Usingfirst principles many-body theory methods (Green s function and Bethe Salpeter equation formalism) we calculated the electronic structure and optical properties of the GaAs monolayer. We computed that the indirect (direct) band gap of the GaAs Monolayer honeycomb using density functional theory is 0.21 eV (0.97 eV), but it has a value of 2.86 eV (3.48 eV) within the quasiparticle correction. The calculations reveal that the optical absorption is sensitive to excitonic effects such as electron–hole interaction with binding energy of the first exciton of over 2.37 eV within the GWþBethe Salpeter equation calculation. The enhanced excitonic effects in the GaAs Monolayer can be used to describe the optical properties in nano-optoelectronic devices.

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