Showing papers on "Silicon carbide published in 2017"

Review of Silicon Carbide Power Devices and Their Applications

Abstract: Silicon carbide (SiC) power devices have been investigated extensively in the past two decades, and there are many devices commercially available now. Owing to the intrinsic material advantages of SiC over silicon (Si), SiC power devices can operate at higher voltage, higher switching frequency, and higher temperature. This paper reviews the technology progress of SiC power devices and their emerging applications. The design challenges and future trends are summarized at the end of the paper.

Bismuthene on a SiC substrate: A candidate for a high-temperature quantum spin Hall material

Abstract: Quantum spin Hall materials hold the promise of revolutionary devices with dissipationless spin currents but have required cryogenic temperatures owing to small energy gaps. Here we show theoretically that a room-temperature regime with a large energy gap may be achievable within a paradigm that exploits the atomic spin-orbit coupling. The concept is based on a substrate-supported monolayer of a high–atomic number element and is experimentally realized as a bismuth honeycomb lattice on top of the insulating silicon carbide substrate SiC(0001). Using scanning tunneling spectroscopy, we detect a gap of ~0.8 electron volt and conductive edge states consistent with theory. Our combined theoretical and experimental results demonstrate a concept for a quantum spin Hall wide-gap scenario, where the chemical potential resides in the global system gap, ensuring robust edge conductance.

Comparative Analysis on Conducted CM EMI Emission of Motor Drives: WBG Versus Si Devices

Abstract: Silicon carbide (SiC) MOSFETs and gallium nitride (GaN) high-electron mobility transistors are perceived as future replacements for Si IGBTs and MOSFETs in medium- and low-voltage drives due to their low conduction and switching losses. However, it is widely believed that the already significant conducted common-mode (CM) electromagnetic interference (EMI) emission of motor drives will be further exacerbated by the high-speed switching operation of these new devices. Hence, this paper investigates and quantifies the increase in the conducted CM EMI emission of a pulse width modulation inverter-based motor drive when SiC and GaN devices are adopted. Through an analytical approach, the results reveal that the influence of dv/dt on the conducted CM emission is generally limited. On the other hand, the influence of switching frequency is more significant. Lab tests are also conducted to verify the analysis.

A review on single photon sources in silicon carbide.

Abstract: This paper summarizes key findings in single-photon generation from deep level defects in silicon carbide (SiC) and highlights the significance of these individually addressable centers for emerging quantum applications. Single photon emission from various defect centers in both bulk and nanostructured SiC are discussed as well as their formation and possible integration into optical and electrical devices. The related measurement protocols, the building blocks of quantum communication and computation network architectures in solid state systems, are also summarized. This includes experimental methodologies developed for spin control of different paramagnetic defects, including the measurement of spin coherence times. Well established doping, and micro- and nanofabrication procedures for SiC may allow the quantum properties of paramagnetic defects to be electrically and mechanically controlled efficiently. The integration of single defects into SiC devices is crucial for applications in quantum technologies and we will review progress in this direction.

Scalable quantum photonics with single color centers in silicon carbide

Abstract: We develop a scalable array of 4H-SiC nanopillars incorporating single silicon vacancy centers, readily available to serve as efficient single photon sources or quantum bits interfaced with free-space or lensed-fiber optics.

Overview of high voltage sic power semiconductor devices: development and application

Abstract: Research on high voltage (HV) silicon carbide (SiC) power semiconductor devices has attracted much attention in recent years. This paper overviews the development and status of HV SiC devices. Meanwhile, benefits of HV SiC devices are presented. The technologies and challenges for HV SiC device application in converter design are discussed. The state-of-the-art applications of HV SiC devices are also reviewed.

Enhanced thermal conductivity of epoxy composites filled with silicon carbide nanowires.

