Showing papers on "Silicon carbide published in 2012"

Silicon Carbide Power Transistors: A New Era in Power Electronics Is Initiated

Abstract: During recent years, silicon carbide (SiC) power electronics has gone from being a promising future technology to being a potent alternative to state-of-the-art silicon (Si) technology in high-efficiency, highfrequency, and high-temperature applications. The reasons for this are that SiC power electronics may have higher voltage ratings, lower voltage drops, higher maximum temperatures, and higher thermal conductivities. It is now a fact that several manufacturers are capable of developing and processing high-quality transistors at cost that permit introduction of new products in application areas where the benefits of the SiC technology can provide significant system advantages.

Radiation effects in SiC for nuclear structural applications

Abstract: Silicon carbide has enjoyed both fundamental study and practical application since the early days of nuclear materials science. In the past decade, with the increased interest in increasing efficiency, solving the real issues of waste disposal, and the constant mission to improve safety of nuclear reactors, silicon carbide has become even more attractive. The purpose of this paper is to discuss recent research that not only strives to understand the remarkable radiation stability of this material, but also the practical application of silicon carbide as waste form and for fission and fusion power applications.

Light-Emitting Two-Dimensional Ultrathin Silicon Carbide

Abstract: Two-dimensional (2D) atomic crystals, especially graphene, have received much attention. However, the main shortcoming of graphene is its zero band gap. Silicon carbide, composed of silicon and carbon, is a typical wurtzite compound semiconductor, with more than 250 alloy types. Herein, we give some evidence of the solution exfoliation of 2D SiC nanoflakes with thickness down to 0.5–1.5 nm. Transmission electron microscopy (TEM) and X-ray diffraction characterizations reveal that graphitic (0001)/(0001) SiC most possibly has been formed by sonication of wurtzite SiC. Graphene, which is also produced in this process, naturally forms the ultrathin substrate facilitating the TEM characterization of 2D SiC. The mechanism of this exfoliation process should be related to the surface reconstruction of wurtzite SiC into graphitic SiC. Photoluminescence spectra show a strong light-emitting ability and a quantum-confinement-induced emission peak at 373 nm for these ultrathin SiC nanosheets.

Resonant addressing and manipulation of silicon vacancy qubits in silicon carbide.

Abstract: Several systems in the solid state have been suggested as promising candidates for spin-based quantum information processing. In spite of significant progress during the last decade, there is a search for new systems with higher potential [D. DiVincenzo, Nat. Mater. 9, 468 (2010)]. We report that silicon vacancy defects in silicon carbide comprise the technological advantages of semiconductor quantum dots and the unique spin properties of the nitrogen-vacancy defects in diamond. Similar to atoms, the silicon vacancy qubits can be controlled under the double radio-optical resonance conditions, allowing for their selective addressing and manipulation. Furthermore, we reveal their long spin memory using pulsed magnetic resonance technique. All these results make silicon vacancy defects in silicon carbide very attractive for quantum applications.

High-Power Modular Multilevel Converters With SiC JFETs

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 submodules of a down-scaled 3 kVA prototype M2C is replaced with a submodule with SiC JFETs without antiparallel diodes It is shown that the diodeless 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 submodule 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 998% if equipped with future 33 kV 12 kA SiC JFETs

Silicon carbide coated silicon nanowires as robust electrode material for aqueous micro-supercapacitor

Abstract: The development of passivated silicon nanowire (SiNW) based micro-supercapacitor electrodes for on-chip applications using an environmentally benign aqueous electrolyte is reported. The SiNWs, produced by low-temperature (50 °C) electrochemical etching, corrode during charge/discharge cycling in the aqueous environment, but upon coating with a silicon carbide passivation layer, the corrosion is mitigated. The as-formed materials are in electrical contact with the substrate, requiring no additional current collector. The passivated NWs achieve capacitance values up to ∼1.7 mF/cm2 projected area (comparable to state-of-the art carbon based micro-supercapacitor electrodes), exhibit robust cycling stability, and maintain capacitive behavior over a wide range of charge/discharge rates.

Tailoring the graphene/silicon carbide interface for monolithic wafer-scale electronics

Abstract: The realization of wafer-scale graphene electronics is envisaged to open up the route to the use of graphene in mainstream electronics. Hertel et al. take a step in this direction by fabricating a transistor with a SiC channel and graphene electrodes, with excellent performance up to megahertz frequencies.

Room Temperature Coherent Spin Alignment of Silicon Vacancies in 4H- and 6H-SiC

Abstract: We report the realization of the optically induced inverse population of the ground-state spin sublevels of the silicon vacancies (V(Si)) in silicon carbide (SiC) at room temperature. The data show that the probed silicon vacancy spin ensemble can be prepared in a coherent superposition of the spin states. Rabi nutations persist for more than 80 μs. Two opposite schemes of the optical alignment of the populations between the ground-state spin sublevels of the silicon vacancy upon illumination with unpolarized light are realized in 4H- and 6H-SiC at room temperature. These altogether make the silicon vacancy in SiC a very favorable defect for spintronics, quantum information processing, and magnetometry.

