Density Functional Theory Study of Electronic Structure of Ga-P Co-Doped Ba8Cu6Ge40 Clathrate

The effect of Ga−P co-doping on the electronic structure has been investigated for p-type clathrate thermoelectric semiconductor Ba8Cu6Ge40 by density functional theory (DFT) to study the possibility of carrier control. In Ba8Cu6Ge40, the Fermi energy EF lies in the valence band, and Ba8Cu6Ge40 is a p-type degenerate semiconductor. For Ga−P, Ga2−P, and Ga3−P co-doping, the EF lies in the conduction band, the energy gap, and the valence band, respectively, indicating that the p/n carrier type and carrier concentration change with the Ga/P ratio. In comparison with Ba8Cu6Ge40, the effect of Ga−P co-doping on the energy dispersion relation at the valence band edge is greater than that at the conduction band edge. Therefore, the effect on the effective mass is greater in the valence band than in the conduction band.