Field Effect Transistor Applications Research Articles

Reconfigurable logic-in-memory circuits with ferroelectric nanosheet field-effect transistors

Abstract To accommodate the requirements of small device dimensions and the application of ferroelectric field-effect transistors (FeFETs) in logic-in-memory circuits, we realize the reconfigurable logic-in-memory circuits with ferroelectric nanosheet field-effect transistors (FeNSFETs) through simulation. By evaluating the memory window and logic performances of the devices, it is demonstrated that the key to constructing logical functions are the magnitudes of the drain current at program (PGM) and erase (ERS) state when V G = 0 V. We find that appropriately increasing the number of nanosheets can enhance the current at PGM state, and appropriately increasing the write voltage can decrease the current at ERS state, which are both beneficial for the achievement of reconfigurable circuits. Thus, it is necessary to take into consideration the trade-offs between the process complexity, power consumption, and logical function realization. This work contributes to the prospective design for ferroelectric reconfigurable logic-in-memory circuits.

Nanoscale Mapping of Carrier Distribution Regulated by Polarization in 2D FeFETs.

The emergence of 2D ferroelectrics, sliding ferroelectrics, and 2D ferroelectric semiconductors has greatly expanded the potential applications of two-dimensional ferroelectric field-effect transistors (2D FeFETs) in nonvolatile memory, neuromorphic synapses, and negative capacitance. However, the interaction between ferroelectric and semiconductor layers remains not well understood, and characterization methods to correlate carriers and polarization dynamics at the nanoscale are still lacking. Utilizing in situ scanning microwave impedance microscopy and piezoresponse force microscopy measurements, we employed a Pb(Zr0.2Ti0.8)O3/MoS2-based 2D FeFET as an example to reveal, with high spatial resolution, the microscopic redistribution of carriers. This study uncovers the microscopic behavior of ferroelectric-semiconductor heterojunctions, paving the way for a deeper understanding of ferroelectric-gating effects and retention issues at the nanoscale in 2D FeFETs.

Synthesis, Structures and Air-stable N-type Organic Field-effect Transistor (OFET) Properties of Functionalized-phenanthrene Conjugated Asymmetric N-heteroacenes.

The development of stable high-performance n-type organic semiconductors for applications in organic field-effect transistors (OFETs) under ambient conditions is desirable but challenging. To address this issue, we here synthesized a series of functionalized-phenanthrene conjugated asymmetric N-heteroacenes, where the phenanthrene moiety was modified by N substitution or Br functionalization at different positions to induce various degrees of asymmetry in their structures. The photophysical and electrochemical properties of these molecules were studied, and their packing patterns were analysed. The OFETs based on these materials were fabricated through simple spin-coating method, and the as-resulted thin films were treated with different conditions. The devices exhibit typical n-type performances under ambient conditions with charge carrier mobilities up to 4.27×10-3 cm2 V-1 s-1. The crystallinities and morphologies of these thin films were studied to investigate the correlations between the device performances and thin-film characteristics. Our study suggests that phenanthrene conjugated N-heteroacenes can be developed as promising air-stable solution-processable n-type semiconducting materials, and Br modification at certain positions of phenanthrene is beneficial in adjusting the thin-film properties for the improvement of OFET performances.

Analysis on density of states and ION/IOFF ratio of GaN/GaN-graphene nanoribbon tunnel FET for enhanced bio-sensing applications

