Effective Schottky Barrier Research Articles

Disinfection of bacteria and viruses under near infrared light by tunable self-assembled nanomaterial NH2-MIL-101-xAu based on photothermal and photodynamic mechanisms

In response to the threat posed by multi-drug resistant "superbugs", a synergistic approach of photothermal therapy (PTT) and photodynamic therapy (PDT) has been developed. In this work, NH2-MIL-101-xAu was prepared by introducing Au nanoparticles on the surface of NH2-MIL-101 n-type semiconductor by means of self-assembly. The introduction of Au nanoparticles greatly improves the light absorption and utilization of nanomaterials. Based on the surface plasma response (SPR), NH2-MIL-101-xAu has an efficient photothermal conversion ability, and under the irradiation of 808 nm (1 W/cm2), NH2-MIL-101–5.0Au (0.50 mg/mL) can be heated to 60℃ in 3 min. And the synergistic effect of plasma-induced interfacial charge-transfer transition and Schottky barriers dramatically enhances the photogenerated carrier separation of NH2-MIL-101-xAu, which in turn generates a large number of reactive oxygen species (ROS). Under the experimental conditions, NH2-MIL-101-xAu with the synergistic effect of PTT and PDT had the sterilization rate of 99.99999 % against Escherichia coli and Staphylococcus aureus, and the inactivation rate of Bacteriophage MS2 was more than 99.9 %. This study shows that NH2-MIL-101-xAu possessing a high degree of tunability is an effective PTT and PDT synergistic means of destroying pathogens, which is very helpful in the application of eliminating drug-resistant bacteria.

Scalable Layer-Controlled Oxidation of Bi2O2Se for Self-Rectifying Memristor Arrays With sub-pA Sneak Currents.

Smart memristors with innovative properties are crucial for the advancement of next-generation information storage and bioinspired neuromorphic computing. However, the presence of significant sneak currents in large-scale memristor arrays results in operational errors and heat accumulation, hindering their practical utility. This study successfully synthesizes a quasi-free-standing Bi2O2Se single-crystalline film and achieves layer-controlled oxidation by developing large-scale UV-assisted intercalative oxidation, resulting β-Bi2SeO5/Bi2O2Se heterostructures. The resulting β-Bi2SeO5/Bi2O2Se memristor demonstrates remarkable self-rectifying resistive switching performance (over 105 for ON/OFF and rectification ratios, as well as nonlinearity) in both nanoscale (through conductive atomic force microscopy) and microscale (through memristor array) regimes. Furthermore, the potential for scalable production of self-rectifying β-Bi2SeO5/Bi2O2Se memristor, achieving sub-pA sneak currents to minimize cross-talk effects in high-density memristor arrays is demonstrated. The memristors also exhibit ultrafast resistive switching (sub-100ns) and low power consumption (1.2 pJ) as characterized by pulse-mode testing. The findings suggest a synergetic effect of interfacial Schottky barriers and oxygen vacancy migration as the self-rectifying switching mechanism, elucidated through controllable β-Bi2SeO5 thickness modulation and theoretical ab initio calculations.

Using photo-assisted Schottky barrier effect of Ni/ZnO/P-rGO foam for detection of phosphate in seawater

As a kind of nutrient salt, the high content of phosphate in seawater has a great impact on fishery production and ecological environment. However, rapid and direct detection of phosphate in seawater faces challenge due to intense disruption because of hypersaline water and complex components. The Ni/ZnO/P-rGO foam is prepared and the direct detection of phosphate in seawater is realized using the electrostatically induced barrier change to drive the electrochemical response to phosphate. Furthermore, the photo-assisted Schottky barrier effect is studied, which makes the sensitivity increase by 2.06 times and the lowest detection limit reduce to 0.20 μM. The Ni foam based electrochemical electrode exhibits a high recovery rate (97.8–105 %) and good stability in seawater detection, as well as excellent resistance to seawater interference. Realization of anti-interference performance by exploiting the photo-assisted Schottky barrier effect is promising for practical application in seawater and other harsh environment detection.

