Effects of Oxygen Vacancy on the Electronic Structure of Cubic LaAlO3

摘要:

采用基于密度泛函理论和广义梯度近似的第一性原理研究了立方相LaAlO3中不同价态氧空位的电子性质。结果表明，氧空位的存在会在立方相LaAlO3的禁带中引入缺陷能级，在氧缺失的条件下，氧空位在立方相LaAlO3中是稳定存在的。随着费米能级位置的改变，具有0价和+2价的氧空位分别为最稳定的电荷状态。LaAlO3中的氧空位具有负U性质，当空位进入到氧化物中时，氧空位会俘获2个空位，达到稳定状态。因此，在LaAlO3高k栅介质中，氧空位为主要俘获电荷的陷阱。

Abstract:

Oxygen vacancies with different charge states in cubic LaAlO3 were investigated using first-principles calculation based on the density functional theory and generalized gradient approximation. In the presence of oxygen vacancy, extra level appears in the energy band gap. From the formation energies, it is found that oxygen vacancy is thermodynamically favorable under O-poor condition. Oxygen vacancies of and are the most stable charge states with the changes of the Fermi level position. Moreover, the oxygen vacancy in LaAlO3 has a negative U behavior and it is energetically favorable for the oxygen vacancy to trap two holes when the holes are injected into the oxide. Therefore, oxygen vacancy is a main source of charge traps in LaAlO3 high-k dielectric.