Graded-interfaces Modeling of Record-Performance Mid and Long-Wave Infrared Quantum Cascade Lasers

Accurate nonequilibrium Green’s-functions simulations of record-performance 4.9 µm- and 8.3 µm-emitting QCLs, employing Photon-Induced Carrier Transport (PICT), require inclusion of graded interfaces when calculating Interface-Roughness (IFR) scattering. Matching threshold-current densities and V-I characteristics, all IFR parameters were extracted. The root-mean-square height and in-plane correlation length are found to be higher and lower, respectively, than when assuming abrupt interfaces. Abrupt-interfaces’ modeled 4.9 µm-emitting QCLs lack PICT action, which reduces the calculated maximum wall-plug efficiency, η(wp,max), value from 27% to 18.7%. Abrupt-interfaces’ modeled 8.3 µm-emitting QCLs have approximately 70% higher relative leakage-current density, which reduces the calculated η(wp,max) value from 17% to 11.7%.