Radiation Effects in Commercial 1200 V 24 A Silicon Carbide Power MOSFETs

Abstract: In 2011, after many years of research and development SiC power MOSFETs became available in the commercial marketplace. This paper presents the results of Co60 total ionizing dose (TID) effects for the new high power-high current 24 A SiC devices irradiated at room temperature and 125°C. These commercially available components remained operational after a radiation dose of more than 100 krad. However, gamma ray irradiation gave rise to changes in current-voltage and capacitance-voltage characteristics. Specifically, threshold voltage decreased, resulting in increased current drive. We also observed rises in interface state densities, as well as input, output and reverse transfer capacitances with increasing accumulated doses.

Rectification of evanescent heat transfer between dielectric-coated and uncoated silicon carbide plates

Abstract: Here, we show analytically that the thermal rectification via evanescent waves is obtained in the parallel semi-infinite bodies of the dielectric-coated silicon carbide and uncoated silicon carbide. The permittivity and the thickness of the dielectric coating are derived for maximizing the thermal rectification. In the nonequilibrium situation holding temperatures of 500 K for one body and 300 K for the other, either a coating with a high permittivity of 14 and a thickness of 1 nm or a coating with a low permittivity of 2 and a thickness exceeding 10 nm, results in rectifying coefficients of 0.4 to 0.44.

Nanoscale engineering of radiation tolerant silicon carbide

Abstract: Radiation tolerance is determined by how effectively the microstructure can remove point defects produced by irradiation. Engineered nanocrystalline SiC with a high-density of stacking faults (SFs) has significantly enhanced recombination of interstitials and vacancies, leading to self-healing of irradiation-induced defects. While single crystal SiC readily undergoes an irradiation-induced crystalline to amorphous transformation at room temperature, the nano-engineered SiC with a high-density of SFs exhibits more than an order of magnitude increase in radiation resistance. Molecular dynamics simulations of collision cascades show that the nano-layered SFs lead to enhanced mobility of interstitial Si atoms. The remarkable radiation resistance in the nano-engineered SiC is attributed to the high-density of SFs within nano-sized grain structures that significantly enhance point defect annihilation.

Spark plasma sintering of silicon carbide and multi-walled carbon nanotube reinforced zirconium diboride ceramic composite

Abstract: In this paper spark plasma sintering (SPS) of silicon carbide and multi-walled carbon nanotube reinforced zirconium diboride ultra-high temperature ceramic matrix composites is reported. Systematic investigations on the effect of reinforcement type (SiC and CNTs) and content (10–40 vol.% SiC and 2–6 vol.% CNTs) on densification behavior, microstructure development, and mechanical properties (microhardness, bi-axial flexural strength, and indentation fracture toughness) are presented. With the similar SPS processing parameters (1900 °C, 70 MPa pressure, and 15 min soaking time), near-full densification (>99% relative density) was achieved with 10–40% SiC (in ZrB 2 –SiC) and 4–6% CNT (in ZrB 2 –CNT) reinforced composites. The SiC and CNT reinforcement further improved the indentation fracture toughness of the composites through a range of toughening mechanisms, including particle shearing, crack deflection at the particle-matrix interface, and grain pull-outs for ZrB 2 –SiC composites, and CNT pull-outs and crack deflection in ZrB 2 –CNT composites.

Intrinsic defects in silicon carbide LED as a perspective room temperature single photon source in near infrared

Abstract: Generation of single photons has been demonstrated in several systems. However, none of them satisfies all the conditions, e.g. room temperature functionality, telecom wavelength operation, high efficiency, as required for practical applications. Here, we report the fabrication of light emitting diodes (LEDs) based on intrinsic defects in silicon carbide (SiC). To fabricate our devices we used a standard semiconductor manufacturing technology in combination with high-energy electron irradiation. The room temperature electroluminescence (EL) of our LEDs reveals two strong emission bands in visible and near infrared (NIR), associated with two different intrinsic defects. As these defects can potentially be generated at a low or even single defect level, our approach can be used to realize electrically driven single photon source for quantum telecommunication and information processing.

Chloride-based CVD growth of silicon carbide for electronic applications.

Abstract: Chloride-Based CVD Growth of Silicon Carbide for Electronic Applications Henrik Pedersen,* Stefano Leone, Olof Kordina, Anne Henry, Shin-ichi Nishizawa, Yaroslav Koshka, and Erik Janz en Department of Physics, Chemistry and Biology, Link€oping University, SE-581 83 Link€oping, Sweden National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan Department of Electrical and Computer Engineering, Mississippi State University, Mississippi State, Mississippi 39762, United States

Schottky barrier inhomogeneities at the interface of few layer epitaxial graphene and silicon carbide

Abstract: In this work, we study electron transport across the heterojunction interface of epitaxial few-layer graphene grown on silicon carbide and the underlying substrate. The observed Schottky barrier is characterized using current-voltage, capacitance-voltage and photocurrent spectroscopy techniques. It is found that the graphene/SiC heterojunction cannot be characterized by a single unique barrier height because of lateral barrier inhomogeneities. A Gaussian distribution of barrier heights with a mean barrier height φBm=1.06eV and standard deviation σ=137±11meV explains the experimental data quite well.

