Showing papers on "Silicon carbide published in 2013"

A room temperature single photon source in silicon carbide

Abstract: We report the first observation of stable single photon sources in an electronic and photonic device-friendly material, silicon carbide (SiC). SiC is a viable material for implementing quantum communication, computation and photonic technologies.

A wide-bandgap metal–semiconductor–metal nanostructure made entirely from graphene

Abstract: The electronic properties of graphene are spatially controlled from metallic to semiconducting by patterning steps into the underlying silicon carbide substrate. This bottom-up approach could be the basis for integrated graphene electronics.

Brittle-ductile transition during diamond turning of single crystal silicon carbide

Abstract: In this experimental study, diamond turning of single crystal 6H-SiC was performed at a cutting speed of 1 m/s on an ultra-precision diamond turning machine (Moore Nanotech 350 UPL) to elucidate the microscopic origin of ductile-regime machining. Distilled water (pH value 7) was used as a preferred coolant during the course of machining in order to improve the tribological performance. A high magnification scanning electron microscope (SEM FIB- FEI Quanta 3D FEG) was used to examine the cutting tool before and after the machining. A surface finish of Ra=9.2 nm, better than any previously reported value on SiC was obtained. Also, tremendously high cutting resistance was offered by SiC resulting in the observation of significant wear marks on the cutting tool just after 1 km of cutting length. It was found out through a DXR Raman microscope that similar to other classical brittle materials (silicon, germanium, etc.) an occurrence of brittle-ductile transition is responsible for the ductile-regime machining of 6H-SiC. It has also been demonstrated that the structural phase transformations associated with the diamond turning of brittle materials which are normally considered as a prerequisite to ductile-regime machining, may not be observed during ductile-regime machining of polycrystalline materials.

Silicon carbide: a versatile material for biosensor applications

Abstract: Silicon carbide (SiC) has been around for more than 100 years as an industrial material and has found wide and varied applications because of its unique electrical and thermal properties. In recent years there has been increased attention to SiC as a viable material for biomedical applications. Of particular interest in this review is its potential for application as a biotransducer in biosensors. Among these applications are those where SiC is used as a substrate material, taking advantage of its surface chemical, tribological and electrical properties. In addition, its potential for integration as system on a chip and those applications where SiC is used as an active material make it a suitable substrate for micro-device fabrication. This review highlights the critical properties of SiC for application as a biosensor and reviews recent work reported on using SiC as an active or passive material in biotransducers and biosensors.

Advances in silicon carbide science and technology at the micro- and nanoscales

Abstract: Advances in silicon carbide microfabrication and growth process optimization for silicon carbide nanostructures are ushering in new opportunities for microdevices capable of operation in a variety of demanding applications, involving high temperature, radiation, or corrosive environment. This review focuses on the materials science and processing technologies for silicon carbide thin films and low dimensional structures, and details recent progress in manufacturing technology, including deposition, metallization, and fabrication of semiconductor microdevices, with emphasis on sensor technology. The challenges remaining in developing silicon carbide as a mainstay materials platform are discussed throughout.

Ab initio study of electronic and optical behavior of two-dimensional silicon carbide

Abstract: Two-dimensional graphene-like silicon carbide (2d-SiC) has emerged as an intriguing new class of layered nanostructure. Using density functional theory, key electronic and optical properties of 2d-SiC nanosheets, in particular, of mono- and bilayer 2d-SiC, are investigated. The properties of these nanosheets are found to be highly dependent on their physical thickness and geometric configuration. Multilayer 2d-SiC exhibits an indirect bandgap. We find that monolayer 2d-SiC, on the other hand, has a direct bandgap (∼2.5 eV) that can be tuned through in-plane strain. We also show that the optical conductivity of multilayer 2d-SiC is sensitive to the interlayer spacing. The results suggest that unlike graphene, silicene and even multilayer 2d-SiC, monolayer 2d-SiC could be a good candidate for optoelectronic devices such as light-emitting diodes.

Silicon carbide light-emitting diode as a prospective room temperature source for single photons

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 the visible and near infrared (NIR) spectral ranges, 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.

