Aluminum and nitrogen impurities in Wurtzite ZnO: first-principles studies

First-principles calculations have been performed to investigate the doping behaviors of Al and N dopant impurities in ZnO. According to the results, in the Al mono-doping case, the impurity states are quite delocalized, the corresponding effective masses are small, and the formation energy is as low as −9.71 eV. In the N mono-doping case, the impurity states are localized, the effective masses are large, and the formation energy is high (4.55 eV in the most favorable extreme O-rich conditions). In the Al-N codoping case, the corresponding effective masses are marked decreased compared to the N mono-doping situations, and the formation energy of the N-Al-N system is as low as −2.54 eV in the O-rich condition. The above results can explain the electrical behaviors of the doped or codoped ZnO systems observed in experiments.