Subband electronic temperatures and electron-lattice energy relaxation in terahertz quantum cascade lasers with different conduction band offsets

The electronic temperatures of the conduction subbands, the local lattice temperature, and the
electron-lattice energy relaxation times E in bound-to-continuum GaAs/AlxGa1-xAs quantum
cascade lasers, operating at 2.9 and 2 THz, are reported. This information has been gathered from
the analysis of microprobe photoluminescence spectra collected during device continuous wave
operation. We find that the electronic distributions in both the active region and the injector are
thermalized and that all subbands share the same electronic temperature. The efficiency of electron