In power electronics, semiconductors are based on elemental silicon-but the energy efficiency of silicon carbide will be much higher. Physicists at the University of Basel, the Paul Scherrer Institute and ABB explained in the scientific journal "Applied Physics Letters" the reasons for preventing the combined use of silicon and carbon.

Energy consumption is increasing globally, and sustainable energy supply such as wind and solar energy is becoming more and more important. However, electricity is usually generated far away from consumers. Therefore, efficient power distribution and transportation systems are as important as substations and power converters that convert the generated direct current into alternating current.
Save a lot of money

Modern power electronic equipment must be able to handle large currents and high voltages. Transistors made of semiconductor materials currently used for field effect transistors are now mainly based on silicon technology. However, the use of SiC on silicon has significant physical and chemical advantages: In addition to higher heat resistance, this material can also provide better energy efficiency, thereby saving a lot of costs.

As we all know, these advantages are obviously affected by the defects at the interface between silicon carbide and the insulating material silicon dioxide. This damage is based on tiny irregular carbon ring clusters crystallized in the crystal lattice, which has been experimentally proven by Professor Thomas Jung of the Swiss Institute of Nanoscience and the Physics Department of the University of Basel and the Paul Scherrer Institute. Using atomic force microscope analysis and Raman spectroscopy, they showed that defects were generated near the interface through the oxidation process.
Experiment confirmed

Interfering carbon clusters with a size of only a few nanometers are formed during the oxidation process of silicon carbide to silicon dioxide at high temperatures. "If we change certain parameters during oxidation, we can influence the occurrence of defects," said doctoral student Dipanwita Dutta. For example, the nitrous oxide atmosphere during heating results in significantly fewer carbon clusters.

The experimental results were confirmed by a team led by Professor Stefan Gödecker from the Department of Physics of the University of Basel and the Swiss Institute of Nanoscience. Computer simulations confirmed the structural and chemical changes caused by graphite carbon atoms observed in the experiment. In addition to experiments, atomic insights were obtained in the generation of defects and their effects on the flow of electrons in semiconductor materials.
Better use of electricity

"Our research has provided important insights to promote the development of silicon carbide-based field effect transistors. Therefore, we expect to make a significant contribution to the more efficient use of electricity," Jung commented. This work was initiated as part of the Nano Argovia Applied Research Project program.