Abstract: In this study, we report a facile approach to fabricate epoxy composite incorporated with silicon carbide nanowires (SiC NWs). The thermal conductivity of epoxy/SiC NWs composites was thoroughly investigated. The thermal conductivity of epoxy/SiC NWs composites with 3.0 wt% filler reached 0.449 Wm−1 K−1, approximately a 106% enhancement as compared to neat epoxy. In contrast, the same mass fraction of silicon carbide micron particles (SiC MPs) incorporated into epoxy matrix showed less improvement on thermal conduction properties. This is attributed to the formation of effective heat conduction pathways among SiC NWs as well as a strong interaction between the nanowires and epoxy matrix. In addition, the thermal properties of epoxy/SiC NWs composites were also improved. These results demonstrate that we developed a novel approach to enhance the thermal conductivity of the polymer composites which meet the requirement for the rapid development of the electronic devices.

Failure and Reliability Analysis of a SiC Power Module Based on Stress Comparison to a Si Device

Abstract: The superior electro-thermal properties of silicon carbide (SiC) power devices permit higher temperature of operation and enable higher power density compared with silicon devices. Nevertheless, the reliability of SiC power modules has been identified as a major area of uncertainty in applications which require high reliability. Traditional power module packaging methods developed for silicon chips have been adopted for SiC and the different thermomechanical properties cause different fatigue stresses on the solder layer of the chip. In this paper, a 2-D finite element model has been developed to evaluate the stress performance and lifetime of the solder layer for Si devices, which has been validated using accelerated power cycling tests on Si IGBTs. The proposed model was extrapolated for SiC devices of the same voltage and current rating using the same solder material and the results show that under the same cyclic power loss profile the induced stress and strain energy in the die attach layer is much higher and concentrates on the die/solder interfacial area for SiC chips. Using the validated stress-based model, the lifetime can be quantified when SiC chips are used. This ability to extrapolate the available power cycling and lifetime data of silicon chips to SiC chips would be a key element for developing reliable packaging methods for SiC devices.

Selective Purcell enhancement of two closely linked zero-phonon transitions of a silicon carbide color center.

Abstract: Point defects in silicon carbide are rapidly becoming a platform of great interest for single-photon generation, quantum sensing, and quantum information science. Photonic crystal cavities (PCCs) can serve as an efficient light–matter interface both to augment the defect emission and to aid in studying the defects’ properties. In this work, we fabricate 1D nanobeam PCCs in 4H-silicon carbide with embedded silicon vacancy centers. These cavities are used to achieve Purcell enhancement of two closely spaced defect zero-phonon lines (ZPL). Enhancements of >80-fold are measured using multiple techniques. Additionally, the nature of the cavity coupling to the different ZPLs is examined.

A 50-kW High-Frequency and High-Efficiency SiC Voltage Source Inverter for More Electric Aircraft

Abstract: High power density is required for power converter in more electric aircraft due to the strict demands of volume and weight, which makes silicon carbide (SiC) extremely attractive for this application. In this paper, a prototype of 50-kW SiC two-level three-phase voltage source inverter is demonstrated with a gravimetric power density of 26 kW/kg (without inclusion of filter). A gate assisted circuit is introduced to reduce the switching loss. In addition, the ringings of voltage and current due to parasitic parameters during the switching transition can also be mitigated. A mathematical model with consideration of various parasitic parameters is developed, which illustrates the parasitic effects in high-speed switching SiC power module. The converter is operated at a switching frequency up to 100 kHz and a narrow dead band of 250 ns. The measured efficiency is 97.91%.

Three-Dimensional Proton Beam Writing of Optically Active Coherent Vacancy Spins in Silicon Carbide

Abstract: Constructing quantum devices comprises various challenging tasks, especially when concerning their nanoscale geometry. For quantum color centers, the traditional approach is to fabricate the device structure after the nondeterministic placement of the centers. Reversing this approach, we present the controlled generation of quantum centers in silicon carbide (SiC) by focused proton beam in a noncomplex manner without need for pre- or postirradiation treatment. The generation depth and resolution can be predicted by matching the proton energy to the material’s stopping power, and the amount of quantum centers at one specific sample volume is tunable from ensembles of millions to discernible single photon emitters. We identify the generated centers as silicon vacancies through their characteristic magnetic resonance signatures and demonstrate that they possess a long spin–echo coherence time of 42 ± 20 μs at room temperature. Our approach hence enables the fabrication of quantum hybrid nanodevices based on ...

