Improved performance of In0.6Ga0.4As∕AlAs0.67Sb0.33∕InP quantum cascade lasers by introduction of AlAs barriers in the active regions

The authors demonstrate that the performance of strain compensated InP-based InGaAs∕AlAsSb quantum cascade lasers (QCLs) can be improved if AlAsSb barriers in the laser active regions are replaced by AlAs layers. The introduction of AlAs is intended to help suppress compositional fluctuations due to interdiffusion at the quantum well/barrier interfaces. An In0.6Ga0.4As∕AlAs0.67Sb0.33 QCL with AlAs barriers displays pulsed laser operation at wavelength of 4.1μm, for temperatures up to at least 320K, with lower threshold current density and higher output optical power than the reference laser with identical design but with AlAs0.67Sb0.33 barriers throughout the entire core region.