Transistor Technology Takes a
Quantum Leap
by Ilan Greenberg
4:58am 8.Dec.97.PST
Isaac Newton wouldn't approve of what Sandia
National Laboratories is doing to the tried-and-true
transistor.
Conventional transistors are based on classical
physics principles, but basic science researchers
at Sandia Labs in Albuquerque, New Mexico,
recently demonstrated a new transistor that
makes use of quantum theory - specifically, it
uses a technique called quantum mechanical
tunneling of electrons.
"It's pretty hard to make high-frequency
transistors. This is true even after the federal
government has pumped millions into funding
university research. So considering that context,
we're pretty happy with our results," says Jerry
Simmons, head of the nanoelectronics group at
Sandia.
Called the Double Electron Layer Tunneling
Transistor, or DELTT, the three-terminal quantum
transistor is considered a breakthrough in
transistor design because quantum tunneling
leapfrogs current transistor technology in terms of
its extremely high speed. The transistor will be
capable of blistering speeds by relying on a single
quantum transition between two electron states,
something traditional transistors are unable to do.
Quantum tunneling can also allow the same
integrated circuit functions to be achieved with far
fewer transistors. And because the transistor only
needs existing nanotechnology to build its
atomically precise two-dimensional layers of
electrons - a new level of miniaturization for
transistors - the DELTT is expected one day to be
reliably manufactured in large numbers using
existing semiconductor production facilities, a
challenge long thought to be a limitation with
quantum transistor design. Manufacturing the
quantum transistor is years in the future, however.
"Right now it's a research device. We've only
demonstrated it in the past year," says Simmons.
"I don't want to get in there worrying about
production yield - it's my function to demonstrate
that it's worthwhile to move it into the next stage."
Simmons expects the device to work at room
temperature by the end of next year, but even then
it may be several more years before the
technology is ready for production. "A real chip
needs a million working transistors, and thus
extremely high yields. We're on our way, but there
still are obstacles to commercialization, and I
can't say when it will actually be manufactured,"
he says.
Regardless of its manufacturing timeline,
transistor researchers who have examined the
fundamental research behind the chip say Sandia
has produced a major advance in electronic
design.
"This is a premier piece of research," says Paul
Berger, associate professor of electrical and
computer engineering at the University of
Delaware. "I've seen some of these things before,
but nothing with this kind of complexity and
sophistication. We're going to have to look for
alternative ways of computation, and this quantum
transistor is certainly noteworthy and needs to be
addressed."
Future applications for the quantum transistor
include cellular phones and eventually desktop
CPUs, Simmons says. Ultimately, Simmons
hopes the transistor will find itself in three broad
categories of devices: ultra-low-power static
memory elements, which will require exceptionally
low currents; ultra-high-speed logical processing
elements, which will require very small feature
sizes and somewhat higher currents; and
far-infrared detectors.
Sandia's interest in transistor design is one part of
the government laboratory's larger charter, which
is to assure the safety, security, and reliability of
nuclear weapons. As part of this mission, the
7,500-person lab also conducts research into
basic science. While at some point the quantum
transistor is likely to find itself attached to a
nuclear warhead, the national defense laboratories
are also increasingly participating in technology
transfer programs with civilian industries.
The Sandia team will present their research
advance at the International Electronic Devices
Meeting in Washington, DC, on Monday, and will
publish various aspects of their research in the
upcoming issue of the journal Applied Physics
Letters.
--
The future has arrived; it's just not evenly distributed.
-William Gibson
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