Gallium arsenide thermal conductivity and optical phonon relaxation times from first-principles calculations

In this paper, thermal conductivity of crystalline GaAs is calculated using first-principles lattice dynamics. The harmonic and cubic force constants are obtained by fitting them to the force-displacement data from density functional theory calculations. Phonon dispersion is calculated from a dynamical matrix constructed using the harmonic force constants and phonon relaxation times are calculated using Fermi's Golden rule. The calculated GaAs thermal conductivity agrees well with experimental data. Thermal conductivity accumulations as a function of the phonon mean free path and as a function of the wavelength are obtained. Our results predict a significant size effect on the GaAs thermal conductivity in the nanoscale. Relaxation times of optical phonons and their contributions from different scattering channels are also studied. Such information will help the understanding of hot phonon effects in GaAs-based devices. Copyright (C) EPLA, 2013