Miniband electronic distribution in superlattice quantum cascade structures

Summary form only given.Assessment of the excited state electronic distribution is crucial for a quantitative description of population inversion and optical gain in quantum cascade lasers either with coupled quantum wells or superlattice (SL) active regions. So far, a simple 4 level model has been used for an approximate description of experimental results. Characteristic of intersubband emission is the negligible dependence of the emitted photon wavelengths from the excess energy of electrons injected in the upper subband. In contrast, the photon energy associated with interminiband transitions are strongly dependent from the initial state energy, owing to the superlattice k/sub z/ energy dispersion. Hence, the electronic distribution in the excited miniband of a finite superlattice can be directly extracted from the analysis of the fine structure at energy higher than the minigap in the mid-infrared electroluminescence spectra.