 New production techniques could allow gallium arsenide semiconductors to edge in on silicon's overwhelming territory. The flexible thin films hold hope for everything from integrated circuits to solar cells. (Source: John Rogers/University of Illinois)
Could silicon's choke hold on the semiconductor universe be threatened?
Silicon
isn't the best semiconductor in the world. But among the features
keeping it nearly ubiquitous in electronic devices is the relative
ease of construction of silicon-based chips in comparison to superior
materials. As with just about any mass-produced product in the world,
quality has long since taken the back seat to quantity.
One
contender for semiconductor superiority is gallium arsenide.
Unfortunately, as one might be led to believe, the vapor deposition
method typically utilized to create gallium arsenide is more costly
than its silicon counterpart. Fortunately for gallium arsenide, a
group of DoE and NSF-funded professors, students and scientists based
at the University of Illinois, has pioneered a new manufacturing
process that will
help even the field.
As the previously utilized methods of
gallium arsenide semiconductor production involved deposition to
create a thin film, devices either needed to be created directly on
the substrate or in a more typical wafer design which could then be
clipped out into multiple pieces much like a standard silicon wafer
technique used for manufacturing computer processor cores. The
cleverness of the UI team's take on the thin films isn't in a
revolutionary deposition process, but in using the same process over
and over on the same substrate. By utilizing the same substrate
multiple times, stacking the thin films on top of each other, they
save time, money and manpower involved in producing the same amount
of film in single sheets.
In order to ensure the layers are
easily disassembled, each layer of gallium arsenide is alternated
with a layer of aluminum arsenide. Once the deposition process is
complete, the finished multi-layer unit can be washed in a solvent
and oxidizing agent to dissolve the layers of aluminum arsenide and
free the sheets of gallium arsenide. A specialized piece of equipment
then peels each layer off, one at a time, and transfers them to their
new home substrate. In this manner, a single "wafer" can
produce ten or more times the amount of semiconductor material of a
single sheet deposition.
The group's initial work with the new
semiconductor process has been with solar cells, where cost versus
efficiency is the breaking point for any new material. A North
Carolinian company, Semprius Inc., has already begun using the
process to manufacture new solar cells. They have also utilized the
process to create light sensors and high-speed transistors. In the
future they hope to find more devices that could benefit from the
more cost-effective process, as well as other materials that may
benefit from it.
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