Optical properties and electronic band structure of CdGa 2Te 4

Abstract

Optical properties of a defect-chalcopyrite-type semiconductor CdGa 2Te 4 have been studied by optical absorption, spectroscopic ellipsometry (SE), and electroreflectance (ER) measurements. Optical absorption measurements suggest that CdGa 2Te 4 is a direct-gap semiconductor having the band gap of ∼1.36 eV at 300 K. The complex dielectric-function spectra, ε( E)= ε 1( E)+i ε 2( E), measured by SE reveal distinct structures at energies of the critical points (CP's) 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 CP's are successfully assigned to specific points in the Brillouin zone.