Surface-state conduction through dangling-bond states

The surface-state conduction through dangling-bond states on the (1 1 1) ideal surfaces of group-IV semiconductors is studied theoretically. Localization strength of wave functions is an important factor determining the surface-state conduction. Approximate expressions for the decay constants of the dangling-bond states are presented using a tight-binding model. The origin of the difference in the decay constants of diamond, Si, and Ge is clarified in terms of linear combination of the states at the top of valence bands and the bottom of conduction bands. The ballistic conductance from a probe to the surfaces is calculated using the Landauer formalism. The surface-state conductance is much larger than the bulk-state one, which is due to small band dispersions of the dangling-bond states.