Spectroscopic ellipsometric analysis of ZnSe1-xOx layers with different O compositions

In this study, ZnSe1-xOx layers with oxygen contents of up to 7.0% are successfully grown at 300 deg. C on semi-insulating GaAs substrates by molecular beam epitaxy. The deposited ZnSe1-xOx films are characterized by Raman spectroscopy and the optical properties studied by spectroscopic ellipsometry. We examine the complex dielectric function obtained by spectroscopic ellipsometry in the photon range from 1.5 to 5 eV. The shifting and broadening of the critical points in the ZnSe1-xOx epilayers as a function of the O composition are investigated for the first time. The characteristics of the peaks change as the O composition increases. The second derivative of the dielectric function is presented and analyzed. The dielectric function spectra reveal distinct structures which can be attributed to the band gap and optical transitions at higher energy.