Schottky Barrier Research Articles

Controllable Ultrathin Nickel Nanoislands With Dense Discrete Space Charge Regions: Steering Hole Extraction for High-Performance Underwater Multispectral Weak-Light Photodetection.

Undersea optical communication (UOC) is vital for ocean exploration and military applications. In the dim-light underwater environment, photodetectors must maximize photon utilization by minimizing optical losses and carrier recombination. This can be achieved by integrating ultrathin metal nanostructures with photocatalysts to form Schottky junctions, which enhance charge separation and injection while mitigating metal-induced light shading. The strategic design of discrete metal nanostructures providing numerous high-depth space charge regions (SCRs) without overlap offers a promising approach to optimize hole transport paths and further suppress recombination. Here, a facile phase-separation lithography technique is explored to fabricate tunable ultrathin Ni nanoislands atop n-Si, yielding high-performance photoelectrochemical photodetectors (PEC PDs) tailored for underwater weak-light environments. This results indicate that key determinant of hole extraction behavior is the relationship between the spacing distance of adjacent Ni nanostructures (ds) and twice the SCR radius (Ws). PEC PDs with optimized 8nm ultrathin Ni nanostructures featuring closely but non-overlapping SCRs, exhibit a 55-fold increase in photoresponsivity (2.2mAW-1) and a 128-fold enhancement in detection sensitivity (3.2 × 1011 Jones) at 0V over Ni film, revealing the exceptional stability. Furthermore, this approach enables effective detection across UV-vis-near infrared spectrum, supporting reliable multispectral UOC and underwater imaging capabilities.

Graphene/black phosphorus-based infrared metasurface absorbers with van der Waals Schottky junctions

Black phosphorus (BP) is a promising candidate for fabricating infrared (IR) photodetectors because its bandgap in the IR region can be controlled by varying the number of layers. BP-based metasurfaces have attracted considerable attention for applications in wavelength-selective and/or polarization-selective IR absorbers. Graphene and BP (Gr/BP) van der Waals (vdW) heterostructures are expected to enhance the performance of BP-based IR photodetectors. However, the Gr/BP vdW heterostructure forms a Schottky junction; thus, the electron transfer between Gr and BP should be investigated to determine the precise optical properties of Gr/BP vdW heterostructure-based metasurfaces. In this study, the electron transfer in the Gr/BP vdW heterostructure is investigated theoretically. The metasurface absorber structure proposed based on the results comprises periodic Gr/BP vdW heterostructure strips on top, a middle dielectric layer, and a bottom reflector. Numerical calculations indicated that the Gr/BP vdW heterostructure has strong wavelength- and polarization-selective near-unity IR absorption. The absorbance is increased and absorption wavelength is shortened compared with those of the monolayer-BP-based metasurface. The absorption wavelength can be controlled by changing the width of the Gr/BP strips owing to the hybrid localized surface plasmons of Gr/BP. This is attributed to the electron transfer through the Schottky junction between Gr and BP with enhanced localized surface plasmon resonance. The results suggest that the Gr/BP vdW heterostructure is a promising platform for realizing wavelength-selective and/or polarization-selective IR photodetectors and IR absorbers/emitters. The resulting photodetectors exhibit high responsivity and low noise because the BP bandgap corresponds to the IR wavelength region.

Constructing Dual Schottky Junctions for High‐Performance Zinc Anode

AbstractAqueous zinc ion batteries provide new solutions for achieving environmentally friendly and safe energy storage devices. Unfortunately, the further application is hampered by the growth of zinc dendrites caused by uneven zinc deposition, hydrogen evolution and other side interfacial reactions at the zinc anode. Herein, a multifunctional Bi‐Bi2O3 hybrid artificial interface layer is constructed on the surface of the zinc anode using an in situ conversion reaction. Among them, the Bi‐Bi2O3 Schottky structure not only significantly accelerates the migration of Zn2+ through its built‐in electric field, but also effectively improves the hydrogen evolution barrier (ΔGH*), thereby suppressing side reactions. Moreover, the Schottky contact formed between the interface layer and the metal zinc interface also regulates the electronic distribution state on the zinc surface and optimizes the deposition process of Zn2+, ensuring a more uniform and orderly zinc deposition process. Based on the synergistic effect of dual Schottky junctions, symmetric batteries achieve stable cycling for 2000 h under the conditions of 1.0 mA cm−2 and 1.0 mAh cm−2. The full cell assembled with α‐MnO2 as the cathode maintains capacity of 112.7 mAh g−1 after 1000 cycles at 1 A g−1 with a capacity retention rate of 84%.

