RWTH: Stability for the future of two-dimensional transistors

Scientists from the Chair of Electronic Components at RWTH Aachen University headed by Professor Max Lemme are researching new electronic components in an international team with the University of Vienna and the Bergische Universität Wuppertal as well as Aachen-based AMO GmbH. The team has now published the latest results of their research work in the journal Nature Electronics.

Stability – in the sense of stable operation over the entire lifetime – is one of the most important properties that an electronic component must have in order to be suitable for applications. And it’s the Achilles’ heel of field effect transistors based on two-dimensional materials, which typically have much poorer stability than silicon-based devices. “One aspect that is often neglected in research is component reliability. This is exactly the point we have been addressing for a number of years, because it will be of central importance for the application,” explains Professor Max Lemme.

However, the instability present is not only caused by 2D materials themselves, but more specifically by charges trapped in the oxide insulator used to fabricate the transistors. “One would prefer to use a different insulator with fewer charge traps,” says Lemme, “but there are still no scalable solutions for this. In our work we have shown instead that it is possible to use a standard insulator such as alumina and by tuning the charge carrier density in the 2D material, significantly suppress the adverse effects of the charge traps in the oxide.”

The work combines a thorough theoretical analysis of the novel approach – dubbed “stability-based design” by the authors – and a basic demonstration of the concept through electrical measurements on different types of graphene transistors.

The core idea of ​​the approach is to construct the 2D material/insulator combination in such a way that the energy of the charge traps in the insulator is as different as possible from that of the charge carriers in the 2D material. “Graphene-based transistors were the ideal test bed for our approach, as it is relatively easy to tune the energy of charge carriers in graphene. In principle, however, the approach can be applied to all transistors based on 2D semiconductors,” explains Professor Lemme. These results represent a major step towards stable and reliable transistors made of 2D materials to be integrated into semiconductor technology.