Dresden 2011 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 31: Postersitzung II
MM 31.55: Poster
Mittwoch, 16. März 2011, 17:15–18:45, P5
Graphene microwave transistors on sapphire substrate — •Christian Benz1,2, Emiliano Pallecchi3, Andreas Betz3, Hilbert v. Löhneysen1,2,4, Bernard Plaçais3 und Romain Danneau1,2 — 1Institute of Nanotechnology, Karlsruhe Institute of Technology, Karlsruhe, Germany — 2Physikalisches Institut, Karlsruhe Institute of Technology, Karlsruhe, Germany — 3Laboratoire Pierre Aigrain, Ecole Normale Supérieure, Paris, France — 4Institute for Solid-State Physics, Karlsruhe Institute of Technology, Karlsruhe, Germany
Graphene, a one atom thick layer of graphite arranged in a honeycomb lattice, has recently drawn a lot of attention and is currently one of the most active research fields. However, only few works concentrate on graphene’s high frequency characteristics. In this work graphene field effect transistors (GFETs) were prepared by mechanical exfoliated mono- and bilayer graphene followed by lift-off. We realized top gates with 230 nm gate length separated by a dielectric layer of variable thickness. To reduce losses at high frequencies, an insulating substrate (sapphire) was employed. The GFETs were characterized in dc- and microwave-measurements. From the S-parameters, the transconductance gm and current gain h21(f) were extracted. We obtained the intrinsic characteristics of our GFETs using de-embedding to subtract the parasitic capacitances of the coplanar waveguide contacting structure. The current gain h21 followed the ideal 1/f slope of typical Si-based FETs. A maximum transconductance of gm=0.32 mS/µm and cut-off frequencies up to fT≈80 GHz were observed, very close to fT estimated from the device geometry. Finally, we compared the performance of mono- and bilayer devices.