In this work, structure, electronic and optical parameters of germanium (Ge) atom substituted monatomic graphene are demonstrated through first-principles study (FPS) computations. The concentration of Ge atoms was changed from 2.5 % to 7.5 % and the effects of varying concentration on aforementioned properties were investigated. It is observed that, replacing C atoms with Ge in graphene leads to a finite bandgap opening at the Dirac K-point, thereby producing a direct bandgap semiconducting graphene. We also found that, Ge doping in graphene significantly changes its refractive index parameter. Moreover, Ge atom doping in graphene reduces the overall absorption coefficient, though it observes a considerable red-shift towards the visible region of spectrum. Graphene reflectivity improves in low lying energy region after Ge atom substitution in its lattice. These results can pave a new route for tuning the electronic and optical properties of graphene to make it functional for nanoelectronics and optoelectronic device applications.
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