Effects of defects on thermal transport across solid/solid heterogeneous interfaces

Abstract

During the fabrication of heterogeneous structures inside chips, impurities and defects are inevitably introduced. However, the mechanism by which defects affect interfacial heat transport remains unclear. This work proposes a heterostructure thermal transport model that incorporates the effects of defects. The Boltzmann transport equation is solved using the Monte Carlo simulation, with full-band phonon properties obtained from first-principles calculations serving as input parameters. The effects of defect concentration and location on thermal transport characteristics are investigated for four heterointerfaces: Si/SiC, GaN/SiC, Si/diamond, and GaN/diamond. Temperature distribution, spectral thermal conductance, average phonon scattering numbers, and interfacial thermal conductance (ITC) are compared under different conditions. The results show that, for Si/SiC, Si/diamond, and GaN/diamond interfaces, introducing defects weakens heat transport. Higher defect concentration leads to lower ITC. Furthermore, when defects are in SiC or diamond, which have broader phonon spectral distributions, their impact on ITC is weaker. For the GaN/SiC interface, defects in GaN reduce ITC, while defects in SiC enhance ITC. At a defect concentration of 0.56%, ITC decreases by 54.1% when defects are present in GaN, but increases by 57.2% when defects are in SiC. This behavior arises from defect-induced phonon energy redistribution near the interface. The redistribution increases the population of low-frequency phonons, which are more capable of crossing the interface, thus enhancing interfacial heat transfer. However, although introducing defects can increase ITC, it also raises the bulk thermal resistance, leading to a higher total thermal resistance of the heterostructure. It remains challenging to enhance heat transfer across heterostructures by defect engineering. This study enriches the fundamental understanding of thermal transport across semiconductor heterointerfaces and guides the design and fabrication of high heat-transfer heterostructures.