Abstract

In 1928 Bloch demonstrated that electrons in a periodic lattice potential with period a subject to a dc electric field E_dc undergo oscillations with characteristic frequency ω_B = ϵe aE_dc/ħ. In naturally occurring solids, observations of Bloch oscillations are precluded by the requirements of the extremely high applied electric fields needed to reduce the Bloch oscillation period below the ever-present scattering times due to impurities and phonons. In 19/0. however. Esaki and Tsu first recognized that because of the inherently longer spatial periodicities in semiconductor superlattices (SSLs). Bloch oscillations in these artificial structures would lie the terahertz (THz) domain- comparable to or higher than the corresponding scattering frequencies- even for modest field strengths (~1 kV/cm). Thus not only should the Bloch oscillations be observable in SSLs, but SSLs could also serve as devices to produce THz radiation.

© 1998 IEEE