Novel Power Semiconductor Material Is Scandium Aluminum Nitride better as GaN?

Ein Forscherteam am Fraunhofer IAF beschäftigt sich bereits seit mehreren Jahren mit den piezoelektrischen Eigenschaften von ScAlN für den Einsatz in Hochfrequenzfiltern. Das Foto zeigt den Test solcher Bauelemente auf einem Wafer.
A team of researchers at Fraunhofer IAF has been working on the piezoelectric properties of ScAlN for the use in high-frequency filters for many years. The picture shows the characterization of such devices on a wafer.

Scientists of different German universities and research institutes have joined forces in order to explore scandium aluminum nitride (ScAlN). This new material structure may be better suited for future power electronics as gallium nitride (GaN).

Up to date, silicon dominates the electronics industry. However, silicon electronics gradually reaches its physical limit. Especially with regard to the required power density and compactness, silicon power electronic components are insufficient.

The limitations of silicon technology have already been overcome 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.

Now, scientists from the University of Freiburg, the Sustainability Center Freiburg, and the Fraunhofer Society are joining forces in order to explore a new material structure that may be even better suited for future power electronics as gallium nitride. The recently launched project »Research of Functional Semiconductor Structures for Energy Efficient Power Electronics« (in short »Power Electronics 2020+«) researches the novel semiconductor material scandium aluminum nitride (ScAlN). Prof. Dr. Oliver Ambacher, director of Fraunhofer IAF and professor of power electronics at the Department of Sustainable Systems Engineering (INATECH) of the University of Freiburg, coordinates the supra-regional collaboration.

First Components Based on ScAlN

ScAlN is a piezoelectric semiconductor material with a high dielectric strength which is largely unexplored worldwide with regard of its usability in microelectronic applications. »The fact that scandium aluminum nitride is especially well suited for power electronic components, due to its physical properties, has already been proven«, explains Dr.-Ing. Michael Mikulla, project manager on the part of Fraunhofer IAF. The aim of the 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 wide bandgap, such as scandium aluminum nitride and gallium nitride, allow for transistors with very high voltages and currents. 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«, adds Prof. Dr. Oliver Ambacher, director of Fraunhofer IAF. »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«, says Mikulla.

Pioneering Work in Materials Research

One of the biggest challenges of the project is crystal growth, considering that there exist structure neither growth recipes nor empirical values for this material, yet. The project team needs to develop these during the next months in order to reach reproducible results and to produce layer structures that can successfully be used for power electronic applications.

This new form of collaboration between university research and application-oriented development shall serve as a role model for future project cooperation. »On the one hand, this model facilitates the cooperation with companies through the prompt transfer of results from basic research to application-oriented development. On the other hand, it opens up synergies between two technically complementary Fraunhofer Centers from two different regions and thus improves both their offers for potential customers of the semiconductor industry«, reasons Prof. Ambacher.