Device Performance Research Articles

Device simulation study of multilayer MoS2 Schottky barrier field-effect transistors

Molybdenum disulfide (MoS2) is a representative two-dimensional layered transition-metal dichalcogenide semiconductor. Layer-number-dependent electronic properties are attractive in the development of nanomaterial-based electronics for a wide range of applications including sensors, switches, and amplifiers. MoS2field-effect transistors (FETs) have been studied as promising future nanoelectronic devices with desirable features of atomic-level thickness and high electrical properties. When a naturallyn-doped MoS2is contacted with metals, a strong Fermi-level pinning effect adjusts a Schottky barrier and influences its electronic characteristics significantly. In this study, we investigate multilayer MoS2Schottky barrier FETs (SBFETs), emphasizing the metal-contact impact on device performance via computational device modeling. We find thatp-type MoS2SBFETs may be built with appropriate metals and gate voltage control. Furthermore, we propose ambipolar multilayer MoS2SBFETs with asymmetric metal electrodes, which exhibit gate-voltage dependent ambipolar transport behavior through optimizing metal contacts in MoS2device. Introducing a dual-split gate geometry, the MoS2SBFETs can further operate in four distinct configurations:p - p,n - n,p - n, andn - p. Electrical characteristics are calculated, and improved performance of a high rectification ratio can be feasible as an attractive feature for efficient electrical and photonic devices.

Saturation Mobility of 100 cm2 V-1 s-1 in ZnO Thin-Film Transistors through Quantum Confinement by a Nanoscale In2O3 Interlayer Using Spray Pyrolysis.

In this study, we present a comprehensive study on the fabrication and characterization of heterojunction In2O3/ZnO thin-film transistors (TFTs) aimed at exploiting the quantum confinement effect to enhance device performance. By systematically optimizing the thickness of the crystalline In2O3 (c-In2O3) layer to create a narrow quantum well, we observed a significant increase in saturation mobility (μSAT) from 12.76 to 97.37 cm2 V-1 s-1. This enhancement, attributed to quantum confinement, was achieved through the deposition of a 3 nm c-In2O3 semiconductor via spray pyrolysis. Various In2O3 layer thicknesses (2-5 nm) were obtained by adjusting precursor solution concentration, flow rate, and number of spray cycles. Post annealing treatments were employed to reduce the defects at the interface and within the oxide film, enhancing device stability and performance. Transmission electron microscopy (TEM) confirmed the uniformity of the c-In2O3 film thickness, while variations in thickness significantly influenced TFT performance, particularly the turn-on voltage (VGS) due to changes in the carrier concentration. Ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS) supported the formation of a potential well with a two-dimensional electron gas (2DEG). The study of single and multiple superlattice structures of consecutive c-In2O3 and c-ZnO layers provided insights into the effects of multiple quantum wells on the TFT performance. This research presents an advanced approach to TFT optimization, highlighting high reliability, and environmental and bias stabilities. These lead to enhanced mobility and performance uniformity through the precise control of c-In2O3 layer thickness for the quantum confinement effect.

Spatially resolved random telegraph fluctuations of a single trap at the Si/SiO2 interface

We use electrostatic force microscopy to spatially resolve random telegraph noise at the Si/SiO2 interface. Our measurements demonstrate that two-state fluctuations are localized at interfacial traps, with bias-dependent rates and amplitudes. These two-level systems lead to correlated carrier number and mobility fluctuations with a range of characteristic timescales; taken together as an ensemble, they give rise to a [Formula: see text] power spectral trend. Such individual defect fluctuations at the Si/SiO2 interface impair the performance and reliability of nanoscale semiconductor devices and will be a significant source of noise in semiconductor-based quantum sensors and computers. The fluctuations measured here are associated with a four-fold competition of rates, including slow two-state switching on the order of seconds and, in one state, fast switching on the order of nanoseconds which is associated with energy loss.

