Influence of ZnO Doping Concentration on the Band Structure and Photocatalytic Performance of GaN/ZnO Solid Solutions

This study investigates the effect of different ZnO doping concentrations on the band structure of GaN/ZnO solid solution. By calculating the band structures of 350 GaN/ZnO solid solution structures and analyzing the corresponding band gap sizes, it was found that the band gap first rapidly decreases and then stabilizes at around 0.05 eV with increasing ZnO content. When the ZnO content is high, the band gap slightly increases to 0.2 eV. The decrease in band gap is attributed to the increase in Zn-N bonds. The study also reveals that the ZnO content in GaN/ZnO solid solution can be continuously increased to achieve continuous band gap tuning.

The study further analyzes the band structures and density of states of GaN and ZnO intrinsic semiconductors and selects three representative structures for analysis. The results show that the repulsion between the N 2p and Zn 3d orbitals causes the valence band position to rise, leading to a decrease in band gap width. The study also finds that the higher ZnO concentration in GaN/ZnO solid solution results in a larger effective mass, limiting the diffusion of photo-generated carriers and reducing the carrier mobility.

Moreover, the study calculates the optical absorption properties of GaN/ZnO solid solution with ZnO doping concentrations up to 25% and finds that the increase in ZnO content significantly enhances visible light response, resulting in an absorption peak in the visible light region and a redshift in the absorption peak. This phenomenon is attributed to the introduction of a mid-gap state by ZnO doping, which reduces the band gap and increases the utilization efficiency of GaN/ZnO solid solution for visible light.

Based on these results and theoretical analysis, it can be concluded that GaN/ZnO solid solution catalysts can effectively improve the efficiency and performance of visible light-driven photocatalytic water splitting.