Variability and high temperature reliability of graphene field-effect transistors with thin epitaxial CaF2 insulators
npj 2D Materials and Applications, vol. 8
Abstract
Abstract Graphene is a promising material for applications as a channel in graphene field-effect transistors (GFETs) which may be used as a building block for optoelectronics, high-frequency devices and sensors. However, these devices require gate insulators which ideally should form atomically flat interfaces with graphene and at the same time contain small densities of traps to maintain high device stability. Previously used amorphous oxides, such as SiO 2 and Al 2 O 3 , however, typically suffer from oxide dangling bonds at the interface, high surface roughness and numerous border oxide traps. In order to address these challenges, here we use 2 nm thick epitaxial CaF 2 as a gate insulator in GFETs. By analyzing device-to-device variability for about 200 devices fabricated in two batches, we find that tens of them show similar gate transfer characteristics. Our statistical analysis of the hysteresis up to 175 o C has revealed that while an ambient-sensitive counterclockwise hysteresis can be present in some devices, the dominant mechanism is thermally activated charge trapping by border defects in CaF 2 which results in the conventional clockwise hysteresis. We demonstrate that both the hysteresis and bias-temperature instabilities in our GFETs with CaF 2 are comparable to similar devices with SiO 2 and Al 2 O 3 . In particular, we achieve a small hysteresis below 0.01 V for equivalent oxide thickness (EOT) of about 1 nm at the electric fields up to 15 MV cm −1 and sweep times in the kilosecond range. Thus, our results demonstrate that crystalline CaF 2 is a promising insulator for highly-stable GFETs.
Authors 15
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Yu. Yu. Illarionov corresponding
TU Wien · Southern University of Science and Technology · Ioffe Institute
Affiliation as printed
Department of Materials Science and Engineering, Southern University of Science and Technology, 1088 Xueyuan Blvd, Shenzhen, 518055, China
Institute for Microelectronics (TU Wien), Gusshausstrasse 27–29, 1040, Vienna, Austria
Ioffe Institute, Polytechnicheskaya 26, 194021, St-Petersburg, Russia
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Affiliation as printed
Institute for Microelectronics (TU Wien), Gusshausstrasse 27–29, 1040, Vienna, Austria
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Affiliation as printed
AMO GmbH, Otto-Blumenthal-Strasse 25, 52074, Aachen, Germany
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Affiliation as printed
Ioffe Institute, Polytechnicheskaya 26, 194021, St-Petersburg, Russia
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Affiliation as printed
Ioffe Institute, Polytechnicheskaya 26, 194021, St-Petersburg, Russia
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Affiliation as printed
Institute for Microelectronics (TU Wien), Gusshausstrasse 27–29, 1040, Vienna, Austria
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Affiliation as printed
AMO GmbH, Otto-Blumenthal-Strasse 25, 52074, Aachen, Germany
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Affiliation as printed
Ioffe Institute, Polytechnicheskaya 26, 194021, St-Petersburg, Russia
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Affiliation as printed
Institute for Microelectronics (TU Wien), Gusshausstrasse 27–29, 1040, Vienna, Austria
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Affiliation as printed
AMO GmbH, Otto-Blumenthal-Strasse 25, 52074, Aachen, Germany
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Affiliation as printed
Institute for Microelectronics (TU Wien), Gusshausstrasse 27–29, 1040, Vienna, Austria
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University of Wuppertal · AMO (Germany)
Affiliation as printed
AMO GmbH, Otto-Blumenthal-Strasse 25, 52074, Aachen, Germany
Bergische Universitat Wuppertal, Gaussstrasse 20, 42119, Wuppertal, Germany
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AMO (Germany) · RWTH Aachen University
Affiliation as printed
AMO GmbH, Otto-Blumenthal-Strasse 25, 52074, Aachen, Germany
Chair of Electronic Devices, RWTH Aachen Univeristy, Otto-Blumenthal-Str. 25, 52074, Aachen, Germany
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Affiliation as printed
Ioffe Institute, Polytechnicheskaya 26, 194021, St-Petersburg, Russia
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Tibor Grasser corresponding
Affiliation as printed
Institute for Microelectronics (TU Wien), Gusshausstrasse 27–29, 1040, Vienna, Austria
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