Double-gate Field-effect Transistor Research Articles

Impacts of Cavity Thickness and Insulating Material on Dielectric Modulated Trench Junction-less Double Gate Field Effect Transistor for Biosensing Applications

Introduction: This work represents the influence of gate dielectric, and the nano-cavity gap of a dielectric modulated trench gate Junction-less Double Gate Field Effect Transistor (JL-DGFET) on the different performance indicators is investigated considering the Low-Frequency Noise. Methods: It is noted that the gate dielectric and the nanogap, both parameters, have a substantial influence on the sensing capacity and performance of noise of the device. Results: A double gate suitable dielectric material and cavity thickness can effectively improve the biosensor’s sensitivity with a minimum amount of noise. Conclusion: The sensitivity is found to increase up to 9.5 for dielectric constant, k = 3.57 and 6.5 for dielectric constant, k = 2.1.

Enhanced Electrical Performance of InAs Nanowire Field-Effect Transistors Based on the Y2O3 Isolation Layer.

Nanowire (NW) field-effect transistors (FETs) have great potential in next-generation integrated circuits. InAs NWs are suitable for N-type transistors because of their excellent electrical properties. However, unlike the Si/SiO2 system, the loose and defective native oxide of InAs is unable to passivate the channel surface and serve as an efficient isolation layer (IL) in the gate stack. Here, we, for the first time, demonstrate that using a stable dielectric Y2O3 to replace the native oxide IL can effectively passivate the NW surface, isolate the channel surface from high-k HfO2, and improve the electrical properties of InAs NW FETs significantly. First, top-gate devices with Y2O3 IL outperform the devices with native oxide or chemically generated oxide of InAs as the IL, exhibiting a small subthreshold swing (SS) of 77 mV/dec, a large on-off ratio, a high field-effect mobility (μFE) of 1845 cm2/V·s, and an extremely low interface trap density (Dit) of 9.1 × 1011 eV-1 cm-2. Double-gate FETs with Y2O3 IL also show excellent gate control (drain-induced barrier lowering (DIBL) down to 35 mV/V) and a high μFE of 2711 cm2/V·s (the highest in the multigate structure). In addition, InAs NW FETs with Y2O3 IL show greater stability after long-term air exposure than those with native oxide IL, demonstrating retained on-off ratio, DIBL, transconductance, and even smaller SS (from 89 to 77 mV/dec). Finally, the results of low-temperature measurement suggest that Y2O3 IL can effectively improve interface qualities. Our results indicate that Y2O3/HfO2 InAs NW FETs have great potential in digital units of integrated circuits for future nodes. Our strategy for improving the interface between InAs NW and the dielectric layer is also valuable for other III-V NW devices.

Analysis and EOT Scaling on Top‐ and Double‐Gate 2D CVD‐Grown Monolayer MoS2 FETs

Abstract2D layered semiconductors have attracted considerable attention for beyond‐Si complementary metal‐oxide‐semiconductor (CMOS) technologies. They can be prepared into ultrathin channel materials toward ultrascaled device architectures, including double‐gate field‐effect‐transistors (DGFETs). This work presents an experimental analysis of DGFETs constructed from chemical vapor deposition (CVD)‐grown monolayer (1L) molybdenum disulfide (MoS2) with atomic layer deposition (ALD) of hafnium oxide (HfO2) high‐k gate dielectrics (top and bottom). This extends beyond previous studies of DGFETs based mostly on exfoliated (few‐nm thick) MoS2 flakes, and advances toward large‐area wafer‐scale processing. Here, significant improvements in performance are obtained with DGFETs (i.e., improvements in ON/OFF ratio, ON‐state current, sub‐threshold swing, etc.) compared to single top‐gate FETs. In addition to multi‐gate device architectures (e.g., DGFETs), the scaling of the equivalent oxide thickness (EOT) is crucial toward improved electrostatics required for next‐generation transistors. However, the impact of EOT scaling on the characteristics of CVD‐grown MoS2 DGFETs remains largely unexplored. Thus, this work studies the impact of EOT scaling on subthreshold swing (SS) and gate hysteresis using current–voltage (I–V) measurements with varying sweep rates. The experimental analysis and results elucidate the basic mechanisms responsible for improvements in CVD‐grown 1L‐MoS2 DGFETs compared to standard top‐gate FETs.

