Joint Centers of Excellence Program

Self-Aligned T-Gate High-Purity Semiconducting Carbon Nanotube RF Transistors Operated in Quasi-Ballistic Transport and Quantum Capacitance Regime

ACS Nano
07 Jul 2012

Carbon nanotube RF transistors are predicted to offer good performance and high linearity when operated in the ballistic transport and quantum capacitance regime; however, realization of such transistors has been very challenging. In this paper, we introduce a self-aligned fabrication method for carbon nanotube RF transistors, which incorporate a T-shaped (mushroom-shaped) aluminum gate, with oxidized aluminum as the gate dielectric. In this way, the channel length can be scaled down to 140 nm, which enables quasi-ballistic transport, and the gate dielectric is reduced to 2–3 nm aluminum oxide, leading to quasi-quantum capacitance operation. A current-gain cutoff frequency (ft) up to 23 GHz and a maximum oscillation frequency (fmax) of 10 GHz are demonstrated. Furthermore, the linearity properties of nanotube transistors are characterized by using the 1 dB compression point measurement with positive power gain for the first time, to our knowledge. Our work reveals the importance and potential of separated semiconducting nanotubes for various RF applications.

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