Abstract This research introduces a new analytical model that studies the effect of ferro-dielectric on the operational performance of TFETs doped with halogens. The effect of source and drain depletions, voltage-drain & gate, thickness and capacitance of gate insulator are all investigated in this study. Accurate measurements of the surface potential are required to ascertain the transconductance, gate-to-drain capacitance, and lateral electric field of the device. Our model, which employs Ferroelectric Halo-Doped double gate (FHDD)-gated device designs, has been demonstrated to produce results that nearly match those produced from TCAD simulations. This was accomplished by doing a comparative analysis of the outcomes derived from both sets of simulations. Furthermore, the performance of the suggested structure of TFET, which integrates a dielectric of Fe and GaN heterostructure, surpasses that of other similar devices (fT) in terms of ON current, ON/OFF ratio, transconductance, and cut-off frequency. A ferroelectric dielectric was used to create a ferroelectric heterostructure. This study also centers on the creation and application of a graphene nanoribbon field effect transistor (GNR-TFET) to detect sugar molecules, specifically fructose, xylose, and glucose. The detecting signal is generated by utilizing the fluctuation in the electrical current of the GNR-TFET caused by the presence of individual sugar molecules. The GNR-TFET exhibits noticeable variations in the density of states, transmission spectrum, and current when exposed to individual sugar molecules. The sensor under investigation is being developed and examined using a combination of semi-empirical modeling and non-equilibrium Green's functional theory (SE + NEGF). According to the research, the modified GNR TFET has the ability to quickly and accurately detect individual sugar molecules in real-time.

Substitution effect and charge transport properties in organic field-effect transistors (OFETs) of simply functionalized carbazole derivatives

Development of low cost, easy-preparation and good performance organic semiconductors is in high demand for the practical application of organic field-effect transistors (OFETs). Even though the π-extended carbazole derivatives have been intensively studied in OFETs, the application potential of simple carbazole derivatives, i.e., owning simple substituents directly at carbazole backbone, remains unclear. In this work, we designed and synthesized a series of carbazole derivatives with simple phenyl or thienyl functionalization directly at 2,7- or 2,6-positions, respectively. The photophysical and electrochemical properties, together with their theoretical frontier molecular orbitals and energy levels were investigated. The molecular conformations and packing structures in the solid state of these molecules were understood by single-crystal structure analysis. In addition, single-crystal based OFETs were fabricated to explore their intrinsic charge transporting properties, in which the 2,7-diphenyl modified carbazole derivative showed hole-transporting mobilities up to 0.16 cm2 V−1 s−1. Our study not only proves that simply functionalized carbazoles have great potentials to act as easy-preparation high-performance p-type semiconducting materials, but also illustrates that 2,7-positon functionalization is more advantageous for balancing the molecular conformations and packing structures of carbazole derivatives to achieve good charge transport performance.

Developments and Applications of Field-Effect Transistor

This review article delves into the development and future prospects of Field-Effect Transistors (FETs), tracing their evolution from the nascent theoretical concept proposed by Julius Lilienfeld in 1925. Over the years, FETs have traversed significant milestones, marking their progression from fundamental ideas to practical applications. Key among these milestones are the advent of the Metal-Oxide-Semiconductor FET (MOSFET), which revolutionized the electronics industry, the Fin FET, offering enhanced performance through three-dimensional structures, and the GateAll-Around FET (GAA-FET), promising even greater control and efficiency. It provides a systematic comparison of these technologies, dissecting their structural differences, evaluating performance metrics such as speed, power consumption, and scalability, and exploring their potential applications across diverse domains. While recent advancements in FET technology have primarily focused on structural innovations to mitigate the short channel effect, researchers are also actively exploring alternative avenues, including the use of novel materials and refined fabrication techniques, to further enhance FET performance and unlock new possibilities for electronic devices. This multifaceted approach underscores the dynamic and ever-evolving nature of FET technology, positioning it as a cornerstone for future advancements in electronics.

Room-temperature modulation of microwave conductivity in ferroelectric-gated correlated oxides

We report the nonvolatile modulation of microwave conductivity in ferroelectric PbZr0.2Ti0.8O3-gated ultrathin LaNiO3/La0.67Sr0.33MnO3 correlated oxide channel visualized by microwave impedance microscopy. Polarization switching is obtained by applying a tip bias above the coercive voltage of the ferroelectric layer. The microwave conductivity of the correlated channel underneath the up- and down-polarized domains has been quantified by finite-element analysis of the tip-sample admittance. At room temperature, a resistance on/off ratio above 100 between the two polarization states is sustained at frequencies up to 1 GHz, which starts to drop at higher frequencies. The frequence-dependence suggests that the conductance modulation originates from ferroelectric field-effect control of carrier density. The modulation is nonvolatile, remaining stable after 6 months of domain writing. Our work is significant for potential applications of oxide-based ferroelectric field-effect transistors in high-frequency nanoelectronics and spintronics.

