The role of oxygen in formation of radiative recombination centers in ZnSe1−xTex crystals

Abstract

The present study was aimed at revealing the influence of oxygen on formation of alloy ZnSe–ZnTe as well as on development of luminescence centers under thermal treatment of scintillators based on isovalently doped ZnSe crystals. The presence of oxygen in ZnSe(Te) crystals as ZnO phase has been shown to hinder formation of (V′_ZnTe^x_Se)′ type luminescence centers responsible for luminescence band peaked at 635–640 nm, which is the principal emission band of this scintillator. In ZnSe(Te) crystals doped by mechanically stimulated ion implantation with active forms of oxygen (O′, O^x, O′₂, etc.), luminescence quenching effects are not observed. However, the luminescence band in these crystals is blueshifted towards 600–610 nm. Strong luminescence band peaked at λ_max=590–610 nm is observed in Te-free ZnSe crystals doped with oxygen in active forms. The experimental results are interpreted by formation of centers (Zn_i^⋅O^x_i)^⋅ or (Zn_i^⋅O^x_Se)^⋅. Having larger charge carrier capture cross-section than (Zn^⋅_iV′_ZnTe^x_Se)^x, the oxygen-containing centers determine kinetics of luminescence in ZnSe_1−xTe_x crystals (x<0.001) treated by active forms of oxygen during mechanical activation of the initial raw material for crystal growth.