In
an advance for nanoscale electronics, researchers
at the National Institute of Standards and Technology
(NIST) have demonstrated a new design for silicon
nanowire transistors that both simplifies processing
and allows the devices to be switched on and off
more easily.
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A schematic diagram of the
NIST nanowire transistor.
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The
NIST design, described in a paper published June
29 by the journal Nanotechnology ,* uses a simplified
type of contact between the nanowire channel and
the positive and negative electrodes of the transistor.
The design allows more electrical current to flow
in and out of the silicon. The researchers believe
the design is the first to demonstrate a "Schottky
barrier" type contact for a nanowire transistor built
using a "top-down" approach. This barrier, an easily
formed metal contact that electrons can tunnel through,
requires much less doping with impurities than do
conventional ohmic contacts, thereby simplifying
processing requirements. Schottky contacts also offer
more resistance and restrict electrical flow to one
direction when the transistor is off.
In
the NIST transistor design, the 60-nanometer-wide
channels exhibit a much greater difference in current
between the on and off states than is true for
larger reference channels up to 5 micrometers wide.
This suggests that when a channel is scaled down
to the nano regime, the ultra-narrow proportions
significantly reduce the current leakage associated
with defects in silicon. As a result, the transistors
are less sensitive to electronic "noise" in the
channel and can be turned on and off more effectively,
according to the paper's lead author, Sang-Mo Koo,
a NIST guest researcher.
Silicon nanowire devices have received considerable
attention recently for possible use in integrated
nanoscale electronics as well as for studying fundamental
properties of structures and devices with very small
dimensions. The NIST work overcomes some key difficulties
in making reliable devices or test structures at
nanoscale dimensions. The results also suggest that
nanowire transistors made with conventional lithographic
fabrication methods can improve performance in nanoscale
electronics, while allowing industry to retain its
existing silicon technology infrastructure.
*S.M. Koo, M.D. Edelstein, Q.Li, C.A. Richter and
E.M. Vogel. 2005. Silicon nanowires as enhancement-mode
Schottky barrier field-effect transistors. Nanotechnology
16. Posted online June 29.
Media Contact:
Laura Ost, laura.ost@nist.gov , (301)
975-4034
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