Growth of the InGaAs/GaAsSb Material System for MIR Quantum Cascade Lasers

Full text: The InGaAs/GaAsSb material system offers many advantages for quantum cascade laser devices, compared to the more commonly used InGaAs/InAlAs and GaAs/AlGaAs material systems. It provides lower effective masses in both, the well and the barrier regions by being Al-free, while having a comparable conduction band offset of 0.36 eV. The lower effective masses allow for the design of lasers structures having thicker layers. This makes their performance less sensitive to layer thickness variations and simplifies post-processing. A 4-well active region design with double phonon depletion was grown on a highly doped InP substrate. The design incorporated 60 active regions and a low-loss plasmon-enhanced InGaAs waveguide. The wavelength was chosen to be around 11 μm. A 50 μm wide Fabry-Perot resonator QCLs, processed from this material system, exhibited a maximum optical output power of 1.2 W at 78 K while showing a low threshold current density of 0.6 kA/cm2. (author)