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Nano Research 2019, 12(1): 143-148 https://doi.org/10.1007/s12274-018-2193-7
Research Article | Issue | Published: 22 September 2018

Quasi-two-dimensional β-Ga2O3 field effect transistors with large drain current density and low contact resistance via controlled formation of interfacial oxygen vacancies

Show Author's Information Zhen Li§,  Yihang Liu§,  Anyi Zhang,  Qingzhou Liu,  Chenfei Shen,  Fanqi Wu,  Chi Xu,  Mingrui Chen,  Hongyu Fu,  Chongwu Zhou( )
Ming Hsieh Department of Electrical Engineering, Mork Family Department of Chemical Engineering and Material Science, Department of Physics and Astronomy, University of Southern California, Los Angeles, California, 90089, USA;

§ Zhen Li and Yihang Liu contributed equally to this work.

Keywords:
field effect transistor, quasi-two-dimensional material, metal-oxides, β-Ga2O3, contact resistance
Topics:
Gallium compoundsMOS devicesOxide semiconductorsTitaniumWide band gap semiconductorsX-ray photoelectron spectroscopy
Cite this article:
Li Z, Liu Y, Zhang A, et al. Quasi-two-dimensional β-Ga2O3 field effect transistors with large drain current density and low contact resistance via controlled formation of interfacial oxygen vacancies. Nano Research, 2019, 12(1): 143-148. https://doi.org/10.1007/s12274-018-2193-7
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Abstract Full text Electronic supplementary material About this article

Quasi-two-dimensional (2D) β-Ga2O3 is a rediscovered metal-oxide semiconductor with an ultra-wide bandgap of 4.6–4.9 eV. It has been reported to be a promising material for next-generation power and radio frequency electronics. Field effect transistors (FETs) that can switch at high voltage are key components in power and radio frequency devices, and reliable Ohmic contacts are essential for high FET performance. However, obtaining low contact resistance on β-Ga2O3 FETs is difficult since reactions between β-Ga2O3 and metal contacts are not fully understood. Herein, we experimentally demonstrate the importance of reactions at the metal/β-Ga2O3 interface and the corresponding effects of these reactions on FET performance. When Ti is employed as the metal contact, annealing of β-Ga2O3 FETs in argon can effectively transform Schottky contacts into Ohmic contacts and permit a large drain current density of ~ 3.1 mA/μm. The contact resistance (Rcontact) between the Ti electrodes and β-Ga2O3 decreased from ~ 430 to ~ 0.387 Ω·mm after annealing. X-ray photoelectron spectroscopy (XPS) confirmed the formation of oxygen vacancies at the Ti/β-Ga2O3 interface after annealing, which is believed to cause the improved FET performance. The results of this study pave the way for greater application of β-Ga2O3 in electronics.


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Electronic supplementary material
About this article

Quasi-two-dimensional β-Ga2O3 field effect transistors with large drain current density and low contact resistance via controlled formation of interfacial oxygen vacancies

Show Author's information Zhen Li§, Yihang Liu§, Anyi Zhang, Qingzhou Liu, Chenfei Shen, Fanqi Wu, Chi Xu, Mingrui Chen, Hongyu Fu, Chongwu Zhou( )
Ming Hsieh Department of Electrical Engineering, Mork Family Department of Chemical Engineering and Material Science, Department of Physics and Astronomy, University of Southern California, Los Angeles, California, 90089, USA;

§ Zhen Li and Yihang Liu contributed equally to this work.

Abstract

Quasi-two-dimensional (2D) β-Ga2O3 is a rediscovered metal-oxide semiconductor with an ultra-wide bandgap of 4.6–4.9 eV. It has been reported to be a promising material for next-generation power and radio frequency electronics. Field effect transistors (FETs) that can switch at high voltage are key components in power and radio frequency devices, and reliable Ohmic contacts are essential for high FET performance. However, obtaining low contact resistance on β-Ga2O3 FETs is difficult since reactions between β-Ga2O3 and metal contacts are not fully understood. Herein, we experimentally demonstrate the importance of reactions at the metal/β-Ga2O3 interface and the corresponding effects of these reactions on FET performance. When Ti is employed as the metal contact, annealing of β-Ga2O3 FETs in argon can effectively transform Schottky contacts into Ohmic contacts and permit a large drain current density of ~ 3.1 mA/μm. The contact resistance (Rcontact) between the Ti electrodes and β-Ga2O3 decreased from ~ 430 to ~ 0.387 Ω·mm after annealing. X-ray photoelectron spectroscopy (XPS) confirmed the formation of oxygen vacancies at the Ti/β-Ga2O3 interface after annealing, which is believed to cause the improved FET performance. The results of this study pave the way for greater application of β-Ga2O3 in electronics.

Keywords: field effect transistor, quasi-two-dimensional material, metal-oxides, β-Ga2O3, contact resistance

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Publication history
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Acknowledgements

Publication history

Received: 03 June 2018
Revised: 31 August 2018
Accepted: 05 September 2018
Published: 22 September 2018
Issue date: January 2019

Copyright

© Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2018

Acknowledgements

Acknowledgements

We would like to acknowledge the collaboration of this research with King Abdul-Aziz City for Science and Technology (KACST) via The Center of Excellence for Nanotechnologies (CEGN). A portion of the images and data used in this article were acquired at The Center for Electron Microscopy and Microanalysis, University of Southern California.

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