi $ -shaped structure tends to have a higher sensitivity while the FIN-shaped counterpart is more responsive with wider dynamic range. For both structures, a measured photoconductive gain of $10^{\textsf {4}} \sim 10^{\textsf {6}}$ % is obtained with spectral responsivity ranging from near UV to near IR, and the photoresponse time in the range of tens of milliseconds. The 3-D dual-gate photosensitive TFT architecture appears to be very promising for large-area, low-level UV, visible, and IR detection applications.

Direct evidence of hidden local spin polarization in a centrosymmetric superconductor LaO0.55 F0.45BiS2

Conventional Rashba spin polarization is caused by the combination of strong spin–orbit interaction and spatial inversion asymmetry. However, Rashba–Dresselhaus-type spin-split states are predicted in the centrosymmetric LaOBiS2 system by recent theory, which stem from the local inversion asymmetry of active BiS2 layer. By performing high-resolution spin- and angle-resolved photoemission spectroscopy, we have investigated the electronic band structure and spin texture of superconductor LaO0.55F0.45BiS2. Here we present direct spectroscopic evidence for the local spin polarization of both the valence band and the conduction band. In particular, the coexistence of Rashba-like and Dresselhaus-like spin textures has been observed in the conduction band. The finding is of key importance for fabrication of proposed dual-gated spin-field effect transistor. Moreover, the spin-split band leads to a spin–momentum locking Fermi surface from which superconductivity emerges. Our demonstration not only expands the scope of spintronic materials but also enhances the understanding of spin–orbit interaction-related superconductivity.

Liquid-Solid Dual-Gate Organic Transistors with Tunable Threshold Voltage for Cell Sensing.

Liquid electrolyte-gated organic field effect transistors and organic electrochemical transistors have recently emerged as powerful technology platforms for sensing and simulation of living cells and organisms. For such applications, the transistors are operated at a gate voltage around or below 0.3 V because prolonged application of a higher voltage bias can lead to membrane rupturing and cell death. This constraint often prevents the operation of the transistors at their maximum transconductance or most sensitive regime. Here, we exploit a solid-liquid dual-gate organic transistor structure, where the threshold voltage of the liquid-gated conduction channel is controlled by an additional gate that is separated from the channel by a metal-oxide gate dielectric. With this design, the threshold voltage of the "sensing channel" can be linearly tuned in a voltage window exceeding 0.4 V. We have demonstrated that the dual-gate structure enables a much better sensor response to the detachment of human mesenchymal stem cells. In general, the capability of tuning the optimal sensing bias will not only improve the device performance but also broaden the material selection for cell-based organic bioelectronics.

Design of Low Complexity Accumulator Using Finfet for Various Technologies

Abstract FINFET terminological in exactitude process reuses a massive part of well accustomed conventional CMOS process. FINFET is a likely-look alternative to conventional MOSFET which has reached its limit and has too much leakage for too little performance gain. FINFET is being suggested as basics for future IC processes because its power or performance benefits, scalability, superior controls over short channel effort etc., In this paper we propose a outlook for scheming accumulator using FINFET for purpose of minimize number of transistor differentiate to CMOS logic. In circuit level, widely used D flip-flop and at constructional level the full adder cells of FINFET (dual gate transistor) 10T can be used. FINFET is the most propitious double gate transistor, forecast as one of the candidate to restore the epic MOSFET. FINFET technology power consumption is compare with CMOS technology to analyze how the area, delay and power can be reduced.

Dual-gate low-voltage organic transistor for pressure sensing

We simultaneously achieved low-voltage operation (−5 V) and large drain current (ID) modulation in a dual-gate organic pressure sensor in which a piezoelectric layer was stacked on a low-voltage organic field-effect transistor (OFET). During testing, ID changed from 3.9 × 10−9 to 2.5 × 10−11 A when a 300 kPa pressure load was applied, and ID clearly responded to the pressure load and release. An endurance cycle test of the device was performed using a pressure load of 100 kPa, and the ID modulation was consistently reproduced throughout the test.

