Showing papers on "Silicon carbide published in 2010"
IBM1
TL;DR: The high-frequency performance of these epitaxial graphene transistors exceeds that of state-of-the-art silicon transistors of the same gate length.
Abstract: The high carrier mobility of graphene has been exploited in field-effect transistors that operate at high frequencies. Transistors were fabricated on epitaxial graphene synthesized on the silicon face of a silicon carbide wafer, achieving a cutoff frequency of 100 gigahertz for a gate length of 240 nanometers. The high-frequency performance of these epitaxial graphene transistors exceeds that of state-of-the-art silicon transistors of the same gate length.
2,415 citations
TL;DR: This work demonstrates the self-organized growth of graphene nanoribbons on a templated silicon carbide substrate prepared using scalable photolithography and microelectronics processing, and proves the scalability of this approach by fabricating 10,000 top-gated graphene transistors on a 0.24-cm(2) SiC chip, which is the largest density of graphene devices reported to date.
Abstract: In spite of its excellent electronic properties, the use of graphene in field-effect transistors is not practical at room temperature without modification of its intrinsically semimetallic nature to introduce a bandgap. Quantum confinement effects can create a bandgap in graphene nanoribbons, but existing nanoribbon fabrication methods are slow and often produce disordered edges that compromise electronic properties. Here, we demonstrate the self-organized growth of graphene nanoribbons on a templated silicon carbide substrate prepared using scalable photolithography and microelectronics processing. Direct nanoribbon growth avoids the need for damaging post-processing. Raman spectroscopy, high-resolution transmission electron microscopy and electrostatic force microscopy confirm that nanoribbons as narrow as 40 nm can be grown at specified positions on the substrate. Our prototype graphene devices exhibit quantum confinement at low temperatures (4 K), and an on-off ratio of 10 and carrier mobilities up to 2,700 cm(2) V(-1) s(-1) at room temperature. We demonstrate the scalability of this approach by fabricating 10,000 top-gated graphene transistors on a 0.24-cm(2) SiC chip, which is the largest density of graphene devices reported to date.
441 citations
TL;DR: In this article, a study of the properties of two-dimensional (2D), monolayer of silicon carbide (SiC) in honeycomb structure and its quasi-one-dimensional armchair nanoribbons using first-principles plane-wave method is presented.
Abstract: We present a study of mechanical, electronic and magnetic properties of two-dimensional (2D), monolayer of silicon carbide (SiC) in honeycomb structure and its quasi-one-dimensional (quasi-1D) armchair nanoribbons using first-principles plane-wave method. In order to reveal dimensionality effects, a brief study of three-dimensional (3D) bulk and 1D atomic chain of SiC are also included. Calculated bond-lengths, cohesive energies, charge transfers and band gaps display a clear dimensionality effect. The stability analysis based on the calculation of phonon frequencies indicates that 2D SiC monolayer is stable in planar geometry. We found that 2D SiC monolayer in honeycomb structure and its bare and hydrogen passivated nanoribbons are ionic, nonmagnetic, wide band gap semiconductors. The band gap is further increased upon self-energy corrections. The mechanical properties are investigated using the strain energy calculations. The effect of various vacancy defects, adatoms, and substitutional impurities on electronic and magnetic properties in 2D SiC monolayer and in its armchair nanoribbons is also investigated. Some of these vacancy defects and impurities, which are found to influence physical properties and attain magnetic moments, can be used to functionalize SiC honeycomb structures.
322 citations
TL;DR: In this article, the electromagnetic (EM) wave absorption properties of 2mm-thick silicon carbide nanowire (SiCNW)−epoxy composites were studied in the range of 2−40 GHz using a free-space antenna-based system.
Abstract: The electromagnetic (EM) wave absorption properties of 2-mm-thick silicon carbide nanowire (SiCNW)−epoxy composites were studied in the range of 2−40 GHz using a free-space antenna-based system. The 35 wt % SiCNW composites exhibited dual-frequency EM wave absorptions of −31.7 and −9.8 dB at 8.3 and 27 GHz, respectively. The minimum reflection loss of −32.4 dB was achieved at 31.1 GHz for the composites containing 25 wt % SiCNW. A study of the loss mechanism of EM wave absorption suggests the combination of the electric conductance loss caused by network-like SiCNWs in the resin matrix and the relaxation polarization loss in the interfaces of SiCNWs and the epoxy resin.
