No abstract

No abstract

The mechanism of self-propagating high-temperature synthesis (SHS) or combustion synthesis of SiC has been investigated using pellets consisting of silicon and carbon powders. The combustion reaction was initiated by rapidly heating the pellet on a graphite strip. The reaction products were analyzed using scanning and transmission electron microscopy, x-ray diffraction, and Raman spectroscopy. The results show that it is possible to produce β-SiC without any residual silicon and carbon. Occasionally, a very small number density of α-SiC precipitates embedded in the β-SiC matrix was observed. Based upon the microstructural features, it is proposed that the formation of SiC involves the dissolution of carbon into liquid silicon, diffusion of C into liquid silicon, and subsequent precipitation of SiC. The size of the SiC crystallites is determined by the diffusion coefficient of carbon in liquid silicon and the time available for SiC precipitation. The activation enthalpy for the SHS process is estimated to be 59±3 kcal/mol.

No abstract

Electron beam induced current (EBIC) techniques were employed in order to understand the role of defects on the breakdown characteristics of SiC. EBIC images revealed that certain defects caused enhanced multiplication leading to the catastrophic failures in SiC diodes. The impact ionization coefficients for holes measured at the defective site (αp,eff) were found to be higher than those measured at a nondefective site. Also, αp,eff measured at the defective site was found to increase with increasing temperature in contrast with a defect free diode where αp decreases with increasing temperature, clearly indicating that the defects produce the observed negative temperature coefficient of breakdown voltage in SiC.