High-Mobility Two-Dimensional Hole Gas at an SrTiO3 Interface：Assistant Professor Le Duc Anh(Institute of Engineering Innovation), Shingo Kaneta(M1)(Department of Electrical Engineering and Information Systems), Associate Professor Munetoshi Seki(Department of Electrical Engineering and Information Systems), Prof.Hitoshi Tabata(Department of Bioengineering/Department of Electrical Engineering and Information Systems), Prof.Masaaki Tanaka(Department of Bioengineering/Department of Electrical Engineering and Information Systems), Associate Professor Shinobu Ohya(Institute of Engineering Innovation/Department of Electrical Engineering and Information Systems), and other researchers

Authors

Le Duc Anh, Shingo Kaneta, Masashi Tokunaga, Munetoshi Seki, Hitoshi Tabata, Masaaki Tanaka and Shinobu Ohya

Abstract

Strontium titanate (SrTiO₃ or STO) is important for oxide‐based electronics as it serves as a standard substrate for a wide range of high‐temperature superconducting cuprates, colossal magnetoresistive manganites, and multiferroics. Moreover, in its heterostructures with different materials, STO exhibits a broad spectrum of important physics such as superconductivity, magnetism, the quantum Hall effect, giant thermoelectric effect, and colossal ionic conductivity, most of which emerge in a two‐dimensional (2D) electron gas (2DEG) formed at an STO interface. However, little is known about its counterpart system, a 2D hole gas (2DHG) at the STO interface. Here, a simple way of realizing a 2DHG with an ultrahigh mobility of 24 000 cm² V⁻¹ s⁻¹ is demonstrated using an interface between STO and a thin amorphous FeO_y layer, made by depositing a sub‐nanometer‐thick Fe layer on an STO substrate at room temperature. This mobility is the highest among those reported for holes in oxides. The carrier type can be switched from p‐type (2DHG) to n‐type (2DEG) by controlling the Fe thickness. This unprecedented method of forming a 2DHG at an STO interface provides a pathway to unexplored hole‐related physics in this system and enables extremely low‐cost and high‐speed oxide electronics.

Advanced Materials: https://onlinelibrary.wiley.com/doi/abs/10.1002/adma.201906003