251 citations
TL;DR: In this article, the authors show that the growth of epitaxial graphene on Si-terminated SiC(0001) differs from growth on the Cterminated siC (0001) surface, resulting in strong and weak coupling to the substrate and to successive graphene layers.
Abstract: This article reviews the materials science of graphene grown epitaxially on the hexagonal basal planes of SiC crystals and progress toward the deterministic manufacture of graphene devices. We show that the growth of epitaxial graphene on Si-terminated SiC(0001) differs from growth on the C-terminated SiC(0001) surface, resulting in, respectively, strong and weak coupling to the substrate and to successive graphene layers. Monolayer epitaxial graphene on either surface displays the expected electronic structure and transport characteristics of graphene, but the non-graphitic stacking of multilayer graphene on SiC(0001) determines an electronic structure much different from that of graphitic multilayers on SiC(0001). This materials system is rich in subtleties, and graphene grown on the two polar faces of SiC differs in important ways, but all of the salient features of ideal graphene are found in these epitaxial graphenes, and wafer-scale fabrication of multi-GHz devices already has been achieved.
200 citations
TL;DR: In this paper, time-dependent dielectric-breakdown measurements are performed on state-of-the-art 4H-SiC MOS capacitors and double-implanted MOS field effect transistors (DMOSFET) with stress temperatures between 225°C and 375°C, and stress electric fields between 6 and 10 MV/cm.
Abstract: The wide-bandgap nature of silicon carbide (SiC) makes it an excellent candidate for applications where high temperature is required. The metal-oxide-semiconductor (MOS)-controlled power devices are the most favorable structure; however, it is widely believed that silicon oxide on SiC is physically limited, particularly at high temperatures. Therefore, experimental measurements of long-term reliability of oxide at high temperatures are necessary. In this paper, time-dependent dielectric-breakdown measurements are performed on state-of-the-art 4H-SiC MOS capacitors and double-implanted MOS field-effect transistors (DMOSFET) with stress temperatures between 225°C and 375°C and stress electric fields between 6 and 10 MV/cm. The field-acceleration factor is around 1.5 dec/(MV/cm) for all of the temperatures. The thermal activation energy is found to be ~ 0.9 eV, independent of the electric field. The area dependence of Weibull slope is discussed and shown to be a possible indication that the oxide quality has not reached the intrinsic regime and further oxide-reliability improvements are possible. Since our reliability data contradict the widely accepted belief that silicon oxide on SiC is fundamentally limited by its smaller conduction-band offset compared with Si, a detailed discussion is provided to examine the arguments of the early predictions.
188 citations
TL;DR: This work provides the first direct evidence that nucleation of epitaxial graphene on silicon carbide occurs along the (110n) plane and shows that the nucleated graphene quality improves as the synthesis temperature is increased.
Abstract: A promising route for the synthesis of large-area graphene, suitable for standard device fabrication techniques, is the sublimation of silicon from silicon carbide at elevated temperatures (>1200 degrees C). Previous reports suggest that graphene nucleates along the (110n) plane, known as terrace step edges, on the silicon carbide surface. However, to date, a fundamental understanding of the nucleation of graphene on silicon carbide is lacking. We provide the first direct evidence that nucleation of epitaxial graphene on silicon carbide occurs along the (110n) plane and show that the nucleated graphene quality improves as the synthesis temperature is increased. Additionally, we find that graphene on the (110n) plane can be significantly thicker than its (0001) counterpart and appears not to have a thickness limit. Finally, we find that graphene along the (110n) plane can contain a high density of structural defects, often the result of the underlying substrate, which will undoubtedly degrade the electronic properties of the material. Addressing the presence of non-uniform graphene that may contain structural defects at terrace step edges will be key to the development of a large-scale graphene technology derived from silicon carbide.
180 citations
TL;DR: A microfabricated electromechanical inverter with SiC complementary NEMS switches capable of operating at 500°C with ultralow leakage current is reported, a promising approach for low-power, high-performance logic operation at temperatures higher than 300°C, beyond the capability of conventional silicon technology.