Identification of Si-vacancy related room-temperature qubits in 4 H silicon carbide

Abstract: The identification of a microscopic configuration of point defects acting as quantum bits is a key step in the advance of quantum information processing and sensing. Among the numerous candidates, silicon-vacancy related centers in silicon carbide (SiC) have shown remarkable properties owing to their particular spin-3/2 ground and excited states. Although, these centers were observed decades ago, two competing models, the isolated negatively charged silicon vacancy and the complex of negatively charged silicon vacancy and neutral carbon vacancy [Phys. Rev. Lett. 115, 247602 (2015)], are still argued as an origin. By means of high-precision first-principles calculations and high-resolution electron spin resonance measurements, we here unambiguously identify the Si-vacancy related qubits in hexagonal SiC as isolated negatively charged silicon vacancies. Moreover, we identify the Si-vacancy qubit configurations that provide room-temperature optical readout.

Mechanical and corrosion behavior of al7075 (hybrid) metal matrix composites by two step stir casting process

Abstract: THIS PAPER INVESTIGATES THE MECHANICAL PROPERTIES AND CORROSION BEHAVIOR OF METAL MATRIX COMPOSITES PREPARED USING AL7075 ALLOY AS A MATRIX, SILICON CARBIDE AND TITANIUM CARBIDE AS REINFORCEMENT PARTICLES. TWO STEP STIR CASTING PROCESS WAS USED TO FABRICATE THE COMPOSITES BY VARYING VOLUME FRACTIONS OF SILICON CARBIDE AND TITANIUM CARBIDE (0 TO 15 VOL. %). MICROSTRUCTURAL ANALYSIS, MECHANICAL AND CORROSION BEHAVIOR WERE USED TO EVALUATE THE PERFORMANCE OF THE COMPOSITES. UNIFORM DISTRIBUTION OF REINFORCEMENT PARTICLE WAS OBSERVED THROUGH OPTICAL PHOTOMICROGRAPHS. VICKERS MICRO HARDNESS TESTS WERE PERFORMED AND THE HARDNESS VALUES WERE INCREASED WITH AN INCREASE IN REIN-FORCEMENT FROM 0 TO 15 VOL. %. THE TENSILE STRENGTH OF THE 10 VOL. % OF ALUMINUM HYBRID MATRIX COMPOSITE WAS BETTER THAN THAT OF THE BASE ALLOY. IN 3.5% NACL SOLUTION, IT WAS OBSERVED THAT THE 15 VOL. % OF THE ALUMINUM HYBRID MATRIX COMPOSITE HAVE HIGHER CORROSION RE-SISTANCE IN COMPARISON THE BASE ALLOY.

Efficient Generation of an Array of Single Silicon-Vacancy Defects in Silicon Carbide

Abstract: For quantum sensing and information processing, nitrogen-vacancy centers in diamond are not the only tool in the box. Silicon-vacancy centers in SiC are also of keen interest, but for successful applications, we must be able to reliably control where these color centers form in a device. Through ion implantation, the authors succeed in generating an array of single-photon emitters in SiC, with an efficiency of 19\ifmmode\pm\else\textpm\fi{}4%. This ability could enable significant progress in spintronic and photonic quantum technologies.

Single Event Effects in Si and SiC Power MOSFETs Due to Terrestrial Neutrons

Abstract: Experimental investigation of neutron induced single event failures and the associated device cross sections as well as low altitude failure-in-time (FIT) curves in silicon (Si) and silicon carbide (SiC) power MOSFETs at room temperature are reported along with possible explanation of failure mechanisms in SiC devices. Neutrons are found to give rise to significantly fewer failures in SiC power MOSFETs compared to their Si equivalents; however, SiC power MOSFETs do exhibit catastrophic failures when exposed to neutrons that simulate the terrestrial spectrum.

