Field-effect Transistor Devices Research Articles

Ferroelectric 2D SnS2 Analog Synaptic FET.

In this study, the development and characterization of 2D ferroelectric field-effect transistor (2D FeFET) devices are presented, utilizing nanoscale ferroelectric HfZrO2 (HZO) and 2D semiconductors. The fabricated device demonstrated multi-level data storage capabilities. It successfully emulated essential biological characteristics, including excitatory/inhibitory postsynaptic currents (EPSC/IPSC), Pair-Pulse Facilitation (PPF), and Spike-Timing Dependent Plasticity (STDP). Extensive endurance tests ensured robust stability (107 switching cycles, 105 s (extrapolated to 10 years)), excellent linearity, and high Gmax /Gmin ratio (>105 ), all of which are essential for realizing multi-level data states (>7-bit operation). Beyond mimicking synaptic functionalities, the device achieved a pattern recognition accuracy of ≈94% on the Modified National Institute of Standards and Technology (MNIST) handwritten dataset when incorporated into a neural network, demonstrating its potential as an effective component in neuromorphic systems. The successful implementation of the 2D FeFET device paves the way for the development of high-efficiency, ultralow-power neuromorphic hardware which is in sub-femtojoule (48 aJ/spike) and fast response (1 µs), which is 104 folds faster than human synapse (≈10ms). The results of the research underline the potential of nanoscale ferroelectric and 2D materials in building the next generation of artificial intelligence technologies.

Ti3C2O2 MXene single-layer as a nanoscale transport device

We considered Ti3C2O2 MXene single-layers with stepped edges as a nanoscale field effect transistor (FET) device. Our model device contains stepped edges at the interface of Ti3C2O2 and Ti2CO2 segments, and a top gate. We suggest that Ti2CO2 semiconducting device region can be obtained by etching the central part of a Ti3C2O2 single-layer. We determined the device characteristic of the proposed device in non-equilibrium Green’s function (NEGF) calculations and observed the transistor behavior. The current through the device is controllable by the total amount of accumulated charge on the gate electrode. Our findings should be applicable to a large number of MXenes: Starting from M3C2O2 MXene single-layers, nanoscale FETs could be produced using conventional mask and etching lithography techniques.

Modeling of non-intrinsic noise in nanometer metal oxide semiconductor field effect transistors

With the proportional reduction of metal–oxide–semiconductor field effect transistor (MOSFET) devices, the short channel effect, the parasitic effect, and the field strength effect are significantly enhanced, the proportion of parasitic resistance increases, and the non-intrinsic noise also increases, which seriously affects the working efficiency of the device. However, existing research mainly focuses on the intrinsic noise of MOSFET, and there is little research on the non-intrinsic noise; furthermore, the models describing the relationship between non-intrinsic noise, device structure, and bias have not yet been addressed. Therefore, in this paper, 90, 65, 32, 10, and 5 nm MOSFETs are studied. The rate of the intrinsic ballistic parameter is introduced to set up the source–drain current model and the non-intrinsic noise model. The source–drain current model is consistent with the theoretical model, numerical simulation, and experimental results in the literature. Finally, the relationship between the non-intrinsic noise and the bias and the device parameters are analyzed, and the conclusion is helpful to improve the working efficiency, lifetime, and response speed of nanoscale MOSFET devices.

