Ellipsometric spectroscopy on polycrystalline CuIn1-xGaxSe2:: Identification of optical transitions

Bulk materials have been synthesized by the Bridgman technique using the elements Cu, Ga, In, Se. Bulk samples have been characterized by EDS (Energy Dispersive Spectrometer), hot point, X-ray diffraction, photoluminescence and spectroscopic ellipsometry (SE). The samples used were well crystallized and lended strong support to the achievement of a good stoechiometry. Energy levels above the gap in the band scheme were determined by measuring the dielectric function at ambient temperature for energies lying between 1.5 and 5.5 eV. Many transitions were observed above the gap for different samples of CuIn1-xGaxSe2 (0 <= x <= 1) alloy. Spectroscopic ellipsometry gave evidence for the interpretation of the choice of gap values which were compatible with that obtained from solar spectrum [1]. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.