The ${\mathrm{Pt}}^{-}$ center in silicon has been identified by its characteristic electron-paramagnetic-resonance (EPR) signal. From photo-EPR measurements, the optical cross sections of holes for the Pt(0/-) transition have been determined at $T=4.2\mathrm{}$ K. A comparison with corresponding optical cross sections obtained for the commonly observed deep acceptor level in Pt-doped Si at $T=80\mathrm{}$ K with junction space-charge methods shows that the ${\mathrm{Pt}}^{-}$ center is, indeed, the impurity which gives rise to the $E_c-0.23\mathrm{}$ eV acceptor level.

• Received 5 June 1987

DOI:https://doi.org/10.1103/PhysRevB.36.6202