Multiphysics Analysis of Screening Effects on Terahertz Photoconductive Devices

Output saturation observed for high power levels of input optical pump is a well-known bottleneck in the operation of terahertz photoconductive devices (PCDs). This saturation is a result of various screening effects that stem from the interactions between electromagnetic fields and semiconductor charge carriers. To simulate these effects, this work uses a time-domain multiphysics approach that solves a coupled system of the Maxwell and the drift-diffusion equations to rigorously take into account the two-way nonlinear coupling between fields and carriers. Furthermore, an optical absorption-based model is used to correctly compute the carrier generation rate. The resulting multiphysics solver is used to simulate realistic PCDs, and excellent agreement is observed between the simulation and experimental results.