Electronic Transport Modulation in Ultrastrained Silicon Nanowire Devices.

In this work, we explore the effect of ultrahigh tensile strain on electrical transport properties of silicon. By integrating vapor-liquid-solid-grown nanowires into a micromechanical straining device, we demonstrate uniaxial tensile strain levels up to 9.5%. Thereby the triply degenerated phonon dispersion relation at the Γ-point of silicon disentangle and the longitudinal phonon modes are used to precisely determine the extent of mechanical strain. Simultaneous electrical transport measurements showed a significant enhancement in the electrical conductance. Aside from considerable reduction of the Si bulk resistivity due to strain-induced band gap narrowing, comparison with quasi-particle GW calculations further reveals that the effective Schottky barrier height at the electrical contacts undergoes a substantial reduction. For these reasons, nanowire devices with ultrastrained channels may be promising candidates for future applications of high-performance silicon-based devices.

ZnIn2S4-based multi-interface coupled photocatalyst for efficient photothermal synergistic catalytic hydrogen evolution

Photothermal synergistic catalysis is a novel technology that converts energy. In this study, ZnIn2S4 with S-vacancy (ZIS-Vs) is combined with Nickel, Nickle Oxide and Carbon Nanofiber aggregates (Ni-NiO@CNFs) to create a multi-interface coupled photocatalyst with double Schottky barrier, double channel and mixed photothermal conversion effect. Theoretical calculation confirms that the Gibbs free energy (ΔG*H) of the S-scheme heterojunction in the composite material is −0.07 eV, which is close to 0. This promotes the adsorption of H* and accelerates the formation of H2. Internal photothermal catalysis is achieved by visible-near infrared (Vis-NIR, RT) irradiation. The internal photothermal catalytic hydrogen production rate of the best sample (0.9Ni-NiO@CNFs/ZIS-Vs) is as high as 17.24 mmol·g−1·h−1, and its photothermal conversion efficiency (η) is as high as 61.42 %. Its hydrogen production efficiency is 20.52 times that of ZIS-Vs (0.84 mmol·g−1·h−1) under visible light (Vis, RT) conditions. When the Vis-NIR light source is combined with external heating (75 ℃), the hydrogen production efficiency is further improved, and the hydrogen production efficiency (29.16 mmol·g−1·h−1) is 26.75 times that of ZIS-Vs (1.09 mmol·g−1·h−1, Vis-NIR, RT). Further analysis shows that the increase in hydrogen production resulted from the apparent activation energy (Ea) of the catalyst decreasing from 16.7 kJ·mol−1 to 9.28 kJ·mol−1. This study provides a valuable prototype for the design of an efficient photothermal synergistic catalytic system.

On the temperature dependence of the current conduction mode in non-homogeneous Pt/n-GaN Schottky barrier diode

Forward current-voltage (I–V) measurements of Pt/n-GaN Schottky barrier diode (SBD) are investigated in a wide temperature range (80–400 K). The temperature dependence of the effective Schottky barrier height (SBH) and ideality factor are analyzed on the basis of the thermionic emission (TE) model by considering a double Gaussian distribution (DGD) of SBH due to the presence of barrier height inhomogeneities at the Pt/n-GaN interface. In the high temperature (HT) region (200–400 K), Pt/n-GaN SBD exhibits nearly an ideal behavior in accordance with the TE conduction mode. The obtained values of the homogeneous SBH Φ‾0bn = 1.33 eV and Richardson constant AHT* = 26.86 A cm−2 K−2are in agreement with the theoretical values for n-type GaN. In the low temperature (LT) region (80–160 K), the corresponding values Φ‾0bn = 0.94 eV and ALT* = 14.74 A cm−2 K−2 deduced within the TE mode deviate strongly from the ideal behavior. This deviation is further confirmed by the large ideality factor. In this work, we provide a strong evidence that the tunneling current including thermionic field emission (TFE) largely dominates the conduction mode at low temperature.