Abstract: Logic circuits capable of operating at high temperatures can alleviate expensive heat-sinking and thermal-management requirements of modern electronics and are enabling for advanced propulsion systems. Replacing existing complementary metal-oxide semiconductor field-effect transistors with silicon carbide (SiC) nanoelectromechanical system (NEMS) switches is a promising approach for low-power, high-performance logic operation at temperatures higher than 300°C, beyond the capability of conventional silicon technology. These switches are capable of achieving virtually zero off-state current, microwave operating frequencies, radiation hardness, and nanoscale dimensions. Here, we report a microfabricated electromechanical inverter with SiC complementary NEMS switches capable of operating at 500°C with ultralow leakage current.
176 citations
TL;DR: Experimental demonstrations of electrostatically actuated, contact-mode nanoelectromechanical switches based on very thin silicon carbide (SiC) nanowires (NWs) find enhanced switching performance in bare SiC NWs, with lifetimes exceeding those based on metallized SiCNWs.
Abstract: We report experimental demonstrations of electrostatically actuated, contact-mode nanoelectromechanical switches based on very thin silicon carbide (SiC) nanowires (NWs). These NWs are lithographically patterned from a 50 nm thick SiC layer heteroepitaxially grown on single-crystal silicon (Si). Several generic designs of in-plane electrostatic SiC NW switches have been realized, with NW widths as small as ∼20 nm and lateral switching gaps as narrow as ∼10 nm. Very low switch-on voltages are obtained, from a few volts down to ∼1 V level. Two-terminal, contact-mode "hot" switching with high on/off ratios (>10 2 or 10 3 ) has been demonstrated repeatedly for many devices. We find enhanced switching performance in bare SiC NWs, with lifetimes exceeding those based on metallized SiC NWs.
175 citations
Patent•
04 Mar 2010TL;DR: In this paper, methods of forming dielectric films comprising silicon, such as, but not limited to, silicon oxide, silicon oxycarbide, silicon carbide, and combinations thereof, are described.
Abstract: Described herein are methods of forming dielectric films comprising silicon, such as, but not limited to, silicon oxide, silicon oxycarbide, silicon carbide, and combinations thereof, that exhibit at least one of the following characteristics: low wet etch resistance, a dielectric constant of 6.0 or below, and/or can withstand a high temperature rapid thermal anneal process. Also disclosed herein are the methods to form dielectric films or coatings on an object to be processed, such as, for example, a semiconductor wafer.
162 citations
01 Nov 2010
TL;DR: In this article, the possibility of building a modular multilevel converter (M2C) using Silicon Carbide (SiC) switches was investigated and the main focus was on a theoretical investigation of the conduction losses of such a converter and a comparison to a corresponding converter with silicon insulated gate bipolar transistors.
Abstract: This paper studies the possibility of building a Modular Multilevel Converter (M2C) using Silicon Carbide (SiC) switches. The main focus is on a theoretical investigation of the conduction losses of such a converter and a comparison to a corresponding converter with silicon insulated gate bipolar transistors. Both SiC BJTs and JFETs are considered and compared in order to choose the most suitable technology. One of the sub-modules of a down-scaled 10 kVA prototype M2C is replaced with a sub-module with SiC JFETs without anti-parallel diodes. It is shown that diode-less operation is possible with the JFETs conducting in the negative direction, leaving the possibility to use the body diode during the switching transients. Experimental waveforms for the SiC sub-module verify the feasibility during normal steady-state operation. The loss estimation shows that a 300 MW M2C for high-voltage direct current transmission would potentially have an efficiency of approximately 99,8 % if equipped with future 3.3 kV 1.2 kA SiC JFETs.
TL;DR: In this article, a survey of the surface energies of SiC and liquid metals, the reactivity and wettability of pure metal/SiC systems, as well as the wetting behavior and mechanisms of (liquid metal + SiC) systems are reviewed for understanding the interfacial bonding and for supporting the development of application-oriented processes like nonreactive brazing.
TL;DR: The presented approach allows for mass fabrication of polycrystalline graphene without transfer steps while using only CMOS compatible process steps.
