Showing papers on "Schottky diode published in 2014"
TL;DR: The first use of Schottky-contacted chemical vapor deposition grown monolayer MoS2 as high-performance room temperature chemical sensors showing clear detection of NO2 and NH3 down to 20 ppb and 1 ppm, respectively is reported.
Abstract: Trace chemical detection is important for a wide range of practical applications. Recently emerged two-dimensional (2D) crystals offer unique advantages as potential sensing materials with high sensitivity, owing to their very high surface-to-bulk atom ratios and semiconducting properties. Here, we report the first use of Schottky-contacted chemical vapor deposition grown monolayer MoS2 as high-performance room temperature chemical sensors. The Schottky-contacted MoS2 transistors show current changes by 2–3 orders of magnitude upon exposure to very low concentrations of NO2 and NH3. Specifically, the MoS2 sensors show clear detection of NO2 and NH3 down to 20 ppb and 1 ppm, respectively. We attribute the observed high sensitivity to both well-known charger transfer mechanism and, more importantly, the Schottky barrier modulation upon analyte molecule adsorption, the latter of which is made possible by the Schottky contacts in the transistors and is not reported previously for MoS2 sensors. This study show...
591 citations
TL;DR: The fabrication of both n-type and p-type WSe2 field-effect transistors with hexagonal boron nitride passivated channels and ionic-liquid (IL)-gated graphene contacts is reported, indicating the possibility to utilize chemically or electrostatically highly doped graphene for versatile, flexible, and transparent low-resistance ohmic contacts to a wide range of quasi-2D semiconductors.
Abstract: We report the fabrication of both n-type and p-type WSe2 field-effect transistors with hexagonal boron nitride passivated channels and ionic-liquid (IL)-gated graphene contacts. Our transport measurements reveal intrinsic channel properties including a metal–insulator transition at a characteristic conductivity close to the quantum conductance e2/h, a high ON/OFF ratio of >107 at 170 K, and large electron and hole mobility of μ ≈ 200 cm2 V–1 s–1 at 160 K. Decreasing the temperature to 77 K increases mobility of electrons to ∼330 cm2 V–1 s–1 and that of holes to ∼270 cm2 V–1 s–1. We attribute our ability to observe the intrinsic, phonon-limited conduction in both the electron and hole channels to the drastic reduction of the Schottky barriers between the channel and the graphene contact electrodes using IL gating. We elucidate this process by studying a Schottky diode consisting of a single graphene/WSe2 Schottky junction. Our results indicate the possibility to utilize chemically or electrostatically high...
415 citations
TL;DR: In this article, the authors report ambipolar charge transport in α-molybdenum ditelluride (MoTe2 ) flakes, whereby the temperature dependence of the electrical characteristics was systematically analyzed.
Abstract: We report ambipolar charge transport in α-molybdenum ditelluride (MoTe2 ) flakes, whereby the temperature dependence of the electrical characteristics was systematically analyzed. The ambipolarity of the charge transport originated from the formation of Schottky barriers at the metal/MoTe2 contacts. The Schottky barrier heights as well as the current on/off ratio could be modified by modulating the electrostatic fields of the back-gate voltage (Vbg) and drain-source voltage (Vds). Using these ambipolar MoTe2 transistors we fabricated complementary inverters and amplifiers, demonstrating their feasibility for future digital and analog circuit applications.
385 citations
TL;DR: In this paper, the authors demonstrate enhanced electron and hole transport in few-layer phosphorene field effect transistors (FETs) using titanium as the source/drain contact electrode and 20 nm SiO2 as the back gate dielectric.
Abstract: In this article, we demonstrate enhanced electron and hole transport in few-layer phosphorene field effect transistors (FETs) using titanium as the source/drain contact electrode and 20 nm SiO2 as the back gate dielectric. The field effect mobility values were extracted to be ∼38 cm2/Vs for electrons and ∼172 cm2/Vs for the holes. On the basis of our experimental data, we also comprehensively discuss how the contact resistances arising due to the Schottky barriers at the source and the drain end effect the different regime of the device characteristics and ultimately limit the ON state performance. We also propose and implement a novel technique for extracting the transport gap as well as the Schottky barrier height at the metal–phosphorene contact interface from the ambipolar transfer characteristics of the phosphorene FETs. This robust technique is applicable to any ultrathin body semiconductor which demonstrates symmetric ambipolar conduction. Finally, we demonstrate a high gain, high noise margin, che...
