Graphene FETs Based on High Resolution Nanoribbons for HF Low Power Applications
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In this paper we present high frequency field effect transistors based on graphene nanoribbons arrays (GNRFETs). The nanoribbons serve as a channel for the transistors and are fabricated with a process based on e-beam lithography and dry etching of high mobility hydrogen intercalated epitaxial graphene. The widths of the nanoribbons vary from 50 to 20 nm, less than half those measured in previous reports for GNRFETs. Hall measurements reveal that the devices are p-doped, with mobility on the order of 2300 cm2/Vs. From DC characteristics, we find that the maximum ratio IMAX/IMIN is 5 obtained at 50 nm ribbons width. The IV characteristics of the GNRFETs are slightly non-linear at high bias without a full saturation. Therefore, despite the aggressive scaling of the graphene nanoribbon width, a bandgap is still not observed in our measurements. The high frequency performances of our GNRFETs are already significant at low bias. At 300 mV drain source voltage, the highest intrinsic (extrinsic) cut-off frequency ft reaches 82 (18) GHz and the extrinsic maximum oscillation frequency fmax is 20 GHz, which is promising for low power applications.
KeywordsNanoribbons Graphene Radio-frequency characterization Field effect transistor Low power
This work was supported by the French Contract No. ANR-2010-BLAN-0304-01-MIGRAQUEL (Agence Nationale de la Recherche). We thank M. Moez and V. Avramovic for the RF characterization. The authors gratefully acknowledge financial support from EU FP7-ICT-2013-FET-F GRAPHENE Flagship Project (No. 604391). This work was also partly supported by the French RENATECH network.