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

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

Author information

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.

Abstract

The discovery of a two-dimensional electron gas (2DEG) at the LaAlO3/SrTiO3 interface 1 has resulted in the observation of many properties2-5 not present in conventional semiconductor heterostructures, and so become a focal point for device applications6-8. 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.

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

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