The team, led by Professor Yongjie Hu of mechanical and aerospace engineering, developed defect-free single crystal boron arsenide with a thermal conductivity of 1300 W/mK, three times more conducting than silicon carbide and copper, currently the best materials in use at heat management industry. This could lead to new substrates to cool high power devices, reducing system size and improving reliability.
“This is a very challenging work that requires highly multidisciplinary expertise from precise materials synthesis, comprehensive structural characterizations, to accurate thermal transport measurement and theoretical calculations,” said Hu, an assistant professor in the Department of Mechanical and Aerospace Engineering at UCLA. “The result established a benchmark thermal material platform for many opportunities in both fundamental science and applications.”
The crystal handles heat in a different way to most other materials. Thermal properties in solids can be described by the interactions of phonons, the quantum mechanical modes of lattice vibrations. For most materials a three-phonon process governs thermal transport, and the effects of four-phonon and higher-order processes were believed to be negligible. This study showed that four-phonon processes make an important contribution in defect-free BAs single crystals.
“This achievement and celebration should go to the whole field,” said Hu. “There are many other leading research groups making progress towards this target. In particular, this success exemplifies the power of combining experiments and theory in new materials discovery, and I believe this approach will continue to push the scientific frontiers in new materials discovery for many areas including energy, electronics, and photonics applications.”