Challenges Regarding Parallel Connection of SiC JFETs

Abstract: State-of-the-art silicon carbide switches have current ratings that are not sufficiently high to be used in high-power converters. It is, therefore, necessary to connect several switches in parallel in order to reach sufficient current capabilities. An investigation of parallel-connected normally ON silicon carbide JFETs is presented in this paper. The device parameters that play the most important role for the parallel connection are the pinch-off voltage, the gate-source reverse breakdown voltage, the spread in the on-state resistances, and the variations in static transfer characteristics of the devices. Moreover, it is experimentally shown that a fifth factor affecting the parallel connection of the devices is the parasitic inductances of the circuit layout. The temperature dependence of the gate-source reverse breakdown voltages is analyzed for two different designs of silicon carbide JFETs. If the spread in the pinch-off and gate-source reverse breakdown voltages is sufficiently large, there might be no possibility for a stable off-state operation of a pair of transistors without forcing one of the gate voltages to exceed the breakdown voltage. A solution to this problem using individual gate circuits for the JFETs is given. The switching performance of two pairs of parallel-connected devices with different combinations of parameters is compared employing two different gate-driver configurations. Three different circuit layouts are considered and the effect of the parasitic inductances is experimentally investigated. It is found that using a single gate circuit for the two mismatched JFETs may improve the switching performance and therefore the distribution of the switching losses significantly. Based on the measured switching losses, it is also clear that regardless of the design of the gate drivers, the lowest total switching losses for the devices are obtained when they are symmetrically placed.

Invited Article: Indenter materials for high temperature nanoindentation.

Abstract: As nanoindentation at high temperatures becomes increasingly popular, a review of indenter materials for usage at high temperatures is instructive for identifying appropriate indenter-sample materials combinations to prevent indenter loss or failure due to chemical reactions or wear during indentation. This is an important consideration for nanoindentation as extremely small volumes of reacted indenter material will have a significant effect on measurements. The high temperature hardness, elastic modulus, thermal properties, and chemical reactivities of diamond, boron carbide, silicon carbide, tungsten carbide, cubic boron nitride, and sapphire are discussed. Diamond and boron carbide show the best elevated temperature hardness, while tungsten carbide demonstrates the lowest chemical reactivity with the widest array of elements.

Active current balancing for parallel-connected silicon carbide MOSFETs

Abstract: In high power applications of silicon carbide (SiC) MOSFETs where parallelism is employed, current unbalance can occur and affect the performance and reliability of the power devices. In this paper, factors which cause current unbalance in these devices are analyzed. Among them, the threshold voltage mismatch is identified as a major factor for dynamic current unbalance. The threshold distribution of SiC MOSFETs is investigated, and its effect on current balance is studied in experiments. Based on these analyses, an active current balancing scheme is proposed. It is able to sense the unbalanced current and eliminate it by actively controlling the gate drive signal to each device. The features of fine time resolution and low complexity make this scheme attractive to a wide variety of wide-band-gap device applications. Experimental and simulation results verify the feasibility and effectiveness of the proposed scheme.

Investigation of single-event damages on silicon carbide (SiC) power MOSFETs

Abstract: Radiation effects were demonstrably observed in silicon carbide power MOSFETs caused by heavy ion and proton irradiation. For higher LET ions, permanent damage (increase in both drain and gate leakage current) was observed similar to SiC Schottky Barrier diodes in our previous study. For lower LET ions, including protons, Single Event Burnouts (SEBs) were observed and there was no leakage current increase just before SEBs. The phenomenon is unique for SiC devices.

Mechanical behavior of zirconium diboride–silicon carbide ceramics at elevated temperature in air

Abstract: The mechanical properties of zirconium diboride–silicon carbide (ZrB2–SiC) ceramics were characterized from room temperature up to 1600 °C in air. ZrB2 containing nominally 30 vol% SiC was hot pressed to full density at 1950 °C using B4C as a sintering aid. After hot pressing, the composition was determined to be 68.5 vol% ZrB2, 29.5 vol% SiC, and 2.0 vol% B4C using image analysis. The average ZrB2 grain size was 1.9 μm. The average SiC particles size was 1.2 μm, but the SiC particles formed larger clusters. The room temperature flexural strength was 680 MPa and strength increased to 750 MPa at 800 °C. Strength decreased to ∼360 MPa at 1500 °C and 1600 °C. The elastic modulus at room temperature was 510 GPa. Modulus decreased nearly linearly with temperature to 210 GPa at 1500 °C, with a more rapid decrease to 110 GPa at 1600 °C. The fracture toughness was 3.6 MPa·m½ at room temperature, increased to 4.8 MPa·m½ at 800 °C, and then decreased linearly to 3.3 MPa·m½ at 1600 °C. The strength was controlled by the SiC cluster size up to 1000 °C, and oxidation damage above 1200 °C.

Power Electronic Devices in the Future

Abstract: This paper discusses extrapolations of current silicon power device technology into the future, followed by discussions of wide band gap (WBG) power devices with a focus on silicon carbide and gallium nitride. Other WBG materials are included from carbon, such as diamond and nanotubes, to various nitrides. Far future material development, that may impact power electronic devices decades out, is also discussed.