Cold Sintered ZnO-Polystyrene (PS) Composites with Modified Interfacial Structures and Properties.

Lightweight and integrated electronic devices with high performance have become an inevitable trend in the development of power electronic systems. However, it is challenging to obtain lightweight and miniaturized varistors due to the low threshold electric field. Herein, (1 - x)ZnO-xPS composites with a high threshold electric field are prepared through a cold sintering process at 220 °C for 50 min, utilizing lightweight PS to modulate the grain boundary structures of ZnO varistors. With PS content ≤1.5 wt %, the relative densities of cold sintered composites exceed 95%. PS thin layers with a thickness of 2-10 nm are distributed at the grain boundaries of ZnO, forming the Schottky barrier, which triggers nonlinear current-voltage responses. With the addition of PS, the threshold electric field is dramatically enhanced from 135 to 2703 V·mm-1, higher than that of commercial ZnO varistors, which is further demonstrated by the electric field simulation of the Finite Element Method. The interfacial resistance obtained from impedance analysis increases with the increase of the PS content, and the activation energy of (1 - x)ZnO-xPS composites is higher than that of pure ZnO ceramics. This study provides a promising approach for the development of lightweight and cost-effective varistor materials.

Methodology of Production of Photo-Sensitive Elements on Ptsi Basis

Schottky barrier diodes based on PtSi-Si contact can be used as detectors for registration of radiation in the infrared spectral region. However, the quantum efficiency of such receivers is very low compared to photodetectors based on narrow-gap semiconductors and p-n junctions. To increase the quantum efficiency of Schottky receivers, as it will be shown below, they are made in the form of the so-called “optical cavity”, and the thickness of PtSi should not exceed 100 A0. For this purpose we have developed a technological mode of multilayer metallization to obtain thin PtSi-Si contacts.

Conductive Islands Assisted Resistive Switching in Biomimetic Artificial Synapse for Associative Learning and Image Recognition

AbstractSolution‐processed memristor devices hold significant potential for advancing synaptic applications, offering scalable, cost‐effective, and efficient solutions for next‐generation neuromorphic systems. These devices replicate the behavior of biological synapses with their gradual and continuous changes in resistance, making them promising for neuromorphic computing and artificial neural networks. However, understanding the temporal characteristics and cumulative effect of successive pulses on the devices is essential for emulating the dynamics of biological synapses. This study proposes a hybrid materials‐based conductive islands‐assisted resistive switching (CIARS) in a solution‐processed active layer consisting of thermally exfoliated graphitic carbon nitride (g‐C3N4 abbreviated as CN) nanosheets embedded with silver nanoparticles (Ag NPs). The fabricated devices demonstrate repeatable and bipolar memory features with a lower operating voltage (≤0.5 V), emulating the frequency and amplitude‐dependent synaptic plasticities. The threshold switching occurs due to the formation of conduction filaments (CFs) of silver ion (Ag+), whereas the analog behavior results from the voltage pulse‐dependent modulation of Schottky barrier height combined with metallic CFs formation. The experimental findings demonstrate the efficacy of the CIARS mechanism within the material platform, highlighting its potential for applications in associative learning, Morse code detection, and image recognition.