Understanding the Electronic Transport of Al-Si and Al-Ge Nanojunctions by Exploiting Temperature-Dependent Bias Spectroscopy.

Understanding the electronic transport of metal-semiconductor heterojunctions is of utmost importance for a wide range of emerging nanoelectronic devices like adaptive transistors, biosensors, and quantum devices. Here, we provide a comparison and in-depth discussion of the investigated Schottky heterojunction devices based on Si and Ge nanowires contacted with pure single-crystal Al. Key for the fabrication of these devices is the selective solid-state metal-semiconductor exchange of Si and Ge nanowires into Al, delivering void-free, single-crystal Al contacts with flat Schottky junctions, distinct from the bulk counterparts. Thereof, a systematic comparison of the temperature-dependent charge carrier injection and transport in Si and Ge by means of current-bias spectroscopy is visualized by 2D colormaps. Thus, it reveals important insights into the operation mechanisms and regimes that cannot be exploited by conventional single-sweep output and transfer characteristics. Importantly, it was found that the Al-Si system shows symmetric effective Schottky barrier (SB) heights for holes and electrons, whereas the Al-Ge system reveals a highly transparent contact for holes due to Fermi level pinning close to the valence band with charge carrier injection saturation due to a thinned effective SB. Moreover, thermionic field emission limits the overall electron conduction, indicating a distinct SB for electrons.

Electrochemiluminescence Enhancement and Passivation Mitigation in Carbon Nitride Semiconductors via an Integrated Ternary Heterostructure Strategy.

In recent years, carbon nitride (CN) has attracted substantial attention in the field of electrochemiluminescence (ECL) applications, owing to its outstanding optical and electronic properties. However, the passivation of CN during the ECL process has contributed to reduced stability and poor repeatability. While some studies have tried to boost ECL performance by altering CN through doping and vacancies, effectively suppressing CN passivation at high potentials continues to be challenge. In this study, the built-in electric field and the Schottky barrier effect is used to expedite the transfer of electrons from CN to the molybdenum disulfide (MoS2) conduction band. This transfer deterred excessive electron injection into the CN band, thus mitigating its electrochemical degradation. Moreover, by introducing nickel nanoparticles (Ni NPs) as catalytic active sites, it is facilitated that the decomposition of potassium persulfate (K2S2O8), thereby enhancing both the stability and intensity of ECL emission. In the end, the application of ternary heterostructure as sensing platform for the cancer biomarker carcinoembryonic antigen (CEA) demonstrated high sensitivity. This research introduces a novel approach to overcome CN passivation, paving the way for more promising applications of CN in energy, environmental, and biosensing fields.

Temperature-Dependent Conduction and Photoresponse in Few-Layer ReS2.

The electrical behavior and the photoresponse of rhenium disulfide field-effect transistors (FETs) have been widely studied; however, only a few works have investigated the photocurrent as a function of temperature. In this paper, we perform the electrical characterization of few-layer ReS2-based FETs with Cr-Au contacts over a wide temperature range. We exploit the temperature-dependent transfer and output characteristics to estimate the effective Schottky barrier at the Cr-Au/ReS2 interface and to investigate the temperature behavior of parameters, such as the threshold voltage, carrier concentration, mobility, and subthreshold swing. Through time-resolved photocurrent measurements, we show that the photocurrent increases with temperature and exhibits a linear dependence on the incident light power at both low and room temperatures and a longer rise/decay time at higher temperatures. We surmise that the photocurrent is affected by the photobolometric effect and light-induced desorption of adsorbates which are facilitated by the high temperature and the low pressure.

