Due to their material properties, components made of the universal semiconductor material silicon reach the limits of their efficiency. Silicon carbide (SiC), a compound of silicon and carbon, is more suitable. Its properties are impressive: high-voltage resistant, high-temperature resistant, chemically robust and suitable for higher switching frequencies, which can ensure a further increase in efficiency. In the field of power electronics, SiC components are being used as an alternative to silicon in an increasing number of applications.
Field-effect transistors (MOSFETs) obtain their functionality from the boundary layer between SiC and a very thin layer of silicon oxide applied to it. It is precisely this layer that confronts researchers with major challenges: Here, unwanted defects occur during production that trap electrical charge carriers and thus reduce the current in the component. The investigation of these defects is therefore extremely important in order to exploit the potential of the material.
Conventional methods for investigating the properties of MOSFETs, mostly from the silicon world, do not take these defects into account at all. Other, more complex measurement methods are either not practicable on a large scale or cannot be applied to finished components at all. For this reason, researchers at the FAU’s Chair of Applied Physics have been looking for new ways to better investigate these defects. They noticed that the interfacial defects always follow the same pattern. “We represented this pattern with a mathematical formula,” explains doctoral student Martin Hauck. “In this way we can include the interfacial defects so cleverly in the calculation that not only the results of the usual parameters such as electron mobility or input voltage can be precisely determined. In addition, the concentration and distribution of the defects is determined almost incidentally, so to speak”.
In experiments carried out by the physicists with the aid of tailor-made transistors from the industrial partner Infineon Technologies Austria AG and its subsidiary Kompetenzzentrum für Automobil- & Industrie-Elektronik GmbH, the method proved to be simple and particularly accurate at the same time. The precise insight into the innermost part of the field effect transistors now allows better and shorter innovation cycles: procedures to reduce defects can be evaluated precisely, quickly and easily in this way – and the development of new, energy-saving power electronics can be accelerated accordingly.
The cooperation with Infineon does not mean that the method will only benefit this company, explained a university spokesperson. “Everyone can do that for themselves,” the spokesperson said. Moreover, the development team is currently working on further improving the process. It is currently based on a simulation, which is quite time-consuming. “We already have ideas on how to get the critical data directly from the measurements,” the speaker said.
More information: Friedrich Alexander Universität