Electronic and Optical Properties of BeO Co-doped 2D GaN using First-principles

For bandgap engineering and tuning optical properties, co-doping is a decade-long-old, well-established, and lucrative concept. In this study, to tune the intrinsic electronic and optical properties of two dimensional (2D) GaN, we have adopted BeO co-doping utilizing first-principles density functional theory (DFT). Two different ways of substitution are considered for BeO co-doping in 2D GaN. Forward co-doping (Ga and N is substituted by Be and O, respectively) and reverse co-doping (Ga (N) is supplanted by O (Be) atom), both show negative formation energy, referring to the exothermic practicability of the substitution. Moreover, forward co-doping successfully transits the bandgap of 2D GaN from indirect to direct, while reverse co-doping retains the indirect bandgap of 2D GaN with a lowering of bandgap by ~1.3 times. Optical properties namely, dielectric function, reflectivity, and absorption coefficient are calculated and they show unique improvement in the properties of co-doped structures from their intrinsic origin. In both co-doping, the absorption coefficient in the visible spectrum increases, and the increment is $\sim$1.2 times. Also, the reflectivity in both cases significantly reduces. These promising outcomes unleash that the BeO co-dopant can be an efficient tool for engineering the bandgap of 2D GaN and improving the optical properties so that the material can be used in advanced photovoltaics and optoelectronics.