Metal-semiconductor Junction Research Articles

P-type Schottky-barrier-free contact to MoS2 via layer-number-assisted interface engineering

Bilayer and few-layer MoS2 show intrinsically higher electronic quality and substantially improved device performance than monolayer, and high-quality MoS2 wafers with controlled layer number have been grown. In addition, MoS2 has different polymorphs such as the semiconducting H phase and semimetallic distorted T (dT) phase, and vertically stacked dT-/H-MoS2 metal-semiconductor junctions (MSJs) have been synthesized. However, the contact mechanism of dT-/H (few layer)-MoS2 MSJs remains to be elucidated, and p-type ohmic contact to MoS2 is difficult to realize due to the high ionization energy of MoS2. In the current work, we reveal a mechanism of two-dimensional (2D) semiconductors (2DSCs) layer-number-assisted metal-semiconductor (SC) interface engineering for Schottky barrier height (SBH) reduction and p-type ohmic contact is achieved based on this mechanism; 2DSCs here mean H (few layer)-MoS2 and metal-SC interfaces are the dT-/H-MoS2 interfaces with increasing 2DSC layers. Specifically speaking, the mechanism is as follows: (1) two competing effects coexist, namely, the interface dipole (ΔV) at the metal-SC interface and the quasibonding (QB) between all adjacent layers, with ΔV (QB) increasing (decreasing) SBH; (2) the effect of QB beats ΔV and hence the overall effect is decreasing SBH at the metal-SC interface; and (3) the SBH reduction effect increases with increasing 2DSC layers. The mechanism of 2DSC layer-number-assisted metal-SC interface engineering should apply also for other 2DSCs with a suitable metal and hence our current work paves an avenue for ohmic contact to few-layer 2DSCs by the accumulated interlayer QBs that widely present in 2DSCs. Published by the American Physical Society 2024

Ni/n-Si Schottky junction: Self-biased infrared photodetection via hot carrier photoemission

Internal photoemission-based hot electron generation at metal-semiconductor junctions holds significant potential for silicon-based sub-bandgap NIR photodetectors. In this work, we designed a simple nickel-silicon Schottky junction using the pulsed laser deposition technique and performed both experimental and theoretical analyses. To reduce the complexity of fabrication and lower costs, we used a planar nickel thin film on top of n-type silicon. The thickness of the nickel thin film was optimized to improve absorption and hot electron generation near the Ni/Si interface. We measured and calculated reflectance using the transfer matrix approach to quantify the effect of thickness on EQE. We also calculated the thickness-dependent absorption profile to estimate hot electron production near the junction. The current-voltage characterization of Ni/n-Si Schottky photodetector was investigated under the dark conditions as well under 1200 nm and 1300 nm light illumination. Under self-bias conditions, a photodiode with a 12 nm Ni thickness exhibits responsivity of 0.124 mA/W and 0.069 mA/W under illumination from 1200 nm and 1300 nm LED light, respectively. Furthermore, we used a comprehensive theoretical model to quantify the planar Ni/Si hot carrier generation and emission efficiency. and experimentally validated the calculated EQEs with the fabricated device. We believe the proposed complementary metal-oxide-semiconductor-compatible and simply structured Ni/Si Schottky photodetector will have potential applications in the silicon-based optoelectronics market.

Inspection and comparative analysis of light and thermal response dynamics of Cu/V₂O₅/n-Si and Cu/La-V₂O₅/n-Si MIS diodes

