A touch of carbon instead of silicon: Researchers have given graphene semiconductor properties, opening up new possibilities in microelectronics. The individual layer of carbon atoms can therefore provide exciting material properties. The technology could, among other things, enable the development of smaller and more powerful microelectronic components, say the scientists.
Under certain conditions they become electrically conductive and can therefore take on switch functions: Thanks to this material property, semiconductors form the basis of microchips etc. So far, the element silicon has mainly been used for this – but the performance of this semiconductor is now increasingly reaching its limits. Innovative semiconductor systems are therefore required to meet the further need for miniaturization, increased performance and functional expansion in microelectronics.
For some time now, researchers have been working on harnessing the characteristics of specially structured carbon: Graphene is a two-dimensional structure made of carbon atoms arranged in a honeycomb shape, which are linked to each other by strong bonds. “We were motivated by the hope of introducing three special properties of graphene into electronics: It is an extremely robust material that can withstand very strong currents without heating up and falling apart,” explains senior author Walter de Heer from the Georgia Institute of Technology in Atlanta.
Graphs made usable
De Heer and his international team of researchers have now been able to overcome a hurdle that previously stood in the way of graphene electronics: the material does not normally have semiconductor properties – graphene lacks the so-called band gap. This is an energetic barrier that the electrons have to overcome in order to become mobile and thus make the material conductive. This happens in semiconductors, for example, when an electric field is applied. The functions of transistors and silicon electronics are based on this effect. The challenge in graphene electronics research was therefore to give the material a band gap so that it could be used in a similar way to silicon.
The concept of the new development is now based on “growing” a single graphene layer on a special base: silicon carbide. This is a chemical compound made of silicon and carbon. Using a heating process, the developers are able to grow a graphene layer on the crystal surface of the silicon carbide in such a way that it has the desired properties and structure. The team was able to show that this graphene combines with the underlying silicon carbide in such a way that the graphene develops semiconductor properties. “Our technology now creates a band gap and is therefore a crucial step in the realization of graphene-based electronics,” says co-author Lei Ma from China’s Tianjin University. De Heer adds: “However, we had to learn how to handle the material, how to make it better and finally how to measure the properties.”
A promising type of semiconductor
The team’s research results showed the potential of their graphene semiconductor. Above all, according to them, it has ten times greater so-called mobility than silicon. This means that the electrons can move with little resistance, which could lead to faster calculations in electronics, the scientists explain. “We now have an extremely robust and powerful graphene semiconductor that has properties that silicon does not offer,” says de Heer. “The material is more efficient, it doesn’t heat up as much and it allows the electrons to move faster. “It’s like driving on a highway instead of a gravel road,” he said.
According to the team, their system has the fundamentally necessary properties for use in electronics. As a result, graphene-based electronics now have the potential to significantly stimulate technological developments. It could enable even smaller and more powerful microelectronic components. The material could also benefit the use of the quantum mechanical wave properties of electrons to create quantum computers, writes the Georgia Institute of Technology. De Heer is convinced that graphene-based electronics could represent a groundbreaking technology.
Source: Georgia Institute of Technology, specialist article: Nature, doi: 10.1038/s41586-023-06811-0