An Improved Carbon Nanotube Semiconductor
Professor Yang-Kyu Choi and his research team
of the School of Electrical Engineering at KAIST collaborated with Professor Sung-Jin
Choi of Kookmin University to develop a large-scale carbon nanotube semiconductor
by using a 3-D fin-gate structure with carbon nanotubes on its top.
Dong Il Lee, a postdoctoral researcher at KAIST’s
Electrical Engineering School, participated in this study as the first author.
It was published in ACS Nano on November
10, 2016, and was entitled “Three-Dimensional Fin-Structured Semiconducting
Carbon Nanotube Network Transistor.”
A semiconductor made with carbon nanotubes
operates faster than a silicon semiconductor and requires less energy, yielding
Most electronic equipment and devices,
however, use silicon semiconductors because it is difficult to fabricate highly
purified and densely packed semiconductors with carbon nanotubes (CNTs).
To date, the performance of CNTs was limited
due to their low density. Their purity was also low, so it was impossible to
make products that had a constant yield on a large-surface wafer or substrate.
These characteristics made the mass production of semiconducting CNTs difficult.
To solve these difficulties, the research
team used a 3-D fin-gate to vapor-deposit carbon nanotubes on its top. They
developed a semiconductor that had a high current density with a width less
than 50 nm.
The three-dimensional fin structure was able
to vapor-deposit 600 carbon nanotubes per micrometer. This structure could have
20 times more nanotubes than the two dimensional structure, which could only
vapor-deposit thirty in the same 1 micrometer width.
In addition, the research team used
semi-conductive carbon nanotubes having a purity rating higher than 99.9% from
a previous study to obtain a high yield semiconductor.
The semiconductor from the research group has
a high current density even with a width less than 50 μm. The new semiconductor
is expected to be five times faster than a silicon-based semiconductor and will
require five times less electricity during operation.
Furthermore, the new semiconductor can be
made by or will be compatible with the equipment for producing silicon-based
semiconductors, so there will be no additional costs.
Researcher Lee said, “As a next generation
semiconductor, the carbon nanotube semiconductor will have better performance,
and its effectiveness will be higher.” He also added, “Hopefully, the new
semiconductor will replace the silicon-based semiconductors in ten years.”
This study received support from the Center
for Integrated Smart Sensors funded by the Ministry of Science, ICT &
Future Planning of Korea as the Global Frontier Project, and from the CMOS (Complementary
Metal-Oxide-Semiconductor) THz Technology Convergence Center of the Pioneer
Research Center Program sponsored by the National Research Foundation of Korea.
Picture 1: 3D Diagram of the Carbon Nanotube Electronic
Device and Its Scanning Electron Microscope (SEM) Image
Picture 2: 3D Transistor Device on an 8-inch Base
and the SEM Image of Its Cross Section