µ-probe photoluminescence study of mid-IR quantum cascade lasers based on antimonide ternary and quaternary barriers

We report on the experimental study of the structural, electronic and thermal properties of state-of-art Sb-based quantum-cascade lasers (QCLs) operating in the range 4.3-4.9 mu m. This information has been obtained by investigating the active region band-to-band photoluminescence signals, detected by means of an GaInAs-array detector. This technique allowed to probe the spatial distribution of conduction electrons as a function of the applied voltage and to correlate the quantum design of devices with their thermal performance. We demonstrate that electron transport in QCLs based on Sb-ternary barriers may be insufficient, thus affecting the tunneling of electrons and the electronic recycling and cascading scheme. Finally, we present the first measurement of the electronic and lattice temperatures and the electron-lattice coupling in Sb-based QCLs based on a quaternary-alloy. We extracted the thermal resistance (R-L = 8.9 K/W) and the electrical power dependence of the electronic temperature (R-e = 11.7 K/W) of Ga0.47In0.53As/Al0.62Ga0.38As1-xSbx structures operating at 4.9 mu m, in the lattice temperature range 50 K = 80 K. The corresponding electron-lattice coupling constant (alpha = 10.8 Kcm(2)/kA) reflects the reduction of the electron-leakage channels associated with the use of a high conduction band-offset.