Abstract: We report on a method for the fabrication of graphene on a silicon dioxide substrate by solid-state dissolution of an overlying stack of a silicon carbide and a nickel thin film. The carbon dissolves in the nickel by rapid thermal annealing. Upon cooling, the carbon segregates to the nickel surface forming a graphene layer over the entire nickel surface. By wet etching of the nickel layer, the graphene layer was allowed to settle on the original substrate. Scanning tunneling microscopy (STM) as well as Raman spectroscopy has been performed for characterization of the layers. Further insight into the morphology of the layers has been gained by Raman mapping indicating micrometer-size graphene grains. Devices for electrical measurement have been manufactured exhibiting a modulation of the transfer current by backgate electric fields. The presented approach allows for mass fabrication of polycrystalline graphene without transfer steps while using only CMOS compatible process steps.
TL;DR: In this article, the maximum electron density induced in monolayer and bilayer graphene was determined by the difference between the work function for electrons in pristine graphene and donor states on/in SiC, and analyzed the responsivity of graphene to the density variation by means of electrostatic gates.
Abstract: We analyze doping of graphene grown on SiC in two models which differ by the source of charge transferred to graphene, namely, from SiC surface and from bulk donors. For each of the two models, we find the maximum electron density induced in monolayer and bilayer graphene, which is determined by the difference between the work function for electrons in pristine graphene and donor states on/in SiC, and analyze the responsivity of graphene to the density variation by means of electrostatic gates.
TL;DR: In this paper, the authors showed that the presence of the nanowires afforded high specific surface area (SSA) values to the macroporous ceramic foams, ranging from 10 to 110 m2/g.
Abstract: Via catalyst-assisted pyrolysis, Si3N4 and SiC nanowires were produced on the cell walls of polymer-derived ceramic foams. The pyrolysis atmosphere and temperature were the main parameters affecting their development: silicon nitride single-crystal nanowires formed under nitrogen, while silicon carbide ones were produced under argon, and their amount increased with the increasing pyrolysis temperature. Brunauer–Emmett–Teller analysis showed that the presence of the nanowires afforded high specific surface area (SSA) values to the macroporous ceramic foams, ranging from 10 to 110 m2/g. Co-containing samples developed higher SSA values, especially after pyrolysis at 1400°C in N2, than samples containing Fe as a catalyst. The differences were explained in terms of morphology (diameter and assemblage), which depended on the processing conditions and the catalyst type (Co or Fe).
TL;DR: In this article, a transient liquid phase (TLP) die attach technique was demonstrated for two binary alloy systems, Ag-In and Au-In, on Si3N4 substrates.
Abstract: Recently, silicon carbide power devices have been receiving attention for applications above 300 °C. For high-temperature applications, the die attached for these devices has to withstand the maximum operating temperature. In this paper, a transient liquid phase (TLP) die attach technique was demonstrated for two binary alloy systems, Ag-In and Au-In, on Si3N4 substrates. A nearly void-free joint was developed using the Ag-In alloy. Two inter-metallic phases of Agln2 and Ag2ln, along with pure Ag were identified. After annealing at 400 °C, the silver appears to be more evenly spread to form a silver-rich Ag-In alloy with a Ag composition of 70-75 wt.%, even though a nearly pure silver phase is still found in the region where the silver was initially deposited on the Si3N4 substrate. For the Au-In system, there was no indication of bonding degradation at the interface after annealing at 400 °C for 100 h in air. Two inter-metallic phases, Auln and Auln2, along with pure gold, were identified in the Au-In TLP joint. After annealing, the bonding interface became a more Au-rich Au-In alloy. The die attach pull strength, after thermal annealing, increased to approximately twice the minimum strength. The uniformity of the bonds improves and they become more homogeneous because the formation of intermetallic phases continues during thermal annealing.
TL;DR: In this article, the authors describe a process for fabricating highvoltage n-channel double-diffused metal-oxide-semiconductor insulated gate bipolar transistors (IGBTs) on free-standing 4H silicon carbide (SiC) epilayers.
Abstract: In this paper, we describe a process for fabricating high-voltage n-channel double-diffused metal-oxide-semiconductor insulated gate bipolar transistors (IGBTs) on free-standing 4H silicon carbide (SiC) epilayers. In this process, all critical layers are epitaxially grown in a continuous sequence. The substrate is then removed, and device fabrication takes place on the carbon face of a free-standing epilayer having a total thickness of about 180 ?m. For a drift layer with doping and thickness values capable of blocking 20 kV, the n-channel IGBT carries 27.3-A/cm2 current at a power dissipation of 300 W/cm2, with a differential on-resistance of 177 m?·cm2. To our knowledge, this is the first detailed report of device fabrication on free-standing SiC epilayers.
