The improvement of phase modulated spectroscopic ellipsometry

Spectroscopic ellipsometry using photoelastic modulator [phase modulated spectroscopic ellipsometry (PMSE)] has been improved in the spectral range. Spectroscopic ellipsometry using the rotating analyzer [rotating analyzer spectroscopic ellipsometry (RASE)] has demonstrated its capability of measuring the reflectivity ratio, ρ(ω), from 1.5 to 6 eV with a single scan, but PMSE has not been able to do so. We demonstrate that PMSE also can measure ρ(ω) from 1.5 to 6 eV with a single scan. We discuss the problems and show their solutions to achieve this goal. We also discuss the accuracy of our PMSE by comparing the spectral data by RASE with those by our PMSE. We find that the simplest possible procedure with our system provides reasonably accurate values, after including the zone average which is easy to perform with our system. The extension of the spectral range is a decisive advantage, especially in studying the E1 structure of the wide band gap materials such as ZnSe.