In this work, the electronic structure and optical spectra of bilayer GeC and the effects of vertical electric field on its band structure and dielectric response are investigated through ab initio calculation. The electronic structure calculations reveal that bilayer GeC exhibits a direct band gap of 1.55 eV at the K point and the band gap width of bilayer GeC is smaller than that of monolayer GeC. A monotonically reduction of the GeC band gap from 1.55 eV to 0.95 eV has been observed by increasing the electric field from 0 to 1 eV. For parallel polarized light, only the low energy region (E < 3eV) of optical spectrum is influenced by application of vertical electric field. For perpendicular polarized light, the peaks are blue shifted upon application of vertical electric field. The value of static dielectric constant for (E‖x) and (E‖z) increases by increasing the electric field. These results are useful for application of two-dimensional GeC in nanoelectronic and optoelectronic devices.
