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Graphene FET on diamond for high-frequency electronics

Transistors operating at high frequencies are the basic building blocks of millimeter-wave communication and sensor systems. The high velocity and mobility of carriers in graphene can open way for ultra-fast group IV transistors with similar or even better performance than can be achieved with III-V based semiconductors. However, the progress of high-speed graphene transistors has been hampered due to fabrication issues, influence of adjacent materials, and self-heating effects. Here, we report a graphene field-effect transistor (FET) on a diamond substrate, with a $f_{max}$ up to 54 GHz for a gate length of 500 nm. The high thermal conductivity of diamond provides an efficient heat-sink, and its relatively high optical-phonon energy improves saturation velocity of carriers in the graphene channel. Moreover, we show that graphene FETs on diamond, with different gate lengths, exhibit excellent scaling behavior. These results indicate that graphene FETs on diamond technology can reach sub-terahertz frequency performance.