Additional Gate Electrode Research Articles

Design and analysis of central gate organic thin film transistor

Abstract This paper presents a novel central gate organic thin-film transistor (OTFT) with electrodes in top-bottom configuration and its comparative performance analysis with conventional single and dual gate OTFTs. The central gate OTFT is comprised of a single gate electrode configured to be the center thin film. A pair of identical dielectric layers viz. top dielectric layer and a bottom dielectric layer on both sides of gate electrode to facilitate the further deposition top and bottom organic semiconductor layer over them respectively. The organic semiconductor layers (OSC) are configured as top OSC layer and a bottom OSC to accommodate two independent conduction channels. The source and drain electrodes are also deposited in pairs in top and bottom configurations. Due to the subtle modifications in the architecture the resultant output drain current of the central gate (CG) OTFT has increased manifold. It has been found in the study that the CG OTFT produces 94%, 76.36%, 80.58% higher drain current than bottom gate bottom contact (BGBC), top gate bottom contact (TGBC) and bottom gate top contact (BGTC) OTFT respectively of similar size, operating under identical voltage regime. Similarly in the case of dual gate (DG) OTFT an improvement of 5.10% has been recorded without any additional gate electrode at the same operating voltages.

Frequency Response of a Six-Electrode MET Sensor at Extremely Low Temperatures.

Four-electrode electrochemical cells are widely used for signal conversion in molecular-electronic transfer (MET) motion sensors. The most used ACCA (anode-cathode-cathode-anode) configuration has proven its performance and usefulness for obtaining a superior conversion factor and a wider frequency range over standard geophones at room temperature. However, the MET sensor conversion factor decreases a thousand-fold or more when the temperature drops from room temperature to 233 K. In the design suggested is this paper, a pair of additional gate (G) electrodes has been added outside the standard ACCA cell. An experimental study of the temperature behavior of the resulting G-ACCA-G six-electrode configuration showed that the effects of temperature changes on the cell conversion factor are 5.2 times weaker compared with the standard ACCA configuration.

Time-Dependent Sensitivity Tunable pH Sensors Based on the Organic-Inorganic Hybrid Electric-Double-Layer Transistor.

In this study, we propose tunable pH sensors based on the electric-double-layer transistor (EDLT) with time-dependent sensitivity characteristics. The EDLT is able to modulate the drain current by using the mobile ions inside the electrolytic gate dielectric. This property allows the implementation of a device with sensitivity characteristics that are simply adjusted according to the measurement time. An extended gate-type, ion-sensitive, field-effect transistor consisting of a chitosan/Ta2O5 hybrid dielectric EDLT transducer, and an SnO2 sensing membrane, were fabricated to evaluate the sensing behavior at different buffer pH levels. As a result, we were able to achieve tunable sensitivity by only adjusting the measurement time by using a single EDLT and without additional gate electrodes. In addition, to demonstrate the unique sensing behavior of the time-dependent tunable pH sensors based on organic–inorganic hybrid EDLT, comparative sensors consisting of a normal FET with a SiO2 gate dielectric were prepared. It was found that the proposed pH sensors exhibit repeatable and stable sensing operations with drain current deviations <1%. Therefore, pH sensors using a chitosan electrolytic EDLT are suitable for biosensor platforms, possessing tunable sensitivity and high-reliability characteristics.

Field-effect silicon-plasmonic photodetector for coherent T-wave reception

Plasmonic internal photoemission detectors (PIPED) have recently been shown to combine compact footprint and high bandwidth with monolithic co-integration into silicon photonic circuits, thereby opening an attractive route towards optoelectronic generation and detection of waveforms in the sub-THz and THz frequency range, so-called T-waves. In this paper, we further expand the PIPED concept by introducing a metal-oxide-semiconductor (MOS) interface with an additional gate electrode that allows to control the carrier dynamics in the device and the degree of internal photoemission at the metal-semiconductor interfaces. We experimentally study the behavior of dedicated field-effect (FE-)PIPED test structures and develop a physical understanding of the underlying principles. We find that the THz down-conversion efficiency of FE-PIPED can be significantly increased when applying a gate potential. Building upon the improved understanding of the device physics, we further perform simulations and show that the gate field increases the carrier density in the conductive channel below the gate oxide to the extent that the device dynamics are determined by ultra-fast dielectric relaxation rather than by the carrier transit time. In this regime, the bandwidth can be increased to more than 1 THz. We believe that our experiments open a new path towards understanding the principles of internal photoemission in plasmonic structures, leading to PIPED-based optoelectronic signal processing systems with unprecedented bandwidth and efficiency.

High-Performance Quantum-Dot Light-Emitting Transistors Based on Vertical Organic Thin-Film Transistors.

