Wannier - Stark localization and Bloch oscillations in semiconductor superlattices: A historical introduction
Résumé
In 1970, Esaki and Tsu invented the concept of semiconductor superlattices for electronics devices purposes (negative differential resistance heterostructures). The successful growth of high quality multiple narrow wells and narrow barriers structures was however highly elusive in the seventies. Consequently, attention quickly focused on structures that functioned on principles already operative in single wells (bound states) or double barriers (resonant tunneling), and were thereby far less demanding from the growth point of view. In addition, a huge market was opened in the telecom area. One had to wait for the mid eighties to see a revival on devices or physical effects that lay on coupled wells through thin barriers. I shall review the experimental (interband optical absorption) and theoretical efforts that have led to understand and control the effect of a static and homogeneous electric field on a system of coupled quantum wells (either 2 or a very large number). This will include the evidence of the Wannier - Stark quantization either in cw or time resolved experiments. The emphasis will be placed (like at that time) on the electric field - induced destruction of the resonant tunneling between consecutive wells.