We compare the electrical power dependence of the lattice temperature and the electronic temperature of THz quantum cascade lasers (QCLs) operating in the range 2.5- 3.8 THz and based on a resonant-phonon and bound-to-continnum quantum design. This analysis is performed by means of microprobe band-to-band photoluminescence experiments carried out on operating THz QCLs both below and above the lasing threshold. Thermalized non-equilibrium hot-electron distributions are found in both classes of QCLs. While in the case of bound-to-continuum devices a unique value of the electronic temperature is found in the active region minibands, in the case of resonant-phonon devices we found that the upper radiative state, in the lasing range, heats up to similar to 200 K, more than 100 K with respect to the ground state levels. From the measured thermal resistance and the power dependence of the ground state electronic temperature we obtain in the case of resonant-phonon structures a value of the electron-lattice energy relaxation rate comparable with that typical of mid-infrared QCLs, in the case of resonant-phonon structures and a value similar to 50 times higher in bound-to-continuum devices.
|Titolo:||Non equilibrium electrons in THz quantum cascade lasers|
|Data di pubblicazione:||2006|
|Nome del convegno:||Conference on Novel In-Plane Semiconductor Lasers V|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.1117/12.641467|
|Appare nelle tipologie:||4.1 Contributo in Atti di convegno|