Growth and surface structrue of hydrogen terminal diamond thin films

The conductivity of hydrogen-terminated diamond is a limiting factor in its application in field-effect transistor devices. The traditional preparation process hinders the improvement of the electrical properties of hydrogen-terminated diamond due to impurity elements in the diamond bulk and surface damage caused by processing near the diamond surface. To overcome this, researchers have explored the epitaxial growth of a high-purity and flat-surfaced diamond thin film on a diamond substrate. However, this approach still faces challenges in film characterization and achieving high surface smoothness. In this study, microwave plasma chemical vapor deposition technology is used to epitaxially grow a sub-micron thick diamond film on a nitrogen-doping chemical vapor deposition diamond substrate of 10 mm × 10 mm × 0.5 mm in size. The influence of methane concentration on the growth and conductivity of diamond film is investigated. The test results reveal that the growth thickness of the diamond film ranges from 230 to 810 nm, and the nitrogen concentration in the epitaxial layer is lower than 1×10<sup>16</sup> atom/cm<sup>3</sup>. Three growth modes are observed for the homoepitaxial growth of the diamond thin film under different methane concentrations. A methane concentration of 4% enables two-dimensional planar growth of diamond, resulting in a smooth and flat surface with a roughness of 0.225 nm (10 μm×10 μm). The formation of different surface morphologies is attributed to the growing process and etching process of diamond. Surface low-energy electron diffraction testing indicates that the surface of the diamond film undergoes a structural transition from oxygen terminal (1×1: O) to hydrogen terminal (2×1: H) when grown for a short period of time. X-ray photoelectron spectroscopy analysis reveals an extremely low ratio of oxygen element to nitrogen element, giving the grown diamond film P-type conductivity characteristics. The Hall test results demonstrate that the hydrogen-terminated diamond film grown with a methane concentration of 4% exhibits the highest conductivity, with a square resistance of 4981 Ω/square and a hole mobility of 207 cm<sup>2</sup>/(V·s). This enhanced conductivity can be attributed to the lower defect density observed under these specific conditions. The findings of this study effectively improve the electrical properties of hydrogen-terminated diamond, and contribute to the development and practical application of high-power diamond devices.

Establishment of analytical model for electrostatic discharge gate-to-source capacitance of power metal-oxide-semiconductor field-effect transistor

In the actual human body model (HBM) test, it is found that the electrostatic discharge (ESD) test results of various power metal-oxide-semiconductor field-effect transistor (MOSFET) devices show asymmetry between forward withstand voltage and reverse withstand voltage, while the ESD process does not distinguish between positive direction and negative direction. Large differences between forward and reverse withstand voltages are unacceptable for power MOSFETs or as ESD protection devices. The problem of its causing device failure is particularly pronounced. In this work, by establishing the analytical model of gate-to-source capacitance of SGT-MOSFET, VUMOSFET and VDMOS under the forward and reverse voltages, we comparatively analyze the reasons for the asymmetry of the forward and reverse withstand voltages and their different ratios of the three kinds of power MOSFETs, which provides a theoretical basis for testing the device’s ESD and the analyzing their reliability. It is found that the ESD forward and reverse withstand voltage asymmetry phenomena of different power MOSFET structures are related to the variation of gate-to-source capacitance, caused by the reverse-type layer. When a forward voltage is applied across the gate and source, the device gate-to-source capacitance consists of the oxide layer capacitance around the gate in parallel; when a reverse voltage is applied, the gate-to-source capacitance consists of the virtual gate-to-drain capacitance in series with the inverse layer capacitance and then in parallel with the other oxide layer capacitance around the gate. This results in a decrease of the gate-to-source capacitance at the reverse voltage, making the device reverse withstand voltage greater than the forward withstand voltage. The difference in the ratio of ESD reverse withstand voltage to forward withstand voltage among different devices is related to the change of the capacitance of the inverse layer in the gate-to-source capacitor under reverse voltage caused by the difference in device structure.

Strain analysis comparison in complementary and nanosheet field-effect transistor devices: Nanobeam vs Bessel electron diffraction

Strain analysis comparison in complementary and nanosheet field-effect transistor devices: Nanobeam vs Bessel electron diffraction

Performance enhancement of aluminium-gated poly(3-hexylthiophene) transistors with polymer electrolyte/PMMA bilayer gate dielectrics