TL;DR: A feasibility study on recovering silicon powder from slurry containing silicon carbide abrasives, silicon kerfs, and iron fragments generated by slicing silicon ingots in the wire-saw process was conducted as discussed by the authors.
TL;DR: In this article, a diamond grinding wheel was used for high removal rate grinding of silicon carbide and the results showed that the material removal was primarily due to the microfracture and grain dislodgement under the grinding conditioned selected.
Abstract: Development of advanced ceramics such as silicon carbide has gained significant importance because of their desirable properties. However, their engineering applications are still limited owing to the limitations in developing damage-free and economical machining techniques. It is often desired to increase the machining rate to improve productivity while maintaining the desired surface integrity. The success of this approach, however, requires a fundamental understanding of the material removal and damage formation mechanism in grinding. In this paper, high removal rate grinding of silicon carbide was investigated with respect to material removal and basic grinding parameters using a diamond grinding wheel. The results showed that the material removal was primarily due to the microfracture and grain dislodgement under the grinding conditioned selected. For grain dislodgement removal mode, the relationship for the removal rate in scratching based on a simple fracture mechanics analysis has been established. This research provides valuable insights into the surface and subsurface integrity and material removal mechanism during high removal rate grinding of silicon carbide.
TL;DR: In this article, a novel gelation-freezing (GF) method was used to obtain ultra high porosity and unidirectionally oriented micrometer-sized cylindrical pores.
Abstract: Silicon carbide (SiC) with ultra high porosity and unidirectionally oriented micrometer-sized cylindrical pores was prepared using a novel gelation–freezing (GF) method. Gelatin, water and silicon carbide powder were mixed and cooled at 7 °C. The obtained gels were frozen from −10 to −70 °C, dried using a vacuum freeze drier, degreased at 600 °C and then sintered at 1800 °C for 2 h. The gels could be easily formed into various shapes, such as cylinders, large pipes and honeycombs using molds. Scanning electron microscopy (SEM) observations of the sintered bodies showed a microstructure composed of ordered micrometer-sized cylindrical cells with unidirectional orientation. The cell size ranging from 34 to 147 μm could be modulated by changing the freezing temperatures. The numbers of cells for the samples frozen at −10 and −70 °C were 47 and 900 cells/mm 2 , respectively, as determined from cross-sections of the sintered bodies. The resulting porous SiC with a total porosity of 86%, exhibited air permeability from 2.3 × 10 −11 to 1.0 × 10 −10 m 2 , which was the same as the calculated ideal permeability, and high compressive strength of 16.6 MPa. The porosity, number of cells, air permeability and strength of the present porous SiC were significantly higher than that reported for other porous SiC ceramics.
TL;DR: X-ray photoelectron spectroscopy and scanning tunneling microscopy were extensively used to characterize the quality of the few-layer graphene (FLG) surface and confirm the graphitic composition and measuring the thickness of the FLG samples.
Abstract: Epitaxial graphene films grown on silicon carbide (SiC) substrate by solid state graphitization is of great interest for electronic and optoelectronic applications. In this paper, we explore the properties of epitaxial graphene films on 3C-SiC(111)/Si(111) substrate. X-ray photoelectron spectroscopy and scanning tunneling microscopy were extensively used to characterize the quality of the few-layer graphene (FLG) surface. The Raman spectroscopy studies were useful in confirming the graphitic composition and measuring the thickness of the FLG samples.
TL;DR: In this paper, temperature dependent properties of wide bandgap semiconductors have been used to calculate theoretical specific on-resistance, breakdown voltage, and thermal run-away temperature in SiC GaN, diamond, and Si vertical power devices for comparison.
TL;DR: The involvement of electromagnetic field effects on 21 selected chemical transformations was evaluated by comparing the results obtained in microwave-transparent Pyrex vials with experiments performed in SiC vials at the same reaction temperature, indicating that the electromagnetic field had no direct influence on the reaction pathway.
