THE STUDY OF DIELECTRIC FUNCTION FOR CD1-XCOXTE SINGLE-CRYSTALS

The complex dielectric function for Cd1-xCoxTe (x=0, 0.008, 0.014) sin gle crystals were measured by spectroscopic ellipsometry in the 1.5 si milar to 5.5 eV photon energy range at room temperature. The measured epsilon(omega) data revealed distinct structures at energies of the E- 1, E-1 + Delta(1), and E-2 critical points (CPs). These data were anal yzed by fitting the second-derivative spectra (d(2) epsilon/d omega(2) ) with theoretical model, i.e. the standard critical point (SCP) line shapes. It is found that SCP model explains the measured derivative sp ectra successfully. The CP energies, Lorentzian broadening (Gamma), an d exitonic phase angle (phi) were determined and we discussed these pa rameters with composition x.