High-field Terahertz Carrier Dynamics in Ge and GaAs

We performed high-field terahertz transmission measurements on germanium (Ge) and gallium arsenide (GaAs). We observed a decrease in sample absorption as electric field strength increased in both cases. To understand the underlying processes, we modeled the change in carrier population as a function of time in Ge and applied a Drude model to calculate absorption. For GaAs, we ascribe the change in signal to carrier generation via impact ionization and Zener tunneling.