High thermal conductivity electronic materials are critical components for
high-performance electronic and photonic devices as either active functional
materials or thermal management materials. We report an isotropic high thermal
conductivity over 500 W m-1K-1 at room temperature in high-quality wafer-scale
cubic silicon carbide (3C-SiC) crystals, which is the second highest among
large crystals (only surpassed by diamond). Furthermore, the corresponding
3C-SiC thin films are found to have record-high in-plane and cross-plane
thermal conductivity, even higher than diamond thin films with equivalent
thicknesses. Our results resolve a long-lasting puzzle that the literature
values of thermal conductivity for 3C-SiC are perplexingly lower than the
structurally more complex 6H-SiC. Further analysis reveals that the observed
high thermal conductivity in this work arises from the high purity and high
crystal quality of 3C-SiC crystals which excludes the exceptionally strong
defect-phonon scatterings in 3C-SiC. Moreover, by integrating 3C-SiC with other
semiconductors by epitaxial growth, we show that the measured 3C-SiC-Si TBC is
among the highest for semiconductor interfaces. These findings not only provide
insights for fundamental phonon transport mechanisms, also suggest that 3C-SiC
may constitute an excellent wide-bandgap semiconductor for applications of
power electronics as either active components or substrates