Electronic structures of semiconducting alkaline-earth metal silicides

Electronic structures and densities of states of the following alkaline-earth metal (AEM) silicides have been calculated using the first-principle pseudopotential method, Mg2Si, BaSi2, Ca2Si, and Sr2Si. Mg2Si and BaSi2 were predicted to be indirect semiconductors while Ca2Si and Sr2Si were direct semiconductors. Estimated band gaps are about 50% or less of the observed values. The valence bands of these are composed of Si 3s, 3p as well as of Mg 3s, 3p, Ca 4s, 4p, 3d, Sr 5s, 5p, 4d or Ba 6s, 6p, 5d. The conduction bands are mainly composed of AEM. s, p, d states and the contributions of Si 3s, 3p are relatively small. Formation energy of stoichiometric Mg2Si was rather successfully predicted. Energetics of the non-stoichiometry and the atomic site of dopants for Mg2Si are also discussed. (C) 2003 Elsevier B.V. All rights reserved.