Ag-N共掺p型ZnO的第一性原理研究

First-principles study of Ag-N dual-doped p-type ZnO

采用基于密度泛函理论的第一性原理赝势法对Ag-N共掺杂ZnO体系以及间隙N和间隙H掺杂p型ZnO:(Ag,N)体系的缺陷形成能和离化能进行了研究.结果表明,在AgZn和NO所形成的众多受主复合体中,AgZn-NO受主对不仅具有较低的缺陷形成能同时其离化能也相对较小,因此,AgZn-NO受主对的形成是Ag-N共掺ZnO体系实现p型导电的主要原因.研究发现,当ZnO:(Ag,N)体系有额外间隙N原子存在时,AgZn-NO受主对容易与Ni形成AgZn-(N2)O施主型缺陷,该施主缺陷的形成降低了Ag-N共掺ZnO的掺杂效率因而不利于p型导电.当间隙H引入到ZnO:(Ag,N)体系时,Hi易与AgZn-NO受主对形成受主-施主-受主复合结构(AgZn-Hi-NO),此复合体的形成不仅提高了AgZn-NO受主对在ZnO中的固溶度,同时还能使其受主能级变得更浅而有利于p型导电.因此,H辅助Ag-N共掺ZnO可能是一种有效的p型掺杂手段.

The formation energies and ionization energies of Ag-N dual-doped ZnO and interstitial N and H monodoped ZnO：（Ag,N） are investigated from the firstprinciples pseudo-potential approach based on density functional theory. It is found that Agzn-No accepter pair has lower formation energy and ionization energy than Ag-N related to acceptor clusters, which demonstrates that the p-type conductivity of Ag-N dual-doped ZnO system is mainly attributed to the formation of the accepter pairs. Moreover, when ZnO：（Ag,N） system has additional N atoms in some interstitial sites of ZnO crystal, interstitial N atom and Agzn-No accepter pair prefer to bind together to form Agzn＇（N2）o donor complex which lowers doping efficiency, which is not conducive to p-type conductivity. For H doping in the ZnO：（Ag,N） system, the interstitial H atoms also prefer to bind to the Agzn-No accepter pair, forming acceptor-donoracceptor （Agzn-Hi-No） triplet, which not only enhances the incorporation of acceptors （Agzn-No） but also gives rise to a shallower acceptor level in the band gap in p-type ZnO crystal. Thus, it is suggested that H-assisted Ag-N codoping is an effective method of p-type doping in ZnO.