First principles study of thermoelectric properties of β -gallium oxide

The thermoelectric effects in bulk β-gallium oxide crystals are investigated in this work using the ab initio calculated electron-phonon interactions and semi-classical Boltzmann transport theory. We have taken all major scattering mechanisms into account, namely, polar and non-polar optical phonon, acoustic phonon, and ionized impurity scattering. To accurately account for the polar phonon scattering rate, we take into account the dynamic screening at higher electron densities. An iterative solution of the Boltzmann transport equation is used in order to account for the inelastic and anisotropic nature of polar optical phonon scattering. The thermoelectric transport coefficients, Seebeck coefficient, Peltier coefficient, and electronic thermal conductivity, are calculated for a wide range of temperatures and doping densities. The calculated Seebeck coefficient is compared with the experimentally measured value and found to be in good agreement considering the mobility of the samples. The value of the Seebeck coefficient at 300 K is found to be -341 μ V K - 1, which is high compared to that of the other commonly studied semiconductors. The larger Seebeck coefficient is due to the higher density of states arising from comparatively high electron effective mass.