Optical properties and electronic band structure of AgGaTe2 chalcopyrite semiconductor.

The optical properties of AgGaTe(2) chalcopyrite semiconductor are studied by optical absorption, spectroscopic ellipsometry (SE), and thermoreflectance (TR) spectroscopy. Optical absorption spectra suggest that AgGaTe(2) is a direct-gap semiconductor having a bandgap of approximately 1.2 eV at T=300 K. The pseudodielectric-function spectra of AgGaTe(2) 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 AgGaTe(2) are determined to be Delta(so)=0.70 eV and Delta(cr)=-0.23 eV, respectively.