Dislocation-induced thermal transport anisotropy in single-crystal group-III nitride films


Dislocations, one-dimensional lattice imperfections, are common to technologically important materials such as III–V semiconductors, and adversely affect heat dissipation in, for example, nitride-based high-power electronic devices. For decades, conventional nonlinear elasticity models have predicted that this thermal resistance is only appreciable when the heat flux is perpendicular to the dislocations. However, this dislocation-induced anisotropic thermal transport has yet to be seen experimentally. Using time-domain thermoreflectance, we measure strong thermal transport anisotropy governed by highly oriented threading dislocation arrays throughout micrometre-thick, single-crystal indium nitride films. We find that the cross-plane thermal conductivity is almost tenfold higher than the in-plane thermal conductivity at 80 K when the dislocation density is ~3 × 1010 cm−2. This large anisotropy is not predicted by conventional models. With enhanced understanding of dislocation–phonon interactions, our results may allow the tailoring of anisotropic thermal transport with line defects, and could facilitate methods for directed heat dissipation in the thermal management of diverse device applications.

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Fig. 1: InN structure design and characterization.
Fig. 2: Temperature-dependent thermal conductivity of InN films with oriented threading dislocations.
Fig. 3: Dislocation density-dependent thermal transport.

Data availability

The data sets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.


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The authors thank R. Wang and B. Huang at NUS for help with the thermal evaporation of Al films. The authors thank M. Li at MIT for explanation of his papers. This work was supported by an NUS Start-up Grant, the Singapore Ministry of Education Academic Research Fund Tier 2 under award no. MOE2013-T2–2–147 and Singapore Ministry of Education Academic Research Fund Tier 1 FRC project FY2016. C.P. and L.L. acknowledge support from the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division and computational resources from the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science User Facility supported by the Office of Science of the US Department of Energy under contract no. DE-AC02-05CH11231. G.K. acknowledges support from the excellence program Nanosystems Initiative Munich (NIM) funded by the German Research Foundation (DFG).

Author information

G.K. and Y.K.K. initialized the idea. B.S. and Y.K.K. designed the experiments. B.S. performed the TDTR measurements and analysed the data. G.H., J.Z.J. and G.K. prepared and characterized the InN samples. C.P. and L.L. performed the first-principles and phonon-defect scattering calculations. All authors discussed the results and contributed to the manuscript.

Correspondence to Yee Kan Koh.

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Supplementary Notes 1–5, Supplementary Figures 1–16, Supplementary Tables 1–4, Supplementary References 1–30

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