A multiphysics numerical technique for THz-frequency carrier transport in semiconductors and metals

We present a novel computational tool for THz-frequency characterization of materials with high carrier densities, such as highly-doped semiconductors and metals. The numerical technique tracks carrier-field dynamics by combining, for the first time, the ensemble Monte Carlo (EMC) simulator of carrier dynamics with the finite-difference time-domain (FDTD) technique for Maxwell's equations and the molecular dynamics (MD) technique for close-range Coulomb interactions. While EMC/FDTD has been proven to accurately characterize high-frequency behavior in electronic systems with low carrier densities ($<$10$^{16}$ cm$^{-3}$), the inclusion of short-range Coulomb interactions via MD becomes necessary at higher carrier densities ($>$10$^{18}$ cm$^{-3}$). This three-pronged multiphysics technique captures electromagnetic wave propagation and transport in materials in which carrier dynamics may be strongly impacted by Coulomb interaction between carriers.