Stability for the Future of Two-Dimensional Transistors

An international research team led by RWTH Professor Max Lemme has published a paper on new electronic components based on two-dimensional materials in the Nature Electronics journal. 

 

A group of researchers from the RWTH Chair of Electronic Devices, headed by Professor Max Lemme, is conducting research on new electronic components in an international team including researchers from the University of Vienna, the University of Wuppertal, and AMO GmbH in Aachen. The team has now published its latest research findings in the Nature Electronics journal.

Stability – meaning stable operations over the entire service life – is one of the most important properties an electronic component must have in order to be suitable for applications. This is a sore point for field-effect transistors based on two-dimensional materials, as they typically have far poorer stability than silicon-based devices. "One aspect that tends to be neglected in research is the reliability of components. This is precisely the topic we have been working on for several years now because it is of central importance for applications," explains Professor Max Lemme.

However, the instability is caused not only by 2D materials themselves but in particular by charges trapped in the oxide insulator used to make the transistors. "Ideally, a different insulator with fewer charge traps would be used," Lemme says, "but there are no scalable solutions for that yet. In our work, we have instead shown that it is possible to use a standard insulator such as aluminum oxide and, by adjusting the charge carrier density in the 2D material, we can significantly suppress the adverse effects of charge trapping in the oxide."

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

The core idea of the approach is to design the 2D material/insulator combination so the energy of the charge traps in the insulator differs as much as possible from that of the charge carriers in the 2D material. "Graphene-based transistors were the ideal test bed for our approach because it is relatively easy to tune the energy of charge carriers in graphene. However, the approach can, in principle, be applied to all transistors based on 2D semiconductors," explains Professor Lemme. These findings represent a major step towards stable and reliable transistors made of 2D materials being integrated into semiconductor technology.

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