Bloch gain in AlGaAs/GaAs semiconductor superlattices
We have investigated terahertz (THz) emission due to dynamical electron transport in wide miniband GaAs/Al0.3Ga0.7As superlattices. By noting that the time-domain THz emission spectroscopy contains the information on the step response of the electron system to the bias electric field, the obtained THz spectra were compared with the high-frequency conductivities predicted for miniband transport. Ex