Variations of Contact Resistance in Dual-Gated Monolayer Molybdenum Disulfide Transistors Depending on Gate Bias Selection

Monolayer molybdenum disulfide (MoS2) is considered an alternative two-dimensional material for high performance ultra-thin field-effect transistors. MoS2 is a triple atomic layer with a direct 1.8 eV bandgap. Bulk MoS2 has an additional indirect bandgap of 1.2 eV, which leads to high current on/off ratio around 108. Flakes of MoS2 can be obtained by mechanical exfoliation or grown by chemical vapor deposition. Intrinsic cut-off frequency of multilayer MoS2 transistor has reached 42 GHz. Chemical doping of MoS2 is challenging and results in reduction of contact resistance. This paper focuses on modeling of dual-gated monolayer MoS2 transistors with effective mobility of carriers varying from 0.6 cm2/V s to 750 cm2/V s. In agreement with experimental data, the model demonstrates that in back-gate bias devices, the contact resistance decreases almost exponentially with increasing gate bias, whereas in top-gate bias devices, the contact resistance stays invariant when varying gate bias.

Improved sensing characteristics of dual-gate transistor sensor using silicon nanowire arrays defined by nanoimprint lithography

This work describes the construction of a sensitive, stable, and label-free sensor based on a dual-gate field-effect transistor (DG FET), in which uniformly distributed and size-controlled silicon nanowire (SiNW) arrays by nanoimprint lithography act as conductor channels. Compared to previous DG FETs with a planar-type silicon channel layer, the constructed SiNW DG FETs exhibited superior electrical properties including a higher capacitive-coupling ratio of 18.0 and a lower off-state leakage current under high-temperature stress. In addition, while the conventional planar single-gate (SG) FET- and planar DG FET-based pH sensors showed the sensitivities of 56.7 mV/pH and 439.3 mV/pH, respectively, the SiNW DG FET-based pH sensors showed not only a higher sensitivity of 984.1 mV/pH, but also a lower drift rate of 0.8% for pH-sensitivity. This demonstrates that the SiNW DG FETs simultaneously achieve high sensitivity and stability, with significant potential for future biosensing applications.

Gate-Tunable Landau Level Filling and Spectroscopy in Coupled Massive and Massless Electron Systems.

We report transport studies on coupled massive and massless electron systems, realized using twisted monolayer-graphene-natural bilayer-graphene stacks. We incorporate the layers in a dual-gated transistor geometry enabling independently tuning their charge density and the perpendicular electric field. In a perpendicular magnetic field, we observe a distinct pattern of gate-tunable Landau level crossings. Screening and interlayer electron-electron interactions yield a nonlinear monolayer gate capacitance. Data analysis enables determination of the monolayer's Fermi velocity and the bilayer's effective mass. The mass obtained is larger than that expected for isolated bilayers, suggesting that the interlayer interactions renormalize the band structure.

Time-dependent simulation of particle and displacement currents in THz graphene transistors

Although time-independent models provide very useful dynamical information with a reduced computational burden, going beyond the quasi-static approximation provides enriched information when dealing with terahertz (THz) frequencies. In this work, the THz noise of dual-gate graphene transistors with DC polarization is analyzed from a careful simulation of the time-dependent particle and displacement currents. From such currents, the power spectral density (PSD) of the total current fluctuations are computed at the source, drain and gate contacts. The role of the lateral dimensions of the transistors, the Klein tunneling and the positive–negative energy injection on the PSD are analyzed. Through the comparison of the PSD with and without band-to-band tunneling and graphene injection, it is shown that the unavoidable Klein tunneling and positive–negative energy injection in graphene structures imply an increment of noise without similar increment on the current, degrading the (either low or high frequency) signal-to-noise ratio. Finally, it is shown that the shorter the vertical height (in comparison with the length of the active region in the transport direction), the larger the maximum frequency of the PSD. As a byproduct of this result, an alternative strategy (without length scaling) to optimize the intrinsic cut-off frequency of graphene transistors is envisioned.