Schottky Barrier Diodes (SBDs) are pivotal in modern electronics for their quick switching and low forward voltage drop, enabled by metal-semiconductor junctions. SBDs are renowned for their performance, primarily due to their metal-semiconductor intersection. This study focuses on Cu/V2O5/n-Si and Cu/La-V2O5/n-Si SBDs, examining the impact of lanthanum doping on their performance. Transition Metal Oxides (TMOs) like Vanadium Pentoxide (V2O5) offer unique electronic, magnetic and optical properties making them suitable for various applications. The fabrication process involved sol-gel spin coating and DC magnetron sputtering to create a thin V2O5 layer on n-type silicon wafers, followed by copper contact deposition. Galvanizing temperatures ranged 300° C to 500° C to study the structural, optical, and morphological changes in V2O5 thin films. Key findings include the significant reduction in ideality factor (n) with increasing annealing temperatures for Cu/V2O5/n-Si SBDs, reaching as low n value of 5.26 at 500°C, indicating improved device performances. For Cu/La-V2O5/n-Si SBDs, the ideality factor consistently decreased with higher light intensities, showcasing enhanced performance due to La doping. Barrier height (ɸB) also varied, with higher values observed for La-doped V2O5, enhancing charge recombination and increasing oxygen vacancies. Photodiode parameters were significantly enhanced by doping of the La. The Cu/La-V2O5/n-Si SBDs demonstrated high photosensitivity (PS = 3327.5 %), photo responsivity (R = 33.39 mA/W) and detectivity (D* = 9.82 × 10¹⁰ Jones), making them highly efficient for optoelectronic applications. Overall, this study highlights the potential of Cu/La-V2O5/n-Si SBDs for high-efficiency, optoelectronic applications, with optimized doping concentrations and annealing conditions significantly improving their performance.

Unveiling Versatile Electronic Properties and Contact Features of Metal-Semiconductor Graphene/γ-Ge2SSe van der Waals Heterostructures.

Recently, searching for a metal-semiconductor junction (MSJ) that exhibits low-contact resistance has received tremendous consideration, as they are essential components in next-generation field-effect transistors. In this work, we design a MSJ by integrating two-dimensional (2D) graphene as the metallic electrode and 2D Janus γ-Ge2SSe as the semiconducting channel using first-principles simulations. All the graphene/γ-Ge2SSe MSJs are predicted to be energetically, mechanically, and thermodynamically stable, characterized by the weak van der Waals (vdW) interactions. The graphene/γ-SGe2Se MSJ-vdWH form the n-type Schottky contact (SC), while the graphene/γ-SeGe2S MSJ-vdWH form the p-type one, suggesting that the switching between p-type and n-type SC in the graphene/γ-Ge2SSe MSJ-vdWHs can occur spontaneously by simply altering the stacking patterns, without requiring any external conditions. Notably, the contact features, including contact types and barriers of the graphene/γ-Ge2SSe MSJs are significant in versatility and can be altered by applying electric gating and adjusting interlayer spacing. Both the applied electric gating and strain engineering induce switchability between p- and n-type and SC to OC in the graphene/γ-Ge2SSE MSJs. This versatility underscores the potential of the graphene/γ-Ge2SSe MSJ for next-generation applications that require low-contact resistance and high performance.

Strongly Coupled NiMo@Alloy‐LDH Interfaces with Low‐Barrier Schottky Junctions for Oxygen Evolution Reaction

AbstractThe main challenge in developing Schottky‐contact OER catalytic devices based on layered double hydroxides (LDHs) is to achieve metal–semiconductor junctions with low contact resistance and high charge transfer capacity. However, due to the presence of high potential barriers and Fermi pinning, conventional Schottky contacts are usually unsatisfactory, resulting in poor‐working electrode performance and high energy consumption. In this study, a new concept of “hindrance factor” is introduced to quantify the difficulty of electron transfer, and a low‐hindrance factor Schottky contact formed by strong coupling of semiconductor LDH and NiMo alloy clusters is designed. This interface guides charge redistribution, optimizes the bonding and orbital states of adsorption sites, and enhances the targeted adsorption of OH intermediates. The results show that the configured NiMo@NiFeCe‐LDH working electrode only needs 1.445 V (vs RHE) to drive the reaction and shows excellent durability in 400 h of testing. At the same time, based on this study, a strategy for screening high‐performance Schottky junctions is developed. This strategy provides a bridge for studying interface properties, orbital hybridization, and charge transfer, reveals the potential mechanism for reducing contact resistance, and has important guiding significance for screening high‐performance metal–semiconductor electrocatalysts and stability.

