Optical properties and electronic band structure of CdGa2Te4 Original Research Article

Optical properties of a defect-chalcopyrite-type semiconductor CdGa2Te4 have been studied by optical absorption, spectroscopic ellipsometry (SE), and electroreflectance (ER) measurements. Optical absorption measurements suggest that CdGa2Te4 is a direct-gap semiconductor having the band gap of ∼1.36 eV at 300 K. The complex dielectric-function spectra, ε(E)=ε1(E)+iε2(E), measured by SE reveal distinct structures at energies of the critical points (CPʹs) in the Brillouin zone. ER spectrum facilitates the precision determination of the CP parameters (energy position, strength, and broadening). By performing the band-structure calculation, these CPʹs are successfully assigned to specific points in the Brillouin zone.