Next-Generation Transistor Outperforms Other Carbon-Based Designs
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A team of engineers from the University of Southern California has constructed the highest-performing carbon nanotube transistor to date.
Transistors are semiconductor switches and amplifiers that are key components of almost all electronic devices, from radios to cell phones to computers.
The new carbon nanotube transistor has an extrinsic performance — the limit of its practical, usable operating frequency — of 25 Gigahertz (GHz). By comparison, its closest competitor (built by the Institut d’Électronique de Microélectronique et de Nanotechnologie (IEMN) in France) peaks at 15 GHz.
“Carbon nanotubes have unique properties and great potential in advanced electronic application. This is the very first report of analog circuits based on self-aligned nanotube array transistors operated in the gigahertz regime,” said Chongwu Zhou, professor at the USC Viterbi School of Engineering, and corresponding author of a paper about the transistor that was published online by ACS Nano on April 16.
“The characterization of nanotube transistor-based analog circuits is of great importance for further exploring the potential of nanotubes in high frequency applications with fast speed and low power consumption requirement,” he said.
Zhou lead a team that included USC Ph.D. students Yuchi Che, Yung-Chen Lin and Pyojae Kim.
The new transistor takes advantage of a new T-shaped design that is a mere 200 nanometers wide. The design helps reduce parasitic effects on the transistor’s performance and boosts the speed of the transistor’s response by scaling down its channel length. Zhou and his team recently patented the design.
Scientists have long eyed carbon nanotubes as a replacement for silicon semiconductors in commercial electronics because carbon has superior electrical properties and can be used to build smaller transistors.
Though current carbon nanotube-based designs come nowhere near the older silicon technology — which can perform at around 500 GHz — they have the potential, theoretically, to reach 1,000 GHz frequency performance.
“It is a significant step toward the practical application of carbon nanotube RF transistor as a promising candidate for next generation electronics,” said Che, the lead author of the ACS Nano paper.
Zhou and his research group continue to work on optimizing carbon nanotube-based analog electronics. Their final goal is to generate carbon nanotube transistors and circuits that offer superior performance to traditional industrial technology.
This research as funded by the Joint KACST/California Center of Excellence and the Office of Naval Research (ONR).
Image: Cross-section scanning electron microscope image of a carbon transistor with a T-shaped gate. (Courtesy of Yuchi Che and Chongwu Zhou / USC)