High-k Dielectrics-Based Electric Field Engineering in β-Ga2O3 Power Diodes

We present β-Ga2O3 high-voltage Schottky barrier diodes (SBD) incorporating advanced electric field engineering approaches through the use of high-permittivity dielectrics. We present two approaches: 1) the lateral dielectric superjunction SBD, where the electric field within the drift layer is modified from triangular to rectangular profile, enhancing the breakdown voltage and enabling the use of higher drift layer doping to reduce on-resistance, and 2) the vertical high-k RESURF trench SBD, which leverages the reduced surface electric field effect (RESURF) to reduce the electric field at the metal-semiconductor junction and reverse leakage currents.A superjunction-like structure uses charge balance to push the VBR-Ron-sp trade-off beyond the material’s unipolar figure of merit. The lack of p-type doping in β-Ga2O3 makes the realization of such structures very difficult. However, field flattening can be achieved in β-Ga2O3 drift layers using a high permittivity material with appropriate choice of dielectric constant, device aspect ratio and semiconductor/dielectric width. An analytical model is discussed to highlight the device design strategy and experimental demonstration is reported in the lateral geometry. 500 nm of Si-doped Ga2O3 epitaxial layer with a sheet charge of 1.6×1013 cm-2 is grown using metal organic vapor phase epitaxy (MOVPE). Trenches with three different fin widths (WFin = 2, 5, 10 µm) were made and high-k dielectric BaTiO3 (BTO) with dielectric constant of 220 is deposited on the sample. A low specific on resistance of 1.65 mΩ-cm2 is observed for LAC = 5µm due to the high charge density epitaxial lateral Fins. For the SBD with LAC = 5µm and WFin = 5µm, a high average electric field of ~3 MV/cm (VBR/ LAC) is estimated across the entire length of the device. A very high Baliga's figure of merit (BFOM) of 1.35 GW/cm2 is observed for the RESURF SBD with LAC=5µm and WFin=2µm (VBR=1.49 kV and Ron-sp=1.65 mΩ-cm2), surpassing SiC unipolar FOM when considering just the conducting area.While superjunction-like structures effectively flatten the electric field inside the drift layer, high electric fields at the metal/semiconductor junction results in increased leakage current at large reverse bias, particularly in the case of vertical Schottky Barrier Diodes (SBDs). To circumvent this challenge, we present the approach of β-Ga2O3 Vertical Trench Schottky Barrier Diode (SBD) with a high-permittivity dielectric RESURF. The incorporation of a trench geometry, coupled with the high-permittivity dielectric RESURF, effectively reduces the surface electric field at the metal-semiconductor junction. This reduction facilitates the use of a lower work-function anode contact, further diminishing the turn-on voltage. The use of high-k dielectric also significantly reduces the dielectric leakage contribution to the overall reverse leakage of the diode. Large-area SBDs with areas of 1mm2 and 4mm2 exhibit pulsed forward current of 6A/20A and a catastrophic breakdown voltage of 1.74kV/1.4kV, surpassing other β-Ga2O3-based large-area power diodes, while small-area SBDs (200×200 µm2) do not exhibit catastrophic breakdown until 3kV. The large-area SBDs also demonstrate lower capacitance, stored charge, and stored energy compared to commercial SiC SBDs, indicating potential for superior switching performance. The combination of lower stored charge and a low forward voltage drop results in an excellent trade-off between conduction and switching power loss, yielding a QCVF figure of merit comparable to commercial bare die SiC SBDs. We demonstrate the potential of high permittivity dielectrics-based extreme field engineering to push the performance limits of β-Ga2O3 diodes for next-generation power electronics.We acknowledge funding from AFOSR MURI program (Dr. Ali Sayir) and Coherent/II-VI foundation.

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

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

Van der Waals Schottky Junction Photodetector with Ultrahigh Rectifying Ratio and Switchable Photocurrent Generation.

