Simulation of surface field THz generation in a magnetic field

Summary form only given. We have developed a three-dimensional numerical model to simulate carrier dynamics in the vicinity of photo-excited semiconductor surfaces. In essence, our model considers the classical trajectories of an ensemble of electrons and holes. The motion of the carriers is calculated using analytic equations of motion according-to self-consistently calculated three-dimensional local electric fields. By calculating the acceleration of the ensemble we are able to reproduce the electric-field waveforms (and hence spectra) of the THz frequency transients produced from semiconductor surfaces in the presence of an external magnetic field. InAs and GaAs were chosen as the two systems to measure and model as a function of magnetic field because these two systems have fundamentally different THz emission mechanisms when excited with sub-picosecond pulses from a near-infrared laser. The simulation results show that THz emission from InAs is mainly the result of the difference between the respective mobilities of hot electrons and holes (Dember field effect), while emission from GaAs primarily results from acceleration of cold electrons in a surface depletion field. In both systems, the emitted THz power saturates with increasing photoexcitation, due to screening effects.