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World's fastest transistor
approaches goal of terahertz device
Kloeppel, Physical Sciences Editor
photo to enlarge
by L. Brian Stauffer
Feng, the Holonyak
Chair Professor of Electrical
and Computer Engineering, right, and
his graduate student William Snodgrass have
taken the transistor to a new range of high-speed operation,
bringing the “Holy Grail” of a terahertz
transistor finally within reach.
CHAMPAIGN, Ill. —
Scientists at the University of Illinois at Urbana-Champaign have again
broken their own speed record for the world’s fastest transistor.
With a frequency of 845 gigahertz, their latest device is approximately
300 gigahertz faster than transistors built by other research groups,
and approaches the goal of a terahertz device.
Made from indium phosphide and indium gallium arsenide, “the new
transistor utilizes a pseudomorphic grading of the base and collector
regions,” said Milton Feng, the Holonyak Chair Professor of Electrical
and Computer Engineering at Illinois. “The compositional grading
of these components enhances the electron velocity, hence, reduces both
current density and charging time.”
With their latest device, Feng and his research group have taken the
transistor to a new range of high-speed operation, bringing the “Holy
Grail” of a terahertz transistor finally within reach. Faster
transistors translate into faster computers, more flexible and secure
wireless communications systems, and more effective combat systems.
In addition to using pseudomorphic material construction, the researchers
also refined their fabrication process to produce tinier transistor
components. For example, the transistor’s base is only 12.5 nanometers
thick (a nanometer is one billionth of a meter, or about 10,000 times
smaller than the width of a human hair).
“By scaling the device vertically, we have reduced the distance
electrons have to travel, resulting in an increase in transistor speed,”
said graduate student William Snodgrass, who will describe the new device
at the International Electronics Device Meeting in San Francisco, Dec.
11-13. “Because the size of the collector has also been reduced
laterally, the transistor can charge and discharge faster.”
photo to enlarge
Scanning electron microscope images of original
base-collector mesa (top) and improved design (bottom).
Operated at room temperature (25 degrees Celsius), the transistor speed
is 765 gigahertz. Chilled to minus 55 degrees Celsius, the speed increases
to 845 gigahertz.
Feng, Snodgrass and graduate student Walid Hafez (now at Intel Corp.)
fabricated the high-speed device in the university’s Micro and
In addition to further increasing the transistor speed, Feng wants to
reduce the current density even more, which will reduce junction temperature
and improve device reliability.
The Defense Advanced Research Projects Agency funded the work.
Editor’s note: To reach Milton Feng, call
217-333-8080; e-mail: firstname.lastname@example.org.