Metal-semiconductor junctions play an important role in the development of electronic and optoelectronic devices. A Schottky junction photodetector based on two-dimensional (2D) materials is promising for self-powered photodetection with fast response speed and large signal-to-noise ratio. However, it usually suffers from an uncontrolled Schottky barrier due to the Fermi level pinning effect arising from the interface states. In this work, all-2D Schottky junctions with near-ideal Fermi level depinning are realized, attributed to the high-quality interface between 2D semimetals and semiconductors. We further demonstrate asymmetric diodes based on multilayer graphene/MoS2/PtSe2 with a current rectification ratio exceeding 105 and an ideality factor of 1.2. Scanning photocurrent mapping shows that the photocurrent generation mechanism in the heterostructure switches from photovoltaic effect to photogating effect at varying drain biases, indicating both energy conversion and optical sensing are realized in a single device. In the photovoltaic mode, the photodetector is self-powered with a response time smaller than 100 μs under the illumination of a 405 nm laser. In the photogating mode, the photodetector exhibits a high responsivity up to 460 A/W originating from a high photogain. Finally, the photodetector is employed for single-pixel imaging, demonstrating its high-contrast photodetection ability. This work provides insight into the development of high-performance self-powered photodetectors based on 2D Schottky junctions.

Unveiling the electronic properties of BiP[formula omitted] triphosphide from bulk to graphene-based heterostructures by first-principles calculations

In our study, we investigated the structural and electronic properties of bismuth triphosphide (BiP3) in its bulk, few-layer, and monolayer forms. We found that BiP3 in bulk exhibits a metallic stable layered structure. The exfoliation energy of 1.07 J/m2 indicates ease exfoliation, comparable to other triphosphides. The band gap varies with thickness, transitioning from semiconductor–metal between four to five layers, influenced by interlayer coupling and quantum confinement. We also investigated the heterostructure created by depositing graphene (G) on few-layer BiP3. In monolayer (G/m-BiP3) and bilayer (G/2L-BiP3) forms, a metal–semiconductor junction is formed, characterized by weak vdW interactions at the interface and exhibiting p-type Schottky contacts. We observed that the Schottky Barrier Height (SBH) can be modulated by altering the interlayer distance between G and BiP3. This adjustment allows transitions between n-type and p-type Schottky contacts in G/m-BiP3 and the formation of an ohmic contact in G/2L-BiP3. Furthermore, applying an electric field affects the SBH, leading to similar transitions and the development of an ohmic contact. Additionally, our study shows that n-doping in graphene increases with the number of BiP3 layers and external electric field application. These properties position BiP3 few-layer as a promising material for nanoelectronic, optoelectronic, and graphene-based devices.

Nanoimprinted cellulose acetate-TiO2 composite thin film

Cellulose acetate is a safe, sustainable, and cost-effective material that is capable of forming nanostructures through facial processing methods such as surface imprinting. Forming optically active structures using cellulose acetate can advance green photonic device design. In this work, we create a hybrid material consisting of nanoscale plasmon active metal–semiconductor Schottky junctions. Demonstrating that such a hybrid material possesses improved performance when applied to Raman-based sensing. Boosting surface-enhanced Raman detection sensitivity through electromagnetic and chemical enhancement mechanisms from the metal-semiconductor junction, in addition to photonic resonances created via the imprinted nanoscale metamaterial array surface features. This work expands the use of cellulose-based materials for sensing-based applications.

Accurate parameter estimation of Au/GaN/GaAs schottky diode model using grey wolf optimization

The Au/GaN/GaAs Schottky diode is a fundamental electronic component with versatile applications. In this study we delve into the parameter estimation of Au/GaN/GaAs Schottky diodes using the Grey Wolf Optimizer (GWO) algorithm. Our research encompasses experimental procedures, mathematical modeling, and optimization techniques to extract critical electrical parameters, including the ideality factor (n), Schottky barrier height (φbn), and series resistance (RS). The primary aim is to enhance our comprehension of the behavior of Au/GaN/GaAs Schottky diodes and showcase the effectiveness of GWO in achieving precise parameter estimates. These diodes, featuring metal-semiconductor junctions, play pivotal roles in electronics, necessitating accurate parameter determination for optimized functionality. The effectiveness of the GWO algorithm was examined through a comparative analysis, employing analytical techniques pioneered by Cheung and Cheung. This study sought to assess the algorithm’s performance and accuracy in parameter estimation for Au/GaN/GaAs Schottky diodes, providing valuable insights into its practical applicability in electronic device characterization and optimization. Keywords: Schottky diodes, Grey Wolf Optimization, Electrical measurement. Parameter estimation, Gan, GaAs

