Spatiotemporal Mapping of Anisotropic Thermal Transport in GaN Thin Films via Ultrafast X-ray Diffraction

TL;DR

This paper introduces a non-contact ultrafast x-ray diffraction technique to map and quantify anisotropic thermal transport in GaN thin films, revealing localized reductions in thermal conductivity and boundary conductance near defects.

Contribution

It presents a novel ultrafast x-ray diffraction method for spatiotemporal mapping of thermal transport in thin films, enabling detailed defect-level analysis.

Findings

Four-fold reduction in thermal conductivity near a wrinkle

25% decrease in interfacial thermal conductance

Asymmetric heat dissipation observed across defects

Abstract

Efficient thermal management is essential for the reliability of modern power electronics, where increasing device density leads to severe heat dissipation challenges. However, in thin-film systems, thermal transport is often compromised by interfacial resistance and microscale defects introduced during synthesis or transfer, which are difficult to characterize using conventional techniques. Here we present a non-contact, spatiotemporal-resolved ultrafast x-ray diffraction method to extract in-plane thermal conductivity and thermal boundary conductance, using GaN thin films on silicon as a model system. By tracking the pump-induced lattice strain, we reconstruct the lateral heat flow dynamics and quantitatively probe thermal transport near a wrinkle defect. We uncover pronounced asymmetric heat dissipation across the wrinkle, with a four-fold reduction in the local thermal conductivity near the wrinkle and a 25% drop in interfacial conductance. Our work demonstrates that ultrafast x-ray diffraction can serve as a precise thermal metrology tool for characterizing heat transport in multilayered thin-film structures for next-generation microelectronic devices.