Optical functions of chalcopyrite CuGaxIn1-xSe2 alloys

We report pseudodielectric functions <epsilon> 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 <epsilon> are analyzed by fitting the numerically differentiated spectra of d(2) <epsilon>(omega)/domega(2) 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.