Optical properties of ZnSe

We have studied the optical response of ZnSe in the 1.5–5.3-eV photon-energy range at room temperature by spectroscopic ellipsometry. The measured dielectric-function spectra reveal distinct structures at energies of the ${\mathit{E}}_0$, ${\mathit{E}}_0$+${\mathrm{\Delta }}_0$, ${\mathit{E}}_1$, and ${\mathit{E}}_1$+${\mathrm{\Delta }}_1$ critical points (CP’s). These data are analyzed on the basis of a simplified model of the interband transitions. The ${\mathit{E}}_0$-(${\mathit{E}}_0$+${\mathrm{\Delta }}_0$) structures are characterized by a three-dimensional ${\mathit{M}}_0$ CP, the ${\mathit{E}}_1$-(${\mathit{E}}_1$+${\mathrm{\Delta }}_1$) structures by a two-dimensional ${\mathit{M}}_0$ CP, and the ${\mathit{E}}_2$ structure by a classical Lorentzian oscillator (damped harmonic oscillator). The experimental data could not be explained within the framework of the one-electron approximation, since excitonic effects may profoundly modify the CP singularity structure. The model is thus made to account for the excitonic effects at these CP’s; our results are in satisfactory agreement with the experiment over the entire range of photon energies. Dielectric-function-related optical constants of ZnSe, such as the refractive index, the extinction coefficient, and the absorption coefficient, are also presented and analyzed.