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New material structure produces
world's fastest transistor
Kloeppel, Physical Sciences Editor
photo to enlarge
by Kwame Ross
Feng, the Holonyak Professor of Electrical and Computer
Engineering and a researcher at the Coordinated Science
Laboratory at Illinois, has broken the 600 gigahertz
speed barrier in a new type of transistor structure.
Ill. — A new type of transistor structure, invented by scientists
at the University of Illinois at Urbana-Champaign, has broken the 600
gigahertz speed barrier. The goal of a terahertz transistor for high-speed
computing and communications applications could now be within reach.
The new device – built from indium phosphide and indium gallium
arsenide – is designed with a compositionally graded collector,
base and emitter to reduce transit time and improve current density.
With their pseudomorphic heterojunction bipolar transistor, the researchers
have demonstrated a speed of 604 gigahertz – the fastest transistor
operation to date.
“Pseudomorphic grading of the material structure allows us to
lower the bandgap in selected areas,” said Milton Feng, the Holonyak
Professor of Electrical and Computer
Engineering and a researcher at the Coordinated
Science Laboratory at Illinois. “This permits faster electron
flow in the collector. The compositional grading of the transistor components
also improves current density and signal charging time.”
Feng and graduate student Walid Hafez fabricated the new device in the
university’s Micro and Nanotechnology Laboratory. They describe
the pseudomorphic HBT concept, and discuss the transistor’s high-speed
operation, in the April 11 issue of the journal Applied Physics Letters.
The goal of a terahertz transistor was not possible using the previous
device structure, Feng said. “To achieve such speed in a typical
HBT, the current density would become so large it would melt the components.
In our pseudomorphic HBT, we can operate at higher frequencies with
less current density. With this new material structure, a terahertz
transistor is achievable.”
Faster transistors could facilitate faster computers, more flexible
and secure wireless communications systems, and more effective electronic
Editor’s note: To reach Milton Feng, call 217-333-8080; e-mail: firstname.lastname@example.org.