Distribution and self-assisted diffusion of Be and Mg impurities in ZnO

Abstract

The band gap width of the Be-doped ZnO correlates strongly with the distribution of the dopants. By performing first-principles calculations, it is found that an interstitial Be (Be_i) atom preferably migrates in a basal plane. During the migration, such a Be_i atom favorably bonds to a substituted Be (Be_Zn) atom, forming a new defect complex (2Be)_Zn, showing a trend of aggregation of Be atoms in ZnO. Furthermore, the stability of the defect complex (2Be)_Zn can be weakened by a substituted Mg (Mg_Zn). So, the Mg impurities in Be-doped ZnO might suppress the aggregation of Be, so as to significantly improve the effect of the doped Be on modulating the band gap of ZnO.