Implementation of Chaotic Neural Key Generation Algorithm For IoT Devices

This paper presents a new method for generating encryption keys for Internet of Things (IoT) devices. This method combines chaos theory with neural networks to create secure and efficient keys. We use the Lorenz chaotic system to generate complex patterns and a Convolutional Neural Network (CNN) to learn and predict these patterns. This approach is designed to address the unique security challenges of IoT devices, which often have limited computing power. We tested our method with different key sizes and evaluated its performance using accuracy, loss, entropy, and correlation metrics. The results show that key sizes between 256 and 512 bits offer the best balance between model performance and security for IoT devices. We also conducted Diehard statistical tests, which our key generation method passed successfully, demonstrating its ability to produce high-quality random keys.

Considerations on time resolution of neutron irradited single pixel 3D structures at fuences up to 1017 neq/cm2 using 120 GeV SPS pion beams

The proven radiation hardness of silicon 3D devices up to fluences of 1 × 1017 neq/cm2 makes them an excellent choice for next generation trackers, providing <10 μm position resolution at a high multiplicity environment. The anticipated pile-up increase at HL-LHC conditions and beyond, requires the addition of <50 ps per hit timing information to successfully resolve displaced and primary vertices. In this study, the timing performance, uniformity and efficiency of neutron and proton irradiated single pixel 3D devices is discussed. Fluences up to 1 × 1017 neq/cm2 in three different geometrical implementations are evaluated using 120 GeV SPS pion beams. A MIMOSA-26 type telescope is used to provide detailed tracking information with a ∼5 μm position resolution. Productions with single- and double-sided processes, yielding active thicknesses of 130 and 230 μm respectively, are examined with varied pixel sizes from 55 × 55 μm2 to 25 × 100 μm2 and a comparative study of field uniformity is presented with respect to electrode geometry. The question of electronics bandwidth is extensively addressed with respect to achievable time resolution, efficiency and collected charge, forming a 3D phase space to which an appropriate operating point can be selected depending on the application requirements.

High-Performance, High-Resolution Quantum Dot Light-Emitting Diodes with Self-Assembly Single-Molecular Interface Modification.

With the development of near-eye displays, the demands for display resolution and performance are increasing. Quantum dot performance is virtually independent of pixel size, making it an efficient way to display ultrahigh resolution. However, the low efficiency of high-resolution quantum dot devices has been an urgent technical bottleneck to be solved. Here, we constructed a dense single-molecule modification layer and a leakage current blocking layer for high-resolution devices using self-assembly, thereby realizing ultrahigh-resolution, high-efficiency, and stable high-resolution quantum dot light-emitting diodes (QLEDs). The peak external quantum efficiencies of the red devices are 24.68% (8759 PPI) and 19.54% (26075 PPI), respectively, with an exceptional long lifetime (T95@1000 nit) up to 4871 h. In addition, we explored the feasibility of this modification strategy on non-Cd-based quantum dots. In conclusion, our strategy effectively improves the performance of high-resolution devices and provides a superior approach for realizing near-eye display applications.

Spin-Lifetime Probe for Detecting Intramolecular Noncovalent Interaction in Organic Semiconductors.

Intramolecular noncovalent interaction (INCI), a crucial strategy for effectively enhancing molecular planarity and extending π-electron delocalization in organic semiconductors (OSCs), has played an increasingly important role in optoelectronic applications. However, though the INCI formation is regularly considered to improve the device performance by literature, there is no feasible approach to directly and reliably characterizing its formation in practical-OSC films thus far. Here in this study, by theoretical analysis and calculation, the generation of INCIs in OSCs is found, normally consisting of relatively heavy elements, such as O···Se, O···S, N···S interactions, etc., can induce enhanced strength of spin-orbit coupling, the primary factor dominating spin lifetime in OSCs. Based on this newly discovered theory, spin lifetime is creatively employed as a probe for sensitively detecting INCIs in OSC films via spin valves or field-induced electron paramagnetic resonance, respectively. This study will highly promote academic and applicable developments of the cross-cutting frontier research field between organic spintronics and electronics.

