Determination of strain and composition in SiC/Si and AlN/Si heterostructures by FTIR-ellipsometry

Heteroepitaxially grown 3C-SiC and 2H-AlN layers on Ge modified Si(111) substrates were investigated by Fourier transform infrared spectroscopic ellipsometry. The obtained phonon frequencies increase with increasing Ge pre-deposition indicating a decrease of the residual stress in both wide band gap materials. Additionally, it is shown that infrared ellipsometry allows the analysis of the polytype content of the grown epitaxial layers.