Variability and high temperature reliability of graphene field-effect transistors with thin epitaxial CaF2 insulators
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...
| Main Authors: | , , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
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Nature Portfolio
2024-03-01
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| Series: | npj 2D Materials and Applications |
| Online Access: | https://doi.org/10.1038/s41699-024-00461-0 |
| _version_ | 1797247189172355072 |
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| author | Yu. Yu. Illarionov T. Knobloch B. Uzlu A. G. Banshchikov I. A. Ivanov V. Sverdlov M. Otto S. L. Stoll M. I. Vexler M. Waltl Z. Wang B. Manna D. Neumaier M. C. Lemme N. S. Sokolov T. Grasser |
| author_facet | Yu. Yu. Illarionov T. Knobloch B. Uzlu A. G. Banshchikov I. A. Ivanov V. Sverdlov M. Otto S. L. Stoll M. I. Vexler M. Waltl Z. Wang B. Manna D. Neumaier M. C. Lemme N. S. Sokolov T. Grasser |
| author_sort | Yu. Yu. Illarionov |
| collection | DOAJ |
| description | 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 SiO2 and Al2O3, 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 CaF2 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 175oC 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 CaF2 which results in the conventional clockwise hysteresis. We demonstrate that both the hysteresis and bias-temperature instabilities in our GFETs with CaF2 are comparable to similar devices with SiO2 and Al2O3. 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 CaF2 is a promising insulator for highly-stable GFETs. |
| first_indexed | 2024-04-24T19:54:44Z |
| format | Article |
| id | doaj.art-3aabc0628c8b44959f15e605e0a876d5 |
| institution | Directory Open Access Journal |
| issn | 2397-7132 |
| language | English |
| last_indexed | 2024-04-24T19:54:44Z |
| publishDate | 2024-03-01 |
| publisher | Nature Portfolio |
| record_format | Article |
| series | npj 2D Materials and Applications |
| spelling | doaj.art-3aabc0628c8b44959f15e605e0a876d52024-03-24T12:22:31ZengNature Portfolionpj 2D Materials and Applications2397-71322024-03-018111010.1038/s41699-024-00461-0Variability and high temperature reliability of graphene field-effect transistors with thin epitaxial CaF2 insulatorsYu. Yu. Illarionov0T. Knobloch1B. Uzlu2A. G. Banshchikov3I. A. Ivanov4V. Sverdlov5M. Otto6S. L. Stoll7M. I. Vexler8M. Waltl9Z. Wang10B. Manna11D. Neumaier12M. C. Lemme13N. S. Sokolov14T. Grasser15Department of Materials Science and Engineering, Southern University of Science and TechnologyInstitute for Microelectronics (TU Wien)AMO GmbHIoffe InstituteIoffe InstituteInstitute for Microelectronics (TU Wien)AMO GmbHAMO GmbHIoffe InstituteInstitute for Microelectronics (TU Wien)AMO GmbHInstitute for Microelectronics (TU Wien)AMO GmbHAMO GmbHIoffe InstituteInstitute for Microelectronics (TU Wien)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 SiO2 and Al2O3, 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 CaF2 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 175oC 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 CaF2 which results in the conventional clockwise hysteresis. We demonstrate that both the hysteresis and bias-temperature instabilities in our GFETs with CaF2 are comparable to similar devices with SiO2 and Al2O3. 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 CaF2 is a promising insulator for highly-stable GFETs.https://doi.org/10.1038/s41699-024-00461-0 |
| spellingShingle | Yu. Yu. Illarionov T. Knobloch B. Uzlu A. G. Banshchikov I. A. Ivanov V. Sverdlov M. Otto S. L. Stoll M. I. Vexler M. Waltl Z. Wang B. Manna D. Neumaier M. C. Lemme N. S. Sokolov T. Grasser Variability and high temperature reliability of graphene field-effect transistors with thin epitaxial CaF2 insulators npj 2D Materials and Applications |
| title | Variability and high temperature reliability of graphene field-effect transistors with thin epitaxial CaF2 insulators |
| title_full | Variability and high temperature reliability of graphene field-effect transistors with thin epitaxial CaF2 insulators |
| title_fullStr | Variability and high temperature reliability of graphene field-effect transistors with thin epitaxial CaF2 insulators |
| title_full_unstemmed | Variability and high temperature reliability of graphene field-effect transistors with thin epitaxial CaF2 insulators |
| title_short | Variability and high temperature reliability of graphene field-effect transistors with thin epitaxial CaF2 insulators |
| title_sort | variability and high temperature reliability of graphene field effect transistors with thin epitaxial caf2 insulators |
| url | https://doi.org/10.1038/s41699-024-00461-0 |
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