Electronic structures and p-d exchange interaction of Mn-doped diluted magnetic semiconductors

Electronic structures of Mn-doped II-VI diluted magnetic semiconductors (DMSs) were studied by $\text{Mn}\text{ }2p$ core absorption (XAS), $\text{Mn}\text{ }2p$ core-level photoelectron (XPS), and $\text{Mn}\text{ }2p\text{\ensuremath{-}}3d$ resonance photoelectron spectroscopy (RPES). The $\text{Mn}\text{ }2p$ XAS, $2p$ XPS, and $2p\text{\ensuremath{-}}3d$ RPES spectra were analyzed by configuration-interaction theory based on the cluster model. We then obtained a strong negative $p\text{\ensuremath{-}}d$ exchange constant between anion $p$ bands and $\text{Mn}\text{ }3d$ orbitals for the wide gap DMSs ${\text{Zn}}_{1\ensuremath{-}x}{\text{Mn}}_{x}\text{Se}$ and ${\text{Zn}}_{1\ensuremath{-}x}{\text{Mn}}_{x}\text{S}$. In contrast, for the narrow gap DMS ${\text{Hg}}_{1\ensuremath{-}x\ensuremath{-}y}{\text{Cd}}_{x}{\text{Mn}}_{y}\text{Te}$, we found a weak negative $p\text{\ensuremath{-}}d$ exchange constant. By comparing these results with the results of the previous work, we found that the $p\text{\ensuremath{-}}d$ exchange constant in wide and narrow gap II-VI DMSs is proportional to the absolute band-gap energy. This phenomenon can be interpreted by the change in the density of states of anion $p$ bands, which hybridized with the $\text{Mn}\text{ }3d$ orbitals, at the valence-band maximum. These results suggest that one can control the $p\text{\ensuremath{-}}d$ exchange interaction in DMSs by changing the band-gap energy.