New family of two-dimensional A2B2C5 single-layer with high carrier mobilities and excellent conversion efficiency for solar cells

Screening high-performance two-dimensional (2D) materials with desirable direct band gaps and high mobility has attracted great interest due to their excellent application in 2D field effect transistors. Herein, we predicted a new family of nine-atomic A2B2C5 (A = Mg, Ba; B= Al, Ga, and In, C = S, Se) single-layer using first-principles calculations. The results indicate that the energies of this A2B2C5 single-layer are slightly lower than that of exfoliated single-layer Mg2Al2S5. Furthermore, most of the A2B2C5 single-layers host not only direct band gaps but also outstanding electron mobilities (up to ∼103 cm2V−1s−1), revealing a desirable range of near-infrared to visible light absorption. Importantly, single-layer Ba2Al2Se5 and Mg2Ga2Se5 are good donor materials, the corresponding Ba2Al2Se5/HfS2 and Mg2Ga2Se5/InS type-II heterostructures exhibit promising power conversion efficiencies of 22.3 % and 19.8 %, respectively. Our work provides some competitive A2B2C5 candidate single-layers for applying high-performance solar cells.

Thienothiophene and benzothiadiazole based conjugated donor-acceptor polymers; synthesis, photophysical properties and organic field effect transistor applications

Novel conjugated donor-acceptor (D-A) type polymers (P1-P3) possessing thieno[3,2-b]thiophenes (TT) as donors having different functional groups and 2,1,3-benzothiadiazole (BT) as an acceptor were designed and synthesized via palladium-catalyzed Sonogashira coupling reaction. Their electronic and optical properties were investigated by UV–Vis and fluorescence spectroscopies and cylic voltammetry analysis. Organic field-effect transistor (OFET) of the polymers were fabricated using biodegradable and environmental-friendly khaya gum as a high dielectric layer to investigate their charge transport characteristics were at low voltage. All the polymers displayed a p-type field-effect behaviour, among which alkyl chain (C9H19) substituted P2 exhibited the highest average saturated hole mobility, μsat, 0.086 cm2 V−1 s−1, on/off current ratio, Ion/Ioff = 1.0 × 103, and subthreshold swing, SS, 425 mV dec−1. The results presented in this work corroborate that the three novel TT-BT polymers have promising potential for electronic and optoelectronic applications, in particular, where tunability of the field-effect behaviour is essential for performance.

Process Development of a Liquid-Gated Graphene Field-Effect Transistor Gas Sensor for Applications in Smart Agriculture

A compact, multi-channel ionic liquid-gated graphene field-effect transistor (FET) has been proposed and developed in our work for on-field continuous monitoring of nitrate nitrogen and other nitrogen fertilizers to achieve sustainable and efficient farming practices in agriculture. However, fabricating graphene FETs with easy filling of ionic liquids, minimal graphene defects, and high process yields remains challenging, given the sensitivity of these devices to processing conditions and environmental factors. In this work, two approaches for the fabrication of our graphene FETs were presented, evaluated, and compared for high yields and easy filling of ionic liquids. The process difficulties, major obstacles, and improvements are discussed herein in detail. Both devices, those fabricated using a 3 μm-thick CYTOP® layer for position restriction and volume control of the ionic liquid and those using a ~20 nm-thick photosensitive hydrophobic layer for the same purpose, exhibited typical FET characteristics and were applicable to various application environments. The research findings and experiences presented in this paper will provide important references to related societies for the design, fabrication, and application of liquid-gated graphene FETs.

