Photoluminescent properties of the ZnSe:Yb crystals in the excitonic region

Currently, II-VI compounds doped with rare-earth elements (REE) are of renewed interest due to possibility to use them as emitting media for near infrared spectral range, but this requires understanding of the excitation mechanism of the rare-earth centers. Even though the rare-earth impurities in A^IIB^VI compounds have been studied for a long time, there is not a common opinion about the sites occupied by the impurities [1,2]. In this work we study the photoluminescent (PL) spectra of ytterbium doped ZnSe samples and try to understand surroundings of the REE ions. The samples were doped by high-temperature annealing of the melt-grown bulk ZnSe samples in Zn + Yb melt. Concentration of the impurity atoms in crystals is considered to be the same as in the doping melt. After the doping the surfaces of the samples were mechanically and chemically polished. The PL spectra were excited by pulsed NL100 laser (E_ex=3.68 eV, W_awer~1.9mW), the MS257 monochromator and Hamamatsu R943-02 photomultiplier tube were used for signal detection.