381 citations
TL;DR: In this paper, metal/semiconductor/metal structured photodetectors were fabricated using as-grown film and annealed film separately, where the Schottky barrier controlled electron transport and the quantity of photogenerated carriers trapped by oxygen vacancy significant decreasing.
Abstract: β-Ga2O3 epitaxial thin films were deposited using laser molecular beam epitaxy technique and oxygen atmosphere in situ annealed in order to reduce the oxygen vacancy. Metal/semiconductor/metal structured photodetectors were fabricated using as-grown film and annealed film separately. Au/Ti electrodes were Ohmic contact with the as-grown films and Schottky contact with the annealed films. In compare with the Ohmic-type photodetector, the Schottky-type photodetector takes on lower dark current, higher photoresponse, and shorter switching time, which benefit from Schottky barrier controlling electron transport and the quantity of photogenerated carriers trapped by oxygen vacancy significant decreasing.
363 citations
TL;DR: The channel length scaling of ultrathin BP field-effect transistors (FETs) is studied and a scheme for using various contact metals to change the transistor characteristics is discussed, showing the potential to realize BP CMOS logic circuits.
Abstract: Although monolayer black phosphorus (BP) or phosphorene has been successfully exfoliated and its optical properties have been explored, most of electrical performance of the devices is demonstrated on few-layer phosphorene and ultra-thin BP films. In this paper, we study the channel length scaling of ultra-thin BP field-effect transistors (FETs), and discuss a scheme for using various contact metals to change transistor characteristics. Through studying transistor behaviors with various channel lengths, the contact resistance can be extracted from the transfer length method (TLM). With different contact metals, we find out that the metal/BP interface has different Schottky barrier heights, leading to a significant difference in contact resistance, which is quite different from previous studies of transition metal dichalcogenides (TMDs) such as MoS2 where Fermi-level is strongly pinned near conduction band edge at metal/MoS2 interface. The nature of BP transistors are Schottky barrier FETs, where the on and off states are controlled by tuning the Schottky barriers at the two contacts. We also observe the ambipolar characteristics of BP transistors with enhanced n-type drain current and demonstrate that the p-type carriers can be easily shifted to n-type or vice versus by controlling the gate bias and drain bias, showing the potential to realize BP CMOS logic circuits.
357 citations
TL;DR: In this paper, molybdenum (Mo) is introduced and evaluated as an alternative contact metal to atomically-thin MoS2, and high-performance field effect transistors are experimentally demonstrated.
Abstract: In this Letter, molybdenum (Mo) is introduced and evaluated as an alternative contact metal to atomically-thin molybdenum disulphide (MoS2), and high-performance field-effect transistors are experimentally demonstrated. In order to understand the physical nature of the interface and highlight the role of the various factors contributing to the Mo-MoS2 contacts, density functional theory (DFT) simulations are employed, which reveal that Mo can form high quality contact interface with monolayer MoS2 with zero tunnel barrier and zero Schottky barrier under source/drain contact, as well as an ultra-low Schottky barrier (0.1 eV) at source/drain-channel junction due to strong Fermi level pinning. In agreement with the DFT simulations, high mobility, high ON-current, and low contact resistance are experimentally demonstrated on both monolayer and multilayer MoS2 transistors using Mo contacts. The results obtained not only reveal the advantages of using Mo as a contact metal for MoS2 but also highlight the fact that the properties of contacts with 2-dimensional materials cannot be intuitively predicted by solely considering work function values and Schottky theory.
333 citations
TL;DR: Polymer electrolytes allow the charge carrier densities to be modulated to very high values, allowing the observation of both the electron- and the hole-doped regimes, and ohmic contacts formed at low temperatures allow us to study the temperature dependence of electron and hole mobilities.
Abstract: Single-layer transition metal dichalcogenide WSe2 has recently attracted a lot of attention because it is a 2D semiconductor with a direct band gap. Due to low doping levels, it is intrinsic and shows ambipolar transport. This opens up the possibility to realize devices with the Fermi level located in the valence band, where the spin/valley coupling is strong and leads to new and interesting physics. As a consequence of its intrinsically low doping, large Schottky barriers form between WSe2 and metal contacts, which impede the injection of charges at low temperatures. Here, we report on the study of single-layer WSe2 transistors with a polymer electrolyte gate (PEO:LiClO4). Polymer electrolytes allow the charge carrier densities to be modulated to very high values, allowing the observation of both the electron- and the hole-doped regimes. Moreover, our ohmic contacts formed at low temperatures allow us to study the temperature dependence of electron and hole mobilities. At high electron densities, a re-en...