In this work, a novel vertical quantum-dot light-emitting transistor (VQLET) based on a vertical organic thin-film transistor is successfully fabricated. Benefiting from the new vertical architecture, the VQLET is able to afford an extremely high current density, which allows most of the organic thin film transistors (OTFT) even with low mobility (for instance, poly(3-hexylthiophene)) to drive a quantum-dot light-emitting diode (QLED), which was previously unavailable. Moreover, the hole injection barrier could be modulated by the additional gate electrode, which precisely optimizes the charge balance in the device, a critical issue in QLED, resulting in the precise control of current density and brightness of the VQLET. The VQLET shows a high performance with a maximum current efficiency of 37 cd/A. Furthermore, integrating OTFT and QLED into a single device, the VQLET features drastic advantages by realizing active matrix quantum-dot light-emitting diodes (AMQLEDs), which significantly reduces the number of transistors and frees the large area fraction occupied by transistors. Hence, these results indicate that the VQLET provides a new strategy for realizing a low-cost, solution-processed, high-performance OTFT-AMQLED for the flat panel display technology. Moreover, the novel design offers a unique method to exquisitely control the charge balance and maximize the efficiency the QLED.

Opposite translocation of long and short oligomers through a nanopore

We consider elongated cylindrical particles, modeling, e.g., DNA fragments or nanorods, while they translocate under the action of an externally applied voltage through a solid state nanopore. Particular emphasis is put on the concomitant potential energy landscape encountered by the particle on its passage through the pore due to the complex interplay of various electrohydrodynamic effects beyond the realm of small Debye lengths. We find that the net potential energy difference across the membrane may be of opposite sign for short and long particles of equal diameters and charge densities (e.g., oligomers). Thermal noise thus leads to biased diffusion through the pore in opposite directions. By means of an additional membrane gate electrode it is even possible to control the specific particle length at which this transport inversion occurs.

An AC-assisted single-nanowire electromechanical switch

A unique two-source controlled nanoelectromechanical switch has been assembled from individual, single-clamped Ge nanowires. The switching behaviour was achieved by superimposing the control signals of specific frequencies to the electrostatic potential of the output terminals, eliminating the need for an additional gate electrode. Using an in situ manipulation technique inside a scanning electron microscope, we demonstrate that the pull-out force required to overcome adhesion at the contact can be significantly reduced by exciting mechanical resonant modes within the nanowire.

An electrostatic gate for mechanically controlled single-molecule junctions

We present a fabrication scheme for a tunable single-molecule transistor that allows for controlling the electrode separation and provides an electrostatic gate. The experimental approach is based on the mechanically controlled break junction technique but integrates an additional bottom gate electrode and an uninterrupted high-κ gate dielectric. The device performance is demonstrated for a single-molecule junction showing Coulomb blockade characteristics.

Out-of-equilibrium admittance of single electron box under strong Coulomb blockade

We study admittance and energy dissipation in an out-of-equlibrium single electron box. The system consists of a small metallic island coupled to a massive reservoir via single tunneling junction. The potential of electrons in the island is controlled by an additional gate electrode. The energy dissipation is caused by an AC gate voltage. The case of a strong Coulomb blockade is considered. We focus on the regime when electron coherence can be neglected but quantum fluctuations of charge are strong due to Coulomb interaction. We obtain the admittance under the specified conditions. It turns out that the energy dissipation rate can be expressed via charge relaxation resistance and renormalized gate capacitance even out of equilibrium. We suggest the admittance as a tool for a measurement of the bosonic distribution corresponding collective excitations in the system.

Reduced contact resistances in organic transistors with secondary gates on source and drain electrodes

Secondary-gate electrodes under source and drain electrodes are introduced in organic thin-film transistors to reduce carrier-injection barriers into air-stable organic semiconductors. The additional gate electrodes buried in the gate insulators form “carrier-rich regions” in the vicinity of the source and drain electrodes with the application of sufficiently high local electric fields. Fabricating the structure with dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene, known for its excellent air stability, the contact resistance is drastically reduced especially at low gate voltages in the main channel. The result demonstrates carrier injection from the same material realizing a minimized potential barrier in the absence of interfacial trap levels for metal-to-semiconductor junctions.

Effects of Charging Energy on SINIS Tunnel Junction Thermometry

We have investigated theoretically the effects of the charging energy to the normal metal--insulator--superconductor (NIS) tunnel junction used as a thermometer. We demonstrate by numerical calculations how the charging effects modify NIS thermometry, and how the voltage--to--temperature response and the responsivity $|dV/dT|$ of a current biased thermometer are affected. In addition, we show that the responsivity of the thermometer can be modulated with an additional gate electrode. The maximum responsivity is achieved when the Coulomb blockade is maximal, i.e. with a closed gate.