Stability Considerations for Silicon Carbide Field-Effect Transistors

Abstract: Owing to their very low intrinsic capacitance and on-resistance, silicon carbide FETs have been shown to produce poor dynamics in certain power electronics applications, particularly those based on the half-bridge configuration. This letter catalogs three separate phenomena that are observed in the context of such applications and provides a detailed treatment of the most troublesome of these behaviors: the occurrence of sustained oscillation at switch turn-off. This behavior is analyzed in the context of established oscillator design theory; both simulation and experimental results are shown to verify this analysis; and practical suggestions are made to application designers to manage this behavior.

A new method for the synthesis of epitaxial layers of silicon carbide on silicon owing to formation of dilatation dipoles

Abstract: A new method is developed for the solid-phase synthesis of epitaxial layers when the substrate itself is involved into a chemical reaction and the reaction product grows in the interior of substrate layer. It opens up new possibilities for the relaxation of the elastic energy due to attraction of point defects formed during the chemical reaction in anisotropic media. In the same time, the attracting point dilatation centers compose relatively stable formations—dilatation dipoles, named by analogy with electric dipoles, providing significant reduction of the total elastic energy. The correspondent theory of interaction of point dilatation centers in anisotropic crystals is developed. It is eliminated that the most advantageous location of the dipoles is the direction (111) in crystals with cubic symmetry. In order to confirm the theory, the single-crystal silicon carbide films with the thickness up to 200 nm have been grown on silicon (111) substrates owing to the chemical reaction with carbon monoxide. Grown high-quality single-crystal silicon carbide films do not contain misfit dislocations despite the huge lattice mismatch value of ∼20%. Also the possibility of growing of thick wide-gap semiconductor films on such templates SiC/Si(111) and, accordingly, its integration into silicon electronics, is demonstrated. In particular, a working LED structure based on gallium nitride has been produced. Finally, the thermodynamic theory of new phase nucleation due to a chemical reaction has been developed and it was shown that in the case under consideration the chemical equilibrium constant generalizes the concentration of adatoms exploited in a one-component nucleation theory.

Three-dimensional printing of SiSiC lattice truss structures

Abstract: Silicon/silicon carbide ceramic composites were fabricated by the three-dimensional printing (3DP™) from Si/SiC/dextrin powder blends. After printing the C/Si/SiC preforms were infiltrated with a liquid silicone resin for transient shape stabilization. The green bodies were pyrolyzed at 1000 °C in nitrogen atmosphere resulting in a residue with a porosity of ∼41%. The porous preforms exhibit excellent infiltration behavior for liquid Si at 1500 °C in vacuum. Bending strength, fracture toughness and Young's modulus were analyzed with respect to Si volume fraction.

Experimental investigations of static and transient current sharing of parallel-connected silicon carbide MOSFETs

Abstract: An Experimental performance analysis of a parallel connection of two 1200/80 MΩ silicon carbide SiC MOSFETs is presented. Static parallel connection was found to be unproblematic. The switching performance of several pairs of parallel-connected MOSFETs is shown employing a common simple totem-pole driver. Good transient current sharing and high-speed switching waveforms with small oscillations are presented. To conclude this analysis, a dc/dc boost converter using parallel-connected SiC MOSFETs is designed for stepping up a voltage from 50 V to 560 V. It has been found that at high frequencies, a mismatch in switching losses results in thermal unbalance between the devices.

Silicon Carbide Whiskers: Preparation and High Dielectric Permittivity

Abstract: Silicon Carbide whiskers have been synthesized using silica sol and activated carbon as reagents via microwave heating without the presence of any of the catalysts, such as Fe, Ni, and Al etc.. The synthesized whiskers were separated and concentrated from the as-synthesized products using the gravity concentration process. The dielectric properties of the concentrated SiC whiskers were investigated in the frequency range 2–18 GHz. The results indicate that the SiC whiskers exhibit higher dielectric permittivity and loss tangent than those of SiC powders, respectively, due to the high density of stacking faults formed in the SiC whiskers prepared by microwave heating.

Nano silicon carbide: a new lithium-insertion anode material on the horizon

Abstract: Bulk-synthesized silicon carbide, hitherto considered inactive for electrochemical lithium insertion, is demonstrated as a potential high-capacity, long-cycling anode material for lithium-ion batteries. In this study, we show that cubic (3C polytype) nano SiC, prepared by a chemical vapour deposition (CVD) method, delivers a reversible lithium insertion capacity of about 1200 mA h g−1 over 200 cycles.