Dual-gate polysilicon nanoribbon biosensors enable high sensitivity detection of proteins

We demonstrate the advantages of dual-gate polysilicon nanoribbon biosensors with a comprehensive evaluation of different measurement schemes for pH and protein sensing. In particular, we compare the detection of voltage and current changes when top- and bottom-gate bias is applied. Measurements of pH show that a large voltage shift of 491 mV pH−1 is obtained in the subthreshold region when the top-gate is kept at a fixed potential and the bottom-gate is varied (voltage sweep). This is an improvement of 16 times over the 30 mV pH−1 measured using a top-gate sweep with the bottom-gate at a fixed potential. A similar large voltage shift of 175 mV is obtained when the protein avidin is sensed using a bottom-gate sweep. This is an improvement of 20 times compared with the 8.8 mV achieved from a top-gate sweep. Current measurements using bottom-gate sweeps do not deliver the same signal amplification as when using bottom-gate sweeps to measure voltage shifts. Thus, for detecting a small signal change on protein binding, it is advantageous to employ a double-gate transistor and to measure a voltage shift using a bottom-gate sweep. For top-gate sweeps, the use of a dual-gate transistor enables the current sensitivity to be enhanced by applying a negative bias to the bottom-gate to reduce the carrier concentration in the nanoribbon. For pH measurements, the current sensitivity increases from 65% to 149% and for avidin sensing it increases from 1.4% to 2.5%.

A Numerical Study of an Amorphous Silicon Dual-Gate Photo Thin-Film Transistor for Low-Dose X-Ray Imaging

The amorphous silicon flat panel X-ray detector (FPD) has gained significant adoption in digital radiography such as chest radiography due to its large size and superior performance. As a fundamental building block of a FPD, the pixel is composed of sensor, storage and readout units to collect charges and transfer them to external electronics. In all current pixel architectures, however, these three aforementioned components are unanimously separate. It would inevitably compromise spatial resolution due to increased pixel size. Thus, we propose a compact design of a “smart” pixel to combine sensor, storage and readout units into one single dual-gate photo thin-film transistor (TFT). Simulation results indicated that an implementation of a $\pi$ -shape channel structure would enhance photo absorption and preserve switching performance as well. The sensitivity of the device is dependent on the threshold voltage shift induced by light illumination, which in turn enlarges the photocurrent. A numerical study also showed a total noise of approximately ${\sim} {\hbox{700}}$ e and a dynamic range of 120 dB can be achieved, which potentially outperforms current available amorphous silicon passive pixel sensor. The “smart” pixel therefore holds a great promise for high-resolution and low-dose X-ray imaging, which may potentially reduce the cancer risk induced by X-ray radiation, especially for pediatric patients.

Dual-gated BN-sandwiched multilayer graphene field-effect transistor fabricated by stamping transfer method and self-aligned contact

To fabricate a BN-sandwiched multilayer graphene field-effect transistor, we developed a self-aligned contact scheme in combination with optimized stamping processes for the stacking of two-dimensional (2D) materials. By using a self-aligned contact method during device fabrication, we can skip the dry-etch process which requires an exact etch-stop at the surface of the graphene layer and is not easy to control. In the structure of a dual-gate transistor, successful device operation at low temperature with and without magnetic fields proves that the self-alignment contact can be an effective tool for reliable device fabrication using 2D materials.

A New Electroluminescent Organic Dual-Gate Field-Effect Transistor

In this letter, we show a new device architecture, which we call field-induced contacts light-emitting transistor (FICOLET), to fabricate high-efficiency electroluminescent dual-gate organic field-effect transistors. The FICOLET is a dual-gate transistor in which two accumulated regions, not completely overlapped, one of electrons and the other of holes, are formed. When a positive bias voltage is applied to the drain contact, electrons and holes are pushed by the combined action of the carrier diffusion and of the electric field to the opposite side of the semiconductor. They recombine far from the electrodes with a theoretical recombination efficiency of 100%, low exciton quenching, and current densities that, in high injection conditions, can exceed the lasing threshold.