Breaking Activity‐Durability Inverse Relationship via Electrode Engineering by Utilizing β‐MnO2/RuO2 Heterostructures for Efficient Seawater Electrolysis

AbstractSignificant efforts are underway to enhance the efficiency of water electrolysis for sustainable hydrogen production. Approaches that were explored are the design of an efficient anode, engineering of electrolytes, and application of diffusion protective layer over the catalyst to protect it from corrosive reactions. Here we are exploring the engineering of electrode fabrication to enhance the efficacy of anode catalysts by ensuring that the materials are carefully selected. β‐MnO2 has been used to develop a cost‐effective method for electrode fabrication that establish a Schottky junction at heterostructure interface. This method transforms commercial RuO2, which is considered to be less active and stable, highly selective for chlorine oxidative reactions, into a highly active, stable, and OER‐selective in alkaline medium and surrogate seawater. With the help of thorough electrochemical techniques, we found that this engineering significantly improves the effective electrochemical surface area, and higher kinetics and conversion per unit site, profoundly affecting the charge transfer mechanism and optimizing the adsorption of OER intermediates, resulting in much‐increased mass activity. It is observed that the selectivity of the OER was enhanced due to the Lewis acid repercussions of β‐MnO2.

Tailor‐Made Buffer Materials: Advancing Uniformity and Stability in Perovskite Solar Cells

AbstractAlong with the growing popularity of the p‐i‐n structure, bathocuproine (BCP) is increasingly recognized as a crucial buffer layer between the electron transport layer and electrode with the role of mitigating Schottky contact and enhancing performance. However, the chemical structure and role of its functional groups have not been thoroughly elucidated. This study introduces a novel modification of BCP in perovskite solar cells (PSCs) by altering functional groups to optimize their geometrical molecular structures and electronic properties. The substitution of aromatic phenyl and p‐tolyl groups to 2,9‐position on the BCP is highly effective in increasing the planarity of the conjugated backbone and protecting the reactive nitrogen atoms of the phenanthroline core, thereby improving charge transport and device stability. Experimental analyses, including electrostatic force microscopy, impedance spectroscopy, and photoluminescence, reveal that the modified BCP significantly enhances charge transport, reduces recombination losses, and markedly improves the structural stability of PSCs, leading to prolonged device lifetimes. The findings highlight the potential of structurally optimized BCP derivatives as a critical component in advancing high‐efficiency and durable PSCs.

Tuning Electronic Friction in Structural Superlubric Schottky Junctions.

Friction at sliding interfaces, even in the atomistically smooth limit, can proceed through many energy dissipation channels, such as phononic and electronic excitation. These processes are often entangled and difficult to distinguish, eliminate, and control, especially in the presence of wear. Structural superlubricity (SSL) is a wear-free state with ultralow friction that closes most of the dissipation channels, except for electronic friction, which raises a critical concern of how to effectively eliminate and control such a channel. In this work, we construct a Schottky junction between a microscale graphite flake and a doped silicon substrate in the SSL state to address the issue and achieve wide-range (by 6×), continuous, and reversible electronic friction tuning by changing the bias voltage. No wear or oxidation at the sliding interfaces was observed, and the ultralow friction coefficient indicated that electronic friction dominated the friction tuning. The mechanism of electronic friction is elucidated by perturbative finite element analysis, which shows that migration of the space-charge region leads to drift and diffusion of charge carriers at Schottky junctions, resulting in energy dissipation.

Structure Engineering of Ga2O3 photodetectors: A Review

Abstract Deep ultraviolet (DUV) photodetectors play important roles in the modern semiconductor industry due to their diverse applications in critical fields. Wide bandgap semiconductor Ga2O3 is considered as one promising material for highly sensitive DUV photodetectors. However, the high responsivity of Ga2O3 DUV photodetectors always comes at the expense of its response speed. Material engineering for high-quality Ga2O3 materials can optimize the photoresponse performance but at the cost of much more complex process. Structure engineering can efficiently improve the performance of Ga2O3 photodetectors based on various physical mechanisms. Owing to the increased modulation probabilities, part schemes of structure engineering even alleviate the tough requirements on Ga2O3 material quality for high-performance DUV photodetectors. This article reviews the recent efforts in optimizing the performance of Ga2O3 photodetectors through structure engineering. Firstly, photodetectors based on Ga2O3 nanostructures and metasurface structures with nanometer size effect are discussed. In addition, junction structures of Ga2O3 photodetectors, which effectively promote carrier separation in the depletion region, are summarized based on a classification of Schottky junction, heterojunction, phase junction, etc. Besides, Ga2O3 avalanche photodiodes, offering ultra-high gain and responsivity, are focused as a promising prototype for commercialization. Furthermore, field effect phototransistors, based on which the scalability and low power performance of Ga2O3 photodetectors have been well proven, are analyzed in detail. Moreover, auxiliary-field configurations with extra tunable dimensions for Ga2O3 photodetectors are introduced. Finally, we conclude this review and discuss the main challenges of Ga2O3 DUV photodetectors from our perspective.

