Electric Field Effect on Thermal Conductivity in Wurtzite GaN*

Gallium nitride (GaN), a wide bandgap semiconductor, has been widely used in high-power electronic devices due to its ability to withstand high breakdown voltage and high temperature. Its relatively high thermal conductivity makes GaN a favorable material for such applications, where heat dissipation is a major concern for the long-term stability. However, in GaN-based transistors, where the active region can withstand extremely strong electric fields, the field effect on thermal transport properties has drawn little attention up to date. In this work, we apply first-principles method to investigate phonon properties of wurtzite GaN in the presence of a near breakdown electric field along different directions. We find that the electric field changes thermal conductivity significantly via impacting the phonon anharmonicity and scattering rates, although it has little effect on phonon dispersions. Our study provides insights into the effect of the extreme external electric field on phonon transport properties in wide-gap semiconductors.