Tremendous progress in device performance has been realized in electrolyte-gated field-effect transistors (FETs). However, due to the formation of oxides at the metal/electrolyte interface, electrochemically stable and corrosion-resistant noble metals (e.g., gold, platinum, or palladium) have been utilized, which makes device fabrication expensive. In this study, we report an enhanced performance in aluminium (Al)-gated poly(3-hexylthiophene) (P3HT) transistors with polymer electrolyte/poly(methyl methacrylate) (PMMA) bilayer gate dielectrics. This cost-effective Al-gated transistor devices with polymer electrolyte/PMMA bilayer dielectrics measured improved operational stability and hole mobility of ∼0.06 cm2 V−1 s−1 at low operating voltage of −15 V compared to the control Al-gated FETs with PMMA dielectric (∼0.03 cm2 V−1 s−1) and Al-gated devices with electrolyte dielectric (∼10−4 cm2 V−1 s−1). The exceptional performance in the FETs with bilayer gate dielectric would be attributed to an improved charge transport and a robust vacuum metalized Al/PMMA interface in contrast to the electrolyte-gated FETs, which was severely influenced by the formation of aluminium oxide layer (Al2O3) at the Al/dielectric interface. This study provides a practical approach for fabricating low-cost, low-voltage, and high-performance FET devices with hybrid polymer electrolyte/PMMA bilayer dielectrics.

Size-Based Norfentanyl Detection with SWCNT@UiO-MOF Composites.

Single-walled carbon nanotube (SWCNT)@metal-organic framework (MOF) field-effect transistor (FET) sensors generate a signal through analytes restricting ion diffusion around the SWCNT surface. Four composites made up of SWCNTs and UiO-66, UiO-66-NH2, UiO-67, and UiO-67-CH3 were synthesized to explore the detection of norfentanyl (NF) using SWCNT@MOF FET sensors with different pore sizes. Liquid-gated FET devices of SWCNT@UiO-67 showed the highest sensing response toward NF, whereas SWCNT@UiO-66 and SWCNT@UiO-66-NH2 devices showed no sensitivity improvement compared to bare SWCNT. Comparing SWCNT@UiO-67 and SWCNT@UiO-67-CH3 indicated that the sensing response is modulated by not only the size-matching between NF and MOF channel but also NF diffusion within the MOF channel. Additionally, other drug metabolites, including norhydrocodone (NH), benzoylecgonine (BZ), and normorphine (NM) were tested with the SWCNT@UiO-67 sensor. The sensor was not responding toward NH and or BZ but a similar sensing result toward NM because NM has a similar size to NF. The SWCNT@MOF FET sensor can avoid interference from bigger molecules but sensor arrays with different pore sizes and chemistries are needed to improve the specificity.

Atomic layer deposition mechanism of hafnium dioxide using hafnium precursor with amino ligands and water

As a unique nanofabrication technology, atomic layer deposition (ALD) has been widely used for the preparation of various materials in the fields of microelectronics, energy and catalysis. Hafnium dioxide (HfO2), as an excellent high-κ oxide, is widely used as a substitute gate dielectric for conventional SiO2 in field effect transistor devices. Currently, HfO2 high-κ gate dielectric in MOSFET devices was prepared via ALD technology using tetrakis(dimethylamino)hafnium(IV) (Hf(NMe2)4, TDMAHf) and water (H2O) as the precursors. In this work, the complicated surface reaction mechanism of HfO2 H2O-based ALD using Hf(NMe2)4 was investigated using density functional theory calculations. In the TDMAHf reaction, the dimethylamino group of the precursor was eliminated by ligand exchange reaction with the hydroxyl group on the surface. Subsequently, a second dimethylamino group of TDMAHf could further be eliminated by another hydroxyl group on the surface. In the H2O reaction, ligand exchange reactions and coupling reactions could both occur. By the ligand exchange reactions, water molecule could react with the dimethylamino group on the surface. Simultaneously, the hydroxyl and amino groups could also react with neighboring hydroxyl groups to eliminate dimethylamine and water molecules via the coupling reactions. All these insights into the complicated surface reaction mechanism of H2O-based ALD could promote the further development of ALD chemistry and materials.

