# Impact of Screw and Edge Dislocation on the Thermal Conductivity of Nanowires and Bulk GaN

## TL;DR

This study uses molecular dynamics simulations to investigate how screw and edge dislocations affect the thermal conductivity of GaN nanowires and bulk material, revealing significant reductions and anisotropic effects.

## Contribution

It provides a detailed analysis of the impact of different dislocation types on thermal conductivity and its temperature dependence in GaN, including the effects of dislocation density.

## Key findings

- Screw dislocations reduce thermal conductivity by about 50%.
- Edge dislocations have a less pronounced effect on thermal conductivity.
- Dislocation density increases anisotropy in thermal conductivity.

## Abstract

We report on thermal transport properties of wurtzite GaN in the presence of dislocations, by using molecular dynamics simulations. A variety of isolated dislocations in a nanowire configuration were analyzed and found to reduce considerably the thermal conductivity while impacting its temperature dependence in a different manner. We demonstrate that isolated screw dislocations reduce the thermal conductivity by a factor of two, while the influence of edge dislocations is less pronounced. The relative reduction of thermal conductivity is correlated with the strain energy of each of the five studied types of dislocations and the nature of the bonds around the dislocation core. The temperature dependence of the thermal conductivity follows a physical law described by a T$^{-1}$ variation in combination with an exponent factor which depends on the material's nature, the type and the structural characteristics of the dislocation's core. Furthermore, the impact of the dislocations density on the thermal conductivity of bulk GaN is examined. The variation and even the absolute values of the total thermal conductivity as a function of the dislocation density is similar for both types of dislocations. The thermal conductivity tensors along the parallel and perpendicular directions to the dislocation lines are analyzed. The discrepancy of the anisotropy of the thermal conductivity grows in increasing the density of dislocations and it is more pronounced for the systems with edge dislocations.