255 citations
TL;DR: It is found that the contact resistivity for metal/MoS2 junctions is defined by contact area instead of contact width, which may reduce the influence of large contact resistance for MoS2 Schottky barrier transistors at the channel length scaling limit.
Abstract: In this article, we study the properties of metal contacts to single-layer molybdenum disulfide (MoS2) crystals, revealing the nature of switching mechanism in MoS2 transistors. On investigating transistor behavior as contact length changes, we find that the contact resistivity for metal/MoS2 junctions is defined by contact area instead of contact width. The minimum gate dependent transfer length is ∼0.63 μm in the on-state for metal (Ti) contacted single-layer MoS2. These results reveal that MoS2 transistors are Schottky barrier transistors, where the on/off states are switched by the tuning of the Schottky barriers at contacts. The effective barrier heights for source and drain barriers are primarily controlled by gate and drain biases, respectively. We discuss the drain induced barrier narrowing effect for short channel devices, which may reduce the influence of large contact resistance for MoS2 Schottky barrier transistors at the channel length scaling limit.
251 citations
TL;DR: A new type of FET device is demonstrated, which enables a controllable transition from NMOS digital to bipolar characteristics and a very high room temperature on/off current ratio (ION/IOFF ∼ 36) in comparison to graphene-based FET devices without sacrificing the field-effect electron mobilities in graphene.
Abstract: Field-effect transistor (FET) devices composed of a MoS2–graphene heterostructure can combine the advantages of high carrier mobility in graphene with the permanent band gap of MoS2 for digital applications. Herein, we investigate the electron transfer, photoluminescence, and gate-controlled carrier transport in such a heterostructure. We show that the junction is a Schottky barrier, whose height can be artificially controlled by gating or doping graphene. When the applied gate voltage (or the doping level) is zero, the photoexcited electron–hole pairs in monolayer MoS2 can be split by the heterojunction, significantly reducing the photoluminescence. By applying negative gate voltage (or p-doping) in graphene, the interlayer impedance formed between MoS2 and graphene exhibits an 100-fold increase. For the first time, we show that the gate-controlled interlayer Schottky impedance can be utilized to modulate carrier transport in graphene, significantly depleting the hole transport, but preserving the electr...
244 citations
TL;DR: It is shown that a fundamentally new transport model is needed to describe the graphene-silicon Schottky junction, and the details of the diode characteristics is best characterized by the Landauer transport formalism, suggesting that the injection rate from graphene ultimately determines the transport properties of this new Schottki junction.
Abstract: The proper understanding of semiconductor devices begins at the metal–semiconductor interface. The metal/semiconductor interface itself can also be an important device, as Schottky junctions often forms when the doping in the semiconductors is low. Here, we extend the analysis of metal–silicon Schottky junctions by using graphene, an atomically thin semimetal. We show that a fundamentally new transport model is needed to describe the graphene–silicon Schottky junction. While the current–voltage behavior follows the celebrated ideal diode behavior, the details of the diode characteristics is best characterized by the Landauer transport formalism, suggesting that the injection rate from graphene ultimately determines the transport properties of this new Schottky junction.
Patent•
PARC1
TL;DR: In this paper, a rectifying circuit that facilitates harvesting multiband RF signals having low energy levels (i.e., tens of mW and below) by utilizing two zero bias Schottky diodes having different forward voltage and peak inverse voltage values is presented.
Abstract: A radio frequency (RF) energy harvesting device (rectenna) includes an antenna structure configured to resonate at RF frequencies, and a rectifying circuit that facilitates harvesting multiband RF signals having low energy levels (i.e., tens of mW and below) by utilizing two Zero Bias Schottky diodes having different forward voltage and peak inverse voltage values. Positive voltage pulses from a captured RF signal generated on a first antenna end point are passed by the first diode to a first internal node where they are summed with a second RF signal generated on the second antenna end point (i.e., after being passed through a capacitor), thereby producing a first intermediate voltage having a substantially higher voltage level. Positive voltage pulses are then passed from the first internal node through the second diode to an output control circuit for conversion into a usable DC output voltage.
