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UCLA uses nanowires as self-aligning gates on graphene transistors

Posted: 23 Sep 2010     Print Version  Bookmark and Share

Keywords:graphene  transistor  fabrication process 

Researchers from the University of California, Los Angeles (UCLA) show that using nanowires as self-aligning gates overcomes the difficulties of fabricating graphene transistors.

Graphene is a one-atom-thick layer of graphitic carbon that has the potential to make electronic devices faster and smaller. However, its properties have led to difficulties in integrating the material into such devices.

In a paper published in the journal Nature, the UCLA researchers demonstrate how they overcame some of these difficulties to make the fastest graphene transistor to date.

Graphene has the highest known carrier mobility—the speed at which electronic information is transmitted by a material—and is a good candidate for high-speed RF electronics. But traditional fabrication techniques have led to quality deterioration.

Led by Xiangfeng Duan, professor of chemistry and biochemistry, the team has developed a new fabrication process for graphene transistors using a nanowire as the self-aligned gate.

Self-aligned gates are a key element in modern transistors, which are semiconductor devices used to amplify and switch electronic signals. Gates are used to switch the transistor between various states, and self-aligned gates were developed to deal with problems of misalignment encountered because of the shrinking scale of electronics.

Duan teamed with Yu Huang, an assistant professor of materials science and engineering at the Henry Samueli School of Engineering and Applied Sciences, and Kang Wang, a professor of electrical engineering at the Samueli School, both also from the California NanoSystems Institute at UCLA.

Duan noted that "This new strategy overcomes two limitations previously encountered in graphene transistors." He explained "First, it doesn't produce any appreciable defects in the graphene during fabrication, so the high carrier mobility is retained. Second, by using a self-aligned approach with a nanowire as the gate, the group was able to overcome alignment difficulties previously encountered and fabricate very short-channel devices with unprecedented performance."

These advances allowed the team to demonstrate the highest speed graphene transistors to date, with a cutoff frequency up to 300GHz, comparable to the very best transistors from high-electron mobility materials such gallium arsenide or indium phosphide.

Another researcher

Lei Liao, a postdoctoral fellow at UCLA, said that the team is "currently taking additional efforts to scale up the approach and further boost the speed."

High-speed radio-frequency electronics may also find wide applications in microwave communication, imaging and radar technologies.

Funding for this research came from the National Science Foundation and the National Institutes of Health.

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