空位对纤锌矿型AlN自发极化影响的最大局域化Wannier函数方法研究  

Influence of vacancy on spontaneous polarization of wurtzite AlN: a maximally localized Wannier function study

作　　者：牛海波[1,2] 陈光德[1] 伍叶龙[1] 耶红刚[1] 

机构地区：[1]西安交通大学应用物理系,西安710049 [2]西安交通大学城市学院物理教学中心,西安710018

出　　处：《物理学报》2014年第16期375-383,共9页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:61176079);陕西省教育厅自然科学基金(批准号:2013JK0621)资助的课题~~

摘　　要：采用基于密度泛函理论的第一性原理平面波超软赝势方法,计算了纤锌矿型AlN中引入不同电荷态的N空位和Al空位时结构中最大局域化Wannier函数,并根据Wannier函数的空间分布及空间分布的几何中心位置,对空位引起的晶体电子结构变化及[0001],[ˉ1010],[ˉ12ˉ10]晶向上的自发极化进行了研究.结果表明,利用最大局域化Wannier函数分析电子结构具有直观的特点,清晰地表明N—Al键具有较强的离子性.研究发现,N空位结构中悬挂键上电荷向空位处转移,而Al空位结构中悬挂键上电荷则远离空位,沿悬挂键方向移动到N原子一侧.同时发现,空位的引入破坏了[ˉ1010],[ˉ12ˉ10]晶向上的中心对称结构,产生了极化,且极化强度随着空位电荷态的增加而增大.在[0001]晶向上,随着N空位电荷态的增加,空位周围电子结构发生了剧烈变化,使得自发极化发生了逆转,极化强度随着电荷态的增加而增大;而在Al空位中,随着电荷态的增加,自发极化沿原方向显著增加,但没有发生极化反转.By using first-principles plane-wave ultrasoft pseudopotential method based on the density functional theory, the maximally localized Wannier functions of N vacancy and Al vacancy with different charge states in wurtzite AlN are calculated. With the shape and center of the computed Wannier function, the electronic structure and the spontaneous polarization of vacancy are studied respectively. The results show that N-Al bond possesses a large ionicity. It is found that the electrons of the dangling bonds displace to the positions of vacancies in N vacancy structure, while in Al vacancy structure the electrons of dangling bonds keep away from vacancies and move to the other side of N atoms. Since the vacancy breaks the centrosymmetry of the [ˉ1010] and [ˉ12ˉ10] orientations, the polarization will be induced in these two directions, and the polarization will increase as the charge increases. In the [0001] orientation, the spontaneous polarization in N vacancy will reverse as charge increases because of the dramatic variation of the electronic structure. Contrary to N vacancy, the reversion does not occur although the spontaneous polarization of Al vacancy increases as charge increases.

关 键 词：空位 最大局域化Wannier函数 自发极化 第一性原理 

分 类 号：O471[理学—半导体物理]