PSP-Equivalent Model for Double-Gate and Surrounding-Gate Field Effect Transistors for Circuit Simulation

We introduce a compact core model for double-gate (DGFET) and surrounding-gate (SGFET) MOSFETs designed for circuit simulations. Despite its high precision, the model is crafted to retain the same analytic formulation of the industry standard Pennsylvania State and Philips (PSP). Instead of linearizing the drain current as in the PSP model, we employ a quadratic symmetric polynomial interpolation of the charge in the channel. This eliminates the need for cumbersome derivatives, simplifications, and intricate coding when integrating into a circuit simulator, thereby preventing singularities during numerical iterations. Moreover, thanks to its mathematical formulation equivalent to PSP, this model simplifies the coding of terminal charges, capacitances, potentials, and electric fields in the channel within circuit simulators. We validate the accuracy of the model through comparisons with numerical solutions and experiments from the literature.

Investigation on Sensitivity Amplification Factor of DGFET Electrochemical Sensors for pH Detection

There has been an increasing interest in the development of chemical and biological FET- based sensors due to their remarkable benefits in label-free detection that has been commonly used in both pH and DNA sensing respectively. In this work, recent Double-Gated Field Effect Transistor (DGFET) as transducers is investigated to understand the super- Nernstian response by amplifying the sensitivity capability in back-gate operations. The BioSensorLab tool was employed to evaluate pH-sensitivity amplification by studying the electrolyte screening and conduction modulation mechanisms which modeled by using Poisson-Boltzmann and Drift-Diffusion equations. The pH sensitivity amplification factors were investigated based on different geometrical configurations of DGFET devices, biasing conditions, and top oxide-electrolyte interfaces. pH sensitivity beyond Nernst limit was observed and increased linearly with the back oxide thickness of the DGFETs. DGFET with a sensitivity of 32.1 mV/pH operated through front-gate operation can be amplified to 195.4 mv/pH through the back-gate operation with a drain voltage of 0.5 V when the back gate oxide thickness increased to 150 nm. Higher pH-sensitivity responses of more than 200 mV/pH were observed where Al2O3 and Ta2O5 are used for the top oxide-electrolyte. It can be concluded that pH sensing of back gate operation ensures the DGFET transducers operated beyond the Nernst limit.

Effects of metal work function and gate-oxide dielectric on super high frequency performance of a non-align junction DG-MOSFET based inverter in the sub-100 nm regime: a TCAD simulation analysis

ABSTRACT This paper presents simulation analysis of an inverter made from non-aligned double gate field effect transistors (NADGFETs) in Sub-100 nm regime. The inverter consists of n-channel NADGFET and p-channel NADGFET device with a channel length of 40 nm and 50% non-alignment between gate and source/drain. The response of the inverter was tested by a combination of gate dielectric constant (k) and metal work function (ϕ). Three gate dielectrics namely, SiO2 (k = 3.9), Si3N4 (k = 7.2), HfO2 (k = 24), and three metal work function namely tungsten (ϕ = 4.5 eV), molybdenum (ϕ = 4.75 eV), gold (ϕ = 5 eV), were considered in the NADGFET inverter. This paper defines a kϕ index as characterising parameter to explore the best response from inverter configuration with minimum propagation delay, and minimum power consumption at super-high frequency. The paper proposes to analyse the NADGNFET device, in term of ION current, ION/IOFF ratio, cut-off frequency, and gate delay. And observes that low k material with moderate metal work function gives best response. The work then simulates the inverter and group the results into voltage transfer curve (VTC), transient response, and power dissipation category. The result shows that when inverter was subjected to high frequency, all the kϕ combination responds good, however when the inverter was subjected to super-high frequency, the low value of kϕ combination performs well. Thus, the result concludes that SiO2-M2 combination will be best selection to get minimum propagation delay and dynamic power dissipation by the inverter. The test strategy presented in this paper on the basis of kϕ index can serve as benchmark to test inverter device at super-high frequency.

