Growth of SiCGe ternary alloy on 6H-SiC in a conventional hot-wall CVD system was initially studied. SiH4, GeH4 and C3H8 were employed as silicon, germanium and carbon source, respectively, while H2 was employed as the carrier gas. To reduce the heavy lattice mismatch between the film and the substrate, a 3C-SiC buffer layer was inserted between them in a CVD process. Optimizing the growth conditions was discussed. The samples were measured by means of SEM, SAXRD (Small Angle X-Ray Diffraction). It is shown that use of the 3C-SiC buffer layer is an effective way to improve the quality of the ternary alloy.
Tan Changxing Chen Zhiming Pu Hongbin Lu Gang Li Lianbi
The Si on SiC heterojunction is still poorly understood, although it has a number of potential applications in electronic and optoelectronic devices, for example, light-activated SiC power switches where Si may play the role of an light absorbing layer. This paper reports on Si films heteroepitaxially grown on the Si face of （0001） n-type 6H-SiC substrates and the use of B2H6 as a dopant for p-Si grown at temperatures in a range of 700-950℃. X-ray diffraction （XRD） analysis and transmission electron microscopy （TEM） tests have demonstrated that the samples prepared at the temperatures ranged from 850℃ to 900℃ are characterized as monocrystalline silicon. The rocking XRD curves show a well symmetry with FWHM of 0.4339° Omega. Twin crystals and stacking faults observed in the epitaxial layers might be responsible for widening of the rocking curves. Dependence of the crystal structure and surface topography on growth temperature is discussed based on the experimental results. The energy band structure and rectifying characteristics of the Si/SiC heterojunctions are also preliminarily tested.
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.
