The choice of electrostatic gating over the conventional chemical doping for phase engineering of quantum materials is attributed to the fact that the former can reversibly tune the carrier density without affecting the system’s level of disorder. However, this proposition seems to break down in field-effect transistors involving ${\mathrm{Sr}\mathrm{Ti}\mathrm{O}}_3$ (STO)-based two-dimensional electron gases. Such peculiar behavior is associated with electron trapping under an external electric field. However, the microscopic nature of the trapping centers remains an open question. In this paper, we investigate electric-field-induced charge-trapping and charge-detrapping phenomena at the conducting interface between the band insulators $\gamma$-${\mathrm{Al}}_2{\mathrm{O}}_3$ and STO. Our transport measurements reveal that the charge trapping under a positive back-gate voltage ($V_g$) above the tetragonal-to-cubic structural transition temperature ($T_c$) of STO has a contribution from electric-field-assisted thermal escape of electrons from the quantum well, and from clustering of oxygen vacancies as well. We observe an additional source of trapping below $T_c$, which arises from the trapping of free carriers at ferroelastic twin walls in the STO. Application of a negative $V_g$ results in charge detrapping, which vanishes above $T_c$. This feature demonstrates the crucial role of structural domain walls in the electrical transport properties of STO-based heterostructures. The number of charges trapped (detrapped) at (from) a twin wall is controlled by the net polarity of the wall and is completely reversible with a sweep of $V_g$.

中文翻译：

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氧化物二维电子气中的电子陷阱和俘获：铁弹性双壁的作用

在量子材料的相工程中，与传统的化学掺杂相比，静电门控的选择归因于这样的事实，即前者可以可逆地调节载流子密度，而不会影响系统的无序水平。然而，这一主张似乎在涉及以下领域的场效应晶体管中被打破了：${r钛\mathrm{Ø}}_3$（STO）的二维电子气。这种特殊的行为与外部电场下的电子俘获有关。但是，捕集中心的微观性质仍然是一个悬而未决的问题。在本文中，我们研究了电场在带绝缘子之间的导电界面处的电荷俘获和电荷俘获现象$\gamma$--${铝}_{\mathrm{2个}}{\mathrm{Ø}}_3$和申通快递。我们的传输测量结果显示，电荷在正背栅电压下陷获（${\mathrm{伏特}}_G$）高于四方到立方的结构转变温度（${Ť}_C$STO的作用来自电场辅助电子从量子阱的热逸散以及氧空位的聚集。我们在下面观察到了另一个诱捕源${Ť}_C$，这是由于自由载流子被困在STO的铁弹性双壁中。负片的应用${\mathrm{伏特}}_G$ 导致电荷陷获，在上方消失 ${Ť}_C$。此功能演示了结构畴壁在基于STO的异质结构的电输运特性中的关键作用。从（从）双壁捕获（释放）的电荷数由壁的净极性控制，并且通过扫描可完全逆转${\mathrm{伏特}}_G$。