TL;DR: In this article, the authors extend the analysis of metal-silicon Schottky junctions by using graphene, an atomically thin semimetal, and show that a fundamentally new transport model is needed to describe the graphene-sensor Schottkky junction.
Abstract: The proper understanding of semiconductor devices begins at the metal-semiconductor interface. The metal/semiconductor interface itself can also be an important device, as Schottky junctions often forms when the doping in the semiconductors is low. Here, we extend the analysis of metal-silicon Schottky junctions by using graphene, an atomically thin semimetal. We show that a fundamentally new transport model is needed to describe the graphene-silicon Schottky junction. While the current-voltage behavior follows the celebrated ideal diode behavior, the details of the diode characteristics is best characterized by the Landauer transport formalism, suggesting that the injection rate from graphene ultimately determines the transport properties of this new Schottky junction.
TL;DR: In this paper, the role of nonlinearity and zero bias resistance in the rectification process of the spindiode has been analyzed, and it has been shown how this technique would shift the design paradigms of diode-based devices and circuits.
Abstract: Since the very beginning of RF and microwave integrated techniques and energy harvesting, Schottky diodes are most often used in mixing and rectifying circuits. However, in specific μW power-harvesting applications, the Schottky diode technique fails to provide a satisfactory RF-dc conversion efficiency mainly because of its high zero-bias junction resistance. This paper examines the state-of-the-art low-power microwave-to-dc energy conversion techniques. A comprehensive picture of the state-of-the-art on this aspect is given graphically, which compares different technologies such as transistor, diode, and CMOS schemes. Subsequent to the highlighted limitations of current devices, this work introduces, for the first time, a nonlinear component for low-power rectification based on a recent discovery in spintronics, namely, the spindiode. Along with an analysis of the role of nonlinearity and zero bias resistance in the rectification process of the spindiode, it is shown how the spindiode could enhance the rectification efficiency even at a very low-power level and how this technique would shift the design paradigms of diode-based devices and circuits.
TL;DR: In this article, the authors demonstrated GaN vertical Schottky and p-n diodes on Si substrates for the first time, achieving a breakdown voltage of 205 V and a soft BV higher than 300 V, respectively, with peak electric field of 2.9 MV/cm in GaN.
Abstract: This letter demonstrates GaN vertical Schottky and p-n diodes on Si substrates for the first time. With a total GaN drift layer of only 1.5- $\mu{\rm m}$ thick, a breakdown voltage (BV) of 205 V was achieved for GaN-on-Si Schottky diodes, and a soft BV higher than 300 V was achieved for GaN-on-Si p-n diodes with a peak electric field of 2.9 MV/cm in GaN. A trap-assisted space-charge-limited conduction mechanism determined the reverse leakage and breakdown mechanism for GaN-on-Si vertical p-n diodes. The on-resistance was 6 and 10 ${\rm m}\Omega\cdot{\rm cm}^{2}$ for the vertical Schottky and p-n diode, respectively. These results show the promising performance of GaN-on-Si vertical devices for future power applications.
TL;DR: A new chemical sensor based on reverse-biased graphene/Si heterojunction diode that exhibits extremely high bias-dependent molecular detection sensitivity and low operating power has been developed and confirmed using capacitance-voltage measurements.
Abstract: A new chemical sensor based on reverse-biased graphene/Si heterojunction diode has been developed that exhibits extremely high bias-dependent molecular detection sensitivity and low operating power. The device takes advantage of graphene's atomically thin nature, which enables molecular adsorption on its surface to directly alter graphene/Si interface barrier height, thus affecting the junction current exponentially when operated in reverse bias and resulting in ultrahigh sensitivity. By operating the device in reverse bias, the work function of graphene, and hence the barrier height at the graphene/Si heterointerface, can be controlled by the bias magnitude, leading to a wide tunability of the molecular detection sensitivity. Such sensitivity control is also possible by carefully selecting the graphene/Si heterojunction Schottky barrier height. Compared to a conventional graphene amperometric sensor fabricated on the same chip, the proposed sensor demonstrated 13 times higher sensitivity for NO₂ and 3 times higher for NH₃ in ambient conditions, while consuming ∼500 times less power for same magnitude of applied voltage bias. The sensing mechanism based on heterojunction Schottky barrier height change has been confirmed using capacitance-voltage measurements.
