Optical functions of chalcopyrite CuGa x In 1-x Se 2 alloys

We report pseudodielectric functions of the quaternary semiconductor alloys CuGaxIn1-xSe2. Measurements were done in polycrystalline samples from 0.7 to 5.2 eV at room temperature by spectral ellipsometry. Accurate values of refractive indices n and extinction coefficients k representative of the bulk materials are obtained from the data. The structures observed in are analyzed by fitting the numerically differentiated spectra of d2 (ω)/dω2 to analytic line shapes. The obtained energies are related to given inter-band transitions by taking into account the electronic band structures of the ternary end-point compounds.