Recent time-domain observations of the dynamics of wavepackets in semiconductor heterostructures are reviewed. The most simple example are coherent tunneling oscillations of a wavepacket in a coupled double quantum well. The composition and the oscillation frequency of the wavepacket are tunable with an electric field. Coherent microwave radiated by the oscillating carriers can be observed. Wavepacket dynamics in biased superlattices are identified as Bloch oscillations of the electrons.
"Ultrafast dynamics of wavepackets in GaAs/AlGaAs heterostructures", Proc. SPIE 1675, Quantum Well and Superlattice Physics IV, (3 September 1992); doi: 10.1117/12.142551; https://doi.org/10.1117/12.142551