First-principles calculations reveal controlling principles for carrier mobilities in semiconductors

Carrier mobilities remain a key qualifying factor for materials competing for next-generation electronics. It has long been believed that carrier mobilities can be calculated using the Born approximation. Here, we introduce a parameter-free, first-principles approach based on complex-wavevector energy bands which does not invoke the Born expansion. We demonstrate that phonon-limited mobility is controlled by low-resistivity percolation paths, which arise from fluctuations that are beyond the Born approximation. We further demonstrate that, in ionized-impurity scattering, one must account for the effect of the screening charge, which cancels most of the Coulomb tail. Calculated electron mobilities in silicon are in agreement with experimental data. The method is easy to use and can provide guidance in the search for high-mobility device designs.