Samsung Advanced Institute of Technology has developed a
new transistor structure utilizing graphene, touted as
the "miracle material."
In a research published in the journal Science on
Thursday, the R&D incubator for Samsung Electronics
described the new structure, which is regarded to have
brought industry one step closer to the development of
transistors that can overcome the limits of conventional
silicon.
Currently, semiconductor devices consist of billions of
silicon transistors. To increase the performance of
semiconductors (the speed of devices), the options have
to been to either reduce the size of individual
transistors to shorten the traveling distance of
electrons, or to use a material with higher electron
mobility which allows for faster electron velocity. For
the past 40 years, the industry has been increasing
performance by reducing size. However, experts believe
we are now nearing the potential limits of scaling down.
Since graphene possesses electron mobility about 200
times greater than that of silicon, it has been
considered a potential substitute. Although one issue
with graphene is that, unlike conventional
semiconducting materials, current cannot be switched off
because it is semi-metallic. This has become the key
issue in realizing graphene transistors. Both on and off
flow of current is required in a transistor to represent
"1" and "0" of digital signals. Previous solutions and
research have tried to convert graphene into a
semiconductor. However, this radically decreased the
mobility of graphene, leading to skepticism over the
feasibility of graphene transistors.
Scientists at Samsung Advanced Institute of Technology
have re-engineering the basic operating principles of
digital switches and developed a device that can switch
off the current in graphene without degrading its
mobility. The demonstrated graphene-silicon Schottky
barrier can switch current on or off by controlling the
height of the barrier. The new device was named
Barristor, after its barrier-controllable feature.
Schottky Barrier is a potential (energy) barrier formed
at a metal-semiconductor interface. It prevents an
electric charge to flow from metal to silicon. Generally, metal-semiconductor junction would have fixed work function (the minimum energy needed to take an
electron out of material) and Schottky barrier height, but as for graphene, Schottky barrier height can be controlled through the work function.
In addition, to expand the research into the possibility
of logic device applications, the most basic logic gate
(inverter) and logic circuits (half-adder) were
fabricated, and basic operation (adding) was
demonstrated.
Samsung Advanced Institute of Technology owns 9 major
patents related to the structure and the operating
method of the Graphene Barristor.
As demonstrated in this research, the institute has
solved the most difficult problem in graphene device
research and has opened the door to new directions for
future studies.
"The timing of commercialization of the device will be earlier than expected as the development is a minor upgrade from current chip-making technology," said Samsung.
Scientists and chip experts are also saying that finding a replacement for silicon is still a long way off as devices with graphene have only ever been demonstrated on a "very small scale."