First principles analysis of atomic configurations of group IV elements in Ge crystal for solar cells

Abstract

AbstractWe focused on group IV semiconductors, i.e., Ge (Si), containing C, Si (C, Ge), and/or Sn atoms as alternative candidates for poly‐Si crystals to achieve higher engineering efficiency in solar cells in this research. The main target of this study was to obtain basic data on atomic configurations, such as bond strain and stable sites for substituted C, Si, and Sn atoms in Ge and for C, Ge, and Sn atoms in Si crystals through first principles analysis. We found that ((C, Si)/C) atoms with smaller covalent radii than (Ge/Si) formed tensile local strain along zigzag bonds in the <110> direction while (Sn/(Ge, Sn)) atoms with larger covalent radii than (Ge/Si) formed compressive local strain. Another important result was that local strains except for zigzag bonds had opposite signs to strains along zigzag bonds. The main results to summarize stable configurations of substitutional IV elements were: (1) C and Sn (Si) atoms were stable at positions next to one another, while Si and Sn atoms were stable at mostly separated positions in Ge crystals. (2) C (Ge) and Sn atoms were stable at positions next to one another, while C and Ge atoms were stable at mostly separated positions in Si crystals. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)