Highly flexible, erosion resistant and nitrogen doped hollow SiC fibrous mats for high temperature thermal insulators

Abstract: Thermally stable and chemical resistant silicon carbide (SiC) fibrous mats have drawn much attention as a high-temperature thermal insulator in top end equipment and technology. Herein, novel free-standing, flexible, acid/alkali-resistant and nitrogen doped (N-doped) hollow SiC fibrous mats bearing ultralow thermal conductivity are reported. The materials were fabricated via a three-step process: the preparation of core–shell fibers from polymeric precursors by co-axial electrospinning, the thermal or electron beam irradiation curing process and pyrolysis process. The as-obtained continuous fibers manifested an oval-shape hollow structure and the thickness of the cavity wall was approximately 1.5 μm. The crystal pattern was obtained after pyrolysis over 1300 °C under a nitrogen atmosphere. The morphology, composition, curing and formation mechanisms of N-containing hollow SiC fibers with texture and porous surfaces were elaborately analysed. These facilely fabricated N-doped hollow SiC fibrous mats possess good flexibility, noninflammability, high thermal stability, erosion resistance, light weight (0.218 g cm−3) and low thermal conductivity at high temperature (0.039 W m−1 K−1), suggesting promising application as a high temperature thermal insulator.

Electromagnetic wave absorption of silicon carbide based materials

Abstract: Increasing research effort has been made aiming at developing electromagnetic (EM) wave absorbing materials with high absorption performance. An ideal EM absorber should be relatively light-weight, thermally stable, capable of absorbing wide EM frequency, and cost effective. As a dielectric material, silicon carbide (SiC) has great potential with relatively low density, good thermal and chemical resistance, and it can function at high temperatures or under harsh working environments. This review summarizes the research progress in the design and characterization of SiC and SiC based composites as EM absorption materials. Pristine SiC with various morphological, phase, and structural features can be tailored to achieve better absorption performance. Moreover, SiC based materials can either be modified using dielectric or magnetic materials, or be designed with variation in geometry, composition, and mass fraction of the filler composition for further improvement in EM absorption. This review intends to inspire new concepts and approaches for designing excellent EM absorbing materials.

An SiC-Based Half-Bridge Module With an Improved Hybrid Packaging Method for High Power Density Applications

Abstract: SiC devices have the potential to structure high power density converters; however, SiC devices have high d i /d t during switching. Therefore, the parasitic inductances in the power loop and gating loop must be reduced to restrain the induced voltage. This paper proposes a SiC-based, half-bridge (HB) module with a hybrid packaging method. Such a module is based on printed circuit board (PCB) plus direct bonding copper (DBC) structure. The DBC provides part of power loops, and the SiC bare dies can be directly soldered on these loops; the PCB provides another part of the power loops, as well as the gating loops. Such a design allows the power loops on the PCB to be soldered with those on the DBC directly; in the meantime, the SiC bare dies soldered on the DBC can be connected to the PCB with bounding wires. Such a structure provides extra degrees of freedom for design so that the parasitic inductances can be minimized by optimizing the current communication loops, driver locations, and the gating connections, and the heat can also be dissipated through the direct cooling structure easily. A 1200 V/24 A SiC HB module is fabricated with the proposed method in the laboratory, and based on the fabricated module, a synchronous buck converter with power density of 379.3 W/in3 is also structured. The double pulse test shows that the fabricated module can be switched within 10 ns and that the drain-source voltage overshoot is only 2.5%. The highest efficiency of the converter based on the fabricated module is up to 99.46%.

