High-Mobility 2D Hole Gas at a SrTiO3 Interface

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

doi:10.1002/adma.201906003

High-Mobility 2D Hole Gas at a SrTiO₃ Interface

Adv Mater. 2020 Apr;32(14):e1906003. doi: 10.1002/adma.201906003. Epub 2020 Feb 27.

Authors

Le Duc Anh^{1

2}, Shingo Kaneta¹, Masashi Tokunaga³, Munetoshi Seki^{1

4}, Hitoshi Tabata^{1

4}, Masaaki Tanaka^{1

4}, Shinobu Ohya^{1

2

4}

Affiliations

¹ Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
² Institute of Engineering Innovation, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
³ Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba, 277-8581, Japan.
⁴ Center for Spintronics Research Network (CSRN), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.

PMID: 32103572
DOI: 10.1002/adma.201906003

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.

Keywords: 2D hole gases; oxide-based electronics; room-temperature deposition.

Abstract

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