Semiconductor superlattices are interesting for two distinct reasons: the
possibility to design their structure (band-width(s),doping, etc.) gives access
to a large parameter space where different physical phenomena can be explored.
Secondly, many important device applications have been proposed, and then
subsequently successfully fabricated. A number of theoretical approaches has
been used to describe their current-voltage characteristics, such as miniband
conduction, Wannier-Stark hopping, and sequential tunneling. The choice of a
transport model has often been dictated by pragmatic considerations without
paying much attention to the strict domains of validity of the chosen model. In
the first part of this paper we review recent efforts to map out these
boundaries, using a first-principles quantum transport theory, which
encompasses the standard models as special cases. In the second part, focusing
in the mini-band regime, we analyze a superlattice device as an element in an
electric circuit, and show that its performance as a THz-photon detector allows
significant optimization, with respect to geometric and parasitic effects, and
detection frequency. The key physical mechanism enhancing the responsivity is
the excitation of hybrid Bloch-plasma oscillations.Comment: 22 pages, 10 figures, uses lamuphys.sty (included); to appear in the
Proceedings of the XVI Sitges Conference, Statistical and Dynamical Aspects
of Mesoscopic Systems (Lecture Notes in Physics, Springer