Modulation Doping of Silicon Nanowires to Tune the Contact Properties of Nano‐Scale Schottky Barriers

AbstractDoping silicon on the nanoscale by the intentional introduction of impurities into the intrinsic semiconductor suffers from effects such as dopant deactivation, random dopant fluctuations, out‐diffusion, and mobility degradation. This paper presents the first experimental proof that doping of silicon nanowires can also be achieved via the purposeful addition of aluminium‐induced acceptor states to the SiO2 shell around a silicon nanowire channel. It is shown that modulation doping lowers the overall resistance of silicon nanowires with nickel silicide Schottky contacts by up to six orders of magnitude. The effect is consistently observed for various channel geometries and systematically studied as a function of Al2O3 content during fabrication. The transfer length method is used to separate the effects on the channel conductivity from that on the barriers. A silicon resistivity is achieved as low as 0.04–0.06 Ω ·cm in the nominal undoped material. In addition, the specific contact resistivity is also strongly influenced by the modulation doping and reduced down to 3.5E‐7 Ω · cm2, which relates to lowering the effective Schottky barrier to 0.09 eV. This alternative doping method has the potential to overcome the issues associated with doping and contact formation on the nanoscale.

PEC-SERS Dual-Mode Detection of Foodborne Pathogens Based on Binding-Induced DNA Walker and C3N4/MXene-Au NPs Accelerator.

In this paper, a photoelectrochemical (PEC)-surface-enhanced Raman scattering (SERS) dual-mode biosensor is constructed coupled with a dual-recognition binding-induced DNA walker with a carbon nitride nanosheet (C3N4)/MXene-gold nanoparticles (C/M-Au NPs) accelerator, which is reliable and capable for sensitive and accurate detection of Staphylococcus aureus (S. aureus). Initially, a photoactive heterostructure is formed by combining C3N4 and MXene via a simple electrostatic self-assembly as they possess well-matched band-edge energy levels. Subsequently, in situ growth of gold nanoparticles on the formed surface results in better PEC performance and SERS activity, because of the synergistic effects of surface plasmon resonance and Schottky barrier. Furthermore, a three-dimensional, bipedal, and dual-recognition binding-induced DNA walker is introduced with the formation of Pb2+-dependent DNAzyme. In the presence of S. aureus, a significant quantity of intermediate DNA (I-DNA) is generated, which can open the hairpin structure of Methylene Blue-tagged hairpin DNA (H-MB) on the electrode surface, thereby enabling the switch of signals for the quantitative determination of S. aureus. The constructed PEC-SERS dual-mode biosensor that can be mutually verified under one reaction effectively addresses the problem of the low detection accuracy of traditional sensors. Experimental results revealed that the effective combination of PEC and SERS is achieved for amplification detection of S. aureus with a detection range of 5-108 CFU/mL (PEC) and 10-108 CFU/mL (SERS), and a detection of limit of 0.70 CFU/mL (PEC) and 1.35 CFU/mL (SERS), respectively. Therefore, this study offers a novel and effective dual-mode sensing strategy, which has important implications for bioanalysis and health monitoring.

Au-MoS2 contacts: Quantum transport simulations using a continuum description

We present a novel method of modeling the contact between a metal and a two-dimensional semiconductor. Using Au on MoS2 as an example, we self-consistently solve the Schrödinger and Poisson equations and obtain the charge density in the contact. We consider open boundary conditions using the quantum transmitting boundary method and model the electron current through the contact region. We then investigate the effect of effective Schottky barrier height, electrostatic doping, and length of the overlap region on the contact resistance in a top contact geometry. By using data from experiments or from ab initio calculations for the fitting of parameters, such as the effective Schottky barrier height, the model can be used to efficiently obtain the contact resistance and, therefore, the quality of the contact. Furthermore, we investigate the effect of sampling of the Brillouin zone in the transverse direction on the numerical calculation of key quantities, such as contact resistance and free charge density. Additionally, we show that the boundary conditions applied to the Poisson equation during the calculation of the free charge density have a significant impact on the calculated contact resistance and that the impact is more pronounced in heterostructures with a larger Schottky barrier. We found that the contact resistance may be significantly underestimated, by up to one order of magnitude, when the height of the simulation domain is not large enough.

