Drain Current Response Research Articles

Voltage-modulated polymer nanopore field-effect transistor for multi-sized nanoparticle detection

Solid-state nanopores offer a range of distinct advantages over biological nanopores, such as structural diversity and greater stability and durability; this makes them highly promising for high-resolution nanoparticle sensing. Biological nanopores can exhibit gating characteristics with stress-responsive switches and can demonstrate specificity toward particular molecules. Drawing inspiration from biological nanopores, this paper introduces a novel polymer nanopore with field-effect characteristics, leveraging a conductive polymer in its construction to showcase intriguing gating behavior. Notably, in this device, the polymer layer serves as the gate, enabling precise control over the source–drain current response inside and outside the pore by simply adjusting the gate voltage. This unique feature allows fine-tuning of the nanopore’s sensitivity to nanoparticles of varying sizes and facilitates its operation in multiple modes. Experimental results reveal that the developed polymer nanopore field-effect transistor demonstrates remarkable selectivity in detecting nanoparticles of various sizes under different applied voltages. The proposed single device demonstrates the exceptional ability to detect multiple types of nanoparticle, showcasing its immense potential for a wide range of applications in biological-particle analysis and medical diagnostics.

Performance improvement in reservoir computing by using HfZrO2 FeFETs through operating voltage optimization

We have investigated how the parameters of an input gate voltage (V g) waveform and a drain voltage (V d) impact the performance of reservoir computing (RC) using a Hf0.5Zr0.5O2 ferroelectric FET (FeFET). The RC performance is maximized by the high swing amplitude of the V g and the most symmetrical polarization switching condition in the triangular-shaped input waveform, obtained by the center V g of 0.5 V, because of the enhanced polarization switching of the FeFETs. Regarding the V d dependence, the amount of the drain current and polarization switching have a trade-off relationship. As a result, a moderate V d of 1.0 V becomes optimum in terms of the RC performance because a difference in drain current responses between different gate input patterns is maximized with this V d. Furthermore, high computing capacities are achieved by combining the above optimal bias condition with drain current responses to both original and inverted gate input patterns.

Nonlinear Dynamics in HfO2/SiO2-Based Interface Dipole Modulation Field-Effect Transistors for Synaptic Applications

In the pursuit of energy-efficient spiking neural network (SNN) hardware, synaptic devices leveraging emerging memory technologies hold significant promise. This study investigates the application of the recently proposed HfO2/SiO2-based interface dipole modulation (IDM) memory for synaptic spike timing-dependent plasticity (STDP) learning. Firstly, through pulse measurements of IDM metal–oxide–semiconductor (MOS) capacitors, we demonstrate that IDM exhibits an inherently nonlinear and near-symmetric response. Secondly, we discuss the drain current response of a field-effect transistor (FET) incorporating a multi-stack IDM structure, revealing its nonlinear and asymmetric pulse response, and suggest that the degree of the asymmetry depends on the modulation current ratio. Thirdly, to emulate synaptic STDP behavior, we implement double-pulse-controlled drain current modulation of IDMFET using a simple bipolar rectangular pulse. Additionally, we propose a double-pulse-controlled synaptic depression that is valuable for optimizing STDP-based unsupervised learning. Integrating the pulse response characteristics of IDMFETs into a two-layer SNN system for synaptic weight updates, we assess training and classification performance on handwritten digits. Our results demonstrate that IDMFET-based synaptic devices can achieve classification accuracy comparable to previously reported simulation-based results.

