Photoluminescence spectra of undoped and Sm3+-doped BaAl2S4 and BaAl2Se4 single crystals

Undoped and Sm3+-doped BaAl2S4 and BaAl2Se4 single crystals were grown by t he chemical transport reaction method. The optical energy band gaps of the BaAl2S4 and BaAl2Se4 were found to be 4.10 and 3.47 eV, respectively, at 5 K. In their photoluminescence spectra measured at 5 K, broad emission peaks at 459 and 601 nm appeared in the BaAl2S4 and at 486 and 652 nm in the BaA l2Se4. These emissions are assigned to donor-acceptor pair recombinations. Sharp emission peaks were observed in the Sm3+-doped BaAl2S4 and BaAl2Se4 s ingle crystals at 5 K. Taking into account the ionic radii of the cations a nd Sm3+, these sharp emission peaks are attributed to the electron transiti ons between the energy levels of Sm3+ substituting with the Ba site.