Al-N共掺杂ZnO电子结构和光学性质

基于密度泛函理论的第一性原理,分析了Al-N共掺杂ZnO的电子结构和光学性质。计算了Al-N复合体共掺ZnO的结合能,发现Al-N复合体可以在ZnO中稳定存在,因此Al-N共掺可以提高N在ZnO的固溶度。研究表明:N掺杂ZnO体系,由于N-2p和Zn-3d态电子轨道杂化作用,在费米能级附近引入深受主能级,价带顶和导带底发生位移,导致禁带宽带变窄。而Al-N共掺杂体系,适当控制Al和N的比例,克服了N单掺杂时受主间的相互排斥,降低了受主能级,对改善ZnO的p型掺杂有重要意义。在Al-N共掺ZnO中,Al的引入,导致共掺体系的禁带宽度减小,吸收带边红移,实验现象证实了这一结果。

The Electronic Structure and Optical Properties of Al-N Codoped ZnO

The electronic structures and optical properties of pure and Al-N codoped wurtzite ZnO were calculated using first principle ultrasoft pseudopotential approach of the plane wave based upon the density func-ational theory.Codoped theory showed that, in the ZnO doped system,when the concentration of Al and N equal,Al-N complex formed,N may be fully compensated,but the concentration of N is twice or more times as the concentration of Al,may be the formation of Al-N2,Al-N3,Al-N4 complex,these complexes are likely to reduce the ionization energy of a single N atom.To verify the feasibility of this approach,we chosen 32-atom supercell model to calculated the electronic structure and related parameters of the Al-N codoped wurtzite ZnO,and analysised the mechanism of the increasing of the hole concentration in Al-N codoped p-type ZnO.Firstly,we calculated the binding energy of Al-N complex codoped ZnO and found that Al-N complex can exist in ZnO stably, therefore Al-N codoped ZnO can improve the N solubility of doping. Studies showed that,due to the orbital hybrid between N-2p and Zn-3d,the Fermi level is deeply into the valence band, the top of the valence band shift up and the bottom of the conduction band shift down,resulting in the band gap narrowed.While proper control the ratio of Al and N, the exclusion between the acceptor atoms weakened and the acceptor level was lower after the Al-N complex doped ZnO.So Al-N codoping is an important method to improve the characteristic of p-type ZnO.Besides,in the Al-N codoped ZnO system, the decrease of band gap and the absorption bandedge red-shift will happen after Al-N codoping, experimental phenomena also approve the result.