Band structures for Ge3N4 polymorphs studied by DFT-LDA and GWA

► GW band gap energy for α-Ge3N4 and γ-Ge3N4 are provided as a theoretical reference for future experimental work. ► γ-Ge3N4 can be a very promising short wavelength optoelectronic wide band gap semiconductor. ► DFT-LDA band gaps for Ge3N4 polymorphs as a function of lattice parameters are presented. ► γ-Ge3N4 can absorb light with longer wavelength comparing to β-Ge3N4.