TL;DR: A bidirectional dc-dc converter that is suitable for hybrid or electric vehicle application is studied based on three sets of device combinations, e.g., all-silicon, hybrid, and all-SiC.
Abstract: Silicon carbide (SiC)-based switching devices provide significant performance improvements in many aspects, including lower power dissipation, higher operating temperatures, and faster switching, compared with conventional Si devices. However, tradeoffs in efficiency, size, and weight between Si- and SiC-based converters are still unclear in the literature. In this paper, a bidirectional dc-dc converter that is suitable for hybrid or electric vehicle application is studied based on three sets of device combinations, e.g., all-silicon [conventional silicon insulated-gate bipolar transistors (IGBTs) and silicon PN diodes], hybrid (silicon IGBTs with SiC Schottky diodes), and all-SiC (SiC metal-oxide-semiconductor field-effect transistors with SiC Schottky diodes). At the switching frequency of 20 kHz, comparative analyses regarding the power loss reduction of power devices and efficiency improvements are carried out for the converters. Possible size and weight reduction is also investigated by increasing the operating frequencies of hybrid and all-SiC converters while reducing the capacitance and inductance values.
TL;DR: In this article, a pseudo-vertical diamond diodes with high forward current density of 103 A/cm2 (at 6 V) and a breakdown field larger than 7.7 MV/cm was demonstrated.
Abstract: High forward current density of 103 A/cm2 (at 6 V) and a breakdown field larger than 7.7 MV/cm for diamond diodes with a pseudo-vertical architecture, are demonstrated. The power figure of merit is above 244 MW/cm2 and the relative standard deviation of the reverse current density over 83 diodes is 10% with a mean value of 10−9 A/cm2. These results are obtained with zirconium as Schottky contacts on the oxygenated (100) oriented surface of a stack comprising an optimized lightly boron doped diamond layer on a heavily boron doped one, epitaxially grown on a Ib substrate. The origin of such performances are discussed.
TL;DR: By analyzing the response/recovery speed of the RGO-based photodetectors, the effects of oxygen-containing functional groups and crystalline defects on the photoelectric conversion are studied.
Abstract: Reduced graphene oxide (RGO) has been employed as an electrode for a series of vertically structured photodetectors. Compared with mechanically exfoliated or chemical vapor deposited graphene, RGO possesses more oxygen containing groups and defects, which are proved to be favorable to enhance the performance of photodetectors. As a matter of fact, RGO with different reduction levels can be readily obtained by varying the annealing temperature. The synthesis procedures for the RGO material are suitable for large scale production and its performance can be effectively improved by functionalization or element doping. For RGO-based devices, the Schottky junction properties and photoelectric conversion have been investigated, primarily by analyzing their current–voltage characteristics. Subsequently, the ON/OFF ratio, responsivity and detectivity of the photodetectors were closely examined, proving that the RGO material could be effectively utilized as the electrode material; also, their relationship with the RGO reduction levels has also been explored. By analyzing the response/recovery speed of the RGO-based photodetectors, we have studied the effects of oxygen-containing functional groups and crystalline defects on the photoelectric conversion.
TL;DR: In this article, the effect of polyvinylidene fluoride (PVDF) polymer interlayer on the rectifying junction parameters of Au/n-InP Schottky diode has been investigated using currentvoltage (I-V) and capacitance-voltage measurements at room temperature.
TL;DR: In this paper, the electrical properties of SCs on (2¯01)-oriented β-Ga2O3 thin films, which have been grown by pulsed laser deposition (PLD), were investigated.
Abstract: We have investigated the electrical properties of Cu Schottky contacts (SCs) on (2¯01)-oriented β-Ga2O3 thin films, which have been grown by pulsed laser deposition (PLD). The I–V characteristics of two different sample structures exhibit rectification ratios at ±2 V up to 7 orders of magnitude. The dominant current transport mechanism is thermionic emission. By fitting the I–V characteristics, we obtained the ideality factor n and the effective barrier height ΦBeff at temperatures between 50 and 320 K. Considering a Gaussian barrier height distribution, we determined a mean barrier height of 1.32 eV. The contacts are stable at high temperatures up to at least 550 K. At this temperature a homogeneous barrier height of 1.32 eV is found, consistent with the determined mean barrier height. The ideality factor for this temperature is 1.03 and barrier inhomogeneities do not influence current transport, making the contact close to ideal.