S-scheme regulated Ni2P-NiS/twinned Mn0.5Cd0.5S hetero-homojunctions for efficient photocatalytic H2 evolution

Effective bulk phase and surface charge separation is critical for charge utilization during the photocatalytic energy conversion process. In this work, the ternary Ni2P-NiS/twinned Mn0.5Cd0.5S (T-MCS) nanohybrids were successfully constructed via combining Ni2P-NiS with T-MCS solid solution for visible light photocatalytic H2 evolution. T-MCS is composed of zinc blende Mn0.5Cd0.5S (ZB-MCS) and wurtzite Mn0.5Cd0.5S (WZ-MCS) and those two alternatively arranged crystal phases endow T-MCS with excellent bulk phase charge separation performance for the slight energy level difference between ZB-MCS and WZ-MCS. S-scheme carriers transfer route between NiS and T-MCS can accelerate the interfacial charge separation and retain the active electrons and holes, meanwhile, co-catalyst Ni2P as electron receiver and proton reduction center can further optimize the H2 evolution reaction kinetics based on the surface Schottky barrier effect. The above-formed homo-heterojunctions can establish multiple charge transfer channels in the bulk phase of T-MCS and interface of T-MCS and Ni2P-NiS. Under the synergistic effect of twinned homojunction, S-scheme heterojunction, and Schottky barrier, the ternary Ni2P-NiS/T-MCS composite manifested an H2 production rate of 122.5 mmol h–1 g–1, which was 1.33, 1.24, and 2.58 times higher than those of the NiS/T-MCS (92.4 mmol h–1 g–1), Ni2P/T-MCS (98.4 mmol h–1 g–1), and T-MCS (47.5 mmol h–1 g–1), respectively. This work demonstrates a promising strategy to develop efficient sulfides photocatalyst toward targeted solar-driven H2 evolution through homo-heterojunction engineering.

Properties of Schottky barrier diodes on heteroeptixial α-Ga2O3 thin films

Schottky barrier diodes on α−Ga2O3:Sn heteroepitaxial thin films grown by pulsed laser deposition on m-plane sapphire substrates are reported. Sets of co-planar diodes were fabricated with different metals and different deposition methods. The current rectification and effective Schottky barrier height of oxidized contacts realized by reactive sputtering significantly exceed the values of non-oxidized contacts realized by thermal evaporation or sputtering in an inert argon atmosphere. The best values obtained are rectification of about eight orders of magnitude (±2 V) and 1.3 eV effective barrier height. The current-voltage characteristics of selected non-oxidized and oxidized platinum diodes have been studied as a function of measurement temperature. The temperature dependence of the effective barrier height and the ideality factor of the diodes were fitted taking into account the lateral potential fluctuations of the barrier potential. The determined mean barrier heights and standard deviations are in the range of 1.76–2.53 and 0.2–0.33 eV, respectively, and are classified with respect to the literature and fulfill a well-established empirical correlation (Lajn’s rule) for a variety of Schottky barrier diodes on different semiconducting materials.

Improvement of Rectification Characteristics of TaOx/Al2O3 Memristors by Oxygen Anion Migration and Barrier Modulation

As we all know, when memories are integrated into arrays on a large scale, the phenomenon of current leakage may occur, which leads to array crosstalk. The selection of memristors with self-rectifying effects can be used to solve crosstalk problems without adding additional device cells, allowing for a higher level of array integration under the same conditions. In this article, by optimizing the thickness of the Al2O3 switching layer in the Au/TaO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{{\text {x}}}$ </tex-math></inline-formula> /Al2O3/TiN self-rectifying memristor (SRM), it is found that the rectification ratio can reach <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim $ </tex-math></inline-formula> 403.79 and the nA level of sneak current can be achieved. The fitting analysis shows that the self-rectification phenomenon related to the thickness of Al2O3 may be related to the effective Schottky barrier between Au/TaO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{{\text {x}}}$ </tex-math></inline-formula> and TaOx/Al2O3 layers and the tunneling effect with increasing voltage. Under the premise of a 10% read margin (RM), it is calculated that the size of the passive array can reach <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${N}$ </tex-math></inline-formula> = 1425. Changing the thickness of the switching layer in the SRM of the stacked structure can significantly improve the rectification effect, thereby increasing the adaptive scale of the array. Our work provides a feasible path for the subsequent optimization of SRMs, which effectively promotes the development of high-density integrated arrays.