Impact of heavy ions on a-Si:H/PolySi bilayer thin film transistors with Schottky barrier source and drain based on Nickel Silicide

This study investigates the influence of heavy ion irradiation on thin film transistors (TFTs) based on an a-Si:H/PolySi active layer and Schottky barrier-based source and drain. Through the use of Technology Computer-Aided Design (TCAD) simulations, we analyze the impact on device performance. We examine the ambipolar device characteristics by varying the thickness of the active layer (Poly-Si) and studying the corresponding physics. Our results reveal that reducing the active layer thickness from 140 to 80 nm decreases the magnitude of the threshold voltage (|VT|) for both nMOS and pMOS operating voltages. Additionally, the subthreshold slope is reduced for both nMOS and pMOS as the active layer thickness is decreased from 140 to 80 nm.Further, we investigated the transient response of the drain current to heavy ion irradiation in the sensitive regions across the Schottky barrier-based source and drain. We specifically analyze the phenomenon of bipolar amplification for various Linear Energy Transfer (LET) values, ranging from 0.1 MeV cm2/mg to 100 MeV cm2/mg. Our findings indicate that increasing the LET values from 0.1 MeV cm2/mg to 100 MeV cm2/mg results in amplified bipolar behavior and a drain current overshoot of over 10 % for both pMOS and nMOS operating voltages. To summarize, this work highlights the effects of heavy ion irradiation on TFTs with an a-Si:H/PolySi active layer and Schottky barrier-based source and drain. The study explores the influence of active layer thickness on device characteristics and demonstrates the transient response of drain current under different LET values. These findings contribute to a better understanding of the behavior and performance of TFTs subjected to heavy ion irradiation.

Design and modeling of the electrostatically controlled nanowire FET for ppt-level hydrogen sensing

We present the design of a H2 gas sensor based on palladium (Pd) decorated silicon-on-insulator (SOI) nanowire field effect transistor (FET) with a standard SOI complementary metal-oxide-semiconductor fabrication process, where a top Pd layer plays a dual role of a catalyst and a surrounding metal gate. A numerical study was conducted based on a simplified steady-state model to describe the sensing mechanism of H2 in dry air at 300 K. The simulation is based on the model of dissociative H2 adsorption on the Pd surface and the formation of a dipole layer at the Pd/SiO2 interface. The H atoms induced dipoles lead to a potential drop which exponentially increases the FET drain current and consequently, the sensor response. The FET drain current is controlled by its back-gate bias and by varying the H2 concentrations; it is shown that the drain current response reaches 1.8 × 108% for 0.8% H2 in air and a superior sensitivity of 4.58 × 104%/ppm in the sub-threshold operation regime. The sensor exhibits an outstanding theoretical detection limit of 50 ppt (response of 1%) and an upper dynamic range limit of 7000 ppm which allow for timely and accurate detection of H2 gas presence. The power consumption ranges between ∼10 fW (dry air) to ∼20 nW (0.8% H2 in dry air) and therefore paves the way for a very large-scale integration commercial sensing platform.

An experimental study on switching waveform design with gate charge control for power MOSFETs

Designing switching waveforms is a technique for mitigating a trade-off between loss and noise in switching power devices. A novel and simple method has been proposed to compute the gate waveform to realize a designed switching waveform. The gate current pulse is calculated to eliminate the deviation between the designed target waveform and the observed waveform at the moment using a linear combination of drain-source voltage or drain current responses to a small gate charge pulse train. In this paper, a verification system including a simple gate current pulse generator consisting of operational amplifiers and transistors was built together with a conventional voltage source gate driver, and validation of the proposed method was experimentally performed using the drain-source voltage waveform of a Si MOSFET during the turn-off phase. Applying the obtained drain-source voltage responses to the proposed method, the gate current pulse to be added to realize a given target waveform was calculated and superimposed on the output of the gate driver. The measured drain-source voltage waveform was well-matched to the target. In addition, the impact of the drain current values on the design of the drain-source waveform was verified.

High temperature stability of H-diamond high frequency MOSFET with 300°C grown Al2O3 dielectric

The high frequency H-diamond metal-oxide-semiconductor field effect transistors (MOSFETs) were fabricated on single diamond substrate using 300°C ALD grown Al2O3 as gate dielectric and passivation layer. The devices gate length, gate/drain spacing and dielectric thickness are 100 nm, 2 μm, and 10 nm, respectively. The direct-current and frequency characteristics were investigated. The device shows a maximum saturation drain current of −492.6 mA/mm and gm of 135.2 mS/mm. The device shows good high temperature working performance, and the maximum saturation drain current only has a little decreasing of 7.6%. at 200°C. In addition, the device exhibits a maximum cut-off frequency of 36.2 GHz and maximum oscillation frequency of 70.5 GHz. The transient drain current response measurement indicates that the drain current can follow the changing of gate voltage at the frequency of 1 MHz. These results indicate that the Al2O3 dielectric is suitable for using in high frequency or the high-speed switching devices.

