Band anticrossing in highly mismatched SnxGe1-x semiconducting alloys

We show that at dilute Sn concentrations (x < 10%), the composition dependence of the direct band gap and spin-orbit splitting energies of Sn(x)Ge(1-x) can be described by a valence band anticrossing model. Hybridization of the extended and localized p-like states of the Ge host matrix and the Sn minority atoms, respectively, leads to a restructuring of the valence band into E(+) and E(-) subbands. The notably large reduction in the band gap follows from an upward shift in the valence band edge by approximately 22 meV per x=0.01. These results demonstrate that like III-V and II-VI compound semiconductors, group IV elements may form highly mismatched alloys in which the band anticrossing phenomenon is responsible for their unique properties.