Theory of metastable group-IV alloys formed from CVD precursors

Using chemical-vapor deposition (CVD) precursors, group-IV compounds such as Si₄C and Ge₄C, which incorporate 20 at. % carbon, have been synthesized. Here we present systematic ab initio studies of the electronic and structural properties of group-IV compounds formed from CVD precursors. We also propose a class of precursor molecules for materials containing 25 at. % carbon. These compounds are energetically comparable to already synthesized materials (e.g., Ge₄C) and are semimetallic within the local-density approximation. In addition, we give information for two previously proposed group-IV compounds, Si₂Sn₂C and Ge₃SnC, which are direct-gap semiconductors and match the lattice of silicon to within 1%.