2018 Fiscal Year Annual Research Report
Single-nanometer-scale graphene tunnel field effect transistors for ultra-low-power nano electronics
| Project/Area Number |
18F18365
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| Research Institution | Japan Advanced Institute of Science and Technology |
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Principal Investigator |
水田 博 北陸先端科学技術大学院大学, 先端科学技術研究科, 教授 (90372458)
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| Co-Investigator(Kenkyū-buntansha) |
HAMMAM AHMED 北陸先端科学技術大学院大学, 先端科学技術研究科, 外国人特別研究員
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| Project Period (FY) |
2018-11-09 – 2021-03-31
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| Keywords | グラフェン / トンネルトランジスタ / ナノイオンビーム / サブサーマルスイッチング |
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| Outline of Annual Research Achievements |
As a channel of graphene tunnel field-effect transistors (GTFETs), graphene nanoribbons (GNRs) in various values of width ranging from few 100 nm down to 20 nm were first fabricated on CVD graphene by using electron beam lithography (EBL) with high-resolution EB resist. Al2O3 gate insulator was then deposited by using the Atomic layer deposition (ALD) technique, and its impacts on the GNR carrier transport properties were characterized at temperature ranging from 4.2 K to room temperature in comparison with those of SiO2 deposition. Graphene sandwiched with h-BN layers was also prepared by using the wet 2-D transfer technique. The bandgap opening Eg was evaluated from the Arrhenius plots for the Al2O3 and SiO2 deposited GNRs, and their dielectric confinement effects on Eg were analyzed.
A new GTFET structure was designed by using the COMSOL Multiphysics with three adjacent top gate electrodes with sub-15 nm proximity, which will be fabricated by using N2+ ion beam of the GFIS (Gas Field Ion Source) nanofabrication system at JAIST. The impact of atomistic edge structures (the mixture of zigzag and armchair structures) of GNRs were studied by using atomistic Quantum ATK simulation by taking account of the edge carrier spin states.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
In the original research plan, we scheduled to conduct the helium ion beam milling process at AIST to pattern ultrathin GNRs. However, we decided to delay this process as the electron beam lithography with high-resolution resist went successful to fabricate GNRs of ～ 15 nm in width. In addition, the ionized nitrogen beam process using the GFIS (Gas Field Ion Source) nanofabrication system at JAIST was found to work very well to pattern graohene as well as the multiple top gates. Therefore the project has progressed as planned by using the HR-EBL and GFIS N2+ beam milling process at JAIST.
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| Strategy for Future Research Activity |
Motorized HF wet etching process followed by supercritical point drying is developed to remove a supporting SiO2 layer and make ultrathin suspended GNRs. Carrier transport properties are measured for suspended GNRs of single-nanometer width fabricated by HIM and correlated to the atomistic analysis of the GNR edge structures. Electrical characteristics are measured using a cryogenic probestation, as a function of temperature ranging from 4.2 K to room temperature. Simulation is conducted using ab initio simulation package ATK for different degree of edge roughness to understand the device characteristics. Atomic layer deposition (ALD) of SiO2 and Al2O3 is then conducted to cover a suspended GNR channel all around and then form multiple control gates to fabricate final top-gated GNR-TFETs.
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