Widely tunable mid-infrared emission from coupled Wannier-Stark ladders in semiconductor superlattices

We report on the observation of mid-infrared electroluminescence associated with transitions between electric-field-induced conduction states forming the Wannier-Stark ladder in strongly coupled GaAs/AlAs superlattices. Both interwell and intra-well radiative transitions have been studied in the whole range of electric fields from the moderate localization to the resonance-induced delocalization regimes. The application of average electric fields in the range 100250 kV/cm, allowed to continuously shift the emission peak related with inter-well 1-->1 diagonal transitions between Stark-localized ground states up to the limit corresponding to the merging of the 1-->1 electroluminescence peak with the 2-->1 intersubband emission. (C) 2002 Elsevier Science B.V. All rights reserved.