Hot electron distribution in quantum cascade and single stage GaAs/AlGaAs periodic superlattice structures

We report the experimental determination of the steady-state electronic distribution in the excited miniband of GaAs/Al0.33Ga0.67As quantum cascade (QC) devices with periodic superlattice (SL) active regions. The populations of the excited subbands in the second miniband were extracted from the analysis of the high-energy tail of interminiband electroluminescence spectra. Single- and multiple-stage structures were investigated. We found that the excited electrons can be described by a thermal distribution, in analogy with the case of InGaAs/InAlAs/InP structures. At powers above the injection threshold a non-equilibrium distribution with a temperature higher than the lattice one is established. (C) 2001 Elsevier Science B.V. All rights reserved.