Photoluminescence spectral lines identification in Ho3+-, Er3+-, and Tm3+-doped MgxZn1-xSe single crystals

MgxZn1-xSi:Ho3+, MgxZn1-x,Se:Er3+, and MgxZn1-xSe:Tm3+ single crystals were grown by the closed-tube sublimation method, The single crystals crystallized into a zincblende structure at the composition x = 0.11 and a wurtzite structure at the composition x = 0.25, 0.32, and 0.41, The trivalent ions (Ho3+, Er3+ and Tm3+) of the rare-earth elements Ho, Er, and Tm site in Td and Cg, symmetries in the single crystals with zincblende and wurtzite structures, respectively, Sharp emission peaks appeared in the photoluminescence spectra of the single crystals. These emission peaks are identified to originate from the radiation recombination between the energy levels of the trivalent ions sited in Td and C-3v symmetries.