Abstract: Silicon carbide (SiC) is a strongly microwave absorbing chemically inert ceramic material that can be utilized at extremely high temperatures due to its high melting point and very low thermal expansion coefficient. Microwave irradiation induces a flow of electrons in the semiconducting ceramic that heats the material very efficiently through resistance heating mechanisms. The use of SiC carbide reaction vessels in combination with a single-mode microwave reactor provides an almost complete shielding of the contents inside from the electromagnetic field. Therefore, such experiments do not involve electromagnetic field effects on the chemistry, since the semiconducting ceramic vial effectively prevents microwave irradiation from penetrating the reaction mixture. The involvement of electromagnetic field effects (specific/nonthermal microwave effects) on 21 selected chemical transformations was evaluated by comparing the results obtained in microwave-transparent Pyrex vials with experiments performed in SiC vials at the same reaction temperature. For most of the 21 reactions, the outcome in terms of conversion/purity/product yields using the two different vial types was virtually identical, indicating that the electromagnetic field had no direct influence on the reaction pathway. Due to the high chemical resistance of SiC, reactions involving corrosive reagents can be performed without degradation of the vessel material. Examples include high-temperature fluorine-chlorine exchange reactions using triethylamine trihydrofluoride, and the hydrolysis of nitriles with aqueous potassium hydroxide. The unique combination of high microwave absorptivity, thermal conductivity, and effusivity on the one hand, and excellent temperature, pressure and corrosion resistance on the other hand, makes this material ideal for the fabrication of reaction vessels for use in microwave reactors.
TL;DR: The influence of the synthesis conditions such as the reaction temperature, reaction duration and chamber pressure on the growth of the SiC nanomaterial was investigated and a vapor–solid reaction dominated nanoribbon growth mechanism was discussed.
Abstract: In this paper, a simple method to synthesize silicon carbide (SiC) nanoribbons is presented. Silicon powder and carbon black powder placed in a horizontal tube furnace were exposed to temperatures ranging from 1,250 to 1,500°C for 5–12 h in an argon atmosphere at atmospheric pressure. The resulting SiC nanoribbons were tens to hundreds of microns in length, a few microns in width and tens of nanometers in thickness. The nanoribbons were characterized with electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy, and were found to be hexagonal wurtzite–type SiC (2H-SiC) with a growth direction of . The influence of the synthesis conditions such as the reaction temperature, reaction duration and chamber pressure on the growth of the SiC nanomaterial was investigated. A vapor–solid reaction dominated nanoribbon growth mechanism was discussed.
TL;DR: The temperature profiles obtained from both an external infrared and internal fiber-optic sensor were compared for heating and synthesizing the ionic liquid 1-butyl-3-methylimidazolium bromide under microwave conditions and significant differences between the two methods of temperature monitoring were revealed.
Abstract: The temperature profiles obtained from both an external infrared and internal fiber-optic sensor were compared for heating and synthesizing the ionic liquid 1-butyl-3-methylimidazolium bromide (bmimBr) under microwave conditions. Utilizing a single-mode microwave reactor that allows simultaneous infrared/fiber-optic temperature measurements, significant differences between the two methods of temperature monitoring were revealed. Due to the strong microwave absorptivity of ionic liquids and the delay experienced in monitoring temperature on the outer surface of a heavy-walled glass vial, external infrared temperature sensors can not be used to accurately control the temperature in the heating of ionic liquids under microwave conditions. The use of internal fiber-optic probes allows the monitoring and control of the heating behavior in a much better way. In order to prevent the strong exotherm in the synthesis of bmimBr under microwave conditions the use of a reaction vessel made out of silicon carbide is the method of choice. Because of the high thermal conductivity and effusivity of silicon carbide, the heat generated during the ionic liquid formation is efficiently exchanged with the comparatively cool air in the microwave cavity via the silicon carbide ceramic.
Patent•
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01 Sep 2010
TL;DR: In this article, the authors proposed a light emitting diode consisting of a mono-crystalline substrate, buffer layer, transition layer, an N-type semiconductor layer, active layer, a P-type contact layer, and a P type electrode sequentially formed on the Mono-Crystal substrate, where the buffer layer close to the transition layer is made of one of gallium nitride, sapphire and silicon carbide material.
