Electronic structure ofNi+inIB−III−VI2chalcopyrite semiconductors

Abstract

Electron-spin-resonance (ESR) and optical-absorption spectra of ${\mathrm{Ni}}^{+} (3{d}^{9})$ impurities have been observed in the ternary chalcopyrite compounds CuAl${\mathrm{S}}_{2}$, CuGa${\mathrm{S}}_{2}$, and AgGa${\mathrm{S}}_{2}$. Identification of the axial ESR centers as being due to Ni has been confirmed by the observation of hyperfine structure in crystals enriched with $^{61}\mathrm{Ni}$. Large axial-field splittings due to the tetragonal crystal-field component in the chalcopyrite structure are inferred from the ESR and optical data. All experimental results can be consistently interpreted within the framework of static crystal-field theory. A complete set of crystal-field parameters is obtained for ${\mathrm{Ni}}^{+}$ in each of the three hosts. No evidence for a Jahn-Teller effect is found.