Fabrication of solid-state plasmonic solar cell device using FTO|TiO2|Ag-nanoparticle assembly to generate hot electrons surpassing Schottky barrier

This work presents a detailed investigation into the fabrication and performance evaluation of plasmonic solar cells, where a thin film of silver nanoparticles is deposited onto a TiO₂ layer, with the silver film itself functioning as the active layer for light absorption and energy conversion. The study compares two deposition techniques—DC Magnetron Sputtering and Thermal Vapor Deposition (TVD)—revealing significant differences in the resulting device performance. The device fabricated using TVD demonstrated a significantly higher open circuit voltage of 440.3 mV and short circuit current density of 1.6 mA/cm² compared to the device fabricated via DC Magnetron Sputtering, which recorded an open circuit voltage of 56.92 mV and a short circuit current density of 0.03 mA/cm². These results indicate that TVD offers superior electron-hole separation, reduced recombination losses, and enhanced light absorption efficiency. The main contribution of this work lies in demonstrating that the TVD technique significantly improves the photovoltaic performance of plasmonic solar cells compared to DC Magnetron Sputtering. The study validates the hot-electron mechanism at the TiO2|Ag junction using Kelvin probe force microscopy, contributing valuable insights into the role of plasmonic effects in enhancing solar cell efficiency. Additionally, it underscores the potential of TVD for developing advanced solar cell technologies with higher energy conversion efficiency.

The evaluation of a novel single-lead biopotential device for home sleep testing.

This paper reports on the clinical evaluation of the sleep staging performance of a novel single-lead biopotential device. 133 patients suspected of obstructive sleep apnea were included in a multi-site cohort. All patients underwent polysomnography and received the study device, a single-lead biopotential measurement device attached to the forehead. Clinical endpoint parameters were selected to evaluate the device's ability to determine sleep stages. Finally, the device's performance was compared to the clinical study results of comparable devices. Concurrent PSG and study device data were successfully acquired for 106 of the 133 included patients. The results of this study demonstrated significant similarity in overall sleep staging performance (5-stage Cohen's Kappa of 0.70) to the best-performing reduced-lead biopotential device to which it was compared (5-stage Cohen's Kappa of 0.73). Contrary to the comparator devices, the study device reported a higher Cohen's Kappa for REM (0.78) compared to N3 (0.61), which can be explained by its particular measuring electrode placement (diagonally across the lateral cross-section of the eye). This placement was optimized to ensure the polarity of rapid eye movements could be adequately captured, enhancing the capacity to discriminate between N3 and REM sleep when using only a single-lead setup. The results of this study demonstrate the feasibility of incorporating a single-lead biopotential extension in a reduced-channel home sleep apnea testing setup. Such incorporation could narrow the gap in the functionality of reduced-channel home sleep testing and in-lab polysomnography without compromising the patient's ease of use and comfort.

Theoretical investigation on crash performance of bamboo-inspired energy absorption systems based on systematic experimental and numerical analysis

The need for energy-absorbing devices with adaptable crashworthiness is increasingly urgent in various engineering fields with diverse load environments. For this aim, bamboo-inspired modular energy absorption systems have recently been proposed to integrate mechanical efficiency, tunability, and robustness. However, their mechanical responses under varying load velocities have not been systematically studied, which limits the effective prediction and optimization of their crashworthiness. In this study, quasi-static and dynamic experiments were performed on bamboo-inspired systems, discretely assembled using 3D printed steel tube specimens. Matched finite element simulations were conducted using ABAQUS/Explicit. Specific energy absorption and efficiency of these systems respectively exceeded 12.9 J/g and 47 %, surpassing existing discretely assembled systems and rivaling typical cellular materials. Efficient deformation mode with self-locking capability was observed, and sharp impact peak was avoided when the crash velocity was less than 50 m/s. Building upon these findings, a modified spherical shell theory under crashing was developed to predict energy absorption performance of bamboo-inspired system based on the traveling plastic hinge model. The average relative error between the analytical solution and finite element results was found less than 6.5 %. The mean effective stress of the system could exceed 35 MPa under thickness-to-diameter ratio of 5 %. This work presents an efficient and effective approach for optimizing and estimating the crash performance of modular protective devices.

