Pushing the boundaries of semiconductors

　　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 for future power electronics.

　　The study, Power Electronics 2020, has led them to explore a piezoelectric semiconductor, a material with a high dielectric strength known as scandium aluminium nitride (ScAlN).

　　Silicon has dominated the electronics industry. With its relatively low cost and an almost perfect crystal structure, it has become a particularly successful semiconductor material. Moreover, its bandgap allows for both a good charge carrier concentration and velocity as well as a good dielectric strength. Despite its benefits, silicon electronics is gradually reaching its physical limit. Especially with regard to the increasing demand for power density and compactness.

　　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 also allows for higher energy efficiency, thereby reducing energy consumption.

　　Fraunhofer 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 work have already been put to commercial use. The Power Electronics 2020 team is now looking towards the next step, enhancing the energy efficiency and durability of next generation electronic systems once more.

　　ScAlN is largely unexplored worldwide with regard of its usability in microelectronic applications. But its suitability for power electronic components has already been proven, says the team. 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 large bandgap, such as ScAlN and GaN, 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. By combining both materials, the researchers want to double the maximal possible output power of our devices while at the same time significantly lowering the energy demand.

　　One of the biggest challenges of the project is crystal growth because their existing structures neither growth recipes nor empirical values. The project team is looking 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.