A Dynamic Concentration-Dependent Analytical I,–V Model for LG-GFET Biosensor

In the past few years, liquid-gated graphene field-effect transistors (LG-GFETs) have been widely used in biological detection due to their unique advantages. An accurate transistor model is the basis of biological detection circuit design, however, the reported GFET models are mainly focusing on solid-gated GFETs. Therefore, it is essential to conduct the research on LG-GFET model. In this article, an improved <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{I}$</tex-math> </inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{V}$</tex-math> </inline-formula> model of LG-GFET is presented based on Fregonese’s model. An improved electric double-layer capacitor model is proposed for LG-GFET. Then, the relationship among iron concentration, bias voltages, and current is studied comprehensively. Furthermore, the drain current response change with time is taken into account and the dynamic concentration-dependent model is established. To verify the accuracy of the proposed model, LG-GFET is simulated in TCAD software and fabricated to perform the measurement. The simulation results and measurement results are compared with the model results, respectively. These results show that the relative root-mean-square error (RMSE) to both simulation and measurement results is less than 5.7%. It is revealed that the proposed model can be applied to biological detection and achieve high accuracy.

Drain-bias dependence of low-frequency Y22 signals for Fe-related GaN traps in GaN HEMTs with different Fe doping concentrations

The bias dependence of trap properties for GaN HEMTs with Fe-doped GaN layers was investigated using low-frequency Y-parameters measurement in the two-port network. This measurement technique can be estimated quasi-equilibrium trap properties and location by changing the combination between gate/drain current response and gate/drain input voltage with small AC signal overlapped fixed DC bias. We focused on Y22 which can be detected only in GaN traps. Activation energies for the GaN traps were estimated bias-by-bias for wide drain voltage (VDS) ranging from 2 V below the knee voltage to 15 V for the saturation region with high current at the gate voltage of 0 V (on-state condition). Fe-related GaN traps with low-frequency Y22 characteristics were identified experimentally using GaN HEMTs including GaN layers with different Fe doping concentrations. The Fe-related GaN trap signals in the imaginary part of Y22 (Im(Y22)) appeared at a peak near 200 Hz at a low VDS of 3 V under on-state conditions and moved to a higher frequency with an increase of VDS. The amplitudes of the trap peaks enhanced around VDS of 3 V. The maximum value in the amplitude of the trap peaks was large for the high-concentration Fe doping. On the other hand, the peak frequency depending on VDS had a similar trend for both the low- and high-concentration Fe doping. The activation energy for the Fe-related trap decreased for VDS up to 7 V and saturated for both Fe doping concentrations. Device simulation was performed to analyze the location in GaN HEMTs for GaN trap response and bias dependence of the activation energy. To simulate the characteristics of Im(Y22), drain current (ID) responses against AC (sine wave) input signal of VDS were calculated at the frequency corresponding to the trap peak. Because ID led VDS in phase, the trap effect is considered to change the trapped charge. From two-dimensional plots for the difference in ionized trap density, trap response regions were located under the gate edge at the drain side. Because the imaginary part of the admittance vector between ID and VDS corresponded with Im(Y22), the Fe-related traps under the gate of the drain side changed the charge condition according to the AC signal and generated the peak in Im(Y22) depending on the frequency. Furthermore, the saturation of the activation energy in the bias-dependence characteristics occurred due to decreasing the thermal conductivity at high temperatures. The temperature in GaN HEMTs at high VDS became high because of the self-heating effect in addition to the high ambient temperature. The internal temperature increase induced the trap peak frequency increase, and the activation energies were saturated.

