Effects of Defects on Thermal Transport across Solid/Solid Heterogeneous Interfaces

TL;DR

This paper investigates how defects influence heat transfer at solid/solid interfaces in chips, revealing that defect location and concentration can either weaken or enhance interfacial thermal conductance depending on the materials involved.

Contribution

A microscale thermal transport model combining first-principles calculations with Monte Carlo simulations to explicitly analyze defect effects on interfacial heat transfer.

Findings

Defects generally weaken heat transfer at interfaces like Si/SiC, Si/Diamond, and GaN/Diamond.

Higher defect concentration reduces interfacial thermal conductance.

Defects in GaN decrease ITC, while defects in SiC increase ITC due to phonon energy redistribution.

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. In this work, a microscale thermal transport model is developed by combining first-principles calculations with Monte Carlo simulations, explicitly accounting for the effects of defects. 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 0.05, ITC decreases by 54.1% when defects are present in GaN, but increases by 57.2% when defects are present 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 heat transfer. This study enriches the fundamental understanding of thermal transport across semiconductor heterointerfaces and guides the design and fabrication of high-ITC heterostructures.