Anisotropic Thermal Conductivity of 4H and 6H Silicon Carbide Measured Using Time-Domain Thermoreflectance

Abstract: Silicon carbide (SiC) is a wide bandgap (WBG) semiconductor with promising applications in high-power and high-frequency electronics. Among its many useful properties, the high thermal conductivity is crucial. In this letter, the anisotropic thermal conductivity of three SiC samples: n-type 4H-SiC (N-doped 1x10^19 cm-3), unintentionally doped (UID) semi-insulating (SI) 4H-SiC, and SI 6H-SiC (V-doped 1x10^17 cm-3), is measured using femtosecond laser based time-domain thermoreflectance (TDTR) over a temperature range from 250 K to 450 K. We simultaneously measure the thermal conductivity parallel to (k_r) and across the hexagonal plane (k_z) for SiC by choosing the appropriate laser spot radius and the modulation frequency for the TDTR measurements. For both k_r and k_z, the following decreasing order of thermal conductivity value is observed: SI 4H-SiC > n-type 4H-SiC > SI 6H-SiC. This work serves as an important benchmark for understanding thermal transport in WBG semiconductors.

Brittle-ductile transition in shape adaptive grinding (SAG) of SiC aspheric optics

Abstract: Silicon carbide is a ceramic material with a desirable combination of high thermal and mechanical stability, making it ideal for optical application in aerospace and next generation lithography. It is however notoriously difficult to machine down to super-fine finish when the shape is other than flat or spherical. In this paper, we describe the application of a “semi-elastic” machining method called shape adaptive grinding (SAG), in which an elastic tool is combined with rigid pellets made of nickel or resin, to which super abrasives are bonded. A comprehensive model of the physical interaction between SAG tool and workpiece is proposed, and used to understand the mechanics driving brittle-ductile transition on ceramic materials such as SiC. Machining parameters adequate for optical finishing are then derived from the model and demonstrated on an aspheric silicon carbide workpiece, which was manufactured by reaction bonding and coated with a layer of pure SiC by chemical vapour deposition (CVD). Through SAG processing and final polishing, this aspheric mirror was improved from an initial form error of 40 µm down to 112 nm Peak-to-Valley, with no residual damage visible on the surface.

Power Electronic Semiconductor Materials for Automotive and Energy Saving Applications - SiC, GaN, Ga2O3, and Diamond.

Abstract: Power electronics belongs to the future key technologies in order to increase system efficiency as well as performance in automotive and energy saving applications. Silicon is the major material for electronic switches since decades. Advanced fabrication processes and sophisticated electronic device designs have optimized the silicon electronic device performance almost to their theoretical limit. Therefore, to increase the system performance, new materials that exhibit physical and chemical properties beyond silicon need to be explored. A number of wide bandgap semiconductors like silicon carbide, gallium nitride, gallium oxide, and diamond exhibit outstanding characteristics that may pave the way to new performance levels. The review will introduce these materials by (i) highlighting their properties, (ii) introducing the challenges in materials growth, and (iii) outlining limits that need innovation steps in materials processing to outperform current technologies.

Effect of grain growth on the thermal conductivity of liquid-phase sintered silicon carbide ceramics

Abstract: The effect of grain growth on the thermal conductivity of SiC ceramics sintered with 3 vol% equimolar Gd2O3-Y2O3 was investigated. During prolonged sintering at 2000 °C in an argon or nitrogen atmosphere, the β → α phase transformation, grain growth, and reduction in lattice oxygen content occurs in the ceramics. The effects of these parameters on the thermal conductivity of liquid-phase sintered SiC ceramics were investigated. The results suggest that (1) grain growth achieved by prolonged sintering at 2000 °C accompanies the decrease of lattice oxygen content and the occurrence of the β → α phase transformation; (2) the reduction of lattice oxygen content plays the most important role in enhancing the thermal conductivity; and (3) the thermal conductivity of the SiC ceramic was insensitive to the occurrence of the β → α phase transformation. The highest thermal conductivity obtained was 225 W(m K)−1 after 12 h sintering at 2000 °C under an applied pressure of 40 MPa in argon.