Room temperature interband cascade lasers near 7.7 <i>µ</i>m and dependence on structural quality

Abstract Interband cascade lasers (ICLs) are becoming desirable mid-infrared semiconductor laser sources particularly in the 3–6 µ m wavelength range due to their low power consumption. In this work, we report the demonstration of room temperature (RT) ICLs based on hybrid-cladding layers and a modified type-II quantum well active region with an emission wavelength near 7.7 µ m, the longest ever reported for RT ICLs. By investigating two ICL wafers with different structural qualities and strains, we show their correlation and importance to the corresponding device performance in terms of their maximum operating temperature, threshold current density and threshold voltage, as well as their operational robustness at high currents. This comparative study also reveals connection between different cladding configurations in terms of electrical resistance and voltage drop across them. Furthermore, by comparing with previous reported ICLs at similar wavelengths, but with different designs, we show and discuss how significantly the doping levels in ICLs could affect free-carrier absorption related device performance in terms of external quantum efficiency, maximum operating temperature and threshold current density. Our experimental results and analyses provide insights and guidance for further development and optimization of ICLs in the long wavelength region.