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SiC/Si(111) heterostructures formed by using an alternative method for stress relaxation were investigated by SIMS and AES. The applied stress reduction method is based on a theoretical approach, which predicts an improvement of the SiC layer quality if Group IV elements are incorporated into the interface between SiC and Si. Germanium was chosen to test this approach. The incorporation of Ge into the heterointerface was carried out by depositing different amounts of Ge prior to the SiC growth process and varying the Ge deposition temperature. SIMS investigations revealed that Ge remains near the SiC/Si interface independently of the pre-deposited amount of Ge. In the case of two monolayers (ML) Ge coverage (with respect to the silicon surface) a surface segregation was observed. This indicates a limited transport of Ge to the SiC surface through the growing SiC layer due to grain boundary diffusion. At Ge coverages between 0.5 ML and 2 ML a sharper interface between the SiC and Si was observed. In this case the tail of the carbon distribution remains within the region occupied by the Ge distribution. The incorporation of Ge at the interface suppresses the out-diffusion of Si from the substrate to the surface of the growing SiC layer and, therefore, impedes the formation of voids at the SiC/Si interface.

An alternative method for stress relaxation in the SiC/Si heteroepitaxial system based on the incorporation of a group-IV element (germanium) into the interface between SiC and Si is presented. We have investigated the effect of the temperature during the predeposition of 1 ML of Ge on a silicon (111) surface, prior to the MBE carbonization. The resulting structures were investigated by transmission electron microscopy (TEM), x-ray diffraction (XRD), secondary ion mass spectrometry (SIMS) and Fourier transform infrared spectroscopy (FTIR). The crystalline quality of the 3C-SiC layer was improved by the Ge predeposition, as shown by XRD measurements and by the smaller damping constants of the TO and LO phonons in the FTIR analysis. As the temperature of Ge predeposition increases, the SiC layer exhibits lower residual strain and larger grain size. Furthermore, the incorporation of Ge at the interface suppresses the outdiffusion of Si from the substrate to the surface of the growing SiC layer and, therefore, impedes the formation of voids at the SiC/Si interface. TEM and SIMS results revealed a strong segregation of Ge at the interface leading to an increased stress relaxation, in agreement with theoretical predictions.

Ternary (Si1-xCy)Gex+y solid solutions were grown on Si-face 4H-SiC applying atomic layer molecular beam epitaxy at low temperatures. The grown layers consist of twinned 3C-SiC revealed by cross section electron microscopy. The germanium was incorporated on silicon lattice sites as revealed by atomic location by channeling enhanced microanalysis transmission electron microscopy studies. The Ge concentration of the grown 3C-(Si1-xCy)Gex+y heteroepitaxial layers decreases with increasing growth temperatures, but exceeds the solid solubility limit.