Abstract: The invention relates to a light emitting diode. The light emitting diode comprises a mono-crystalline substrate, a buffer layer, a transition layer, an N-type semiconductor layer, an active layer, a P-type semiconductor layer, a P-type contact layer and a P-type electrode sequentially formed on the mono-crystalline substrate, and an N-type electrode arranged on the N-type semiconductor layer, wherein the buffer layer which is formed by combining two or more of silicon, silicon dioxide, silicon nitride, titanium dioxide, zinc oxide, gallium nitride, sapphire and silicon carbide material is arranged between the mono-crystalline substrate and the transition layer; and the buffer layer close to the transition layer is made of one of gallium nitride, sapphire and silicon carbide material. Compared with the conventional structure, the structure of the light emitting diode can improve the heat dissipation of the light emitting diode, has a simple structure, is convenient to manufacture and reduces the production cost.
18 Mar 2010
TL;DR: In this paper, two different chip sizes were fabricated and tested: 15A (0.225cm×0.45cm) and 30A (1.5V) devices, and the 30A MOSFET was used for fabrication of 150A all-SiC modules.
Abstract: Emerging silicon carbide (SiC) MOSFET power devices promise to displace silicon IGBTs from the majority of challenging power electronics applications by enabling superior efficiency and power density, as well as capability to operate at higher temperatures. This paper reports on the recent progress in development of 1200V SiC power MOSFETs. Two different chip sizes were fabricated and tested: 15A (0.225cm×0.45cm) and 30A (0.45cm×0.45cm) devices. First, the 30A MOSFETs were packaged as discrete components and static and switching measurements were performed. The device blocking voltage was 1200V and typical on-resistance was less than 50 mΩ with gate-source voltages of 0V and 20V, respectively. The total switching losses were 0.6 mJ, over five times lower than the competing devices. Next, a buck converter was built for evaluating long-term stability of the MOSFETs and typical switching waveforms are presented. Finally, the 15A MOSFETs were used for fabrication of 150A all-SiC modules. The module on-resistance values were in the range of 10 mQ, resulting in the best-in-class on-state voltage values of 1.5V at nominal current. The module switching losses were 2.3 mJ during turn-on and 1 mJ during turn-off, also significantly better than competing designs. The results validate performance advantages of the SiC MOSFETs, moving them a step closer to power electronics applications.
TL;DR: The results illustrate the feasibility of using graphene as an inexpensive Q-switcher for solid-state lasers and its promising applications in integrated optics.
Abstract: Graphene grown by thermal decomposition of a two-inch 6H silicon carbide (SiC) wafers surface was used to modulate a large energy pulse laser. Because of its saturable absorbing properties, graphene was used as a passive Q-switcher, and because of its high refractive index the SiC substrate was used as an output coupler. Together they formed a setup where the passively Q-switched neodymium-doped yttrium aluminum garnet (Nd:YAG) crystal laser was realized with the pulse energy of 159.2 nJ. Our results illustrate the feasibility of using graphene as an inexpensive Q-switcher for solid-state lasers and its promising applications in integrated optics.
TL;DR: In this article, homogeneously dispersed Pt nanoparticles were deposited on β-SiC (Pt/SiC) using an ethylene glycol reduction method, and carbon was introduced into this Pt/Sic catalyst to improve its electrocatalytic performance by increasing the electrical conductivity.
Abstract: Nano-silicon carbide was applied as a novel catalyst support in proton exchange membrane (PEM) fuel cells to improve catalyst stability, due to its excellent resistance to electrochemical oxidation. Homogeneously dispersed Pt nanoparticles were deposited on β-SiC (Pt/SiC) using an ethylene glycol reduction method. Furthermore, carbon was introduced into this Pt/SiC catalyst, (Pt/SiC/C), to improve its electrocatalytic performance by increasing the electrical conductivity. The electrochemical stability of SiC was investigated and showed almost no changes in the redox region after oxidation for 48 h at 1.20 V. Based on accelerated durability tests (ADT) and high-resolution transmission electron microscopy (HRTEM), the electrochemical stability of Pt/SiC/C was remarkably enhanced compared with the Pt/C catalysts, which could be attributed to the excellent stability of the SiC support and the addition of high electrical conductivity carbon.