Electronic distribution in superlattice quantum cascade lasers

The electron population in the excited miniband of quantum cascade structures with intrinsic superlattice active regions is extracted from the fine structure analysis of spontaneous interminiband electroluminescence spectra. At current densities typical of laser thresholds, the electrons injected into the excited miniband of a (GaInAs)(6 nm)/(AlInAs)(1.8 nm) superlattice are described by a nonequilibrium thermal distribution characterized by temperatures T-e> 200 K, much higher than the lattice temperature T-L=15 K. (C) 2000 American Institute of Physics. [S0003-6951(00)04534-4].