Bias-tunable temperature coefficient of resistance in Ge transistors

Ge-based bolometers are widely used for near-infrared detection for a broad range of applications such as thermography or chemical analysis. Notably, for the thermometers used in bolometers, integration, scaling, and sensitivity as well as functionality are of utmost importance. In this regard, Ge exhibits a favorable temperature sensitivity due to the relatively low bandgap and a high intrinsic charge carrier concentration. In this work, we demonstrate a nanoscale thermometer for bolometric applications on the base of Ge-on-insulator nanosheets with monolithic Al source/drain contacts envisioned for future wafer-scale integration. Importantly, electrostatic gating of the nanosheets allows the operation as a Schottky barrier field-effect transistor, providing tunability of the energy landscape and the involved charge carrier injection in interaction with the metal-semiconductor junctions. In this approach, the top-gate electrode and drain contact are connected, thus resembling a two-terminal device with bias-tunable temperature coefficient of resistance (TCR) values between 0%/K and −3.8%/K in the temperature range of T = 125–150 K. Moreover, in this configuration, even at room temperature, a maximum TCR value of −1.6%/K is achieved. The bias-tunable TCR exhibited in these devices may enable advanced concepts for room temperature bolometric applications and allow co-integration with nanoelectronics.

Tuning Polarity in WSe2/AlScN FeFETs via Contact Engineering.

Recent advancements in ferroelectric field-effect transistors (FeFETs) using two-dimensional (2D) semiconductor channels and ferroelectric Al0.68Sc0.32N (AlScN) allow high-performance nonvolatile devices with exceptional ON-state currents, large ON/OFF current ratios, and large memory windows (MW). However, previous studies have solely focused on n-type FeFETs, leaving a crucial gap in the development of p-type and ambipolar FeFETs, which are essential for expanding their applicability to a wide range of circuit-level applications. Here, we present a comprehensive demonstration of n-type, p-type, and ambipolar FeFETs on an array scale using AlScN and multilayer/monolayer WSe2. The dominant injected carrier type is modulated through contact engineering at the metal-semiconductor junction, resulting in the realization of all three types of FeFETs. The effect of contact engineering on the carrier injection is further investigated through technology-computer-aided design simulations. Moreover, our 2D WSe2/AlScN FeFETs achieve high electron and hole current densities of ∼20 and ∼10 μA/μm, respectively, with a high ON/OFF ratio surpassing ∼107 and a large MW of >6 V (0.14 V/nm).

Transition from Schottky to Ohmic contacts in 2D Ge/GaAs heterostructures with high tunneling probability.

The metal-semiconductor (M-S) contact is usually an Ohmic contact or a Schottky contact, which greatly affects the electronic properties of devices, and it remains a huge challenge to realize a low-resistance Ohmic contact in a metal-semiconductor junction (MSJ). Herein, we systematically studied the band structures, electrostatic potential, charge transfer, Schottky barrier height of carriers, effective carrier masses, and tunneling probability of carriers of a germanene (Ge)/GaAs MSJ. The transition from the Schottky to the Ohmic contact can be caused by applying certain biaxial strains or electric fields, which weakens the Fermi level pinning (FLP) effect and reduces contact resistance. Meanwhile, the electron injection efficiency of Ge/(GaAs)As MSJ (PTB > 27%) is far superior to that of other two-dimensional (2D) vdW MSJs. This work indicates that Ge/GaAs heterostructures are the most compatible for applying high-effective 2D electronic nanodevices under controllable conditions.

Optical spectroscopic detection of Schottky barrier height at a two-dimensional transition-metal dichalcogenide/metal interface.

