We explored the electronic properties of 2D gallium nitride (GaN) monolayer doped with group III-VI elements, such as boron (B), carbon (C), phosphorous (P) and oxygen (O), using a first-principles based density-functional theory approach. In the analyses, we consider that the doping atoms are substituted at Ga or N positions. Our results explains that electronic properties of 2D GaN are modified upon doping with the aforementioned elements. We found that 2D GaN retains semiconducting properties when a Ga or N atom is replaced with an equivalent-valence atom (B or P). On the other hand, 2D GaN displays spin-polarized behavior with a finite magnetic moment when an O (C) atom is substituted at the Ga (N) site. Conversely, the doped GaN exhibits n-type semiconducting behavior when Ga (N) is replaced with a C (O) atom. Moreover, the doped GaN shows direct band gap behavior based on the dopant type …