The discovery of a two-dimensional electron gas (2DEG) at the LaAlO₃/SrTiO₃ interface¹ has resulted in the observation of many properties^2,3,4,5 not present in conventional semiconductor heterostructures, and so become a focal point for device applications^6,7,8. Its counterpart, the two-dimensional hole gas (2DHG), is expected to complement the 2DEG. However, although the 2DEG has been widely observed⁹, the 2DHG has proved elusive. Herein we demonstrate a highly mobile 2DHG in epitaxially grown SrTiO₃/LaAlO₃/SrTiO₃ heterostructures. Using electrical transport measurements and in-line electron holography, we provide direct evidence of a 2DHG that coexists with a 2DEG at complementary heterointerfaces in the same structure. First-principles calculations, coherent Bragg rod analysis and depth-resolved cathodoluminescence spectroscopy consistently support our finding that to eliminate ionic point defects is key to realizing a 2DHG. The coexistence of a 2DEG and a 2DHG in a single oxide heterostructure provides a platform for the exciting physics of confined electron–hole systems and for developing applications.

在 LaAlO ₃ /SrTiO ₃界面¹处二维电子气 (2DEG) 的发现导致观察到许多传统半导体异质结构中不存在的特性^2,3,4,5，因此成为研究的焦点设备应用^6,7,8。它的对应物，二维空穴气体 (2DHG)，有望补充 2DEG。然而，虽然 2DEG 已被广泛观察⁹，但 2DHG 已被证明是难以捉摸的。在此，我们展示了在外延生长的 SrTiO ₃ /LaAlO ₃ /SrTiO _{3 中}高度移动的 2DHG异质结构。使用电传输测量和在线电子全息术，我们提供了 2DHG 与 2DEG 在相同结构的互补异质界面上共存的直接证据。第一性原理计算、相干布拉格棒分析和深度分辨阴极发光光谱始终支持我们的发现，即消除离子点缺陷是实现 2DHG 的关键。2DEG 和 2DHG 在单一氧化物异质结构中的共存为受限电子空穴系统的激发物理和开发应用提供了平台。