Structural and dynamical properties of two dimensional disordered metal chalcogenides AB (A [formula omitted] Zn, Cd; B [formula omitted] S, Se): A classical molecular dynamic study

In recent years, the synthesis of two-dimensional (2D) materials, particularly the crystalline and disordered phases of 2D transition metal chalcogenides (TMCs), has gained considerable attention due to their wider electronic band gaps. This distinctive feature is pivotal in shaping their potential applications in solar cells, sensors, field-effect transistors (FETs), and photocatalysis for water decomposition. In the present study, we report molecular dynamics simulation of 2d disordered configuration of ZnX and CdX (X: S, Se) compounds using the Stillinger–Weber potential. We have explored their structural features by calculating their radial distribution functions and ring statistics. These systems are thermodynamically stable. The disordered network with numerous voids in these compounds play a pivotal role in lowering their melting temperature compared to their 2D crystalline counterparts, which falls within the range of 600 K to 700 K. The phonon density of states for all these systems shows a higher number of lower frequency (acoustic) modes than optical modes, which is understandably due to the presence of open regions and 2-fold sites in such systems.

First-principles prediction of high carrier mobility for β-phase MX2N4 (M = Mo, W; X = Si, Ge) monolayers

The recently synthesized monolayer MoSi2N4 (Science 2020, 369, 367) exhibits exceptional environmental stability, a moderate band gap, and excellent mechanical properties, presenting exciting opportunities for the exploration of two-dimensional (2D) MX2Z4 materials. However, the low carrier mobility of α-phase MoSi2N4 significantly limits its potential applications in field-effect transistor (FET) devices. In this study, we systematically investigate the structural stability, elastic properties, and carrier mobility of a novel family of β-phase MX2N4 (M = Mo, W; X = Si, Ge) monolayers through first-principles calculations. Our findings reveal that these β-phase MX2N4 monolayers demonstrate remarkable dynamic, thermal, and mechanical stability. Specifically, we identify the MoSi2N4, MoGe2N4, WSi2N4, and WGe2N4 monolayers as semiconductors with band gaps of 2.70 eV, 1.57 eV, 3.12 eV, and 1.93 eV, respectively, as calculated using the HSE06 functional. Moreover, the MX2N4 monolayers exhibit significant elastic anisotropy, characterized by high ideal tensile strengths and a critical tensile strain exceeding 25%. Notably, the WGe2N4 monolayer displays exceptional anisotropic in-plane charge transport, achieving mobility levels of up to 104 cm2V− 1S− 1, surpassing those of the α-phase MX2N4 monolayers. These novel ternary monolayer structures have the potential to broaden the 2D MX2Z4 material family and emerge as promising candidates for applications in field-effect transistors.

A method to detect enzymatic reactions with field effect transistor

Study of enzyme-substrate interactions is a task of great practical and scientific importance. This paper describes the application of ion-sensitive field effect transistors in quasi-equilibrium state for examination of enzymatic reactions. A reaction occurring in the liquid gate affects the chemical potential of electrons in this gate, and this phenomenon may be used to explore biochemical interactions. This strategy can be applied to detect interactions of enzymes with substrates, inhibitors and activators regardless of their optical and electrochemical properties. Using the developed method, the reactions catalyzed by the enzymes belonging to six different EC classes were analyzed, and Michaelis constants for their substrates were determibed. Km values obtained using the proposed method were in good agreement with those obtained with standard colorimetric and fluorimentric assays. Practical potential of the described method was demonstrated by studying the interactions of a diagnostically significant enzyme α-D-galactosidase with its natural and artificial substrates and its inhibitor. Km values for α-D-galactosidase using melibiose and raffinose as substrates and IC50 value for the enzyme inhibitor 1-deoxygalactonojirimycin were determined. The described method allows rapid and label-free investigation of enzyme interactions with substrates, inhibitors and activators for a wide range of biocatalysts.