Electrochemical properties of plasticized PVA-based electrolyte inserted with alumina nanoparticles for EDLC application with enhanced dielectric constant

In the current study, the role of alumina nanoparticles was examined in the electrochemical and device performance of PVA-based electrolytes. The NaSCN was used as a cation provider for the host electrolyte, and the glycerol plasticizers were used to enhance conductivity and flexibility. The ratio of salt and plasticizer was fixed, while nanoparticles were varied. The results of impedance AC conductivity confirm that 3 wt% of alumina insertion results in high DC conductivity, which is sufficient for electrochemical device application. Electrode polarization region and plateau area are clearly distinguished in AC spectra. The study of the Dielectric constant reveals that charge storage is maximum at 3 wt% of alumina. The dielectric constant values are about twice the dielectric loss value, which is the topic of immense scientific discussion. The contribution of ion fraction was found to be 0.94, which is excellent compared to the negligible contribution of electrons, which is about 0.05. Electrochemical stability is an additional crucial factor and was found to be 2.47 V. To identify any Redox or non-Redox phenomena occurring in the electrical double-layer capacitor (EDLC) cyclic voltammetry (CV) as the simplest analysis method has been carried out on the sample having the highest DC value. A leaf-like form of the CV plot was noticed at high scan rates, while a rectangular shape was identified at low scan rates. The charge-discharge shape is almost close to the ideal triangular pattern. The discharge part was used to calculate critical EDLC device parameters such as ESR, efficiency, specific capacitance power density, and energy density over 2000 cycles. Low ESR (below 60 Ω) and stable efficiency (almost 100 %) of the device results in high capacitance (≈87 F/g), power density (2978 Wh/kg), and energy density (12.86 W kg−1). The results established that nan-fillers alongside plasticizer is crucial to deliver EDLC devices with improved performances.

Transmission electron microscopy of epitaxial semiconductor materials and devices

Abstract The transmission electron microscope (TEM) is a powerful imaging, diffraction and spectroscopy tool that has revolutionized the field of microscopy. It has contributed to numerous breakthroughs in various scientific disciplines. TEM-based techniques can offer atomic resolution as well as elemental analysis, which benefit the study of epitaxial semiconductors and their related optoelectronic devices on the atomic scale. The design and optimization of the device performance depend on three key factors: the control of strain at nanometer scale, control of the formation and propagation of defects as well as the control of local electronic properties. Manipulation and optimization are only possible if the key factors can be characterized precisely. Herein, the TEM techniques for strain analysis, defect characterization and bandgap evaluation are reviewed and discussed. Lately, with the development of in-situ TEM techniques, researchers have been able to observe dynamic processes and study the behaviour of materials and devices under realistic conditions (in gaseous atmosphere or in liquids, at elevated or cryogenic temperatures, under strain, bias or illumination) in real-time with extremely high spatial resolution. This review explores the impact and significance of in-situ TEM in the field of semiconductors.

The impact of charge carrier dynamics on the outdoor performance of cesium-lead-halide perovskite photovoltaics

We investigated the optoelectronic characteristics of cesium-based perovskite using various techniques. The steady-state photoluminescence (PL) spectroscopy of this perovskite solar cell composition shows the presence of strong peaks at a wavelength of 759 nm, which that corresponds to a band gap energy 1.63 eV. This band gap energy was estimated using two complementary methods, the PL emission spectra and the UV–vis absorption spectra. The study describes the dependence of photon energy on wavelength using a Gaussian mathematical model. Real-outdoor performance testing was conducted in Ethiopia’s climate during the hottest seasons to study the device performance under outdoor conditions at varying irradiances. Moreover, we investigated power generation from the devices using current–time measurements and analyzed charge carrier dynamics through transient photocurrent measurements.