First‐Principles Design of Ohmic FET Devices from 2D Transition Metal Dichalcogenides

AbstractA chlorine‐doped ultrathin phase of hafnium disulfide (HfS2) is proposed as an ideal candidate material for 2D field‐effect transistor (FET) device applications, down to the extreme sub‐5 nm miniaturization limit. This transition metal dichalcogenide 2D material is designed to combine features of both a metal and a semiconductor, exhibiting a high electric conductivity comparable with ordinary metals, that can be abruptly cut down via gating due to an energy gap immediately below the Fermi level and its anomalous metallic properties. These unique features enable realizing an alternative design of a FET device in which electrode and channel are made of the same Cl‐doped ML HfS2 phase, a potential breakthrough bypassing all issues associated with electronic (Schottky) and structural dis‐homogeneities or low conductivity that have hindered progress in this field. This material/design combination shall lead to a FET device with purely ohmic behavior, high metallic conductance, no interfacial contact resistance, and facile gating with extremely high on/off ratio.

Highly crystalline and fluorescent BODIPY-labelled phenyl-triazole-coumarins as n-type semiconducting materials for OFET devices

In this work, the synthesis of BODIPY-phenyl-triazole labelled coumarins (BPhTCs) using a two-step approach is described. The influence of the BODIPY appending on the photophysical, electrochemical and thermal properties of the phenyl-triazole-coumarin precursors (PhTCs) was investigated. Band gap energies were measured by absorption spectroscopy (2.20 ± 0.02 eV in the solid and 2.35 ± 0.01 eV in solution) and cyclic voltammetry (2.10 ± 0.05 eV). The results are supported by DFT calculations confirming the presence of lowest LUMO levels that facilitate the electron injection and stabilize the electron transport. Their charge-transport parameters were measured in Organic Field-Effect Transistor (OFET) devices. BPhTCs showed an ambipolar transistor behavior with good n-type charge mobilities (10−2 cm2V−1s−1) allowing these derivatives to be employed as promising semiconducting crystalline and fluorescent materials with good thermal and air stability up to 250 °C.

Multiple SiGe/Si layers epitaxy and SiGe selective etching for vertically stacked DRAM

Fifteen periods of Si/Si0.7Ge0.3 multilayers (MLs) with various SiGe thicknesses are grown on a 200 mm Si substrate using reduced pressure chemical vapor deposition (RPCVD). Several methods were utilized to characterize and analyze the ML structures. The high resolution transmission electron microscopy (HRTEM) results show that the ML structure with 20 nm Si0.7Ge0.3 features the best crystal quality and no defects are observed. Stacked Si0.7Ge0.3 ML structures etched by three different methods were carried out and compared, and the results show that they have different selectivities and morphologies. In this work, the fabrication process influences on Si/SiGe MLs are studied and there are no significant effects on the Si layers, which are the channels in lateral gate all around field effect transistor (L-GAAFET) devices. For vertically-stacked dynamic random access memory (VS-DRAM), it is necessary to consider the dislocation caused by strain accumulation and stress release after the number of stacked layers exceeds the critical thickness. These results pave the way for the manufacture of high-performance multivertical-stacked Si nanowires, nanosheet L-GAAFETs, and DRAM devices.

A Comparative Study of n- and p-Channel FeFETs with Ferroelectric HZO Gate Dielectric

This study investigates the electrical characteristics observed in n-channel and p-channel ferroelectric field effect transistor (FeFET) devices fabricated through a similar process flow with 10 nm of ferroelectric hafnium zirconium oxide (HZO) as the gate dielectric. The n-FeFETs demonstrate a faster complete polarization switching compared to the p-channel counterparts. Detailed and systematic investigations using TCAD simulations reveal the role of fixed charges and interface traps at the HZO-interfacial layer (HZO/IL) interface in modulating the subthreshold characteristics of the devices. A characteristic crossover point observed in the transfer characteristics of n-channel devices is attributed with the temporary switching between ferroelectric-based operation to charge-based operation, caused by the pinning effect due to the presence of different traps. This experimental study helps understand the role of charge trapping effects in switching characteristics of n- and p-channel ferroelectric FETs.