Realizing n-type carbon nanotubes via halide perovskite nanowires Cs4MX5 inner filling

N-type carbon nanotubes (CNTs)-based field-effect transistors (FETs) have huge potential applications in low-power consumption tunnel FETs. However, the low-work function metal electrodes can achieve n-type CNTs, but they are easily oxidized due to poor environmental stability. Therefore, based on first-principles calculations, we proposed halide perovskite nanowires Cs4MX5 (M = Pb, Sn; X = Cl, Br, I) inner filling to achieve n-type single-walled CNTs (SWCNTs). The results indicated that all the perovskite nanowires located at the center of the SWCNTs possess high stability. Moreover, the diameter of SWCNTs is a crucial factor affecting the inner filling of perovskite nanowires with an optimal diameter of about 1.4 nm. Furthermore, all the perovskite nanowires Cs4MX5 are excellent electron donors, and the largest charge transfer is up to 1.72 e/nm for Cs4SnI5. Their interaction mechanism reveals that the low work function and the large internal bandgap are two important factors for cubic-phase nanowires to realize the n-type CNTs. Our findings provide some candidate materials and a feasible way to achieve n-type CNTs for applying CNTs-based FETs.

The increase of the scattering at high electric fields in multilayer ReS2 FETs: Output characteristics and 1/f noise

Field-effect transistors (FETs) employing two-dimensional (2D) materials have attracted significant attention as a potential alternative to silicon FETs. Among these materials, multilayer rhenium disulfide (ReS2) has emerged as a focal point of interest owing to its distinctive direct bandgap properties. While there is extensive research on the electrical characteristics and doping, studies on the changes in electrical properties during scale-down for practical applications are insufficient. In this study, we investigated the mobility reduction of ReS2 FETs at high drain bias of ReS2 FETs by comparing the different channel lengths of 0.24 μm and 1.5 μm. A reduction in mobility was observed for the shorter channel length, attributed to the enhanced scattering factor at high electric field. To assess the impact of scattering degradation, we conducted a low-frequency noise analysis at drain-source voltage (VDS) = 0.4 V and VDS = 3.0 V for the 0.24 μm length FET. The decrease of the Hooge parameter (αH) at high VDS was observed, which was attributed to an augmentation in Coulomb scattering. This study observed mobility degradation under high electrical fields during scale-down and identified the cause of mobility degradation through low-frequency noise analysis. This contributes to scaling down for practical applications of 2D FETs.

Electrodes for High‐𝜅 Molecular Crystal Antimony Trioxide Gate Dielectrics for 2D Electronics

AbstractWafer‐scale deposition of high‐𝜅 gate dielectrics compatible with atomically thin van der Waals layered semiconductors (e.g., MoS2, WS2, WSe2) is urgently needed for practical applications of field effect transistors based on 2D materials. A study on a high‐𝜅 molecular crystal antimony trioxide (Sb2O3) gate dielectric examined the role of electrode material on dielectric degradation and breakdown. It is demonstrated that the thin films of Sb2O3 can be uniformly deposited on a wafer scale. The current–voltage (I–V) curves show tightly controlled distributions of both leakage current and breakdown voltage. Electrical measurements reveal that defects are generated gradually upon electrical stressing. The evaluation of degradation is based on charge trapping, stress‐induced leakage current, and dielectric breakdown measurements. The breakdown voltage distribution follows a tight monomodal Weibull distribution suggesting a high quality of the film. Comparing Ti and Au as gate electrodes, both the breakdown field and the tunnel current are affected by the choice of electrode material. Transmission electron microscopy reveals that the chemistry at the electrode/Sb2O3 interface plays an important role and that Ti scavenges oxygen from the Sb2O3, forming a defective oxide layer at the Ti/Sb2O3 interface. For the Au electrode, this interfacial reaction is completely absent, improving the dielectric performance.

Probing charge redistribution at the interface of self-assembled cyclo-P5 pentamers on Ag(111)

Phosphorus pentamers (cyclo-P5) are unstable in nature but can be synthesized at the Ag(111) surface. Unlike monolayer black phosphorous, little is known about their electronic properties when in contact with metal electrodes, although this is crucial for future applications. Here, we characterize the atomic structure of cyclo-P5 assembled on Ag(111) using atomic force microscopy with functionalized tips and density functional theory. Combining force and tunneling spectroscopy, we find that a strong charge transfer induces an inward dipole moment at the cyclo-P5/Ag interface as well as the formation of an interface state. We probe the image potential states by field-effect resonant tunneling and quantify the increase of the local change of work function of 0.46 eV at the cyclo-P5 assembly. Our experimental approach suggest that the cyclo-P5/Ag interface has the characteristic ingredients of a p-type semiconductor-metal Schottky junction with potential applications in field-effect transistors, diodes, or solar cells.

