Dmitry Svintsov, head of MIPT's Laboratory of Optoelectronics and Two-Dimensional Materials, said: "The point is not so much about saving electricity. At a lower power, electronic components heat up less, and that means that they are able to operate at a higher clock speed - not 1GHz, but 10 for example, or even 100."
Building transistors that are capable of switching at voltages less than 0.5V is one of the greatest challenges of modern electronics. Tunnel transistors are the most promising candidates to solve this problem. Unlike in conventional transistors, where electrons ‘jump’ through the energy barrier, in tunnel transistors the electrons ‘filter’ through the barrier due to the quantum tunnelling effect. However, in most semiconductors the tunnelling current is very small and this prevents transistors that are based on these materials from being used in real circuits.
The scientists proposed a new design for a tunnel transistor based on bilayer graphene, and using modelling, they proved that this material is an ideal platform for low-voltage electronics.
"Bilayer graphene is two sheets of graphene that are attached to one another with ordinary covalent bonds. It is as easy to make as monolayer graphene, but due to the unique structure of its electronic bands, it is a highly promising material for low-voltage tunnelling switches," Svintsov explained.
An important feature of the proposed transistor is the use of ‘electrical doping’ (the field effect) to create a tunnelling p-n junction. The complex process of chemical doping, which is required when building transistors on three-dimensional semiconductors, is not needed, and can even be damaging, for bilayer graphene. In electrical doping, additional electrons occur in graphene due to the attraction towards closely positioned doping gates.
Under optimum conditions, a graphene transistor can change the current in a circuit 10,000 times with a gate voltage swing of only 150mV.
"This means that the transistor requires less energy for switching, chips will require less energy, less heat will be generated, less powerful cooling systems will be needed, and clock speeds can be increased without the worry that the excess heat will destroy the chip," Svintsov concluded.
