New graphene transistor created with record high-switching performance
By Darren Quick
February 8, 2011
Graphene has already brought us the world’s smallest transistor, a triple-mode, single transistor amplifier and a supercapacitor that can store as much energy as a battery while recharging in seconds. And these are sure to just be the tip of the iceberg. The latest breakthrough from the wonderful world of graphene is a new graphene field effect transistor (GFET) that boasts a record high-switching performance. The device promises improved performance for future electronic devices and means graphene could potentially replace silicon, or at least be used side by side with silicon, in electronic devices.
Although graphene boasts high electrical conductivity, it is what is known as a zero bandgap semiconductor. This means that there is no difference between its conductive and nonconductive state and transistors made of the material cannot be easily turned on and off.
Dr Zakaria Moktadir of the Nano research group at the University of Southampton discovered that by introducing geometrical singularities such as sharp beds and corners in bilayer graphene nanowires, the current could be turned off efficiently. According to Professor Hiroshi Mizuta, Head of the Nano research group, this engineering approach has achieved an on/off switching ratio 1,000 times higher than previous attempts.
"Enormous effort has been made across the world to pinch off the channel of GFETs electrostatically, but the existing approaches require either the channel width to be much narrower than 10 nanometres or a very high voltage to be applied vertically across bilayer graphene layers," he says. “This hasn't achieved an on/off ratio which is high enough, and is not viable for practical use."
The researchers believe the breakthrough will enable electronics that progress beyond current silicon complementary metal-oxide semiconductor (CMOS) technology, which is reaching its limits.
"It will have major implications for next generation computer, communication and electronic systems. Introducing geometrical singularities into the graphene channel is a new concept which achieves superior performance while keeping the GFET structure simple and therefore commercially exploitable,” says Professor Harvey Rutt, Head of Electronics and Computer Science at the University of Southampton.
Now that he’s created the transistor, Dr Moktadir is now carrying out further research to understand the mechanism that causes the current to stop flowing in the channel. He is also testing the transistor’s reliability and performance under various noise and temperature conditions.