Microtubular Nanoporous g-C3N4@Ag as an Efficient Photocarrier Transfer Agent and Visible Light-Harvesting for Photodegradation of Methylene Blue

Microtubular nanoporous graphitic carbon nitride@silver (MN-g-C3N4@Ag) was synthesized in order to investigate the efficiency of a photocarrier transfer agent and visible light-harvesting to improve the applicability of photocatalytic reactions in solving the environmental pollution problem. The content of AgNPs was optimized, and MN-g-C3N4 with 5% of Ag shows the best performance. The results indicated that Ag nanoparticles were homogeneously distributed onto the MN-g-C3N4 surface, which leads to the absorption and harvesting of more visible light on the catalyst. The statistical analysis of the experimental data showed that the kinetic model and the adsorption isotherms for the surface adsorption process are consistent with the Langmuir isotherm [Qmax = 272.0 (mg g–1)] and the pseudo-second-order kinetics [Qe.cal = 280.0 (mg g–1)]. Also, the kinetic rate constant of photocatalytic degradation for the MN-g-C3N4@Ag photocatalyst is 7.5 times higher than that of MN-g-C3N4 and 59.0 times higher than that of bulk g-C3N4. Also, the mechanism of photocatalytic degradation showed that holes and •O2– are the main species for photocatalytic degradation of MB through surface adsorption. As a result, the MN-g-C3N4@Ag nanocomposite can use silver metal as both a Schottky barrier and plasmonic effects generator and MN-g-C3N4 itself as a porous photocatalyst with unique charge transfers in the axial direction. Which can synergistically be prolonged lifetime and photocarrier diffusion length, proving that MN-g-C3N4@Ag can efficiently be operated in environmental pollutant remediation.

Interfacial properties of In-plane monolayer 2H-MoTe2/1T'-WTe2 heterostructures

One of the most appealing aspects of the two-dimensional transition-metal dichalcogenides (2D-TMDs) is that they have a variety of crystal types, which can exist in three different atomic lattices, 2H, 1 T and 1 T', and can therefore exhibit diverse electronic properties. In addition, 2D-TMD heterostructures with distinctive features can be generated by combining two monolayers either vertically or laterally (in-plane). In this work, we used first-principles calculations to explore the structural and electronic properties of the H-phase MoTe2 monolayer, the T'-phase WTe2 monolayer, and their in-plane heterostructures (H-MoTe2/T'-WTe2). The H-phase MoTe2 monolayer has a band structure with a direct band gap, whereas the 1 T'-WTe2 monolayer is projected to be a Weyl semimetal based on our findings. We constructed a series of five relatively stable in-plane H-MoTe2/T'-WTe2 heterostructures with metal–semiconductor and studied their electronic properties. The band structures of these in-plane heterostructures were shown to be strongly related to the relative orientations of the monolayers at the interface. In particular, the band gaps of the heterostructures joined along the armchair direction were found to be smaller than 0.1 eV. By sewing the MoTe2 and WTe2 monolayers along the zigzag direction, two relatively stable structures were created, with according to the band structure analysis, exhibited metallic characteristics. Surprisingly, band inversion appeared near the Fermi level due to boundary effects. Therefore, topological properties may be present in such in-plane heterostructures. Moreover, some of these in-plane H-MoTe2/T'-WTe2 heterostructures have effective Schottky barrier heights smaller than 0.25 eV for holes, and could thus be used to construct field effect transistors (FETs). We also found that the effective Schottky barrier height was largely determined by the interfacial bonding environment, the external electric field, and uniaxial strains. Our findings enrich the diversity of the 2D-TMDs heterostructures and point to a viable approach for the design of high-performance electronic and optoelectronic devices.