Atomically thin two-dimensional transition-metal dichalcogenides (2D-TMDs) have emerged as semiconductors for next-generation nanoelectronics. As 2D-TMD-based devices typically utilize metals as the contacts, it is crucial to understand the properties of the 2D-TMD/metal interface, including the characteristics of the Schottky barriers formed at the semiconductor-metal junction. Conventional methods for investigating the Schottky barrier height (SBH) at these interfaces predominantly rely on contact-based electrical measurements with complex gating structures. In this study, we introduce an all-optical approach for non-contact measurement of the SBH, utilizing high-quality WS2/Au heterostructures as a model system. Our approach employs a below-bandgap pump to excite hot carriers from the gold into WS2 with varying thicknesses. By monitoring the resultant carrier density changes within the WS2 layers with a broadband probe, we traced the dynamics and magnitude of charge transfer across the interface. A systematic sweep of the pump wavelength enables us to determine the SBH values and unveil an inverse relationship between the SBH and the thickness of the WS2 layers. First-principles calculations reveal the correlation between the probability of injection and the density of states near the conduction band minimum of WS2. The versatile optical methodology for probing TMD/metal interfaces can shed light on the intricate charge transfer characteristics within various 2D heterostructures, facilitating the development of more efficient and scalable nano-electronic and optoelectronic technologies.

Contact engineering for 2D Janus MoSSe/metal junctions.

The flourish of two-dimensional (2D) materials provides a versatile platform for building high-performance electronic devices in the atomic thickness regime. However, the presence of the high Schottky barrier at the interface between the metal electrode and the 2D semiconductors, which dominates the injection and transport efficiency of carriers, always limits their practical applications. Herein, we show that the Schottky barrier can be controllably lifted in the heterostructure consisting of Janus MoSSe and 2D vdW metals by different means. Based on density functional theory calculations and machine learning modelings, we studied the electrical contact between semiconducting monolayer MoSSe and various metallic 2D materials, where a crossover from Schottky to Ohmic/quasi-Ohmic contact is realized. We demonstrated that the band alignment at the interface of the investigated metal-semiconductor junctions (MSJs) deviates from the ideal Schottky-Mott limit because of the Fermi-level pinning effects induced by the interface dipoles. Besides, the effect of the thickness and applied biaxial strain of MoSSe on the electronic structure of the junctions are explored and found to be powerful tuning knobs for electrical contact engineering. It is highlighted that using the sure-independence-screening-and-sparsifying-operator machine learning method, a general descriptor WM3/exp(Dint) was developed, which enables the prediction of the Schottky barrier height for different MoSSe-based MSJ. These results provide valuable theoretical guidance for realizing ideal Ohmic contacts in electronic devices based on the Janus MoSSe semiconductors.

Pt-loaded Bi2WO6 microdiscs for highly sensitive and selective triethylamine monitoring

Pt-loaded curling-like Bi2WO6 (BWO) microdiscs were fabricated via a simple one-step hydrothermal and impregnation route. Various characterization methods, such as XRD, EDS and TEM, were conducted to prove the successful Pt loading. Electron migration from the semiconductor BWO to the precious metal Pt was revealed by the blue shift of the Bi 4f and W 4f XPS peaks with the increase of the Pt loading amount and the ∼10-fold baseline resistance elevation of the BWO-based sensor by the Pt loading, proving the formation of Schottky junction. Among the pristine BWO and Pt-loaded BWO with different Pt loading amounts, 1 wt % Pt-loaded BWO exhibits the highest gas response of 209 in sensing 500 ppm triethylamine at 300 °C, a minimal selectivity coefficient of 130.6 against some typical interfering gases at the same concentration and a low detection threshold of 1 ppm. Additionally, the sensitization mechanism is discussed as the synergistic effect of noble metal catalytic effect and metal-semiconductor junctions.

