Kavli Institute Delft and Philips demonstrate
integration of semiconductor and superconductor electronics
on the nanoscale
Eindhoven, the Netherlands – In
the July 8 issue of Science, scientists from the
Kavli Institute of Nanoscience Delft and Philips
present the first superconducting transistors based
on semiconductor nanowires. These nanoscale superconductor/semiconductor
devices enable the fabrication of new nanoscale
superconducting electronic circuits and at the
same time they provide new opportunities for the
study of fundamental quantum transport phenomena.
After the invention of the first solid-state transistor (Bardeen, Brattain and
Shockley, 1947), semiconductors have become the reference material system for
electronics. This success results from the possibility to control the resistance
of a semiconductor with an electrical voltage applied to a nearby gate electrode.
Despite the astonishing number of different types of semiconductor devices it
has always been difficult to combine semiconductors with superconducting materials,
i.e. materials with vanishing resistance at low temperatures. This exotic combination
has captured the attention of both experimental and theoretical physicists already
since the 80s. It enables new technology for electronic circuits based on dissipation-less
superconducting elements which could be exploited for advanced applications where
the requirement of low-temperature operation is not a limiting factor.
The results presented in the Science article show that the combination of indium
arsenide semiconductor nanowires with aluminum-based superconducting contacts
results in very reproducible superconducting transistors. In these devices a
supercurrent (i.e. a current without resistance) can flow through the nanowire
from one superconducting contact to the other. This quantum effect can be described
as the “leakage” of Cooper pairs (i.e. paired electrons responsible for superconductivity)
from the superconducting contacts into the semiconductor nanowire. Moreover,
this supercurrent can be controlled by a gate voltage making it a supercurrent
The use of a recently developed method to grow semiconductor nanowires plays
a central role in this achievement. The nanowires are made in a “bottom up” technology,
i.e. instead of growing layers of material and removing the regions that are
not needed, a device is constructed from small building blocks. In this case
the nanowires grow from small gold particles by a vapor-liquid-solid (VLS) process.
The size of these nanoparticles is in the range between 10 and 100 nm and this
sets the diameter of the nanowires. The length of the nanowires is proportional
to the growth time and can easily reach tens of microns providing a convenient
aspect ratio for post-growth device fabrication.
The demonstrated high yield of the superconducting devices is an important requirement
for the successful up scaling to small superconducting circuits incorporating
multiple nanowire devices. For instance, two nanowire devices could be used to
build an electrically tunable superconducting quantum interference device (SQUID).
Such a device could be useful in solid-state quantum computer architectures as
a switchable coupling element between superconducting quantum bits. Another possibility
could be the combination of a nanowire light-emitting diode (LED; this can be
made by alternating the semiconductor vapor between n- and p-doped during growth)
with superconductivity in order to transfer quantum information from electrons
Rendering of a semiconductor nanowire contacted
by two superconducting metal electrodes. An opening
in the side of the nanowire allows the viewer to
look in the inside and see the conduction electrons.
Close to the superconducting contacts the electrons
are paired due to induced superconductivity, the
main result of our work. The sky is formed by one
of the measurements presented in the article. At
the end of the nanowire the catalytic gold particle
is located, a clear signature of the 'bottom-up'
nature of the nanowires.
Scanning electron micrograph of one of the
semiconductor nanowire devices. The nanowire is
contacted by three superconducting aluminum contacts
that induce the superconductivity in the nanowire.
The device is fabricated on an oxidized doped silicon
wafer that is used as a gate electrode in order
to control the supercurrent. At the end of the
wire the gold nanoparticle is clearly visible.
information Kavli Institute Delft:
Tel.: +31 15 2786064
Mobile: +31 6 26014370
Internet : http://qt.tn.tudelft.nl/
Contact information Philips Research:
Tel.: +31 40 27 43703
Mobile: +31 6 10888824
About Kavli Institute Delft
The Kavli Institute of Nanoscience at Delft University of Technology consists
of six research groups and a nanofabrication cleanroom facility. With a staff
of 16 professors and over 80 PhD students and postdocs, the Institute studies
new physics and exploits novel principles in nanostructured devices with a new
functionality. The nanostructures vary from superconductors to biopolymers and
are obtained from nature or fabricated with bottom-up methods (starting with
atoms or molecules) or top-down techniques (such as electron-beam lithography).
More information can be found on http://nanoscience.tudelft.nl.
About Royal Philips Electronics
Royal Philips Electronics of the Netherlands (NYSE: PHG, AEX: PHI) is one of
the world's biggest electronics companies and Europe's largest, with sales of
EUR 30.3 billion in 2004. With activities in the three interlocking domains of
healthcare, lifestyle and technology and 160,900 employees in more than 60 countries,
it has market leadership positions in medical diagnostic imaging and patient
monitoring, color television sets, electric shavers, lighting and silicon system
solutions. News from Philips is located at www.philips.com/newscenter.
story has been adapted from a news release -
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