Manganese(II) in superlattices consisting of alternate cadmium telluride and zinc sulfide layers

Abstract

Superlattices of CdTe:Mn–ZnS grown epitaxially on a (100) or (111) surface of GaAs prepared by a hot-wall epitaxy (HWE) technique have been studied by means of EPR spectroscopy in order to elucidate the mechanisms of the unusual photoluminescence observed ca. 680 nm at room temperature. The g-value of 2.0038 ± 0.0001 and hyperfine splitting constant of 64.6 × 10^–4 cm^–1 obtained at 77 K for these superlattices indicates that the lattice mismatch between alternate CdTe:Mn and ZnS layers leads to the presence of a strong crystal field surrounding manganese(II). This results not only from the compressive distortion of the bond length between manganese(II) and telluride but also by an increase in the ionicity of the bond itself due to electron transfer from telluride to manganese(II) being less significant. Narrow hyperfine lines observed at room temperature suggest that the change in the valence and/or conduction bands of CdTe manganese(II), relative to the 3d⁵ energy levels of manganese(II), decreases the charge transfer between manganese(II) and vacancies, which would be a non-radiative bypass for photoluminescence. In addition, there is no significant difference observed between the EPR parameters for the superlattices grown on (100) and (111) surfaces of GaAs in spite of the different type of distortion which they receive.