This year, the Millennium Technology Prize was awarded to Professor Bantval Jayant Baliga, the inventor and developer of a semiconductor component known as insulated gate bipolar transistor (IGBT). The component has increased the efficiency of electricity consumption and reduced the demand for fossil fuels, for example, by reducing production costs to such an extent that Forbes Magazine in 2016 named Baliga as the man with the world’s largest negative carbon footprint.
Converting electricity from high to low voltage requires couplings and transformers. In the process, the power output may be reduced by tens of per cents. This phenomenon recurs throughout society, from power lines to electrical appliances.
According to Professor of Experimental Materials Physics Filip Tuomisto, this loss of energy could be considerably reduced with new semiconductor materials.
“The amount of loss depends on the properties of the coupling material, and often on very small impurities. We are talking about parts per million,” Tuomisto says.
Effects of wanted and unwanted impurities
For several years, Tuomisto’s research group at the University of Helsinki has been developing extremely low-loss semiconductor materials for the needs of green electronics. In practice, the aim is to make the electrical conductivity of component materials as high as possible while simultaneously maximizing their breakdown voltage, in order to reduce the loss of energy.
"The material must enable the maintenance of the highest possible voltage without current leakage conducted through the coupling when it is switched off. Conversely, when switched on the coupling should conduct electricity as efficiently as possible to avoid loss of energy because of resistance," says Tuomisto, explaining the challenge.
Aluminium gallium nitride and aluminium gallium oxide show particular promise as replacements for silicon carbide, a compound of silicon and carbon currently used in high-voltage transformers and couplings.
Conductivity is naturally needed in transformers and couplings, but as little as possible. Even an extremely small amount of the desired impurity in the semiconductor activates it to conduct electricity. In the case of oxide and nitride compounds, the desired impurity is silicon.
At the Accelerator Laboratory of the University of Helsinki, Tuomisto’s group investigates the optimal distribution of silicon within these compounds. They are able to study the effects of wanted and unwanted impurities atom by atom, for example, by firing silicon and positrons into the compound.
Further information
Filip Tuomisto, Professor
Accelerator Laboratory, University of Helsinki
filip.tuomisto@helsinki.fi +358 50 384 1799