Failure mechanisms and toughness of Al2O3 ductile-particle toughened ceramics and SiC fibre-ceramic composites

The development of high performance ceramics and ceramic composites often relies on assumptions about their behaviour during loading and at failure. A crucial influence on the mechanical properties of these materials is the degree of sub-critical cracking, which post mortem investigations cannot adequately reveal. Hence a clear picture of the dynamic micromechanisms of cracking is required if applications of fracture and damage mechanics to theoretical models is to be meaningful.

Theoretical and numerical investigation of SiC JFET and MOSFET at 6.5 kV

This paper presents a preliminary theoretical and numerical investigation of 4H-SiC JFET and MOSFET at 6.5 kV. To improve the on-state/breakdown performance of the JFET, buried layers in conjunction with a highly doped buffer layer have been used. Trench technology has been employed for the MOSFET. The devices were simulated and optimized using MEDICI[I] simulator. From the comparison between the two devices, it turns out that the JFET offers a better on-state/breakdown trade-off, while the trench MOSFET has the advantage of MOS-control.

Microwave power effects on the properties of phosphorus-doped SiC:H films prepared using ECR-CVD

There has been a growing interest in hydrogenated silicon carbide films (SiC:H) prepared using the electron cyclotron resonance-chemical vapour deposition (ECR-CVD) technique. Using the ECR-CVD technique, SiC:H films have been prepared from a mixture of methane, silane and hydrogen, with phosphine as the doping gas. The effects of changes in the microwave power (from 150 to 900 W) on the film properties were investigated in a series of phosphorus-doped SiC:H films. In particular, the changes in the deposition rate, optical bandgap, activation energy and conductivity were investigated in conjunction with results from Raman scattering and Fourier transform infra-red (FTIR) analysis. It was found that increase in the microwave power has the effect of enhancing the formation of the silicon microcrystalline phase in the amorphous matrix of the SiC:H films. This occurs in correspondence to a rapid increase in the conductivity and a reduction in the activation energy, both of which exhibit small variations in samples deposited at microwave powers exceeding 500 W. Analysis of IR absorption results suggests that hydrogen is bonded to silicon in the Si-H stretching mode and to carbon in the sp3 CHn rocking/wagging and bending mode in films deposited at higher microwave powers.

Physical modelling of large area 4H-SiC PiN diodes

The recent developments in SiC PiN diode research mean that physics-based models that allow accurate, rapid prediction of switching and conduction performance and resulting converter losses will soon be required. This is especially the case given the potential for very high voltage converters to be used for enabling distributed and renewable power generation. In this work an electro-thermal compact model of a 4.5 kV silicon carbide PiN diode has been developed for converter loss modelling in Simulink. Good matching of reverse recovery has been achieved between 25 and 200 °C. The I-V characteristics of the P+ anode contact have been shown to be significant in obtaining good matching for the forward characteristics of the diode, requiring further modelling work in this area. © 2009 IEEE.

Highly efficient spin transport in epitaxial graphene on SiC

Spin information processing is a possible new paradigm for post-CMOS (complementary metal-oxide semiconductor) electronics and efficient spin propagation over long distances is fundamental to this vision. However, despite several decades of intense research, a suitable platform is still wanting. We report here on highly efficient spin transport in two-terminal polarizer/analyser devices based on high-mobility epitaxial graphene grown on silicon carbide. Taking advantage of high-impedance injecting/detecting tunnel junctions, we show spin transport efficiencies up to 75%, spin signals in the mega-ohm range and spin diffusion lengths exceeding 100μm. This enables spintronics in complex structures: devices and network architectures relying on spin information processing, well beyond present spintronics applications, can now be foreseen. © 2012 Macmillan Publishers Limited. All rights reserved.

Half-bridge SIC inverter for hybrid electric vehicles: Design, development and testing at higher operating temperature

In recent years, Silicon Carbide (SiC) semiconductor devices have shown promise for high density power electronic applications, due to their electrical and thermal properties. In this paper, the performance of SiC JFETs for hybrid electric vehicle (HEV) applications is investigated at heatsink temperatures of 100 °C. The thermal runaway characteristics, maximum current density and packaging temperature limitations of the devices are considered and the efficiency implications discussed. To quantify the power density capabilities of power transistors, a novel 'expression of rating' (EoR) is proposed. A prototype single phase, half-bridge voltage source inverter using SiC JFETs is also tested and its performance at 25 °C and 100 °C investigated.