Electronic Temperature In Phonon-Photon-Phonon Terahertz Quantum Cascade Devices With High-Operating Temperature Performance

We report on the experimental measurement of active region lattice (T-L) and electronic temperatures (T-e) in terahertz quantum cascade devices based on the phonon-photon-phonon scheme, by means of microprobe band-to-band photoluminescence spectroscopy. Three mesa devices, differing for doping region and number of quantum wells composing the active region, have been investigated. With device on, under band alignment for lasing condition, we measured a difference (T-e - T-L) similar to 40 K much smaller than the typical value (T-e - T-L similar to 100 K) reported for resonant-phonon THz QCLs.