Power electronic devices control the flow of electricity and convert it for electric vehicles, renewable energy and industrial equipment. Some of the energy is lost as heat, which reduces efficiency and can harm the device's operation. Semiconductors able to withstand high voltage, conduct current well and dissipate heat would make such devices more reliable.
One candidate is alpha-gallium oxide (a-Ga2O3): it withstands very strong electric fields. But scientists still have a poor understanding of how easily electrons move in it and how well it dissipates heat. These are precisely the properties that matter for reliable electronics.
Specialists at Hokkaido University and Kyoto University grew thin films of alpha-gallium oxide by mist chemical vapor deposition: the material is deposited onto a substrate from a fine mist of a solution. Small amounts of germanium, an element that supplies the material with conducting electrons, were added to the films. By varying the germanium concentration, the authors studied how it affects the transfer of electricity and heat. The work was published in the journal ACS Applied Electronic Materials.
First the team measured the electrical properties of the films, including electron concentration and thermoelectric power, the voltage generated per unit temperature difference. The researchers then estimated the effective mass of the electrons, that is, how heavy they behave inside the material. The result was about 40 percent of the mass of a free electron, more than the theoretically predicted 25 percent. This discrepancy may partly explain why electrons in alpha-gallium oxide move more slowly than expected.
Next the scientists measured how efficiently the films conduct heat. Thermal conductivity was about 19 watts per meter-kelvin and hardly changed as the germanium concentration increased. Together the results show that adding germanium improves electron movement but does not noticeably affect heat transfer.
The authors emphasize that the data obtained are a basis for designing future power devices, not a ready-made solution. Turning this understanding into improved device performance requires further research.