Ultra-low reverse leakage in large area kilo-volt class β-Ga2O3 trench Schottky barrier diode with high-k dielectric RESURF

We introduce vertical Schottky barrier diodes (SBDs) based on β-Ga2O3 with trench architecture, featuring a high-permittivity dielectric RESURF structure. These diodes are designed for application demanding high voltage and current capacities while maintaining ultra-low reverse leakage currents. The trench design plays a pivotal role in reducing the electric field at the metal–semiconductor junction, thereby yielding minimal reverse leakage attributed to field emission under high reverse bias conditions. Additionally, the incorporation of a high-k dielectric helps to suppress leakage through the trench bottom corner dielectric layer. The small area trench SBD (200 × 200 μm2) demonstrates a breakdown voltage exceeding 3 kV, accompanied by a reverse leakage current of less than 1 μA/cm2 at 3 kV. Moving on to larger area devices, the 1 × 1 and 2 × 2 mm2 devices exhibit breakdown voltages of 1.8 and 1.4 kV, while accommodating pulsed forward currents of 3.5 and 15 A, respectively. The capacitance, stored charge, and switching energy of the trench SBDs are also found to be less than the similarly rated commercial SiC SBDs, reinforcing their potential for enhanced switching efficiency.

Unveiling the red electroluminescence in LSMO-SRO thin film heterostructures

Herein, intense red electroluminescence (674 nm) in a La0.7Sr0.3MnO3(LSMO)-SrRuO3(SRO) thin films heterostructure obtained by RF-magnetron sputtering is reported for the first time. This novel phenomenon may open a new door in the field of optoelectronics and new generation devices based on multiferroic heterostructure. The structural properties were analyzed using grazing incidence x-ray diffraction demonstrating a rhombohedral structure for LSMO with (024) preferential orientation and an orthorhombic structure for SRO films with (121) preferential orientation. Raman and x-ray photoelectron spectroscopy (XPS) results demonstrated a mix of phases present in LSMO thin films. The thickness analysis was performed using scanning electron microscopy (SEM) in cross section and the thickness was found to be 123 nm and 49 nm for LSMO and SRO, respectively. XPS analysis for LSMO revealed that point defects associate to Mn cations and oxygen vacancies modify the total electrical conductivity and due to Mott transitions, suggest a p-type semiconductor behavior. For the SRO film, the XPS analysis demonstrated a change in the stoichiometry of the film surface, which provides a large amount of oxygen vacancies indicating a metal oxide transition with effects that involve multiple degrees of freedom (charge, spin, and lattice). The electrical behavior observed in the heterostructure corresponds to a metal-semiconductor junction showing a Schottky conduction mechanism in positive bias and a space charge limited conduction mechanism in negative bias. The red electroluminescence effect is discussed considering both a radiative recombination process occurred at the interface due to the presence of Mn2+ ions and an energy transfer mechanism assisted by the migration of the high amount of oxygen vacancies present in the interface.

Formula omitted]-[formula omitted] junction from localized doping of metal-WSe2 contact with N2H4, NH4 and BF4 molecules: A first-principles investigation

Using the density-functional theory, we investigate the possibility of obtaining a p–n junction in transition metal–semiconductor junctions. The systems consist in metal surfaces, M = Ti(0001), Co(0001), Pd(111) or Pt(111) in proximity to the semiconductor WSe2 monolayer. The latter is doped with hydrazine (N2H4), ammonium (NH4), or tetrafuoroborate (BF4). We determine for the M-WSe2 systems the binding energy, work function of metal surfaces, the Schottky barrier energy with and without molecular doping and the spin polarization. Results show a strong binding between the metal and WSe2 which implies a stable M-WSe2 contacts. The Spin-polarization in Ti-WSe2 (35%), Co-WSe2 (37,5%), Pd-WSe2 (13%) and Pt-WSe2 (-0.2%) suggest a significant metal-to-WSe2 spin injection in M-WSe2. Localization of hydrazine or ammonium on the WSe2 in M-WSe2 (M = Pd, Pt) changes its conductivity from p to n-type. The strong binding, the finite spin-injection, the change in conductivity and the reduction in Shottky barrier, raise the potential for a molecule-based p–n junction in metal-WSe2 field-effect transistor.