Leakage current in quantum-cascade lasers through interface roughness scattering

Abstract

The impact of interface roughness (IFR)-scattering on the quantum efficiency of quantum-cascade lasers (QCLs) is demonstrated and analyzed both experimentally and theoretically. An InGaAs/InAlAs strain-compensated QCL emitting at λ ∼ 5.4 μm is analyzed in pulsed mode at liquid nitrogen temperatures. Measurements of the differential slope efficiency as a function of laser resonator length allow the pumping efficiency to be measured as a function of electron temperature. Excellent agreement is obtained when comparing the data to a calculation of the leakage current into higher-lying states via IFR-scattering, providing evidence of the importance of IFR-scattering on the QCLs quantum efficiency.