High-Performance Field-Effect Sensing of Ammonia Based on High-Density and Ultrathin Silicon Nanowire Channels.

Ultrathin silicon nanowires (SiNWs), grown via a high-yield and low-cost catalytic approach, are ideal building blocks for the construction of highly sensitive field-effect transistor (FET) sensors. In this work, we demonstrate a high-density growth integration of an ultrathin SiNW array, with diameter down to DNW = 24 ± 3 nm and narrow NW-to-NW spacing of only 120 nm, fabricated via an in-plane solid-liquid-solid (IPSLS) approach. Junctionless bottom-gated SiNW FETs are successfully constructed, exhibiting a high on/off current ratio of >107 and a sharp subthreshold swing of 156 mV/dec These provide an excellent platform for realizing high-performance NH3 sensing at room temperature, with a high response of 96.9% at 25 ppm and 38.6% at 2.5 ppm, rapid response time of 7.9 s for 5% response (or 85.8 s for 50% response), and superior selectivity against common volatile organic compound gases in ambient environments. Finally, the field-effect sensing mechanism is attributed to the Schottky barrier modulation by the adsorbed NH3 molecules at the metal/SiNW interface, as confirmed through an epoxy-masked selective region comparative analysis. These results provide a solid basis for the ultrathin catalytic IPSLS-SiNWs to serve as advantageous one-dimensional (1D) channels for the scalable integration of various high-performance and flexible gas sensing applications.

Core–Shell–Satellite Au@CeO2–Pd Plasmonical Photocatalysts for Suzuki–Miyaura Coupling Reaction

ABSTRACTIntegration of localized surface plasmon resonance (LSPR) metallic nanocrystals into photocatalysis is an intriguing approach for light‐driven organic transformations. However, uncertain direction of hot carriers is a grand challenge, which fails to take full advantage of the LSPR excitation. In this work, core–shell gold@ceria nanosphere–supported segregated palladium species (Au@CeO2–Pd) have developed to steer the light absorption capability and charge carrier migration. Under simulated solar light irradiation, the core–shell–satellite Au@CeO2–Pd exhibited efficient light harvesting and colossal activity in the Suzuki coupling reaction. The plasmon‐induced hot electrons overpassed the Schottky barrier at the Au@CeO2 interfaces and migrated from Au core to CeO2 shell accordingly. Subsequently, the photogenerated electrons and hot electrons migrated from Au@CeO2 core–shells to Pd, which acted as an electron acceptor. Detailed photocatalytic mechanism studies revealed that both photoexcited electrons and holes were the main active species involved in the photocatalytic Suzuki coupling reaction process. In particular, the diphenyl yield over Au@CeO2–Pd catalyst was ~1.7 times higher than that of core–shell–satellite Au@SiO2–Pd, where a 19‐nm‐thick SiO2 shell was introduced to prevent the migration of hot electrons. This distinctly certified that the hot electrons transfer in the core–shell–satellite Au@CeO2–Pd under illumination played an important role to drive Suzuki reaction. Overall, this design of core–shell–satellite Au@CeO2–Pd plasmonic photocatalyst has the potential in the field of photo‐driven organic transformations.

Measuring the radiation hardness of terahertz devices for space applications

The application of terahertz technology in space is frontier for the development of 6G technologies. Terahertz transceiver devices based on gallium arsenide Schottky barrier diodes (GaAs SBDs) have the characteristics of small size, light weight and low power consumption, making them suitable for application on spacecraft. However, there is currently a lack of experimental assessments on their space adaptability. Here, we study the radiation hardness of terahertz devices to determine their adaptability in complex space environments. We exposed GaAs SBDs and terahertz multipliers as typical terahertz devices to gamma rays and protons. The experimental results showed that the terahertz devices exhibited good tolerance to protons, but prolonged exposure to gamma rays could significantly increase the leakage current of the GaAs SBDs and alter its C-V characteristics, leading to the failure of the terahertz multiplier. Nevertheless, the terahertz devices maintained a good level of radiation hardness, making them highly suitable for use in Low Earth Orbit (LEO) satellites. The comparison between the results of proton and gamma ray tests indicated that the terahertz devices exhibited high inherent radiation hardness against displacement damage but were more sensitive to ionization damage, requiring higher shielding requirements.