Tunable Band Alignment and Optoelectronic Structure of Cu2Se/PtX2 (X=Se,Te) Heterostructures: under Strain and Electric Field

Two-dimensional (2D) material-based van der Waals heterostructures (vdWHs) are an emerging strategy for regulating the electronic properties of two-dimensional materials. This study investigated the effects of a vertical electric field and strain on the band alignment transition and optoelectronic properties of Cu2Se/PtSe2 (PtTe2) vdWHs using density functional theory calculations. Cu2Se/PtSe2 vdWHs exhibited type-I to type-II band alignment transformation under an in-plane strain, interlayer distance, and electric field of 2%, 2.40 Å, and -0.40 V/Å, respectively. Moreover, Cu2Se/PtTe2 vdWH demonstrated a rich transition of types I, II, and III band alignments with in-plane strain. The absorption spectra of Cu2Se/PtSe2 (PtTe2) vdWHs show a certain degree of blue and red shift phenomenon upon the application of strain and electric fields. The predicted power conversion efficiencies at 3% in-plane strain with an interlayer distance of 3.40 Å for Cu2Se/PtSe2 (PtTe2) vdWHs were observed to be as high as 22.58% (19.80%). Thus, our work demonstrated that both strain and electric field can effectively and flexibly control the electronic properties of Cu2Se/PtSe2 (PtTe2) vdWHs, making them a promising candidate material for applications in photodetectors and field-effect transistors.

Simultaneous engineering of the conductivity and work function of biphenylene via fluorine adsorption

Biphenylene (BP) is a new member of the two-dimensional C nanomaterial family, and successful fabrication of BP offers an excellent opportunity for developing innovative C-based electronics. However, its unusual metallicity critically restricts its applications in field-effect transistors (FETs) and photocatalysis. Simultaneously, its relatively low work function (ϕ, 4.33 eV) seriously restricts its applications in anode materials of electronic devices. Therefore, understanding the tunabilities of electronic properties and ϕ of BP-based nanomaterials is crucial to guide experimental exploration; nevertheless, to date, little attention has been paid to this area. Herein, we theoretically demonstrate that conductivity of fluorinated BP (Fn-BP) evolves in the order metallic → semimetallic → semiconductivity with increasing F concentration, attributed to a bonding transition of BP (sp2 → sp2 + sp3 → sp3). Particularly, ϕ of BP can be significantly improved (4.82–6.97 eV) by fluorination, approximately two-fold higher than that of Fn-graphene owing to p electron transfer between F and BP. Consequently, metallic F2D-BP and semimetallic F4S-BP with favorable ϕs can be utilized as substitutes for Au and Pt anodes, respectively. Specifically, F8D-BP, F16D-BP, and F24D-BP with exceptional band gaps of 0.40, 2.80, and 3.44 eV, respectively, exhibit high potentials for making channel materials in FETs, candidate materials in photocatalysis, and buffer layers in solar cells, respectively.

Transport properties of multilayer NbxMo1−xS2/MoS2 in-plane heterostructure tunnel FETs on hexagonal boron nitride substrate

In-plane heterostructures based on transition metal dichalcogenides are promising for applications in tunnel field-effect transistors (TFETs). However, the transport properties of the in-plane heterostructures have not been fully understood due to the presence of generation current derived from the in-gap state of the heterointerface. For further performance improvement, it is important to identify and suppress the origin of the in-gap states at the heterointerface. In this work, we investigated the transport properties of TFETs based on multilayer NbxMo1−xS2/MoS2 in-plane heterostructures on atomically flat hexagonal boron nitride substrate. We observed a transition from staggered gap to broken gap band alignment by electron doping to MoS2 and that band-to-band tunneling current was dominant below 80 K, a higher temperature compared with the heterostructure on an SiO2 surface. These results indicate that the use of atomically flat substrates helps reduce generation current from strain-derived in-gap states in NbxMo1−xS2/MoS2 in-plane heterostructures.