Effect of Co doping of (Ga, In) and 2N preferred orientation on the magnetic and optical properties of ZnO

Abstract

Current research on the Zn1−xMxO1−yNy (M = Ga, In) system mainly focuses on the p-type property, where Ga–N or In–N has different preferred orientations for bonding. Studies on the magnetic, bandgap, and optical properties of ZnO co doped with N are also lacking. The generalized gradient approximation (GGA+U) plane wave ultrasoft pseudopotential method based on density functional theory is used to systematically investigate the effects of the magnetic, band gap, and optical properties of the system for addressing the aforementioned problems. Results show that the formation energy of the Zn1−xMxO1−yNy (M = Ga, In) system is negative, all doping is easy, and all doped systems are stable and magnetic. The magnetism comes from the double exchange effect of electron spin polarization. Research has found that the band gap in Ga–N or In–N bonding along the c-axis direction is narrower than that along the a-axis direction. In the low-energy region, the redshift of the absorption spectrum is more significant, and the absorption or reflection coefficient and the carrier polarization and activity are stronger. In particular, In–N forms bonds along the c-axis direction and is co doped with another N in ZnO, which results in the narrowest band gap and the most significant redshift in the absorption spectrum. The absorption of sunlight can also be achieved in the ultraviolet visible near-infrared region. The absorption or reflection coefficient and the carrier polarization and activity are relatively strongest. This work has certain reference value for the design and preparation of new solar cell light absorbing materials based on ZnO.