  Electric fields commonly exist in semiconductor structures of electronics,
bringing to bear on phonon thermal transport. Also, it is a popular method to
tune thermal transport in solids. In this work, phonon and thermal transport
properties of GaN with wurtzite and zincblende structures at finite electric
field are investigated using first principles calculations from perspectives of
symmetry breaking and lattice deformation. Effects of electric field on phonon
transport properties including phonon dispersion and thermal conductivity from
response of electron density distribution only and response from lattice
changes are studied in zincblende GaN. It is found that the former has a small
but qualitative impact on phonon dispersion relations, i.e., splitting of
phonon branches, since it breaks symmetry of zincblende lattice. While the
latter affects both lattice symmetry and size, causing significant changes of
phonon properties and increase of thermal conductivity. In wurtzite GaN,
space-group-conserved lattice changes at finite electric field are studied with
lattice deformation only, where thermal conductivity decreases at electric
fields significantly with increase of anisotropy, much different from the
changes in zincblende GaN. This work provides a comprehensive understanding on
phonon thermal transport properties in GaN at finite electric field, which
promises to benefit phonon transport tuning and provide reference for thermal
management in GaN-based information and power electronics.
