Two-dimensional electron and hole gases in complex oxide heterostructures for device applications

Hyungwoo Lee

Department of Physics, Ajou University

The two-dimensional electron gas (2DEG) emerging at complex oxide heterostructures has attracted much scientific attention for a couple of decades. Recent studies have revealed that the highly mobile 2DEG has fascinating physical properties such as metal-insulator transition, ferromagnetism, and superconductivity, and suggested potential applications. By analogy with the mechanism of 2DEG formation, a lot of efforts have also been devoted to finding the counterpart — two-dimensional hole gas (2DHG) — at oxide heterointerfaces. However, while 2DEG has long been observed in various oxide systems, the 2DHG has been found just recently. In this talk, I will introduce the highly-mobile 2DHG in oxide heterostructures. The electrical transport measurements and in-line electron holography provide direct evidence of a 2DHG that coexists with a 2DEG at complementary heterointerfaces in the same structure. In addition, I will present the recent progress on the study of 2DEG in complex oxide heterostructures, guided by a motivation to develop advanced nano-device applications. Particularly, I will introduce the enhanced photoresponsivity of 2DEG in ultrathin oxide heterostructures. Notably, the comprehensive study on 2D transport at oxide interfaces are actively on progress. The highly-conducting 2D system based on the strongly-corelated transition metal oxides will enable us to study emergent phenomena and to develop novel device applications.