A light-activated Darlington heterojunction transistor based on a SiCGe/3C-SiC hetero-structure is proposed for anti-EMI（electromagnetic interference） applications. The performance of the novel power switch is simulated using ISE. In comparison with the switches based on other polytypes of SiC,the design benefits from having fewer lattice mismatches between the SiCGe and 3C-SiC. A maximum common emitter current gain of about 890 and superb light-activation characteristics may be achievable. The performance simulation demonstrates that the device has a good I-V characteristic with a turn-on voltage knee of about 4V.
A method for estimating the defects density in SiC bulk crystals by defect-selective etching in molten KOH has already been successfully demonstrated. In this paper, the results of applying this technique to bulk SiC crystals are reported. Etching produced hexagonal pits on the Si-polar （0001） plane,while round pits formed on the C face. The etching rate and the nature of etch pits for SiC depends on the growth process. For SiC crystals grown by the PVT process with high growth gas flow rate,the edge and screw dislocation density and the MP density are about 2. 82 × 10^5 ,94,and 38cm^-2 ,respectively. For SiC crystals grown by the PVT process with low growth gas flow rate,those defects densities are about 9.34 × 10^5 ,2, and 29cm^-2 respectively. The results indicate that as the growth gas flow rate increases, the edge dislocation density decreases to avoid N2 impurity.
