Ch. Förster

Ge-modified Si(100) substrates for the growth of 3C-SiC(100)

An alternative route to improve the epitaxial growth of 3C-SiC(100) on Si(100) was developed. It consists in covering the silicon wafers with germanium prior to the carbonization step of the silicon substrate. Transmission electron microscopy and μ-Raman investigations revealed an improvement in the residual strain and crystalline quality of the grown 3C-SiC layers comparable to or better than in the case of 3C-SiC grown on silicon on insulator substrates. These beneficial effects were reached by using a Ge coverage in the range of 0.5–1 monolayer.

α-SiC–β-SiC heteropolytype structures on Si (111)

Nanoscale α-SiC(0001) on β-SiC(111) heterostructures on Si (111) substrates fabricated by ultralow-pressure chemical vapor deposition are demonstrated. The intentional formation of the α-β structure was achieved by adjusting the SiH4 to C2H4 flux ratios to carbon rich conditions and by controlling the diffusion length. The developed method allows the formation of heteropolytypic structures with a controlled thickness of the intermediate cubic β-SiC layer.

Electromechanical resonances of SiC and AlN beams under ambient conditions

MEMS resonators offer great potential for RF sensor and filter applications. A semiconductor process has been used to prepare SiC and AlN beam resonators. The metallised beams are excited by an RF current in a permanent magnetic field. The resonant response is detected by the induced voltage. Despite the weakness of the signal, accurate detection has been achieved in the time domain, under ambient conditions in a magnetic field of about 0.5 T. The resonant response bears valuable information on the structural quality of the material and identifies potential for further improvement. The time domain technique presents an elegant approach to sensing applications.

Beta to alpha transition and defects on SiC on Si grown by CVD

The features of α-SiC (0001) epitaxially grown on top of β-SiC(l11)/Si(111) is reported by means of transmission electron microscopy (TEM). Hexagonal and rhombohedral polytype nuclei, mainly 4H-SiC, appear after the growth of a fixed cubic SiC thickness which is related to the selected growth conditions: Si/C ratio and growth temperature. The defect structure of these multilayer systems (voids, planar defects, facets and polycrystalline top clusters) and the hexagonality of the SiC surface are determined and described.