DFT calculation of the electronic and optical properties of a 2D GaAs monolayer with amphoteric impurities (Si, Ge, and Sn)

Two-dimensional materials have emerged as highly relevant elements in contemporary research due to their remarkable electronic, optical, and chemical properties. Prominent examples include graphene, silicene, phosphorene, borophene, among others. Additionally, two-dimensional gallium arsenide has been studied in this context, investigated both in heterostructures and monolayers, with potential applications in fields such as electronics, optics (including nonlinear phenomena), photocatalysis, and gas adsorption, among others. In line with this research trend, this work presents results on the band structure, density of states (DOS), and optical responses of a monolayer of 2D gallium arsenide, both in its pristine state and with amphoteric substitutional impurities, such as silicon (Si), germanium (Ge), and tin (Sn), considering spin polarization as well. The analysis clearly reveals the effect of impurities on energy bands, where levels close to the conduction (or valence) band are observed, depending on the type of impurity ($n$-type or $p$-type). In the density of states (DOS), the impact of impurities in relation to spin polarization is evident, showing the emergence of two asymmetric states for $n$-type near the Fermi level (one for spin up and another for spin down), while for $p$-type only one is observed (for spin down). Likewise, absorption coefficient and reflectance in the visible region of the electromagnetic spectrum are analyzed, revealing impurity-induced changes. These findings provide crucial information on properties relevant for future applications and further studies.