Ultrafast carrier dynamics in THz-field-biased semiconductor superlattices

Ultrafast carrier dynamics in semiconductor superlattices are numerically investigated in the presence of a THz field. In particular, when the Bloch type period is shorter, over 1.5 times, than the THz frequency, the carriers have a combined periodic motion with two frequencies, which are a Bloch type frequency due to the strength of the THz field and the applied THz frequency. In other cases, the carriers have a periodic motion with the applied THz frequency. In addition, we observe that the LO-phonon replicas in the energy relaxation of the carriers disappear and that some of the carriers are more slowly relaxed by the broadened distributions due to the THz field.