Direct to indirect band gap transition in two-dimensional germanium carbide through Si substitution

Abstract

In this work, the structural, electronic and optical properties of Si substituted single-layer GeC are studied by performing density functional theory calculations. Single-layer GeC possesses a direct band gap of 2.11 eV at the K point. The direct band gap feature in single-layer GeC does not change by incorporation of one or two Si atom in a (2 × 2) GeC supercell, while a direct band gap (K–K) into indirect band gap (K–Γ) transition is observed by incorporation of three Si atom in the supercell. After substitution of three Si atom in (2 × 2) GeC supercell, for parallel polarized light, the first absorption peak at 3.09 eV slightly shifted to higher energy of 3.22 eV along with an increase in peak intensity. For (E‖z), the first two peaks show small shifts to higher energies by about 0.3 eV. These results are useful for application of two-dimensional GeC in nanoelectronic and optoelectronic devices.