Absorption of visible light by GaAs and GaN nanosheets

The electronic and optical properties of GaAs and GaN nanosheet (2D monolayer) are calculated by using the Full Potential Linearized Augmented Plane Wave (FP-LAPW) method with the Generalized Gradient Approximation (GGA) within wien2k package. The dielectric tensor is derived within the random phase approximation (RPA). We compared the electronic structure and the optical properties between GaAs and GaN nanosheet such as the dielectric function, reflectivity, absorption coefficient and optical conductivity which are calculated for both perpendicular and parallel electric field polarizations. We show that GaN nanosheet has an indirect band gap but GaAs nanosheet has a direct band gap. The reflectivity of GaN nanosheet is lower than that of GaAs nanosheet. Finally, we show that the absorption coefficient of GaAs nanosheet is higher than that of GaN nanosheet.