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

TL;DR

This study experimentally demonstrates significant thermal transport anisotropy in single-crystal InN films caused by dislocation arrays, challenging conventional models and offering new avenues for thermal management in electronic devices.

Contribution

It provides the first experimental evidence of dislocation-induced thermal anisotropy in III-nitride films, revealing large deviations from traditional predictions.

Findings

Cross-plane thermal conductivity is over ten times higher than in-plane at 80 K.

Dislocation density is around 3x10^10 cm^-2.

Conventional models do not predict the observed anisotropy.

Abstract

Dislocations, one-dimensional lattice imperfections, are common to technologically important materials such as III-V semiconductors, and adversely affect heat dissipation in e.g., nitride-based high-power electronic devices. For decades, conventional models based on nonlinear elasticity theory have predicted this thermal resistance is only appreciable when heat flux is perpendicular to the dislocations. However, this dislocation-induced anisotropic thermal transport has yet to be seen experimentally. In this study, we measure strong thermal transport anisotropy governed by highly oriented threading dislocation arrays along the cross-plane direction in micron-thick, single-crystal indium nitride (InN) films. We find that the cross-plane thermal conductivity is more than tenfold higher than the in-plane thermal conductivity at 80 K when the dislocation density is on the order of ~3x10^10 cm^-2. This large anisotropy is not predicted by the conventional models. With enhanced understanding of dislocation-phonon interactions, our results open new regimes for tailoring anisotropic thermal transport with line defects, and will facilitate novel methods for directed heat dissipation in thermal management of diverse device applications.