High-density amorphous phase of silicon carbide obtained under large plastic shear and high pressure

Abstract: Valery I. Levitas,1,* Yanzhang Ma,2 Emre Selvi,2 Jianzhe Wu,2 and John A. Patten3 1Departments of Aerospace Engineering, Mechanical Engineering, and Material Science and Engineering, Iowa State University, Ames, Iowa 50011, USA 2Department of Mechanical Engineering, Texas Tech University, Lubbock, Texas 79409, USA 3Department of Manufacturing Engineering, Western Michigan University, Kalamazoo, Michigan 49008, USA (Received 20 September 2011; revised manuscript received 4 December 2011; published 29 February 2012)

Temperature-Dependent Characteristics of SiC Devices: Performance Evaluation and Loss Calculation

Abstract: Silicon Carbide (SiC) devices have obvious advantages compared with conventional Si devices, and especially so at high temperatures. This paper aims at developing a method for the characterization of SiC JFET conduction and switching losses at high temperatures as well as the calculation of semiconductor losses in SiC JFET-based converters. To this end, the steady-state performance of SiC JFET and Schottky diodes at different temperatures is studied, and an improved conduction loss evaluation is proposed considering the bidirectional conduction paths of the JFET. Specifically, a SiC JFET bridge test bed is built to measure the switching losses at different temperatures with and without antiparallel diodes, where experimental results show that using SiC Schottky diodes in antiparallel eliminates the reverse recovery of the JFET body diode, improving the switching behavior and reducing the losses of the devices. Further, these test results are used to estimate the losses of a 10-kW ac-dc-ac converter, which shows that the use of Schottky diodes as freewheeling devices helps reduce both conduction and switching losses, presenting an even greater reduction at higher operating temperatures.

Coherent thermal infrared emission by two-dimensional silicon carbide gratings

Abstract: The thermal emission of cross-slit silicon carbide grating is studied in the Restrahlen region over all emission angles. We show experimentally that the thermal excitation of surface-phonon polaritons on the surface of 2D grating allows us to get a high emissivity in both polarizations, which is collimated in $p$ polarization for a specific wavelength determined by the periodicity of the grating. We also show numerically that 2D gratings optimized to efficiently out-couple thermally excited surface-phonon polaritons of the flat part of the dispersion relation can have a high efficiency for all emission directions for both polarizations.

Thermal Stability of Silicon Carbide Power Diodes

Abstract: Silicon carbide (SiC) power devices can operate at much higher junction temperature than those made of silicon. However, this does not mean that SiC devices can operate without a good cooling system. To demonstrate this, the model of a merged p-i-n Schottky (MPS) SiC diode is presented, and its parameters are identified with experimental measurements. This model is then used to study the ruggedness of the diode regarding the thermal runaway phenomenon. Finally, it is shown that, where a purely unipolar diode would be unstable, the MPS structure brings increased stability.

Preparation and properties of polystyrene/SiCw/SiCp thermal conductivity composites

Abstract: The silicon carbide whisker (SiCw) and silicon carbide particle (SiCp) were employed to prepare polystyrene/silicon carbide whisker/silicon carbide particle (PS/SiCw/SiCp) thermal conductivity composites, and the titanate coupling reagent of NDZ-105 was introduced to functionalize the surface of fillers. The thermal conductive coefficient λ improved from 0.18 W/mK for native PS to 1.29 W/mK for the composites with 40% volume fraction of SiCw/SiCp (volume fraction, 3 : 1) hybrid fillers. Both the thermal decomposition temperature and dielectric constant of the composites increased with the addition of SiCw/SiCp hybrid fillers. At the same addition of SiCw/SiCp hybrid fillers, the surface modification of hybrid fillers by NDZ-105 could improve the thermal conductivity and the mechanical properties of the composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Growth of tapered SiC nanowires on flexible carbon fabric : toward field emission applications

Abstract: Tapered silicon carbide (SiC) nanowires were directly grown on the surface of flexible carbon fabric by a chemical vapor deposition process. The products were systemically characterized by X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy, selected area electronic diffraction, and energy-dispersive X-ray spectroscopy. The results revealed that the tapered nanowires were of single crystalline β-SiC phase with the growth direction along [111] and had a feature of zigzag faceting over the wire surfaces. Such faceting was created by a quasi-periodic placement of twinning boundaries along the wire axis, which can be explained by surface energy minimization during the growth process. Based on the characterizations and thermodynamics analysis, the Fe-assisted vapor–liquid–solid (VLS) growth mechanism of tapered SiC nanowires was discussed. Furthermore, field emission measurements showed a very low turn-on field at 1.2 V μm–1 and a high field-enhancem...