The first-principles study on the electronic and optical properties of (Ga$_{\mathrm{1-x}}$Zn$_{\mathrm{x}})$(N$_{\mathrm{1-x}}$O$_{\mathrm{x}})$ from many-body perturbation theory

Gallium zinc oxynitride (Ga$_{\mathrm{1-x}}$Zn$_{\mathrm{x}})$(N$_{\mathrm{1-x}}$O$_{\mathrm{x}})$ is one of the promising candidates as overall water-splitting photocatalyst under visible light. In 2005, the high photocatalytic activity was reported on the GaN-rich alloys$^{\mathrm{[1]}}$ and nowadays, the ZnO-rich ones with the higher visible-light absorption were also synthesized by some groups$^{\mathrm{[2,\thinspace 3]}}$. Thus the further improvement of the photocatalytic water splitting is being expected. In spite of such a huge potential of this material, the origin of the visible-light absorption is not well understood. The first-principles methods based on many-body perturbation theory (MBPT), GW approximation and Bethe-Salpether equation, combining with density functional theory, enable us to do reliable analysis of the electronic and optical properties. On this meeting, we will discuss the origin of visible-light absorption of (Ga$_{\mathrm{1-x}}$Zn$_{\mathrm{x}})$(N$_{\mathrm{1-x}}$O$_{\mathrm{x}})$ by MBPT results focusing on the non-isovalent character. [1]K. Maeda. et al. \textit{J.Am.Chem.Soc}. 127, 8286 (2005), [2]H. Chen. et al. \textit{J.Phys.Chem.C}, 114, 1809 (2010), [3]K. Lee. et al. \textit{Nano Lett}, 12, 3268 (2012)