Shallow donor muonium states in II-VI semiconductor compounds

Abstract

Experimental data on shallow donor muonium states in the $\mathrm{II}\mathrm{\ensuremath{-}}\mathrm{VI}$ semiconductor compounds CdS, CdSe, CdTe, and ZnO are presented. These are characterized by very weak hyperfine interactions amounting to approximately ${10}^{\ensuremath{-}4}$ of the free-atom value, and by donor levels with binding energies comparable to those calculated on the hydrogenic model of the shallow centers. The data are discussed in terms of a model generalizing the knowledge of muonium and hydrogen states in tetrahedrally bonded semiconductors. Within this model the shallow muonium state is attributed to muonium bound to the anion of the $\mathrm{II}\mathrm{\ensuremath{-}}\mathrm{VI}$ compound and located at the antibonding site or close to it in the bond direction.