Optical absorption of ZnGa 2Se 4: Cr 2+ single crystals

Abstract

Single crystals of ZnGa 2Se 4: Cr 2+ were grown by the chemical transport reaction method. To identify the energy band gap and origin of the impurity optical absorption, the optical absorption spectra of the single crystals were investigated in the temperature region 20–300 K. The temperature dependence of the energy band gap had good agreement with the Varshni equation. The broad band absorption peaks observed at 6317 and 12315 cm −1 in the impurity optical absorption spectrum are attributed to the electron transition 5 T 2( 5 D) → 5 E( 5 D) and 5 T 2( 5 D) → 3 T 2( 3 H) of the Cr 2+ ions sited with T d symmetry in the doping ZnGa 2Se 4: Cr 2+ single crystal with chromium as the impurity. The crystal field parameter is given by Dq = 632 cm −1 in case of the above.