Optical properties of cubic and hexagonal CdSe

Abstract

The complex dielectric function, ε(E)=ε1(E)+iε2(E), of hexagonal CdSe has been measured by spectroscopic ellipsometry in the photon-energy range between 1.2 and 5.3 eV at room temperature. The measured spectroscopic-ellipsometry data are analyzed on the basis of a simplified model of the interband transitions. The model is based on the Kramers–Kronig transformation and includes the E0 (E0α ; α=A,B,C), E1 (E1α ; α=A,B,C), and E0′ gaps as the main dispersion mechanisms. The recent SE data of cubic, zinc-blende-type CdSe have also been analyzed with the same model by considering the critical points for the cubic phase (i.e., E0, E0+Δ0, E1, E1+Δ1, and E2). Results are in satisfactory agreement with the experimental data over the entire range of photon energies. To facilitate design of various optoelectronic devices, dielectric-function-related optical constants, such as the complex refractive index, absorption coefficient, and normal-incidence reflectivity, of these crystals are also presented.