Direct observation of a two-dimensional hole gas at oxide interfaces

H Lee; N Campbell; J Lee; T J Asel; T R Paudel; H Zhou; J W Lee; B Noesges; J Seo; B Park; L J Brillson; S H Oh; E Y Tsymbal; M S Rzchowski; C B Eom

doi:10.1038/s41563-017-0002-4

Direct observation of a two-dimensional hole gas at oxide interfaces

Nat Mater. 2018 Mar;17(3):231-236. doi: 10.1038/s41563-017-0002-4. Epub 2018 Feb 5.

Authors

H Lee¹, N Campbell², J Lee³, T J Asel⁴, T R Paudel⁵, H Zhou⁶, J W Lee¹, B Noesges⁴, J Seo³, B Park^{3

7}, L J Brillson^{4

8}, S H Oh³, E Y Tsymbal⁵, M S Rzchowski², C B Eom⁹

Affiliations

¹ Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, USA.
² Department of Physics, University of Wisconsin-Madison, Madison, WI, USA.
³ Department of Energy Science, Sungkyunkwan University (SKKU), Suwon, Korea.
⁴ Department of Physics, The Ohio State University, Columbus, OH, USA.
⁵ Department of Physics and Astronomy, Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, USA.
⁶ X-Ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL, USA.
⁷ Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Korea.
⁸ Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH, USA.
⁹ Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, USA. eom@engr.wisc.edu.

PMID: 29403056
DOI: 10.1038/s41563-017-0002-4

Abstract

The discovery of a two-dimensional electron gas (2DEG) at the LaAlO₃/SrTiO₃ interface ¹ has resulted in the observation of many properties^2-5 not present in conventional semiconductor heterostructures, and so become a focal point for device applications^6-8. Its counterpart, the two-dimensional hole gas (2DHG), is expected to complement the 2DEG. However, although the 2DEG has been widely observed ⁹ , 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.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.
Research Support, Non-U.S. Gov't