Thin film SiC beats diamond with record thermal conductivity
Researchers in Japan have shown that the thermal conductivity of thin films of cubic 3C-silicon carbide can be higher than diamond.
The team, led by Associate Professor Jianbo Liang and Professor Naoteru Shigekawa from the Osaka Metropolitan University Graduate School of Engineering, used thermal conductivity evaluation and atomic-level analysis to show that the cubic version, 3C-SiC, exhibits high thermal conductivity equivalent to the theoretical level.
First, they demonstrated that 3C-SiC bulk crystals, using chemicals from supplier Air Water Inc in Osaka grown on a small silicon wafer, exhibit high thermal conductivity of 500 W/mK, which is second only to diamond. Then, they showed that a thin film of 3C-SiC crystals at 1.75um could exhibit a thermal conductivity higher than that of diamond at with record-high in-plane and cross-plane thermal conductivity.
The results resolve a long-standing puzzle that the literature values of thermal conductivity for 3C-SiC are lower than the structurally more complex 6H-SiC. The high thermal conductivity arises from the high purity and high crystal quality of 3C-SiC crystals which avoids the exceptionally strong defect-phonon scatterings.
3C-SiC is a SiC polytype which can be epitaxially grown on silicon, and the 3C-SiC-Si thermal boundary conductance is among the highest for semiconductor interfaces. This suggests that thin film 3C-SiC is an excellent wide-bandgap semiconductor for applications of next-generation power electronics as both active components and substrates.
The atomic-level analysis to investigate why they were able to measure the high thermal conductivity, which had not been previously observed. They found that the 3C-SiC crystal contained almost no impurities: the atoms in the crystal were regularly arranged, indicating a very high-quality single crystal.
Furthermore, they formed 3C-SiC crystals on a silicon substrate and performed an atomic-level analysis of the thermal conductivity of the interface, which revealed no significant disorder in the atomic arrangement at the interface and exhibited a high thermal conductance.
“Both the freestanding 3C-SiC crystal and thin films on a silicon substrate have high thermal conductivity and we expect large-diameter wafers can be fabricated at a low cost. This should lead to improved heat dissipation on a practical level in electronic devices,” said Liang.
The research results were published in Nature Communications.
Osaka Metropolitan University is a new public university established in April 2022, formed by merger between Osaka City University and Osaka Prefecture University.
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