Optical properties of silicon carbide polytypes below and around bandgap

The optical properties of SiC polytypes are discussed with relation to the structure of SiC. The main part of the paper review the detailed measurements of the uniaxial dielectric function below and around the minimum band gap, using phase-modulated spectroscopic ellipsometry, polarised light transmission measurements or crossed polariser variable angle of incidence interferometry. In particular, the oscillations in the recorded ellipsometric intensities, due to interference between the ordinary and extraordinary modes, specific to thick uniaxial wafers, are used to accurately measure the below band gap dielectric difference. It is focussed on the differences in optical properties among the polytypes, in order to investigate SE and closely related techniques as a candidate for bulk-material wafer inspection and characterisation.