Self-aligned graphene transistor array

Graphene,
a one-atom-thick layer of graphitic carbon, has the potential to make
consumer electronic devices faster and smaller. But its unique
properties, and the shrinking scale of electronics, also make graphene
difficult to fabricate and to produce on a large scale.

In September 2010, a UCLA research team reported that they had overcome some of these difficulties and were able to fabricate graphene transistors with unparalleled speed.
These transistors used a nanowire as the self-aligned gate — the
element that switches the transistor between various states. But the
scalability of this approach remained an open question.

Now
the researchers, using equipment from the Nanoelectronics Research
Facility and the Center for High Frequency Electronics at UCLA, report
that they have developed a scalable approach to fabricating these
high-speed graphene transistors.

The
team used a dielectrophoresis assembly approach to precisely place
nanowire gate arrays on large-area chemical vapor deposition–growth
graphene — as opposed to mechanically peeled graphene flakes — to enable
the rational fabrication of high-speed transistor arrays. They were
able to do this on a glass substrate, minimizing parasitic delay and
enabling graphene transistors with extrinsic cut-off frequencies
exceeding 50 GHz. Typical high-speed graphene transistors are fabricated
on silicon or semi-insulating silicon carbide substrates that tend to
bleed off electric charge, leading to extrinsic cut-off frequencies of
around 10 GHz or less.

Taking
an additional step, the UCLA team was able to use these graphene
transistors to construct radio-frequency circuits functioning up to 10
GHz, a substantial improvement from previous reports of 20 MHz.

According
to the team, this research opens a rational pathway to scalable
fabrication of high-speed, self-aligned graphene transistors and
functional circuits and it demonstrates for the first time a graphene
transistor with a practical (extrinsic) cutoff frequency beyond 50 GHz.

This
represents a significant advance toward graphene-based, radio-frequency
circuits that could be used in a variety of devices, including radios,
computers and mobile phones. The technology might also be used in
wireless communication, imaging and radar technologies.

Study abstract

SOURCE