Synergetic effect of microfluidic flow and ultrasonication on chains pre-ordering in conjugated polymer solution

Multi-physical fields solution processing strategy provides a universal and facile way to prepare various conjugated polymer (CP) films and high-performance devices, whereas the hierarchical structures evolution and crystallization of the polymer chains are elusive particularly under the far-from-equilibrium state in solution. In this work, we employed a combined microfluidic flow and ultrasonication strategy (FU) for CP solution processing and found a pronounced synergetic effect of these fields in promoting the pre-ordering of chains in solution. This conformation order and anisotropy of the solution were revealed by using UV–Vis absorption, polarized optical microscopy (POM) and cryogenic transmission electron microscopy (Cryo-TEM) characterizations. A non-classical nucleation model for the conjugated polymer crystallization in the procedure of non-equilibrium solution processing was confirmed. The roles of microfluidic flow and ultrasonication on the chain aggregation and crystallization were addressed with the aim of a multi-physical simulation based on pressure acoustics streaming, fluid heat transfer and thermoviscous boundary layer impedance. Compared to pristine solutions, the FU strategy showed improved solution anisotropy and crystallization kinetics, substantially giving rise to a larger crystallinity in films and much increased mobilities for the organic field-effect transistor (OFET) devices by more than an order of magnitude. With an appropriate balance between the solvation and interchain interactions, the FU processing strategy is universal for regulation of chains conformation and aggregation in conjugated polymer solution.

Controllable Carrier Doping in Two-Dimensional Materials Using Electron-Beam Irradiation and Scalable Oxide Dielectrics.

Two-dimensional (2D) materials, characterized by their atomically thin nature and exceptional properties, hold significant promise for future nano-electronic applications. The precise control of carrier density in these 2D materials is essential for enhancing performance and enabling complex device functionalities. In this study, we present an electron-beam (e-beam) doping approach to achieve controllable carrier doping effects in graphene and MoS2 field-effect transistors (FETs) by leveraging charge-trapping oxide dielectrics. By adding an atomic layer deposition (ALD)-grown Al2O3 dielectric layer on top of the SiO2/Si substrate, we demonstrate that controllable and reversible carrier doping effects can be effectively induced in graphene and MoS2 FETs through e-beam doping. This new device configuration establishes an oxide interface that enhances charge-trapping capabilities, enabling the effective induction of electron and hole doping beyond the SiO2 breakdown limit using high-energy e-beam irradiation. Importantly, these high doping effects exhibit non-volatility and robust stability in both vacuum and air environments for graphene FET devices. This methodology enhances carrier modulation capabilities in 2D materials and holds great potential for advancing the development of scalable 2D nano-devices.

Alzheimer's Disease Biomarker Detection Using Field Effect Transistor-Based Biosensor.

Alzheimer's disease (AD) is closely related to neurodegeneration, leading to dementia and cognitive impairment, especially in people aged > 65 years old. The detection of biomarkers plays a pivotal role in the diagnosis and treatment of AD, particularly at the onset stage. Field-effect transistor (FET)-based sensors are emerging devices that have drawn considerable attention due to their crucial ability to recognize various biomarkers at ultra-low concentrations. Thus, FET is broadly manipulated for AD biomarker detection. In this review, an overview of typical FET features and their operational mechanisms is described in detail. In addition, a summary of AD biomarker detection and the applicability of FET biosensors in this research field are outlined and discussed. Furthermore, the trends and future prospects of FET devices in AD diagnostic applications are also discussed.

Interfacial Engineering of Quantum Dots–Metal–Organic Framework Composite Toward Efficient Charge Transport for a Short‐Wave Infrared Photodetector

AbstractShort‐wave infrared (SWIR) quantum dot (QD)‐converted photodetectors are one of the promising devices used in artificial intelligence and automatic navigation systems. However, compared to semi‐conductor‐type photodetectors, they suffer from poor chemical stability and weak electronic conductivity. In this study, a PbS QD and conductive metal–organic framework (MOF) hybrid composite is designed with SWIR detection capability. The Fourier‐transform infrared spectroscopy confirms the surface modification of PbS QDs with MOF. X‐ray absorption near‐edge structures spectra reveal the chemical bonding between MOF and PbS QDs. Furthermore, 2D grazing‐incidence small‐ and wide‐angle X‐ray scattering is utilized to unveil the particle stacking and the preferred orientation of the PbS@MOF thin film. By integrating the PbS@MOF thin film directly on top of the graphene field effect transistor (FET) device, the chemical stability and photoelectric properties of graphene FET are enhanced, and these are investigated using a focus ion beam with a high‐resolution transmission electron microscope. This study offers a strategy to simultaneously improve the chemical stability and the photoelectronic properties of the nanomaterials as well as contribute to the advancement of a QD‐converted SWIR photodetector.

