calculations of phonon-limited carrier mobilities in semiconductors*

One of the fundamental properties of semiconductors is their ability to support electric currents in the presence of electric fields (drift) or carrier concentration gradients (diffusion). These properties are described by transport coefficients such as electron and hole mobilities and diffusion coefficients. During the past decade there has been considerable progress in first-principles calculations of carrier transport starting from density functional theory, however the accuracy, reliability, and predictive power of current approaches are not fully established. Within this broad context, I will discuss our recent work on ab initio calculations of carrier mobilities in semiconductors. I will review the formalism leading to the Boltzmann transport equation, and discuss the key approximations underlying this approach. I will describe our implementation of the Boltzmann formalism within the electron-phonon software package EPW [1], and discuss the computational challenges associated with the evaluation of the scattering integrals, the singular behavior of Fröhlich polar electron-phonon coupling at long wavelengths [2,3], and the necessity to include many-body quasiparticle corrections to the electron band structures. I will illustrate these concepts using our recent calculations on well-known semiconductors such as silicon, as well as new systems such as halide perovskites. I will conclude the talk by discussing the outstanding challenges in this area, and by pointing out promising avenues for future research [4].

[1] S. Poncé, E. R. Margine, C. Verdi and F. Giustino, Comput. Phys. Commun. 209, 116 (2016).
[2] C. Verdi and F. Giustino, Phys. Rev. Lett. 115, 176401 (2015).
[3] C. Verdi, F. Caruso and F. Giustino, Nat. Commun. 8, 15769 (2017).
[4] F. Giustino, Rev. Mod. Phys. 89, 015003 (2017).