Consideration on the possibility of band gap widening of BaSi2 by incorporation of alkali metal elements (Na, K, and Cs) using electronic energy and structure calculation

The electronic energies of (1), Na-, K-, or Cs- substituted BaSi2 lattice, (2), Ba- substituted CsSi and KSi lattice, and (3), Na2BaSi4, have been calculated using a first-principle pseudopotential method to clarify the possibility of band gap widening of BaSi2 by alloying with alkali metals. Ba–Si, Na2BaSi4 will be formed, which is an intrinsic semiconductor. In K–Ba–Si and Cs–Ba–Si, solid solution with the KSi (CsCi) structure will be formed by a substitution of K(2) (Cs(2))sites by Ba. It will be an n-type semiconductor when doping concentration is well-controlled. Solid solution with the BaSi2 structure may also be formed by a substitution of Ba(1) sites by K (Cs), which is predicted to be p-type semiconductors. However, solubility will be small. Their band gaps will be wider than that of BaSi2 but narrower than that of NaSi, KSi, and CsSi, respectively.