Reflectivity spectra of CdGa2Se4, CdGa2S4 and CdA12S4 crystals have been investigated in the range 1-6 eV for the polarization E It c and E Z c at 300 and 77 K. The valence band splitting caused by spin-orbital interaction and by crystal field are calculated for the point k = 0. The band model has been built in actual points of the Brillouin zone F, N, T, P.
The compounds of AnBnlC vl group which have nonlinear optical characteristics have not been investigated enough so far. The fundamental absorption edge and reflectivity spectra of CdGa2Se4 and CdGazS4 have been investigated in Refs. [1][2][3][4][5]. The theoretical calculations of the band structure of these crystals have been reported in Refs. [6,7]. The compound CdAlzS4 is not practically investigated.
In recent years the technology of crystal growth and experimental equipment have improved. Theoretical calculations made at the same time make it possible to better comprehend the experimental data and electron transition structure.
In this work the reflectivity spectra of CdGazSe4, CdGa2S4 and CdA12S4 crystals have been investigated in the polarization Efl c and E _L c at 300 and 77 K. The fine structure of reflectivity spectra is obtained and on the basis of the analogy of their properties and available theoretical calculations the energetic band structure of these compounds