Self-consistent one-electron states of substitutional and interstitial 5d transition-atom impurities in silicon.

Abstract

The electronic structure of the 5d transition-metal impurities Hg, Au, Pt, Ir, Os, Re, and W in silicon has been studied theoretically within the framework of a nonrelativistic self-consistent one-particle model. The energy spectra of the substitutional and tetrahedral-site interstitial neutral atoms have been obtained by using the Watson-sphere-terminated multiple-scattering X\ensuremath{\alpha} molecular cluster method. The role played by the metal 5d states in the formation of impurity levels within the crystal band gap and resonances in the valence band has been established. The observed chemical trends of the impurity level positions for the 5d elements are analyzed and compared with those inferred from previous cluster and Green's-function calculations for the 3d transition-metal series. The results of our one-electron theory provide a good description of the observed physical properties of the widely studied Au and Pt impurities in silicon. A good correlation between our calculations and the sparse data which are available for Hg, Ir, Os, Re, and W has been established.