Organic Electrochemical Transistor with Molecularly Imprinted Polymer-Modified Gate for the Real-Time Selective Detection of Dopamine

Because of their low operation voltage, high transconductance, and good aqueous compatibility, organic electrochemical transistors (OECTs) have been widely applied in the sensing of small redox-active molecules such as dopamine. However, selective detection of dopamine (DA) can be challenging since its sensing mechanism relies on the gate voltage offset caused by the redox chemistry at the gate electrode. To introduce selectivity toward dopamine detection, a polypyrrole film was electrochemically deposited on the Pt gate electrode with the presence of dopamine as a template and then overoxidized in an alkaline solution. The resultant OECT sensor with an overoxidized MIP (o-MIP/Pt) gate shows a similar detection limit of ∼34 nM as compared to the device with a bare Pt gate. At the same time, when compared to the drain current response of a representative interferent, ascorbate (AA), a good selectivity of DA/AA signal ratio of larger than 5 can be achieved in the concentration range between ∼0.4 and ∼10 μM, whereas OECT sensor with bare Pt gate shows little selectivity toward DA. The selectivity of the OECT sensor toward DA can be maintained in the copresence of 1-fold DA (∼0.4 μM) and 10-fold AA (∼4 μM), regardless of the order of the additions.

Enhanced Selectivity in Volatile Organic Compound Gas Sensors Based on ReS2-FETs under Light-Assisted and Gate-Bias Tunable Operation.

Using a single-device two-dimensional (2D) rhenium disulfide (ReS2) field-effect transistor (FET) with enhanced gas species selectivity by light illumination, we reported a selective and sensitive detection of volatile organic compound (VOC) gases. 2D materials have the advantage of a high surface-area-to-volume ratio for high sensitivity to molecules attached to the surface and tunable carrier concentration through field-effect control from the back-gate of the channel, while keeping the top surface open to the air for chemical sensing. In addition to these advantages, ReS2 has a direct band gap also in multilayer cases, which sets it apart from other transition-metal dichalcogenides (TMDCs). We take advantage of the effective response of ReS2 to light illumination to improve the selectivity and gas-sensing efficiency of a ReS2-FET device. We found that light illumination modulates the drain current response in a ReS2-FET to adsorbed molecules, and the sensing activity differs depending on the gas species used, such as acetone, ethanol, and methanol. Furthermore, wavelength and carrier density rely on certain variations in light-modulated sensing behaviors for each chemical. The device will distinguish the gas concentration in a mixture of VOCs using the differences induced by light illumination, enhancing the selectivity of the sensor device. Our results shed new light on the sensing technologies for realizing a large-scale sensor network in the Internet-of-Things era.

A New Simulation Approach of Transient Response to Enhance the Selectivity and Sensitivity in Tunneling Field Effect Transistor-Based Biosensor

In this work, a new simulation approach of transient analysis on single cavity dielectric-modulated (DM) p -type of tunnel field-effect transistor (TFET) is examined for biosensing applications. The device operation and performance are investigated using the 2D device simulator and results are well-calibrated with experimental data. In this work, we have examined DC transfer characteristics, the transient response of drain current, drain current sensitivity (S), and selectivity (AS). Focussing more on the transient results, we have obtained maximum sensitivity of orders greater than 108 for APTES biomolecule with respect to air and a significant selectivity value in orders of 103 for APTES with respect to Biotin biomolecule. The performance of the device in terms of selectivity can be further improved (~10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> ) by optimizing the back-gate bias, and therefore, the impact of back-gate bias has been analysed. The results for charged biomolecules and partially filled cavity are further investigated & highlighted. The DM p-TFET biosensor shows a significant improvement in the results with the transient response for biosensing applications with the feasibility of operating at low voltages (gate voltage of -2.0 V, drain voltage of -0.5 V and back gate voltage 0 to 0.5 V).

Understanding and Mapping Sensitivity in MoS2 Field-Effect-Transistor-Based Sensors.

