Electronic and optical properties of body-centered tetragonal Si and Ge

ORAL

Abstract

We present a first-principles calculation of the quasiparticle and optical excitation spectra of recently predicted silicon and germanium polytypes in the bct structure. The quasiparticle spectra, calculated within the GW approximation, predicts that both silicon and germanium in the bct structure are small band gap materials with direct gaps of 1.1 eV and 0.79 eV, respectively. The optical spectra is evaluated by solving the Bethe-Salpeter equation taking into account electron-hole interactions. We then make comparison to the cubic phases of Si and Ge which suggest the possible utility of the bct phases in photovoltaic applications.

*This work was supported by National Science Foundation Grant No. DMR07-05941, the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Computational resources have been provided by NSF through Teragrid resources at NICS.

–

Authors

  • Brad D. Malone

    • Department of Physics, University of California, Berkeley, and Materials Science Division, Lawrence Berkeley National Laboratory

  • Steven G. Louie

    • UC Berkeley and Lawrence Berkeley National Laboratory
    • Department of Physics, University of California, Berkeley. Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California
    • University of California at Berkeley and Lawrence Berkeley National Lab
    • University of California at Berkeley and Lawrence Berkeley National Laboratory
    • University of California, Berkeley and Lawrence Berkeley National Laboratory
    • UC Berkeley
    • Department of Physics, University of California, Berkeley and Materials Sciences Division, Lawrence Berkeley National Laboratory
    • UC Berkeley and Lawrence Berkeley National Lab
    • UC Berkeley and LBNL
    • Department of Physics, University of California, Berkeley, and Materials Science Division, Lawrence Berkeley National Laboratory
    • Dept. of Physics, University of California Berkeley and The Molecular Foundry, LBNL
    • Department of Physics, University of California at Berkeley and Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720

  • Marvin L. Cohen

    • UC Berkeley and Lawrence Berkeley National Laboratory
    • Department of Physics, University of California, Berkeley. Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California
    • UC Berkeley
    • Department of Physics, University of California, Berkeley and Materials Sciences Division, Lawrence Berkeley National Laboratory
    • Department of Physics, University of California, Berkeley; Material Science Division, Lawrence Berkeley National Laboratory
    • Deptartment of Physics, University of California, Berkeley; Materials Science Division, Lawrence Berkeley National Laboratory
    • Department of Physics, University of California, Berkeley, and Materials Science Division, Lawrence Berkeley National Laboratory
    • Department of Physics, University of California at Berkeley and Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720