TCAD simulation on an UACCUFET inserted with 3C/4H–SiC hetero-crystalline junctions for accumulation-channel and fly-back

Due to high channel mobility, SiC accumulation-channel field-effect transistors (ACCUFETs) exhibit important research and application values in high-frequency and large-power fields, but still encounter poor reverse recovery, etc. An enhancement-mode U-shaped gate ACCUFET integrated with 3C/4H–SiC hetero-crystalline junctions (HCJs) and semi-super-junction (SSJ) is constructed, where a (n−)4H–SiC-layer in (n)3C–SiC/(n−)4H–SiC HCJ is adopted to form accumulation-channel for conduction due to field-effect, another HCJ composed of (n)3C–SiC and (n)4H–SiC drift region is employed for fly-back under low cut-in voltage (VF) to shorten reverse recovery time (trr). Additionally, a SSJ is used to raise the breakdown voltage (VB). The device structure and performance are optimized by the Silvaco TCAD, which illustrates the values of VB and static figure of merit (FOMHM) are increased by 15.6 % and 5.6 % respectively compared to those of the counterpart with Schottky barrier diode. This paper can provide new ideas for devising high-performance ACCUFETs.

High‐Performance Self‐Powered PEC Photodetectors Based on 2D BiVO4/MXene Schottky Junction

AbstractAs an emerging field, self‐powered photoelectrochemical (PEC) photodetectors have gradually attracted extensive attention thanks to the unique working characteristics of low preparation cost, strong tunability of device performance, and environmental friendliness. However, short absorption wavelength range, low efficiency of visible light utilization, and low responsivity remain challenges for performance improvements. Here, the PEC photodetectors based on the 2D BiVO4/MXene Schottky junction structure, which shows excellent performance with high photocurrent density (≈3.90 mA cm−2 at 0 VSCE under AM 1.5 G, 150 mW cm−2), good responsivity (790.2 mA W−1 under 447 nm), fast response time (tr/tf = 8/14 ms), and long‐term stability (keep 17 000 s and 22 000 cycles) are fabricated. These can be attributed to the built‐in electric field at the BiVO4/MXene Schottky junction interface, which accelerates the transfer of photogenerated electrons and holes, and inhibits interfacial charge recombination. Additionally, the MXene nanosheets improve the absorption of visible‐light‐induced photons on the valence band of BiVO4. These excellent properties show that this work provides a scientific experimental reference for the further development of PEC photodetectors.

Structural and Electrical Characterization of Solution‐Deposited β‐Ga2O3:Al

The wide bandgap oxide semiconductor thin films are synthesized using tetrahydroxogallate (III) ammonium {NH4Ga(OH)4} precursor at a concentration of 10 at% Ga and varying amounts of hydrated aluminum nitrate between 0.6 and 3.2 at%. Thin films of β‐Ga2O3:Al are synthesized by spin coating and spray pyrolysis with postannealing in nitrogen ambient at 930 °C. The structural properties of the thin films are investigated using XRD and Raman spectroscopy, while the electrical characteristics are determined using 4‐point probe, current–voltage (I–V), and capacitance–voltage (C–V) measurements with Ti/Al/Ni/Au Ohmic contacts and Pd/Au Schottky contacts. The β‐Ga2O3 with 2.2 at% Al is found to be the optimal concentration in this study, resulting in ideality factors of 1.10 and 1.09, saturation currents of 3.17 × 10−6 and 3.10 × 10−6 A, Schottky barrier heights of 0.73 and 0.88 eV, and series resistances of 948 and 955 Ω, for the spin‐coated and pyrolytically sprayed samples respectively.

