First-principles and experimental studies of impurity doping into Mg2Si

The formation energy, structural relaxation, and Mulliken charge of impurities in Mg2Si are systematically investigated using first-principles calculations based on the density functional theory. Among the elements in groups Ib, IIIb, and Vb, As, P, Sb, Bi, Al, and N are suggested as n-type dopants, whereas Ga is suggested as a p-type dopant. For In, Ag, Cu, and Au, the conduction type depends on the atomic chemical potentials of Mg and Si. The formation energies of As, P, Sb, and Bi in the Si-site substitution are negative at Mg- and/or Si-rich limits, suggesting that these impurities have good solubility. The transport properties of impurity-doped Mg2Si, fabricated by spark plasma sintering, have been characterized by Hall effect measurements at 300 K. The carrier type of impurity-doped Mg2Si is influenced by the types of dopants and the substitution site.