Sensors based on two-dimensional (2D) field-effect transistors (FETs) are extremely sensitive and can detect charged analytes with attomolar limits of detection (LOD). Despite some impressive LODs, the operating mechanisms and factors that determine the signal-to-noise ratio in 2D FET-based sensors remain poorly understood. These uncertainties, coupled with an expansive design space for sensor layout and analyte positioning, result in a field with many reported highlights but limited collective progress. Here, we provide insight into sensing mechanisms of 2D molybdenum disulfide (MoS2) FETs by realizing precise control over the position and charge of an analyte using a customized atomic force microscope (AFM), with the AFM tip acting as an analyte. The sensitivity of the MoS2 FET channel is revealed to be nonuniform, manifesting sensitive hotspots with locations that are stable over time. When the charge of the analyte is varied, an asymmetry is observed in the device drain-current response, with analytes acting to turn the device off leading to a 2.5× increase in the signal-to-noise ratio (SNR). We developed a numerical model, applicable to all FET-based charge-detection sensors, that confirms our experimental observation and suggests an underlying mechanism. Further, extensive characterization of a set of different MoS2 FETs under various analyte conditions, coupled with the numerical model, led to the identification of three distinct SNRs that peak with dependence on the layout and operating conditions used for a sensor. These findings reveal the important role of analyte position and coverage in determining the optimal operating bias conditions for maximal sensitivity in 2D FET-based sensors, which provides key insights for future sensor design and control.

The Effect of Doping on Different FET Structures: MOSFET, TFET and FinFET

MOSFET have been scaled down over the past few years in order to give rise to high circuit density and increase the speed of circuit. But scaling of MOSFET leads to issues such as poor control gate over the current which depends on gate voltage. Many short channel effects (SCE) influence the circuit performance and leads to the indeterminist response of drain current. These effects can be decreased by gate excitation or by using multiple gates and by offering better control gate the device parameters. In Single gate MOSFET, gate electric field decreases but multigate MOSFET or FinFET provides better control over drain current. In this paper, different FET structures such as MOSFET, TFET and FINFET are designed at 22nm channel length and effect of doping had been evaluated and studied. To evaluate the performance donor concentration is kept constant and acceptor concentration is varied.

Enhanced piezoelectric tactile sensing behaviors of high-density and low-damage CF4-plasma-treated IGZO thin-film transistors coated by P(VDF-TrFE) copolymers

Piezoelectric pressure sensing behaviors of high-density and low-damage CF4-plasma-treated indium gallium zinc oxide (IGZO) thin-film transistors (TFTs) coated by poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) films have been investigated. The CF4 plasma treatment was performed on the IGZO channel by using an inductively coupled plasma (ICP) system with a quartz filter. Prior to the fabrication of devices, X-ray diffractometer (XRD) and atomic force microscopy (AFM) were applied to identify the enhancement in the crystallinity of P(VDF-TrFE) films on the plasma-fluorinated IGZO films. With the analyses of X-ray photoelectron spectroscopy (XPS), it is proved that the fluorine radicals reacted with the metal-oxygen bonds will increase the oxygen vacancies in IGZO films, contributing to an enhancement in field effect mobility (μFE) and drain current (IDS) of IGZO TFTs. Furthermore, the fluorine atoms diffused from the IGZO channel into the bottom SiO2 layer were confirmed by secondary ion-mass spectroscopy (SIMS), reducing the interfacial and oxide charges of the devices for a negative shift in threshold voltage (Vt). Under a 0.5-kg applied force press/release cyclic test, a 4.8-fold increase in drain current response of 1-min CF4-plasma-treated piezoelectric pressure sensors was optimized, because of the enhanced electrical behaviors of IGZO TFTs and an increase in aligned dipole moments of P(VDF-TrFE) copolymers. The promising results make the piezoelectric pressure sensors with high-density and low-damage CF4-plasma-treated IGZO TFTs coated by P(VDF-TrFE) copolymer suitable for future high-performance tactile sensing applications.

