Optical and electro-optical behaviour of polished and etched zinc selenide single crystals

Abstract

Reflectivity and electrolyte electroreflectance measurements have been performed on ZnSe single crystals polished and etched like those used in electrochemical and photoelectrochemical studies. From the reflectivity measurements in the energy range 2-26 eV, a determination of the principal optical constants (absorption coefficient alpha , complex dielectric constant epsilon and complex refractive index n) has been possible by Kramers-Kronig analysis. The various features of the reflectivity spectrum between 2-10 eV may be correlated to the different band to band transitions in the Brillouin zone. Complementary information concerning the fundamental transition and its spin-orbit splitting are provided by electrolyte electroreflectance measurements. In particular, the existence of excitons at room temperature is demonstrated and an energy gap value Eg=2.72 eV is determined.