Phonon and Carrier Transport in Semiconductors from First Principles

Abstract

We present fundamental studies of phonon and electron transport in semiconductors. First principles density functional theory (DFT) is combined with exact numerical solutions of the Boltzmann transport equation (BTE) for phonons and electrons to calculate various transport coefficients. The approach is used to determine the lattice thermal conductivity of three hexagonal polytypes of silicon carbide. The calculated results show excellent agreement with recent experiments. Next, using the infinite orders T-matrix approach, we calculate the effect of various neutral and charged substitution defects on the thermal conductivity of boron arsenide. Finally, we present a general coupled electron-phonon BTEs scheme designed to capture the mutual drag of the two interacting systems. By combining first principles calculations of anharmonic phonon interactions with phenomenological models of electron-phonon interactions, we apply our implementation of the coupled BTEs to calculate the thermal conductivity, mobility, Seebeck and Peltier coefficients of n-doped gallium arsenide. The measured low temperature enhancement in the Seebeck coefficient is captured using the solution of the fully coupled electron-phonon BTEs, while the uncoupled electron BTE fails to do so. This work gives insights into the fundamental nature of charge and heat transport in semiconductors and advances predictive ab initio computational approaches. We discuss possible extensions of our work.