The role of Ge predeposition temperature in the MBE epitaxy of SiC on Ssilicon

Abstract

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. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)