Electrical Properties of Double-Gate Field-Effect Transistor Based on MA2N4 (M = Ti, Zr, and Hf; A = Si, Ge, and Sn) Monolayers

Electrical Properties of Double-Gate Field-Effect Transistor Based on MA₂N₄ (M = Ti, Zr, and Hf; A = Si, Ge, and Sn) Monolayers

Scalable Charge-Based Compact Model for Drain Current in Fin-Shaped GaN HEMTs

We present a novel charge-based compact model for drain current in fin-shaped GaN high-electron-mobility transistors (Fin-HEMTs). A positive threshold voltage shift is observed in Fin-HEMTs due to better gate control of the channel. The combined effect of top and side gates on the channel charge density is studied with the help of detailed TCAD simulation. For the first time, a closed-form expression for 2-D electron gas (2-DEG) density in Fin-HEMTs is derived. The fin width dependence of the 2-DEG current is modeled in a unique way by considering the modified gate capacitance and threshold voltage in Fin-HEMTs. The total drain current is modeled as the sum of 2-DEG and double-gate field effect transistor (FET) currents. In addition, the total gate capacitance including the side-gate capacitance for fin structure is also formulated. The model is generic and can be used for different fin geometries using the proposed equivalent circuits as demonstrated. A fin-width-dependent thermal resistance model is proposed and included in the drain current model using a thermal subcircuit. The proposed model is completely analytical and does not require any iteration or fitting parameters in contrast to the available models discussed in the literature. Our model shows excellent agreement with the state-of-the-art experimental data.

Device Performance of Double-Gate Schottky-Barrier Graphene Nanoribbon Field-Effect Transistors with Physical Scaling

Moore’s law is approaching its limit due to various challenges, especially the size limit of the transistors. The International Roadmap for Devices and Systems (IRDS), the successor of International Technology Roadmap for Semiconductors (ITRS), has included 2D materials as an alternative approach for the More-than-Moore nanoelectronic applications. Among the 2D materials, graphene nanoribbons (GNRs) have been widely used as the alternative channel materials of field-effect transistors (FETs). In this paper, the impacts of physical scaling on the device performance of double-gate Schottky-barrier GNR FETs (DG-SB-GNRFETs) are investigated by using NanoTCAD ViDES simulation tool based on the tight-binding Hamiltonian and self-consistent solutions of 3D Poisson and Schrödinger equations with open boundary conditions within the nonequilibrium Green’s function formalism. The extracted device performance parameters include the subthreshold swing and on-to-off current ratio. The results suggest that the performances of DG-SB-GNRFETs are strongly dependent on their physical parameters, especially the widths of the GNRs.

Dual-Channel Detection of Breast Cancer Biomarkers CA15-3 and CEA in Human Serum Using Dialysis-Silicon Nanowire Field Effect Transistor.

Breast cancer (BC) is the most common malignant tumors and the leading cause of cancer deaths among women. The early diagnosis and treatment of BC are effective measures that can increase survival rates and reduce mortality. Carbohydrate antigens 15-3 (CA15-3) and carcinoma embryonic antigens (CEA) have been regarded as the most two valuable tumor markers of BC. The combined detection of CA15-3 and CEA could improve the sensitivity and accuracy of early diagnosis for BC. The multi-channel double-gate silicon nanowire field effect transistor (SiNW-FET) biosensors were fabricated by using the top-down semiconductor manufacturing technology. By surface modification of the different SiNW surfaces with monoclonal CA15-3 and CEA antibodies separately, the prepared SiNW-FET was processed into biosensor for dual-channel detection of CA15-3 and CEA. The prepared SiNW-FET biosensors were proved to have high sensitivity and specificity for the dual-channel detection of CA15-3 and CEA, and the detection limit is as low as 0.1U/mL CA15-3 and 0.01 ng/mL CEA. Moreover, the SiNW-FET biosensors were able to detect CA15-3 and CEA in serum by connecting a miniature hemodialyzer. The present study reported a SiNW-FET biosensor for dual-channel detection of breast cancer biomarkers CA15-3 and CEA in serum, which has potential clinical application value for the early diagnosis and curative effect observation of BC.

