DETERMINATION OF THE OPTICAL-CONSTANTS OF ZNSE FILMS BY SPECTROSCOPICELLIPSOMETRY

Spectroscopic ellipsometry was used to determine the real and imaginar y parts of the dielectric function of ZnSe thin films grown on (001) G aAs substrates by molecular-beam epitaxy, for energies between 1.5 and 5.0 eV A sum of harmonic oscillators is used to fit the dielectric fu nction in order to determine the values of the threshold energies at t he critical points. The fundamental energy gap was determined to be at 2.68 eV The E0+DELTA0 and E1 points were found to be equal to 3.126 a nd 4.75 eV, respectively. Below the fundamental absorption edge, a Sel lmeir-type function was used to represent the refractive index. At the critical points, E0 and E0+DELTA0, the fitting was improved by using an explicit function combining the contributions of these two points t o the dielectric function.