论文标题
高运动二维电子气体中的$γ$ -AL $ _2 $ o $ $ _3 $/srtio $ _3 $杂质结构
High-mobility two-dimensional electron gas in $γ$-Al$_2$O$_3$/SrTiO$_3$ heterostructures
论文作者
论文摘要
二维电子气体（2DEG）的起源在$γ$ -AL $ _2 $ o $ _3 $（GAO）和SRTIO $ _3 $（sto）（gao/sto）之间，以及2DEG高移动性的原因仍在辩论中。在本文中，根据密度功能理论，通过第一原则计算研究了[001]面向的GAO/Sto异质结构的电子结构。计算结果表明，2DEG形成的必要条件是GAO/Sto异质结构具有由Al和Tio $ _2 $层组成的接口。对于GAO侧没有氧气空位的异质结构，2DEG起源于界面附近的极性不连续性，而GAO膜的厚度为临界厚度，在下面，2DEG不存在，并且异质结构具有绝缘体特性。对于只有GAO膜包含氧空位的情况，界面附近的极性不连续性消失了，但2DEG仍然存在。在这种情况下，也不存在GAO膜的临界厚度。当Gao膜和Sto底物都包含氧空位时，只要Sto侧的氧空位不太接近界面，2DEG就会保留长时间。这些GAO/Sto异质结构中2DEG的低温迁移率被视为由电离杂质散射支配，$ \ sim $ 3至$ \ sim $ \ sim $ \ sim $ 11 $ 11倍于Laalo $ _3 $/srtio $ _3 $ _3 $ heterojunction。 2DEG的高迁移率主要是由于GAO/Sto异质结构中的小电子有效质量。
The origin of the two-dimensional electron gas (2DEG) in the interface between $γ$-Al$_2$O$_3$ (GAO) and SrTiO$_3$ (STO) (GAO/STO) as well as the reason for the high mobility of the 2DEG is still in debate. In this paper, the electronic structures of [001]-oriented GAO/STO heterostructures with and without oxygen vacancies are investigated by first-principle calculations based on the density functional theory. The calculation results show that the necessary condition for the formation of 2DEG is that the GAO/STO heterostructure has the interface composed of Al and TiO$_2$ layers. For the heterostructure without oxygen vacancy on the GAO side, the 2DEG originates from the polar discontinuity near the interface, and there is a critical thickness for the GAO film, below which the 2DEG would not present and the heterostructure exhibits insulator characteristics. For the case that only the GAO film contains oxygen vacancies, the polar discontinuity near the interface disappears, but the 2DEG still exists. In this situation, the critical thickness of the GAO film for 2DEG formation does not exist either. When the GAO film and STO substrate both contain oxygen vacancies, it is found that the 2DEG retains as long as the oxygen vacancies on the STO side are not very close to the interface. The low-temperature mobilities of the 2DEGs in these GAO/STO heterostructures are considered to be governed by the ionized impurity scattering, and $\sim$3 to $\sim$11 times as large as that in LaAlO$_3$/SrTiO$_3$ heterojunction. The high mobility of the 2DEG is mainly due to the small electron effective mass in GAO/STO heterostructure.