Comparative Study on Indium Precursors for Plasma-Enhanced Atomic Layer Deposition of In2O3 and Application to High-Performance Field-Effect Transistors.

Indium oxide (In2O3) is a transparent wide-bandgap semiconductor suitable for use in the back-end-of-line-compatible channel layers of heterogeneous monolithic three-dimensional (M3D) devices. The structural, chemical, and electrical properties of In2O3 films deposited by plasma-enhanced atomic layer deposition (PEALD) were examined using two different liquid-based precursors: (3-(dimethylamino)propyl)-dimethyl indium (DADI) and (N,N-dimethylbutylamine)trimethylindium (DATI). DATI-derived In2O3 films had higher growth per cycle (GPC), superior crystallinity, and low defect density compared with DADI-derived In2O3 films. Density functional theory calculations revealed that the structure of DATI can exhibit less steric hindrance compared with that of DADI, explaining the superior physical and electrical properties of the DATI-derived In2O3 film. DATI-derived In2O3 field-effect transistors (FETs) exhibited unprecedented performance, showcasing a high field-effect mobility of 115.8 cm2/(V s), a threshold voltage of -0.12 V, and a low subthreshold gate swing value of <70 mV/decade. These results were achieved by employing a 10-nm-thick HfO2 gate dielectric layer with an effective oxide thickness of 3.9 nm. Both DADI and DATI-derived In2O3 FET devices exhibited remarkable stability under bias stress conditions due to a high-quality In2O3 channel layer, good gate dielectric/channel interface matching, and a suitable passivation layer. These findings underscore the potential of ALD In2O3 films as promising materials for upper-layer channels in the next generation of M3D devices.

Controlled synthesis of van der Waals CoS2 for improved p-type transistor contact

Two-dimensional (2D) van der Waals (vdW) p-type semiconductors have shown attractive application prospects as atomically thin channels in electronic devices. However, the high Schottky hole barrier of p-type semiconductor–metal contacts induced by Fermi-level pinning is hardly removed. Herein, we prepare a vdW 1T-CoS2 nanosheet as the contact electrode of a WSe2 field-effect transistor (FET), which shows a considerably high on/off ratio > 107 and a hole mobility of ∼114.5 cm2 V−1 s−1. The CoS2 nanosheets exhibit metallic conductivity with thickness dependence, which surpasses most 2D transition metal dichalcogenide metals or semimetals. The excellent FET performance of the CoS2-contacted WSe2 FET device can be attributed to the high work function of CoS2, which lowers the Schottky hole barrier. Our work provides an effective method for growing vdW CoS2 and opens up more possibilities for the application of 2D p-type semiconductors in electronic devices.

Enhancing Gating Performance in Organic Molecular Field-Effect Transistors by Introducing Polar Azulene Components.

Organic molecular field-effect transistors (FETs) are promising building components for future electronic circuits. Efficient control of charge transport properties is one key issue in the design of organic molecular FETs. In this study, we propose a redesign of a naphthalene-based FET by introducing two azulene components in opposite dipole moment directions. Using density functional theory combined with non-equilibrium Green's function, the simulated electronic transport characteristics reveal that the introduction of polar azulene components effectively narrows the frontier molecular orbitals gap, leading to an increase in the ON-state current. Meanwhile, the OFF-state current is significantly suppressed by highly localizing the dominant electronic transport channel. As a result, improved gate controllability is achieved with a higher ON-OFF current ratio, which is nearly seven times higher than that of the naphthalene-based FET device. These findings provide theoretical directions for future design of organic molecular FET devices with enhanced gating regulation efficiency.