Polarization and the Haldane-Anderson model of defects in nonmetals

Abstract

We have generalized the Haldane-Anderson (HA) model of defects in semiconductors and insulators by adding a term to the Hamiltonian which arises from polarization of the host when the defect is charged. The resulting Hamiltonian retains the form of that due to Haldane and Anderson, but with new input parameters: The defect electron-electron Coulomb interaction U is reduced to U-2K, where -K is a polarization energy, while the electron-core energy $E_D$ is shifted to $E_D$+K(2$n_0$-1), where $n_0$ is the number of valence electrons of the neutral defect. Hybridization, a key feature of the HA model, can then lead to an even smaller ‘‘effective U.’’ A calculation of level positions and net defect charge for the dangling bond in silicon is presented as an example.