Device modeling of two-steps oxygen anneal-based submicron InGaZnO back-end-of-line field-effect transistor enabling short-channel effects suppression

Amorphous oxide semiconductor (AOS) field-effect transistors (FETs) have been integrated with complementary metal-oxide-semiconductor (CMOS) circuitry in the back end of line (BEOL) CMOS process; they are promising devices creating new and various functionalities. Therefore, it is urgent to understand the physics determining their scalability and establish a physics-based model for a robust device design of AOS BEOL FETs. However, the advantage emphasized to date has been mainly an ultralow leakage current of these devices. A device modeling that comprehensively optimizes the threshold voltage (VT), the short-channel effect (SCE), the subthreshold swing (SS), and the field-effect mobility (µFE) of short-channel AOS FETs has been rarely reported. In this study, the device modeling of two-steps oxygen anneal-based submicron indium-gallium-zinc-oxide (IGZO) BEOL FET enabling short-channel effects suppression is proposed and experimentally demonstrated. Both the process parameters determining the SCE and the device physics related to the SCE are elucidated through our modeling and a technology computer-aided design (TCAD) simulation. In addition, the procedure of extracting the model parameters is concretely supplied. Noticeably, the proposed device model and simulation framework reproduce all of the measured current–voltage (I–V), VT roll-off, and drain-induced barrier lowering (DIBL) characteristics according to the changes in the oxygen (O) partial pressure during the deposition of IGZO film, device structure, and channel length. Moreover, the results of an analysis based on the proposed model and the extracted parameters indicate that the SCE of submicron AOS FETs is effectively suppressed when the locally high oxygen-concentration region is used. Applying the two-step oxygen annealing to the double-gate (DG) FET can form this region, the beneficial effect of which is also proven through experimental results; the immunity to SCE is improved as the O-content controlled according to the partial O pressure during oxygen annealing increases. Furthermore, it is found that the essential factors in the device optimization are the subgap density of states (DOS), the oxygen content-dependent diffusion length of either the oxygen vacancy (VO) or O, and the separation between the top-gate edge and the source-drain contact hole. Our modeling and simulation results make it feasible to comprehensively optimize the device characteristic parameters, such as VT, SCE, SS, and µFE, of the submicron AOS BEOL FETs by independently controlling the lateral profile of the concentrations of VO and O in two-step oxygen anneal process.

Low-power double-gate MoS2 negative capacitance transistors with near-zero DIBL

Negative capacitance (NC) devices hold great promise for improving subthreshold slope (SS). However, the theoretical exploration of the short-channel effect in NC and two-dimensional (2D) materials remains an ongoing challenge in device scaling. The present work demonstrates a double-gate MoS2 negative capacitance field-effect transistor (MoS2 DG-NCFET) with low power and near-zero drain-induced barrier lowering (DIBL) by exploring its design space considering the impact of various MoS2 layers, with the aid of the developed 2D short-channel model containing the NC effect and numerical simulation. The proposed monolayer MoS2 DG-NCFET model is solved by unifying the long and short channel models coupled with the one-dimensional Landau-Khalatnikov equation. The study indicates that a lower SS, considerable voltage saving (), and even the ability to achieve zero DIBL are seen in monolayer MoS2 devices when compared with those of non-2D MoS2, due to the combination of the atomic-scale thickness of channels and the double-gate structure. This study provides an insight for further reducing the feature size of ultralow power transistors.

