Effect of p-type doping on the electronic characteristics of negative electron affinity Al0.5Ga0.5N nanowire photocathodes

Abstract

Based on the first principles calculation method, we explored the impacts of p-type doping on the electronic characteristics of Al0.5Ga0.5N nanowire. Firstly, Al0.5Ga0.5N nanowires are simulated with different doping elements (Be, Mg and Zn), as well as different doping strategies (interstitial doping and substitutional doping). The estimated formation energies show that the p-type doping of Al0.5Ga0.5N nanowire is an endothermic process. Also, in the substitutional doping process, it is easier for dopant atoms to replace Ga atoms than Al atoms. The substitutional doping of Mg atom drops the nanowire electron affinity obviously, which promotes the transition of surface photoelectrons. Furthermore, it can be concluded that the substitutional doping contributes to the Fermi level cross the valence band and causing the nanowires to exhibit distinct p-type properties. Also, the charge density maps show that for Be and Mg substitutional doping system, the electron density around the dopant significantly decreases, which further verifies the p-type conductivity. Meanwhile, the p-type characteristic of Mg atom substitution doping is the most obvious. This work not only thoroughly explored the impacts of different doping schemes on the electronic characteristics of Al0.5Ga0.5N nanowires but also serves as a significant resource for developing high-quality p-type AlxGa1-xN nanowire photocathodes.

Keywords

• Al0.5Ga0.5N nanowire
• p-type doping
• Interstitial doping
• Substitutional doping