Ab-Initio Study of Electronic Structure of Dilute Si Alloys Containing I–B Impurity Atoms

We have made a first principles calculation of the electronic structure and charge density of the dopants I–B group impurities Au, Ag and Cu in crystalline silicon by employing a full potential self-consistent linear muffin tin orbital (LMTO) method along with the local density functional theory. The scalar relativistic effects have also been included. A supercell containing 54 atoms, Si₅₃X with X as impurity has been considered for these investigations. The states lying deep into the energy gap show a fast decaying behaviour and the corresponding wave-functions of the impurities lying in the neighbouring supercells show quite small overlap. The impurities lying in the adjacent supercells are the sixth neighbours among themselves in the direction of the lattice vectors of the fcc lattice. In all cases, impurity bands arising from the p-like orbitals appear in the gap region although some mixing with the d-like states is also observed. This p-like impurity state is a triply degenerate T state at the Γ-point. The impurity bands are peaked at 0.65, 0.61 and 0.56 eV for Au, Ag and Cu, respectively. The d-type impurity states appear in the middle of the valence band. The results in the valance band region are in good agreement with the available experimental data.