Design and Investigation of Double Gate Field Effect Transistor Based H2 Gas Sensor Using Ultra-Thin Molybdenum Disulfide

In this article, a low-power hydrogen (H2) gas sensor has been proposed using a two-dimensional (2D) material based Double Gate Field Effect Transistor (2D-FET). It is imperative to highlight that the conventional three-dimensional (3D) materials cannot be scaled down to an ultra-low dimension due to the presence of dangling bonds, surface roughness scattering etc. This creates a major challenge in developing low-dimensional sensors for next generation sensing and computing. In this context, we have developed an extensive simulation model, which articulates the physical phenomena behind a catalytic metal gate-based hydrogen gas sensor using a 2D-FET. A 5 nm thin Molybdenum disulfide (MoS2) film has been used as the channel material for the proposed 2D-FET based gas sensor. The sensor has been modelled by emphasizing on the catalytic metal (Palladium) gate approach, where the work function of the gate metal deposited on top of the channel region varies after the absorption of the hydrogen gas. Moreover, the Technology Computer Aided Design (TCAD) based gas sensor model has been developed by considering a change in the pressure of H2 gas as well. We have also highlighted the effect of Metal/MoS2 contact on sensor performance. In terms of the performance, a maximum threshold voltage (Vth) shift of 100 mV has been obtained against a gas pressure of 10−10 torr, whereas the maximum percentage of change in ION/IOFF is 100. Lastly, the authors have shown the thermal noise characteristics of the gas sensor.

Logic and memory functions of an inverter comprising reconfigurable double gated feedback field effect transistors

In this study, we propose an inverter consisting of reconfigurable double-gated (DG) feedback field-effect transistors (FBFETs) and examine its logic and memory operations through a mixed-mode technology computer-aided design simulation. The DG FBFETs can be reconfigured to n- or p-channel modes, and these modes exhibit an on/off current ratio of ~ 1012 and a subthreshold swing (SS) of ~ 0.4 mV/dec. Our study suggests the solution to the output voltage loss, a common problem in FBFET-based inverters; the proposed inverter exhibits the same output logic voltage as the supply voltage in gigahertz frequencies by applying a reset operation between the logic operations. The inverter retains the output logic ‘1’ and ‘0’ states for ~ 21 s without the supply voltage. The proposed inverter demonstrates the promising potential for logic-in-memory application.

