Photoluminescence excitation spectroscopy of 3d transition-metal ions in GaP and ZnSe

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Abstract
Photoluminescence and photoluminescence excitation spectra are presented for ZnSe:Ni, GaP:Co and GaP:Ni. Comparison of the excitation spectra with published absorption spectra leads to the identification of Ni2+(d8) as the luminescent charge state in ZnSe:Ni, and Co2+(d7) as the radiative ion in GaP:Co. In GaP-Ni this procedure demonstrates that while Ni2+(d8) may dominate the near-infrared absorption spectrum, the photoluminescence band with zero-phonon line (ZPL) at 5354 cm-1 is attributable to Ni+(d9) as concluded previously by Kaufmann et al. The photoluminescence excitation spectrum of GaP:Ni is shown to contain peaks corresponding to absorption by the inverse of the 2E-2T2 emitting transition of Ni+(d9) and dips corresponding to competing absorption by the 3T1(F)-3T1(P) transition of the Ni2+(d8) charge state which is also present.