Reduced Contact Resistances in Organic Transistors with Secondary Gates on Source and Drain Electrodes

AbstractSecondary-gate electrodes are introduced in organic thin-film transistors to reduce carrier-injection barriers into air-stable organic semiconductors. The additional gate electrodes buried in the gate insulators under the source and drain electrodes form “carrier-rich regions” in the vicinity of source and drain electrodes with the application of sufficiently high local electric fields. Fabricating the structure with dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene, known for its excellent air-stability, it turned out that the contact resistance is drastically reduced especially when operated at low gate voltage in the main channel. The result demonstrates carrier injection with a minimized potential barrier realizing that from the same semiconductor material in the absence of peculiar interfacial trap levels at metal-to-semiconductor junctions.

Electronic properties of 1-4, dicyanobenzene and 1-4, phenylene diisocyanide molecules contacted between Pt and Pd electrodes: First-principles study

Using first-principles calculations, we study the electronic properties of 1-4, dicyanobenzene and 1-4, phenylene diisocyanide molecules sandwiched between two Pt(111) and Pd(111) electrodes. For these metal-molecule-metal systems, we calculate the total and local density of states and the charge transfers. Our results suggest that the tunneling is the dominant mechanism of charge transport. By inducing a shift of the Fermi level of about 2 eV via an additional gate electrode, the electronic transmission could be significantly increased through the metal-1-4, phenylene diisocyanide-metal systems, but a higher voltage would be required in the metal-1-4, dicyanobenzene-metal devices.

Control of Subthreshold Characteristics of Narrow-Channel Silicon-on-Insulator n-Type Metal–Oxide–Semiconductor Transistor with Additional Side Gate Electrodes

A silicon-on-insulator (SOI) n-type metal–oxide–semiconductor (MOS) transistor with additional side gate electrodes is fabricated and its subthreshold characteristics are discussed. Since its device structure provides independent biasing to gates, flexible device-characteristic control for the respective device is expected. The key fabrication process is the formation of transistor gates. Additional side gate electrodes are formed by reactive ion etching (RIE) with a SiO2-covered top gate as an etching mask. Subthreshold characteristics are improved by negative side-gate biasing. In addition, the side-gate voltage VSG required to decrease off-leakage current by one decade is around 100 mV. Since the sidewall oxide thickness is chosen to be 5 nm, which is the same as the top-oxide thickness, rather sensitive subthreshold-characteristic control compared with that of biasing through a thick buried-oxide layer is achieved in response to performance requirement. In the viewpoint of stand-by-power suppression, these provide a certain controllability to a circuit operation.

Silicon single-electron transistors with sidewall depletion gates and their application to dynamic single-electron transistor logic

Novel single-electron transistors (SETs) with side-wall depletion gates on a silicon-on-insulator nanometer-scale wire are proposed and fabricated, using the combination of the conventional lithography and process technology. Clear Coulomb oscillation originated from the two electrically induced tunnel junctions and the single Si island between them is observed at 77 K. The island size dependence of the electrical characteristics shows the good controllability and reproducibility of the proposed fabrication method. Furthermore, the device characteristics are immune to gate bias conditions, and the position of Coulomb oscillation peak is controlled by the sidewall depletion gate voltage, without the additional gate electrode. Based on the current switching by sidewall gate voltage, the basic operation of the dynamic four-input multifunctional SET logic circuit is demonstrated at 10 K. The proposed SET offers the feasibility of the device design and optimization for SET logic circuits, in that its device parameters and circuit parameters are controllable by the conventional VLSI technology.

Gated delta -layer structures

A theoretical description of a single non-compensated delta -layer with an additional gate electrode is presented. For layers with varying impurity density, the energy level positions, electron concentrations and mobilities in different subbands as well as the net layer conductivity have been calculated as functions of applied depleting voltage phi 0. Changing the number of the energy levels in a quantum well and transforming the electron wavefunctions, the voltage produces a specific transconduction versus phi 0 dependence in the structure.

Field-Induction-Drain Thin-Film Transistors for Liquid-Crystal Display Applications

A field-induction-drain (FID) poly-Si thin-film transistor (TFT), in which an electrically induced layer is used as a drain, is proposed. This TFT achieves a low OFF current and a high ON/OFF current ratio by simply incorporating an additional gate electrode. Moreover, the structure can be modified to make it suitable for complementary MOS (CMOS) applications. In this unified-structure FID (UFID) TFT, n-channel operation and p-channel operation are interchangeable. This paper presents this electrically induced layer which works well as a TFT drain and has beneficial influence on TFT characteristics.

Noise contribution of the offset-gate i.g.f.e.t. with an additional gate electrode

The 1/f noise power of the offset-gate i.g.f.e.t. with an additional gate electrode (i.g.t.) is, under certain bias conditions, considerably lower in comparison to the full-gate i.g.f.e.t. of similar dimensions. This behaviour can be explained by a field dependent 1/f noise component from the pinchoff region. The i.g.t. allows the separation of the 1/f noise from the channel region and from the pinchoff region.