Cd:O共掺杂AlN的电子结构和p型特性研究

Study of the electronic structure and the properties of p-type doping in Cd:O codoped AlN

为研究Cd:O共掺杂纤锌矿AlN的p型特性,进而揭示导致纤锌矿AlN空穴浓度增加的机理,对Cd:O共掺杂AlN进行了基于密度泛函理论的第一性原理研究.通过计算Cdn-O(n=1,2,3,4)复合体掺杂AlN的结合能,发现Cd:O在AlN中可以稳定存在,共掺杂提高了Cd在AlN中的固溶度.分析Cd和Cd2-O掺杂AlN体系的激活能,发现Cd2-O的激活能比Cd减小0.21eV,表明Cd2-O的空穴浓度比单掺Cd大约提高了103倍.对比各掺杂体系的能带及态密度,发现Cd-4d和N-2p态由轨道杂化在费米能级附近形成的杂质能级始终位于价带顶,空穴态随着Cdn-O复合体中Cd数目的增加占据了更多的能态密度.研究表明共掺体系中,适当控制Cd和O的浓度,可以减小Cd和O的复合概率,加强Cd-N的共价特性,对改善AlN的p型特性有重要意义.

In order to investigate the properties of the p-type doping and reveal the mechanism of the hole concentration increasing after Cd：O codoping of wurtizite AlN,we have carried out first-principles calculations based on density-functional theory （DFT） for wurtizite AlN system. By calculating the binding energy of the Cdn-O（n = 1,2,3,4）complex codoped AlN we found that Cd：O can be stabilized and the solubility of Cd can be increased in the system. We analysed the activation energies of the Cd and Cd2-O doped AlN and found that the activation energy of Cd2-O was decreased by 0. 21 eV from that of Cd,which showed that the hole concentration of Cd2-O doped system was raised 103 times as that of Cd. We compared the band structures and densities of states,and found that the electrons of Cd atom on the 4d orbit moving to 2p orbit of N atom results in that the impurity levels which appeared near the Fermi level always occupy the highest valence band. Increasing the number of Cd atoms,the holes can occupy more states. In order to reduce the combining probability of Cd and O,hence,to enhance the Cd-N covalent characteristics and improve the hole concentration,it is important to control properly the concentrations of Cd and O.