First-principles Study Of (Ni,Co) Single-doped And Al-n Co-doped ZnO

Zinc oxide (ZnO), as a new direct and wide band gap semiconductor materials, owingto its wide band gap of3.37eV, high exciton binding energy of60meV and better stabilityat room temperature, non-toxic, lower cost, higher radio-resistance, goodelectromechanical coupling Property and better stability etc. it has been concerned atworldwide in the field of optoelectronic material.The electronic structure and the optical properties of wurtzite ZnO doped with Ni andCo in a various doping concentration using the first-principles. The calculated results showthat the impurity band and conduction band of wurtzite ZnO are degeneration by Ni dopedin, the conduction band and valence band undergo a greater shift toward the low-energyregion at the same time, the band gap is narrowed, this is because the conduction bandundergoes a greater shift toward the low-energy region than the valence band, this leads tothe red-shift of absorption edge, and the heavier the doping concentration is, the narrowerthe band gap and the more significant red-shift will be; For Co doped wurtzite ZnO, wediscover that formation energy increases and the doping becomes more difficult with theincrease of doping concentration. Meanwhile, the equivalent total energy increases and thedoping model becomes less stable with increasing doping concentration. The impurityband and conduction band of wurtzite ZnO are degeneration by Co doped in, the change ofconduction band and valence band is not obviously, so the band gap becomes more broad,the optical absorption edge exhibits a blue-shift, and the heavier the doping concentrationis, the broader the band gap and more significant the blue-shift will be.In this paper, the electronic structure and optical properties of Al and N co-dopedwurtzite ZnO was investigated with various doping concentration ratio by usingfirst-principles. The calculated results showed that the lattice parameters have not beenobviously changed by Al-N co-doped in wurtzite ZnO, the total energy of all modelsincrease with the increase doping concentration of N, that is to say, the system becomesless stable with the increase doping concentration of N, based on the analysis of formationenergy, we can know that the formation energy increases with the increase of N dopingconcentration, this indicates the doping becomes more difficult. Meanwhile, Hole concentration increases with the increase doping concentration of N in Al-N co-doped ZnOsystem, this is good for the P-type doping, and when the doping ratio of Al and N is1：4,the hole concentration is the highest.Moreover, we investigated the absorption spectrum of Al-N co-doped wurtzite ZnO,combining with band structure and absorption spectrum chart we know that, in allcalculated models, when the doping concentration ratio ofAl and N is1：4, the band gap isthe broadest of3.62eV, compared with3.37eV of pure ZnO, the band gap is broaden for0.25eV, the blue-shift of absorption spectrum is the most significant one, this is good forthe preparation of short wavelength optical device, and it will provide a certain theoryguidance for the design and preparation of new type optical devices.