Radiation Response of Large-Area 4H-SiC Schottky Barrier Diodes

We report on the effects of large-area 4H-SiC Schottky barrier diodes on the radiation response to ionizing particles. Two different diode areas were compared: 1 mm × 1 mm and 5 mm × 5 mm. 6LiF and 10B4C films, which were placed on top of the diodes, were used as thermal neutron converters. We achieved a thermal neutron efficiency of 5.02% with a 6LiF thermal neutron converter, which is one of the highest efficiencies reported to date. In addition, a temperature-dependent radiation response to alpha particles was presented. Neutron irradiations were performed in a JSI TRIGA dry chamber and an Am-241 wide-area alpha source was used for testing the alpha response of the 4H-SiC Schottky barrier diodes.

Vertical Nonvolatile Schottky‐Barrier‐Field‐Effect Transistor with Self‐Gating Semimetal Contact

AbstractEmerging 2D nonvolatile Schottky‐barrier‐field‐effect transistors (NSBFETs) are envisaged to build a promising reconfigurable in‐memory architecture to mimic the brain. Herein, a vertically stacked multilayered graphene (MGr)‐molybdenum disufide (MoS2)‐tungsten ditelluride (WTe2) NSBFET is reported. The semimetal WTe2 with the charge‐trapping effect enables the simultaneous integration of the electrode and the self‐gating function. The effective Schottky barrier height offset ΔΦB is programed from ΔΦB‐p = 132.6 meV to ΔΦB‐n = 109.4 meV, inducing the reversed built‐in electric field to make the NSBFET, so as to provide one with a multifunctional platform to integrate the nonvolatility and the reconfigurable self‐powered photo response. The reversible open‐circuit voltages of NSBFET synapse are programmed from −0.1 to 0.25 V and the self‐powered responsivity with reversed signs is tuned from 290 to −50 mA W−1, which enables the representation of a signed weight in a single device to enrich multiple optical sensing and computing capabilities.

Ultrawide bandgap vertical β-(AlxGa1−x)2O3 Schottky barrier diodes on free-standing β-Ga2O3 substrates

Ultrawide bandgap β-(AlxGa1−x)2O3 vertical Schottky barrier diodes on (010) β-Ga2O3 substrates are demonstrated. The β-(AlxGa1−x)2O3 epilayer has an Al composition of 21% and a nominal Si doping of 2 × 1017 cm−3 grown by molecular beam epitaxy. Pt/Ti/Au has been employed as the top Schottky contact, whereas Ti/Au has been utilized as the bottom Ohmic contact. The fabricated devices show excellent rectification with a high on/off ratio of ∼109, a turn-on voltage of 1.5 V, and an on-resistance of 3.4 mΩ cm2. Temperature-dependent forward current-voltage characteristics show effective Schottky barrier height varied from 0.91 to 1.18 eV while the ideality factor from 1.8 to 1.1 with increasing temperatures, which is ascribed to the inhomogeneity of the metal/semiconductor interface. The Schottky barrier height was considered a Gaussian distribution of potential, where the extracted mean barrier height and a standard deviation at zero bias were 1.81 and 0.18 eV, respectively. A comprehensive analysis of the device leakage was performed to identify possible leakage mechanisms by studying temperature-dependent reverse current-voltage characteristics. At reverse bias, due to the large Schottky barrier height, the contributions from thermionic emission and thermionic field emission are negligible. By fitting reverse leakage currents at different temperatures, it was identified that Poole–Frenkel emission and trap-assisted tunneling are the main leakage mechanisms at high- and low-temperature regimes, respectively. Electrons can tunnel through the Schottky barrier assisted by traps at low temperatures, while they can escape these traps at high temperatures and be transported under high electric fields. This work can serve as an important reference for the future development of ultrawide bandgap β-(AlxGa1−x)2O3 power electronics, RF electronics, and ultraviolet photonics.