Two-Dimensional Gallium Selenide (GaSe) Material for Nanoelectronics Application

As silicon-based transistors have approached their physical limits, it is urgent to explore alternative materials with a suitable bandgap and high mobility for next generation electronic logic devices. Two‐dimensional (2D) materials have attracted significant attention in the last few years due to their potential exotic transport physics and technological applications in various fields, such as a significant device downscaling for high intensity integration. Recently, a variety of 2D materials have been explored, including graphene [1] and transition metal dichalcogenides (TMDs), e.g., MoS2 [2,3], WS2 [4], and PtSe2 [5-7]. Although most research has focused on TMDs, recently 2D layered metal monochalcogenides, e.g., GaSe, have attracted increasing interest as a result of their unique electronic properties, making this class of materials different from TMDs.GaSe crystal structure comprises vertically stacked Ga-Se-Se-Ga layers with relatively weak van der Waals interactions. There are two main GaSe polytypes which differ in the stacking sequence of the basis layer units. Side- and top-view schematics of β‐GaSe and ε‐GaSe are shown in Fig. 1a. In this study, the electronic structure of both GaSe layered material polytypes is investigated using density functional theory (DFT) as implemented in QuantumATK [8]. Brillouin-zone integrations were performed according to the Monkhorst-Pack scheme [9] with a density of approximately 10 k-points per angstrom. Geometry optimizations were performed with the convergence criterion of 0.02 eV/Å [10]. Van der Waals (vdW) interactions improve the structural and electronic properties description obtained by DFT calculations and is included in our calculations through D3 version of Grimme’s dispersion corrections [11].To provide an improved determination of the bandgap energies, the GW (G: Green's function and W: screened Coulomb interaction) method in conjunction with a many body perturbation theory (MBPT) correction could be used. However, GW technique is computationally very expensive and could be implemented for systems with very limited number of atoms [12,13]. Hence, for this study, methods such as Heyd-Scuseria-Ernzerhof (HSE) hybrid functional [14,15] and GGA-1/2 [16] methods were included in our model to achieve more accurate bandgap compared to the experimental values. The β‐GaSe exhibits a DFT-obtained direct bandgap of ~1 eV while the corrected value is 2 eV. ε‐GaSe, however, shows slight indirect bandgap of 0.8 eV (DFT) and 1.7 eV (corrected), with just 25 meV difference between the indirect gap and indirect gap.A double-gate Schottky barrier field-effect transistor (FET) consisting of Ti source and drain contacts and ultrathin GaSe channel is also investigated. Schematic of the FET is shown in Fig. 1b. The device performance analysis such as current-voltage characteristics, subthreshold slope, and on/off ratio are carried out by means of non-equilibrium Green’s function together with DFT Hamiltonian [17]. The output characteristic of the proposed device exhibits an ON/OFF current ratio of more than 7 orders of magnitude.The presence of point defects in ultrathin 2D films is largely inevitable [18], even under optimized synthesis conditions, which can be either engineered and considered as a useful feature, or undesirable. In either case, understanding the impacts of point defects on the electronic structure of 2D materials are required to allow application-based optimization. In this talk, to provide insight into the defect-induced modifications to the GaSe electronic properties, in particular the properties of the states associated with the defects, we will compare the band-structure of the pristine GaSe with the band-structure of the GaSe with Ge and Se vacancies, for both GaSe polytypes.We have also fabricated back-gated devices by mechanically exfoliating ultrathin GaSe flakes from bulk crystal onto oxide-on-Si substrate. Fig. 1c shows an SEM image of the device. Our experimental results demonstrate the basic transport characteristics of thin-film transistor, which may offer more opportunities for potential applications such as photodetectors, gas sensors, and optoelectronic devices, in addition to nanoelectronics FETs, due to GaSe large bandgap.

Device and Circuit Analysis of Double Gate Field Effect Transistor with Mono-Layer WS2-Channel at Sub-2 nm Technology Node

In this work, WS2 was adopted as a channel material among transition metal dichalcogenides (TMD) materials that have recently been in the spotlight, and the circuit power performance (power consumption, operating frequency) of the monolayer WS2 field-effect transistor with a double gate structure (DG WS2-FET) was analyzed. It was confirmed that the effective capacitance, which is circuit power performance, was greatly changed by the extrinsic capacitance components of DG WS2-FET, and the spacer region length (LSPC) and dielectric constant (KSPC) values of the spacer that could affect the extrinsic capacitance components were analyzed to identify the circuit power performance. As a result, when LSPC is increased by 1.5 nm with the typical spacer material (KSPC = 7.5), increased operating speed (+4.9%) and reduced active power (–6.8%) are expected. In addition, it is expected that the spacer material improvement by developing the low-k spacer from KSPC = 7.5 to KSPC = 2 at typical LSPC = 8 nm can increase the operating speed by 36.8% while maintaining similar active power consumption. Considering back-end-of-line (BEOL), the change in circuit power performance according to wire length was also analyzed. From these results, it can be seen that reducing the capacitance components of the extrinsic region is very important for improving the circuit power performance of the DG WS2-FET.

