Equilibrium Bandstructure of a Phosphorus δ-doped Layer in Silicon using a Tight-binding Approach

Emerging STM technology opens the possibility of creating ultra-high doped silicon devices. For the theoretical analysis of Si:P QW devices, an atomistic tight-binding approach with self-consistent potential calculation is used. Fermi-level, 1Γ, 2Γ and 1∆ bands are of the same order with previous studies. Impurity bands can be simply explained by the band projection of silicon bulk bandstructure. The potential profile, in comparison with the single impurity potential, indicates that ionized donors are not only coupled to each other but also the impurity ions are screened by the electron charge. To demonstrate the advantage of atomistic simulation, the equilibrium bandstructures of δlayers with different doping density and dopant configuration are computed. Increased number of dopants causes down-shift of valleys and the disordered configuration of donor atoms breaks the symmetry of 2D bands. This approach allows us to study more realistically extended and disordered devices in the future.