Experimental observation of extremely strong defect–phonon scatterings in cubic SiC single crystals

Doping, which has been extensively studied in the past century, is essential for tuning the electrical conductivity of semiconductors. However, the effect of doping on the thermal conductivity of semiconductors has been much less studied despite the growing importance of electronics cooling. A clear understanding of defect–phonon scatterings remains elusive due to difficulties in well-controlled growth of crystals and advanced thermal and structural characterizations. Herein, by combining advanced characterizations and high-quality growth of cubic silicon carbide (3C-SiC) single crystals with well-controlled boron doping, we experimentally observe an extremely strong defect–phonon scattering intensity. This effect exceeds the prediction of the classic mass-difference model by tens of times in magnitude. At the doping level of 1019 cm−3, a 50% reduction of thermal conductivity was achieved—the highest reductions reported for common semiconductors. The measured thermal conductivity of B-doped 3C-SiC matches first-principles predictions with excellent agreement, demonstrating the critical role of low-frequency phonon resonant scattering. The influence of strain gradients on thermal transport was excluded by local vibrational spectra scanning through atomic-resolution phonon-level electron energy loss spectroscopy. Our findings not only shed light on the fundamental understanding of defect–phonon interactions but will also impact applications such as thermal management of electronics.