Optical properties and electronic structure of polycrystalline Ag1-xCuxInSe2 alloys -: art. no. 103515

The dielectric function epsilon(omega) of polycrystalline bulk samples of the quaternary chalcopyrite semiconductors Ag1-xCuxInSe2 with x=0.0, 0.2, 0.4, 0.6, 0.8, 1.0 has been determined by spectroscopic ellipsometry in the energy range from 0.5 to 4.7 eV at room temperature. Accurate values of refractive indices n and extinction coefficients k representative of bulk materials are obtained from the data. The value of the main energy gap is very sensitive to the composition and varies from 1.225 to 1.009 eV as x increases (Cu content). The structures observed in epsilon(omega) have been analyzed by fitting the numerically differentiated experimental spectrum (second derivative) to analytical line shapes. As a result, the energies corresponding to different electronic transitions have been determined as a function of the composition, and they have been identified within the electronic band structure of chalcopyrites. (c) 2005 American Institute of Physics.