Assessing the quality of relaxation-time approximations with fully automated computations of phonon-limited mobilities

Abstract

The mobility of carriers, as limited by their scattering with phonons, can now routinely be obtained from first-principles electron-phonon coupling calculations. However, so far, most computations have relied on some form of simplification of the linearized Boltzmann transport equation based on either the self-energy or the momentum relaxation-time or constant relaxation-time approximations. Here, we develop a high-throughput infrastructure and an automatic workflow and we compute 67 phonon-limited mobilities in semiconductors. We compare the results resorting to the approximations with the exact iterative solution. We conclude that the approximate values may deviate significantly from the exact ones and are thus not reliable. Given the minimal computational overhead, our paper encourages reliance on this exact iterative solution.