Schematic band diagram of a Cu/β-Ga2O3 Schottky contact at a temperature of 550 K. The inset shows a photographic image of the sample.
TL;DR: In this paper, instead of low-bandgap semiconductors, a graphene layer on top of a dielectric can dramatically influence the ability of the material for radiative heat transfer, which is used to improve the performance and reduce costs of near-field thermophotovoltaic cells.
Abstract: A graphene layer on top of a dielectric can dramatically influence the ability of the material for radiative heat transfer. This property of graphene is used to improve the performance and reduce costs of near-field thermophotovoltaic cells. Instead of low-band-gap semiconductors it is proposed to use graphene-on-silicon Schottky photovoltaic cells. One layer of graphene absorbs around 90% of incoming radiation and increases the heat transfer. This strong absorption is due to the excitation of plasmons in graphene, which are automatically tuned in resonance with the emitted light in the midinfrared range. The absorbed radiation excites electron-hole pairs in graphene, which are separated by the surface field induced by the Schottky barrier. For a quasimonochromatic source the generated power is one order of magnitude larger and the efficiency is on the same level as for semiconductor photovoltaic cells.
TL;DR: The direction of electric fields within the semiconductor is found to play a crucial role in the separation of photogenerated charges, and thus strongly influences the photocatalytic efficiency.
Abstract: The relationship between the contact type in metal-semiconductor junctions and their photocatalytic efficiencies is investigated. Two metal-semiconductor junctions, silver on zinc oxide (Ag/ZnO) and platinum on zinc oxide (Pt/ZnO) serve as model system for Ohmic and Schottky metal-semiconductor contact, respectively. Ag/ZnO, with Ohmic contact, exhibits a higher photocatalytic efficiency than Pt/ZnO, with Schottky contact. The direction of electric fields within the semiconductor is found to play a crucial role in the separation of photogenerated charges, and thus strongly influences the photocatalytic efficiency.
TL;DR: The all-layered-material Schottky barrier solar cell employing WS2 as a photoactive semiconductor exhibits efficient photon absorption in the visible spectral range, yielding 3.3% photoelectric conversion efficiency with multilayer graphene as the Schottki contact.
Abstract: Schottky barriers formed by graphene (monolayer, bilayer, and multilayer) on 2D layered semiconductor tungsten disulfide (WS2) nanosheets are explored for solar energy harvesting. The characteristics of the graphene–WS2 Schottky junction vary significantly with the number of graphene layers on WS2, resulting in differences in solar cell performance. Compared with monolayer or stacked bilayer graphene, multilayer graphene helps in achieving improved solar cell performance due to superior electrical conductivity. The all-layered-material Schottky barrier solar cell employing WS2 as a photoactive semiconductor exhibits efficient photon absorption in the visible spectral range, yielding 3.3% photoelectric conversion efficiency with multilayer graphene as the Schottky contact. Carrier transport at the graphene/WS2 interface and the interfacial recombination process in the Schottky barrier solar cells are examined.
TL;DR: In this article, a facile method for the preparation of magnetic graphene oxide (GO)-Fe 3 O 4 (GO-Fe 3 o 4 ) nanocomposites and the rectifying properties of (GO−Fe 3O 4 )/p-Si junction in a Schottky diode were discussed.
TL;DR: In this paper, the authors report on the design, facile fabrication, and outstanding NO2 gas sensing properties of monolayer graphene (GP)/snO2 nanowire (NW) Schottky junction (SJ) devices.
Abstract: Schottky junctions (SJ) are considered devices for sensing applications due to their unique properties. Herein, we report on the design, facile fabrication, and outstanding NO2 gas sensing properties of monolayer graphene (GP)/SnO2 nanowire (NW) SJ devices. The devices were prepared by directly growing single crystal SnO2 NWs on interdigitated Pt electrodes via thermal evaporation, followed by transferring a GP layer grown by chemical vapor deposition on top of the NW chip. The SJ-based sensor showed a reversible response to NO2 gas at concentrations of ppb levels with detection limits of about 0.024 ppb at a low operating temperature of 150 °C and bias voltage (1 V) with a response/recovery time of less than 50 s. The outstanding gas-sensing characteristics of the device were attributed to tuning the Schottky barrier height and barrier width at the tiny area of contact between GP and SnO2 NW through the adsorption/desorption of gas molecules.