Nanoparticle-based Biosensors for Detection of Heavy Metal Ions

Heavy metal pollution is one of the most serious environmental problems in the world. Many efforts have been made to develop biosensors for monitoring heavy metals in the environment. Development of nanoparticle-based biosensors is the most effective way to solve this problem. This review presents the latest technology of nanoparticle-based biosensors for environment monitoring to detect heavy metal ions, which are magnetic chitosan biosensor, colorimetric biosensor, and electrochemical biosensor. Magnetic chitosan biosensor acts as a nanoabsorbent, which can easily detect and extract poisonous heavy metal ions such as lead ions and copper ions. There are several methods to prepare the chitosan based on the nanoparticle, which are cross-linking, co-precipitation, multi-cyanoguanidine, and covalent binding method. In colorimetric biosensor, gold and silver nanoparticles are commonly used to detect the lead and mercury ions. In addition, this biosensor is very sensitive, fast and selective to detect metal ions based on the color change of the solution mixture. Meanwhile, electrochemical biosensor is widely used to detect heavy metal ions due to a simple and rapid process, easy, convenient and inexpensive. This biosensor is focused on the surface area, which leads to significant improvement in the performance of devices in terms of sensitivity. The wide surface area can affect the performance of the biosensor due to a limited space for operation of electrode. Therefore, reduced graphene oxide is a suitable material for making the electrochemical biosensor due to a wide surface area, good conductivity and high mechanical strength. In conclusion, these three technologies have their own advantages in making a very useful biosensor in the detection of heavy metal ions.

Operation of Amorphous TiO2-Protected Photocathodes Described with the Maxwell Equivalent Circuit.

The use of amorphous TiO2 (a-TiO2), deposited by atomic layer deposition, is a common strategy to protect semiconductors from degradation when used in water-splitting photoelectrochemical (PEC) cells. Electrochemical impedance spectroscopy (EIS) is a suitable technique to study these PEC cells because it is capable of deconvoluting multiple processes occurring during operation, therefore providing information about mechanisms leading to the overall device performance. When biased under hydrogen evolution conditions, EIS shows that two simultaneous processes occur in a-TiO2-protected photocathodes, which introduces an ambiguity in choosing the correct equivalent circuit to describe the operating device. In this report, a model p-Si|a-TiO2|Pt photocathode system is used to show that the Maxwell circuit best describes the operating mechanism, as opposed to the more commonly used Voight and nested circuits. This indicates that, under hydrogen evolution conditions, both faradaic and nonfaradaic processes are occurring. Whereas the faradaic process corresponds to the hydrogen evolution reaction itself, the nonfaradaic process is traced to the p-Si|a-TiO2 interface.

Design and Optimization of High Performance Multi-Step Separated Trench 4H-SiC JBS Diode

In this paper, a novel 3300 V/40 A 4H-SiC junction barrier Schottky diode (JBS) with a multi-step separated trench (MST) structure is proposed and thoroughly investigated using TCAD simulations. The results show that the introduction of MST expands the Schottky contact area, resulting in a decrease in the forward voltage drop. Furthermore, the combination of the deep P+ shielded region and the central P+ region effectively reduces the leakage current, leading to a 43.7% increase in the blocking voltage compared to conventional 4H-SiC JBS. The effects of the step depth (ds) and the width of the central P+ region (wm) on the device performance are analyzed in depth. In addition, a multi-step trenched linearly graded field-limiting rings (MTLG-FLR) termination ensures a more uniform electric field distribution, and the terminal protection efficiency reaches up to 90%, which further enhances the reliability of the terminal structure.

Out‐Diffusion and Uphill‐Diffusion of Mg in Czochralski‐Grown (100) β‐Ga2O3 Under High‐Temperature Annealing and Its Influence on Lateral MOSFET Devices

AbstractIn this work, the out‐diffusion and uphill‐diffusion of Mg inside (100) β‐Ga2O3 epilayers and substrates are reported. The Mg accumulates toward the (100) surface upon annealing under an oxidizing environment, whereas the concentration profile changes with annealing temperatures and durations. Furthermore, the out‐diffusion of Mg from the substrate into the epilayer is observed at temperatures above 800 °C, which continues during the film growth. The substitutional‐interstitial‐diffusion (SID) mechanism is suggested to be the driving mechanism for the former, and the latter is related to the diffusion of mobile Mg interstitials. The accumulation profile of Mg can be used to identify the interface between the epilayer and the substrate. Furthermore, significant differences in device performance are observed for power transistors fabricated on annealed and non‐annealed epitaxial β‐Ga2O3 wafers. Increased breakdown voltages of annealed samples are attributed to the Mg diffusion into the first few nanometers of the epitaxial layer close to the interface to the semi‐insulating substrate, leading to compensation of residual dopants (donors) in that region.