A Comprehensive Approach to Optimization of Silicon-Based Solar Cells

In this work, we report a detailed scheme of computational optimization of solar cell structures and parameters using PC1D and AFORS-HET codes. Each parameter’s influence on the properties of the components of heterojunction silicon-based solar cells (HIT) has been thoroughly examined. The proposed approach follows a stringent sequence of steps to optimize various parameters of the studied HITs. Furthermore, we have revealed the effects of the metal-semiconductor contact, and a model of a photocell with an ohmic contact and a Schottky contact has been simulated. The optimal model of HIT for available materials has been proposed and fabricated based on the results of these simulations. A comparison of predicted and measured performance unequivocally demonstrates the efficiency of the proposed scheme in developing silicon-based HITs, providing reassurance about its practical application.

H-BN-assisted-transferred metal contacts to InSe for twodimensional multifunctional electronic devices

Abstract Metal contacts to two-dimensional semiconductors play a crucial role in determining the electrical performance of the electronic devices. However, traditional three-dimensional metal deposition processes will bring damage to two-dimensional semiconductors and cause significant Fermi-level-pinning effects. In this work, we report a hexagonal boron nitride (h-BN)-assisted-transferred method for metal contacts to few-layered InSe for construction of two-dimensional functional electronic devices. Using transferred Pt electrodes as the contact, p-type dominated ambipolar conduction behavior with the hole Schottky barrier height (SBH) approaching 0 meV was observed in field-effect transistors (FETs) based on multilayered InSe. Based on this, using a dual-gate modulating method, multiple types of InSe homojunctions, including p-p, n-n, p-n and n-p junctions, could be constructed. For InSe p-n homojunctions, a current rectification ratio of over 104 and optoelectronic detection capabilities were achieved. Furthermore, a complementary metal-oxide-semiconductor (CMOS) inverter with an ultra-high voltage gain exceeding 60 at VDD = -1 V was constructed. Our h-BN-assistedtransferred metal contact method can be easily extended to other two-dimensional semiconductors for the construction of complementary electronic and optoelectronic devices.

Huge photosensitivity gain combined with long photocurrent decay times in various polymorphs of Ga2O3: effects of carriers trapping with deep centers

Abstract The materials system of ultra-wide bandgap Ga2O3 has already shown great promise in the field of solar-blind photodetectors with high photoresponsivity, high photoresponsivity gain and low dark current. These promising results have been achieved on Ga2O3 films of different polymorphs and by different methods, often not with particularly high crystalline quality. In fact, it would often seem the case that the lower the crystalline quality of the films, the higher the photosensitivity and its gain. This, however, is in most cases accompanied by unusually long photocurrent build-up and decay times. We show that the experimental results can be explained by models in which the high photosensitivity gain is related to the effects of holes being trapped by deep states that, in Schottky diodes, results in the decrease of the Schottky barrier height with consequent increase of electron current, and in Metal-Semiconductor-Metal (MSM) structures additionally gives rise to the usual gain increase due to the increased concentration and lifetime of electrons. We present and discuss the models describing the effects in Ga2O3 Schottky diodes, MSM structures, unipolar and bipolar heterojunctions and propose possible candidates for the role of the hole traps in different Ga2O3 polymorphs. We also discuss the existing results for the photocurrent build-up and decay times and offer possible explainations of the observed temperature dependences of the characteristic times where such data are present.

Impacts of single Shockley-type stacking faults on current conduction in 4H-SiC PiN diodes

The impacts of single Shockley-type stacking faults (1SSFs) on the electrical characteristics of 4H-SiC PiN diodes were examined by fabricating the PiN diodes containing the 1SSF monolayer in the active area with a covering ratio of unity and evaluating the forward current–voltage (I–V) characteristics at various temperatures from 296 to 523 K. The measured I–V characteristics were compared with the previous results for Schottky barrier diodes (SBDs) containing the 1SSF monolayer. Based on the comparison, we clarified the similarity and differences between the impacts of the 1SSFs on the unipolar and bipolar conductions. The forward current conduction of the PiN diodes is limited by the 1SSF similar to that of the SBDs, while the forward current in the PiN diodes exceeds that in the SBDs at elevated temperatures. The difference was attributed to the contribution of hole and recombination currents, the insights into which were obtained by analyzing several experimental results, including dependences of the forward current on the temperature and thickness of the blocking-voltage layer. A simulation analysis was also conducted by adopting the model proposed in the previous study.