TL;DR: In this article, the influence of localized surface plasmon resonance on hot electron flow at a metal-semiconductor interface was observed with a Schottky diode composed of a thin silver layer on TiO2.
Abstract: Over the last several decades, innovative light-harvesting devices have evolved to achieve high-efficiency solar energy transfer. Understanding the mechanism of plasmon resonance is very desirable to overcome the conventional efficiency limits of photovoltaics. The influence of localized surface plasmon resonance on hot electron flow at a metal–semiconductor interface was observed with a Schottky diode composed of a thin silver layer on TiO2; subsequent X-ray photoelectron spectroscopy characterized how oxygen in the Ag/TiO2 nanodiode influenced the Schottky barrier height. Photoexcited electrons generate photocurrent when they have enough energy to travel over the Schottky barrier formed at the metal–semiconductor interface. We observed that the photocurrent could be enhanced by optically excited surface plasmons. When the surface plasmons are excited on the corrugated Ag metal surface, they decay into energetic hot electron–hole pairs, contributing to the total photocurrent. The abnormal resonance peaks...
TL;DR: In this article, a thermally integrated packaging structure for an all silicon carbide (SiC) power module was used to realize highly efficient cooling of power semiconductor devices through direct bonding of the power stage and a cold baseplate.
Abstract: A thermally integrated packaging structure for an all silicon carbide (SiC) power module was used to realize highly efficient cooling of power semiconductor devices through direct bonding of the power stage and a cold baseplate. The prototype power modules composed of SiC metal-oxide-semiconductor field-effect transistors and Schottky barrier diodes demonstrate significant improvements such as low-power losses and low-thermal resistance. Direct comparisons to their silicon counterparts, which are composed of insulated gate bipolar transistors and PiN diodes, as well as conventional thermal packaging, were experimentally performed. The advantages of this SiC module in efficiency and power density for power electronics systems have also been identified, with clarification of the SiC attributes and packaging advancements.
TL;DR: In this article, the formation of a Schottky barrier at the interface between a metal and hexagonal boron nitride (h−BN) is studied using density functional theory.
Abstract: The formation of a Schottky barrier at the interface between a metal and hexagonal boron nitride (h−BN) is studied using density functional theory. For metals whose work functions range from 4.2 to 6.0 eV, we find Schottky barrier heights for holes between 1.2 and 2.3 eV. A central role in determining the Schottky barrier height is played by a potential step of between 0.4 and 1.8 eV that is formed at the metal|h−BN interface and effectively lowers the metal work function. If h−BN is physisorbed, as is the case on fcc Cu, Al, Au, Ag, and Pt(111) substrates, the interface potential step is described well by a universal function that depends only on the distance separating h−BN from the metal surface. The interface potential step is largest when h−BN is chemisorbed, which is the case for hcp Co and Ti (0001) and for fcc Ni and Pd (111) substrates
TL;DR: In this paper, a comparative design study of high-power medium-voltage three-level neutral-point-clamped converters with a 6.5-kV Si-IGBT/Si-PiN diode, and a 10-kv SiC-MOSFET/SiC-JBS diode is presented.
Abstract: In this paper, a comparative design study of high-power medium-voltage three-level neutral-point-clamped converters with a 6.5-kV Si-IGBT/Si-PiN diode, a 6.5-kV Si-IGBT/SiC-JBS diode, and a 10-kV SiC-MOSFET/SiC-JBS diode is presented. A circuit model of a 100-A power module, including packaging parasitic inductances, is developed based on device die SPICE-based circuit models for each power device. Switching waveforms, characteristics, and switching power and energy loss measurements of the power modules, including symmetric/asymmetric parasitic inductances, are presented. High-power converter designs and SPICE circuit simulations are carried out, and power loss and efficiencies are compared for a pulsewidth-modulated (PMW) 1-MW power converter at 1-, 5-, and 10-kHz switching frequencies for application in shipboard power system and a PWM vector-controlled and a line-frequency angle-controlled 20- to 40-MVA power converter at 60-Hz, 540-Hz, and 1-kHz switching frequencies for active mobile substation application. It is shown that the 6.5-kV Si-IGBT incorporating an antiparallel SiC-JBS diode, with its high efficiency performance up to 5-kHz switching frequency, is a strong candidate for megawatt-range power converters. The 10-kV SiC-MOSFET/SiC-JBS diode remains an option for higher switching frequency (5-10 kHz) high-power converters.