High temperature (300 °C) ALD grown Al2O3 on hydrogen terminated diamond: Band offset and electrical properties of the MOSFETs

Hydrogen-terminated diamond (H-diamond) metal-oxide-semiconductor field effect transistors (MOSFETs) were fabricated on a polycrystalline diamond substrate. The device has a gate length of 2 μm and uses Al2O3 grown by atomic layer deposition at 300 °C as a gate dielectric and passivation layer. The Al2O3/H-diamond interfacial band configuration was investigated by X-ray photoelectron spectroscopy, and a large valence band offset (3.28 eV) that is very suitable for p-channel H-diamond FETs was observed. Meanwhile, the measured O/Al ratio hints that there are Oi or VAl defects in the Al2O3 dielectric, which can work as an acceptorlike transfer doping material on a H-diamond surface. The device delivers the maximum saturation drain current of over 200 mA/mm, which is the highest for 2-μm H-diamond MOSFETs with the gate dielectric or passivation layer grown at 300 °C or higher temperature. The ultrahigh on/off ratio of 1010 and ultralow gate leakage current of below 10−12 A have been achieved. The high device performance is ascribed to the ultrahigh carrier density, good interface characteristics, and device processes. In addition, the transient drain current response of the device can follow the gate voltage switching on/off pulse at a frequency from 100 kHz to 1 MHz, which indicates the potential of the H-diamond FETs in power switch applications.

Enhancement of Sensor Response in Graphene Gas Sensors by Gate-Induced Field

The effects of the gate-induced field on sensor response in functionalized graphene sensor have not been fully understood yet. In this letter, graphene sensors decorated with Pd nanoparticles were fabricated, and gate voltage dependences of drain current and sensor response to hydrogen were experimentally and numerically examined. The sensor response was enhanced in the gate-induced electron conduction regime, compared to that in hole conduction regime. By utilizing the non-equilibrium Green’s function calculations, the origin of the response enhancement was modeled as asymmetric potentials for holes and electrons. We conclude that the sensor response of graphene can be enhanced using the gate-induced electric field in various types of graphene sensors.

Investigation of the atmosphere influence on device characteristics and NO2 sensing performance of organic field-effect transistors consisting of polymer bulk heterojunction

Abstract Organic field-effect transistors (OFETs) using polymer as the active layer are being intensively developed for flexible electronics including gas sensor. The strategy of polymer blends comprising semiconducting polymer mixed into an insulating polymer matrix has shown great potential in improving the electrical and sensing performance of OFETs. Herein two semiconducting polymers of poly(3-hexylthiophene-2,5-diyl) (P3HT) and poly(9-vinylcarbazole) (PVK) are used to construct a polymer bulk heterojunction, through exploring the atmosphere influence on device characteristics and NO2 sensing performance of the transistors, an in-depth illumination of the underlying sensing mechanism is carried out. Firstly, by using nitrogen (N2) and dry air as carrier gases, the individual device characteristics and sensing performance under certain NO2 concentrations are investigated. It can be observed that O2 has a greater effect on the electrical performance than other atmospheric components, which is different from the previous report of neat P3HT-based device. Specifically, at the high gate voltage, the response of drain current under N2 is more than 2 times higher than that under dry air, and the mobility variation exhibits a 2-fold enhancement. In contrast, at a low gate voltage (0 V) under dry air, the response is 2-fold greater than under N2. Then, the underlying sensing mechanism of these gas sensors consisting of various P3HT fractions in different operating environment is discussed. Finally, the OFET gas sensor with a high sensitivity to NO2 under dry air is obtained, i.e., the highest current sensitivity is ∼12381% for 15 ppm with 50% P3HT, which is more than 30 times higher than that of pure one. This study on gas sensing mechanism of OFET consisting of semiconducting polymer bulk heterojunction can offer novel inspiration to realize high performance OFET and the corresponding gas sensor.

Analysis of Drain Current Transient Response of Gate Pulse Voltage in AlGaN / GaN High Electron Mobility Transistors

Analysis of Drain Current Transient Response of Gate Pulse Voltage in AlGaN / GaN High Electron Mobility Transistors

Drain current response delay high frequency model of SOI MOSFET with inductive parasitic elements

Drain current response delay high frequency model of SOI MOSFET with inductive parasitic elements