Methylammonium-Free Ink for Blade-Coating of Pure-Phase α-FAPbI3 Perovskite Films in Air.

The α-c (α-FAPbI3) has been extensively employed in the fabrication of high-efficiency perovskite solar cells, yet heavily relied on multiple additives in upscalable fabrication in air. In this work, a simple α-FAPbI3 ink is developed for the blade-coating fabrication of phase-pure α-FAPbI3 in ambient air free from any additives containing extrinsic ions. The introduction of 2-imidazolidinone (IMD) to the FAPbI3 precursor inks leads to the formation of intermediate phases that change the phase transition pathway from δ-FAPbI3 to α-FAPbI3 by tilting the PbI6 octahedrons with strong coordination to Pb2+. Furthermore, the IMD ligands in the intermediate phase gradually escape from the perovskite film during the annealing, leaving a phase-pure α-FAPbI3 film vertically grown with large grains. Consequently, the small-sized PSCs fabricated with blade-coated α-FAPbI3 film achieve an efficiency of up to 23.14%, and the corresponding mini-module yields an efficiency of 19.66%. The device performance is among the highest reported for phase-pure α-FAPbI3 PSCs fabricated in the air without non-native cations or chloride additives, offering a simple and robust fabrication approach of phase-pure α-FAPbI3 films for PV application.

2D Embedded Ultrawide Bandgap Devices for Extreme Environment Applications.

Ultrawide bandgap semiconductors such as AlGaN, AlN, diamond, and β-Ga2O3 have significantly enhanced the functionality of electronic and optoelectronic devices, particularly in harsh environment conditions. However, some of these materials face challenges such as low thermal conductivity, limited P-type conductivity, and scalability issues, which can hinder device performance under extreme conditions like high temperature and irradiation. In this review paper, we explore the integration of various two-dimensional materials (2DMs) to address these challenges. These materials offer excellent properties such as high thermal conductivity, mechanical strength, and electrical properties. Notably, graphene, hexagonal boron nitride, transition metal dichalcogenides, 2D and quasi-2D Ga2O3, TeO2, and others are investigated for their potential in improving ultrawide bandgap semiconductor-based devices. We highlight the significant improvement observed in the device performance after the incorporation of 2D materials. By leveraging the properties of these materials, ultrawide bandgap semiconductor devices demonstrate enhanced functionality and resilience in harsh environmental conditions. This review provides valuable insights into the role of 2D materials in advancing the field of ultrawide bandgap semiconductors and highlights opportunities for further research and development in this area.

Investigation of the Electrical Characteristics of AlGaN/AlN/GaN Heterostructure MOS-HEMTs with TiO2 High-k Gate Insulator

This paper investigates the impact of TiO2 high-k gate insulator on the electrical characteristics of AlGaN/AlN/GaN MOS-HEMT transistors using MATLAB and Atlas-TCAD simulation software. The physical analytical model of the MOS-HEMTs is used for simulation from Al2O3, HfO2, and TiO2 as the gate dielectric materials, which provide higher performance and reliability of the MOS-HEMT devices. The device shows a good improvement in its result of the DC and AC characteristics with different permittivity of insulator materials. Thus, the DC and AC performance of GaN MOS-HEMTs is higher than with other insulators, such as Al2O3 and HfO2 by using TiO2 as the gate dielectric. Moreover, the simulation results proved that TiO2 is the better gate dielectric material to enhance the electrical reliability of the power switching devices for high-temperature applications such as electric automobiles.