Modeling the optical constants of Cu_(2)In_(4)Se_(7) and CuGa_(3)Se_(5) crystals

摘要

Spectral dependence of the pseudodielectric function epsilon(E)(velence)(epsilon)_(1)(E)+i(epsilon)_(2)(E) as well as of the complex refractive index, extinction coefficient, absorption coefficient, and normal-incidence reflectivity of Cu_(2)In_(4)Se_(7) and CuGa_(3)Se_(5) ordered vacancy compound crystals are modeled in the 0.8-4.4 eV photon energy range using a modification of Adachi's model T. Kawashima et al. J. Appl. Phys. 84, 5202 (1998) for optical properties of semiconductors. Model parameters are determined using the acceptance-probability-controlled simulated annealing method. Excellent agreement with experimental data is obtained; the relative errors for the real (epsilon)_(1) and for imaginary (epsilon)_(2) part of the dielectric function are equal to 0.9percent-1.5percent and 3.2percent-4.1percent for the studied compounds.