A higher-order accurate operator splitting spectral method for the Wigner–Poisson system

An accurate description of 2-D quantum transport in a double-gate metal oxide semiconductor field effect transistor (dgMOSFET) requires a high-resolution solver for a coupled system of the 4-D Wigner equation and 2-D Poisson equation. In this paper, we propose an operator-splitting spectral method to evolve such Wigner–Poisson (WP) system in 4-D phase space with high accuracy. After the operator splitting of the Wigner equation, the resulting two sub-equations can be solved analytically with spectral approximation in phase space. Meanwhile, we adopt a Chebyshev spectral method to solve the Poisson equation. Spectral convergence in phase space and a fourth-order accuracy in time are both numerically verified. Finally, we apply the proposed solver to the simulation of a dgMOSFET, develop the steady states via long-time simulations and obtain numerically converged current–voltage (I–V) curves.

DOUBLE GATE JFET IMPROVED MODEL FOR ANALOG INTEGRATED CIRCUITS

A double gate JFETs are often used in analog integrated circuits to provide an extremely low input current and capacitance when the top gate is controlled. Circuit synthesis and modeling of analog IC with such a field-effect transistor are possible only if there are models that adequately describe the features of its operation, namely, changing of the current-voltage characteristics by the top gate controlling when a constant reverse voltage is applied to the bottom gate. The article considers the modernization of the well-known electrical model of the double gate field-effect transistor for the LTSpice software, which includes taking into account the influence of the top gate voltage by connecting two series-connected functional voltage sources to the top gate, one of which ensures the coincidence of the measurement results and the simulation of the drain current at a low voltage between the top gate and the source, and the second – when the voltage between the top gate and the source is close to the cutoff voltage. A method for identifying the parameters of functional voltage sources is presented. The proposed model of a double gate field-effect transistor is advisable to use in the IC design of various analog devices, especially electrometric operational amplifiers and charge-sensitive amplifiers.

High-Performance Bidirectional Chemical Sensor Platform Using Double-Gate Ion-Sensitive Field-Effect Transistor with Microwave-Assisted Ni-Silicide Schottky-Barrier Source/Drain

This study proposes a bidirectional chemical sensor platform using ambipolar double-gate ion-sensitive field-effect transistors (ISFET) with microwave-assisted Ni-silicide Schottky-barrier (SB) source and drain (S/D) on a fully depleted silicon-on-insulator (FDSOI) substrate. The microwave-assisted Ni-silicide SB S/D offer bidirectional turn-on characteristics for both p- and n-type channel operations. The p- and n-type operations are characterized by high noise resistance as well as improved mobility and excellent drift performance, respectively. These features enable sensing regardless of the gate voltage polarity, thus contributing to the use of detection channels based on various target substances, such as cells, antigen-antibodies, DNA, and RNA. Additionally, the capacitive coupling effect existing between the top and bottom gates help achieve self-amplified pH sensitivity exceeding the Nernst limit of 59.14 mV/pH without any additional amplification circuitry. The ambipolar FET sensor performance was evaluated for bidirectional electrical characteristics, pH detection in the single-gate and double-gate modes, and reliability in continuous and repetitive operations. Considering the excellent characteristics confirmed through evaluation, the proposed ambipolar chemical sensor platform is expected to be applicable to various fields including biosensors. And through linkage with subsequent studies, various medical applications and precision detector operations for specific markers will be possible.

Polycrystalline-silicon-based double-gate ion-sensitive field-effect transistors using APTES/SiO2 stack-sensing membrane

This study demonstrated a polycrystalline-silicon (poly-Si)-based double-gate (DG) ion-sensitive field-effect transistors (DG-ISFETs) using APTES/SiO2 stack-sensing membrane. The APTES/SiO2 stack-sensing membrane enhanced the single-gate (SG) sensitivity, and suppressed the hysteresis. The DG structure was preferred to have a capacitive coupling effect and to amplify the sensitivity of ISFETs. The sensitivities of SG- and DG-ISFETs were approximately 56.8 and 294 mV pH−1, respectively. In addition, the corresponding amplifying factor was approximately 5.2. With this approach, the poly-Si DG-ISFETs can be a candidate for future high-performance biochemical sensing applications.