We report on the complex dielectric tensor components of four chalcopyrite semiconductors in an optical energy range (1.4–5.2 eV, from 0.9 eV for ${\mathrm{CuInSe}}_2)$ determined at room temperature by spectroscopic ellipsometry. Our results were obtained on single crystals of ${\mathrm{CuInSe}}_2,$ ${\mathrm{CuGaSe}}_2,$ ${\mathrm{CuInS}}_2,$ and ${\mathrm{CuGaS}}_2.$ Values of refractive indices n, extinction coefficients k, and normal-incidence reflectivity R in the two different polarizations are given and compared with earlier data where available. We analyze in detail the structures of the dielectric function observed in the studied energy region. Critical-point parameters of electronic transitions are obtained from a fitting of numerically calculated second-derivative spectra $d^2\varepsilon \left(\omega \right)/d{\omega }^2.$ Experimental energies and polarizations are discussed on the basis of published band-structure calculations.

• Received 28 July 2000

DOI:https://doi.org/10.1103/PhysRevB.63.075203