Advances in Computing Charge Transport and Hot Carrier Dynamics from First Principles*

Calculations of transport and ultrafast dynamics of charge carriers have relied on heuristic approaches for the past several decades. Recent progress in combining density functional theory and related methods with kinetic equations, such as the Boltzmann transport equation (BTE), are enabling spectacular advances in computing carrier dynamics in materials from first principles. A special role is played by the interaction between charge carriers and lattice vibrations, also known as the electron-phonon (e-ph) interaction, which dominates carrier dynamics near room temperature and for carrier energies within a few eV of the band edges in semiconductors. We will discuss methods we recently developed that advance the understanding of carrier dynamics in materials, including:
1) Accurate calculations of the carrier mobility in polar semiconductors and oxides, where we show new methods to treat complex materials with structural phase transitions (e.g., perovskites) and provide insight into charge transport in organic molecular crystals with tens of atoms in the unit cell.
2) The ultrafast dynamics and detailed scattering mechanisms of excited (so-called “hot”) carriers. We will discuss a new parallel algorithm to propagate in time the electron BTE, and efforts to extend it to the coupled electron and phonon dynamics. The application of this framework will focus on hot carriers in gallium nitride light emission technologies.
Code development efforts, open problems and future directions will be outlined.