Crossover of miniband, Wannier-Stark quantization,and Zener tunneling regimes in wide miniband superlattices investigated by time-domain terahertz spectroscopy

摘要

We have investigated terahertz (THz) emission due todynamical electron transport in wide miniband GaAs/Al0.3Ga0.7Assuperlattices. By noting that the time-domain THz emissionspectroscopy inherently measures the step-response of the electronsystem to the bias electric field, the obtained THz spectra were comparedwith the high-frequency conductivities predicted for miniband transport.Excellent agreement between theory and experiment strongly supportsthat the THz gain due to Bloch oscillating electrons persists at least up to1.7 THz. It is also found that Zener tunneling into the second minibandsets the high-frequency limit of the THz gain for the samples studiedhere.