New material to replace silicon-based power electronics

The electronics market is growing constantly, and so is the demand for increasingly compact and efficient power electronic systems. In the foreseeable future, electronic components based on silicon will no longer be able to meet industrial requirements.

That’s why scientists from the University of Freiburg, the Sustainability Center Freiburg and the Fraunhofer-Gesellschaft have joined forces in order to explore a new material structure that may be better suited to future power electronics.

Silicon technology reaches its physical limit

Currently, silicon dominates the electronics industry. With its relatively low cost and an almost perfect crystal structure, silicon has become a particularly successful semiconductor material, with its bandgap allowing for a good charge carrier concentration and velocity as well as a good dielectric strength. However, silicon electronics are gradually reaching their physical limit, with silicon power electronic components proving insufficient in regards to power density and compactness.

Innovative material composition for more power and efficiency

The limitations of silicon technology have already been overtaken by the use of gallium nitride (GaN) as a semiconductor in power electronics. GaN performs better in conditions of high voltages, high temperatures and fast switching frequencies compared to silicon. This goes hand in hand with significantly higher energy efficiency — with numerous energy-consuming applications, this means a significant reduction in energy consumption.

The Fraunhofer Institute for Applied Solid State Physics IAF has been researching GaN as a semiconductor material for electronic components and systems for many years. With the help of industrial partners, the results of this research have already been put to commercial use. Researchers at the institute will now go even further in order to once more enhance the energy efficiency and durability of the next generation of electronic systems. For this purpose, a different and novel material will be used: scandium aluminium nitride (ScAlN).

First components based on ScAlN

ScAlN is a piezoelectric semiconductor material with a high dielectric strength which is largely unexplored worldwide with regards to its usability in microelectronic applications. With the material having already been proven as “especially well suited for power electronic components”, according to Fraunhofer IAF Project Manager Dr-Ing Michael Mikulla, the aim of the new project is to grow lattice-matched ScAlN on a GaN layer and to use the resulting heterostructures to process transistors with high current-carrying capacity.

“Functional semiconductor structures based on materials with a large bandgap, such as scandium aluminium nitride and gallium nitride, allow for transistors with very high voltages and currents,” said Fraunhofer IAF Director Prof Dr Oliver Ambacher. “These devices reach a higher power density per chip surface as well as higher switching speeds and higher operating temperatures. This is synonymous with lower switching losses, higher energy efficiency and more compact systems.”

“By combining both materials, GaN and ScAlN, we want to double the maximal possible output power of our devices while at the same time significantly lowering the energy demand,” Dr-Ing Mikulla added.

Researchers at Fraunhofer IAF have been working on the piezoelectric properties of ScAlN for use in high-frequency filters for many years. The picture shows the characterisation of such devices on a wafer. Image© Fraunhofer IAF

Collaboration and knowledge transfer

The research project will be a collaborative effort between the University of Freiburg, Fraunhofer IAF, the Sustainability Center Freiburg and the Fraunhofer Institute for Integrated Systems and Device Technology IISB — an approach that is likely to serve as a model for future project cooperation.

“On the one hand, this model facilitates cooperation with companies through the prompt transfer of results from basic research to application-oriented development,” Prof Dr Ambacher said. “On the other hand, it opens up synergies between two technically complementary Fraunhofer centres from two different regions and thus improves both their offers for potential customers of the semiconductor industry.”