Temperature dependence of the key electro-optical characteristics for midinfrared emitting quantum cascade lasers

The equations for threshold-current density J(th), differential quantum efficiency eta(d), and maximum wallplug efficiency eta(wp,max) for quantum-cascade lasers (QCLs) are modified for electron leakage and backfilling. A thermal-excitation model of "hot" injected electrons from the upper laser state to upper active-region states is used to calculate leakage currents. The calculated characteristic temperature T(0) for J(th) is found to agree well with experiment for both conventional and deep-well (DW) QCLs. For conventional QCLs eta(wp,max) is found to be strongly temperature dependent; explaining experimental data. At 300 K for optimized DW-QCLs, front-facet, continuous-wave eta(wp,max) values >20% are projected. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3478836]