Researchers at the University of Notre Dame and Pennsylvania State University
have announced breakthroughs in the development of tunneling field effect
transistors (TFETs), a semiconductor technology that takes advantage of the
quirky behavior of electrons at the quantum level.
Transistors are the building blocks of the electronic
devices that power the digital world, and much of the growth in computing power
over the past 40 years has been made possible by increases in the number of
transistors that can be packed onto silicon chips.
But that growth, if left to current technology, may soon be
coming to an end.
Many in the semiconductor field think that the industry is
fast approaching the physical limits of transistor miniaturization. The major
problem in modern transistors is power leakage leading to the generation of
excessive heat from billions of transistors in close proximity.
The recent advances at Notre Dame and Penn State—who are
partners in the Midwest Institute for Nanoelectronics Discovery (MIND)—show
that TFETs are on track to solve these problems by delivering comparable
performance to today’s transistors, but with much greater energy efficiency.
They do this by taking advantage of the ability of electrons
to “tunnel” through solids, an effect that would seem like magic at the human
scale but is normal behavior at the quantum level.
“A transistor today acts much like a dam with a moveable
gate,” says Alan Seabaugh, professor of electrical engineering at Notre Dame and
the Frank M. Freimann Director of MIND. “The rate at which water flows, the
current, depends on the height of the gate.”
“With tunnel transistors, we have a new kind of gate, a gate
that the current can flow through instead of over. We adjust the thickness of
the gate electrically to turn the current on and off.”
“Electron tunneling devices have a long history of
commercialization,” adds Seabaugh, “You very likely have held more than a
billion of these devices in a USB flash drive. The principle of quantum
mechanical tunneling is already used for data storage devices.”
While TFETs don’t yet have the energy efficiency of current
transistors, papers released in December 2011
by Penn State and March 2012 by Notre Dame
demonstrate record improvements in tunnel transistor drive current, and more
advances are expected in the coming year.
“Our developments are based on finding the right combination
of semiconductor materials with which to build these devices,” says Suman Datta,
professor of electrical engineering at Penn State University.
“If we’re successful, the impact will be significant in
terms of low power integrated circuits. These, in turn, raise the possibility
of self-powered circuits which, in conjunction with energy harvesting devices,
could enable active health monitoring, ambient intelligence, and implantable
medical devices.”
Another benefit of tunneling transistors is that using them
to replace existing technology wouldn’t require a wholesale change in the
semiconductor industry. Much of the existing circuit design and manufacturing
infrastructure would remain the same.
“Strong university research on novel devices such as TFETs
is critical for continuing the rapid pace of technology development,” said Jeff
Welser, director of the Nanoelectronics Research Initiative. “Much of the
industry recognizes that it will take collaborations with both academia and
government agencies to find and develop these new concepts.”
Two other partners in the MIND center—Purdue University and
The University of Texas at Dallas—have made significant contributions to the
development of TFETs through the development of key modeling and analytical tools.
