Optical properties and electronic band structure of AgGaTe2 chalcopyrite semiconductor

The optical properties of AgGaTe2 chalcopyrite semiconductor are studied by optical absorption, spectroscopic ellipsometry (SE), and thermoreflectance (TR) spectroscopy. Optical absorption spectra suggest that AgGaTe2 is a direct-gap semiconductor having a bandgap of similar to 1.2 eV at T = 300 K. The pseudodielectric-function spectra of AgGaTe2 are determined by SE in the range between E = 1.2 and 5.2 eV for both states of polarization. These spectra reveal distinct structures at energies of the critical points in the Brillouin zone. The TR spectra are also measured in the E = 1.0-5.3 eV ranges at T = 20 K-300 K. The spin-orbit and crystal-field splitting parameters of AgGaTe2 are determined to be Delta(so) = 0.70 eV and Delta(cr) = -0.23 eV, respectively. (C) 2010 Optical Society of America