Abstract
We demonstrate quantum cascade lasers in the InAs/AlSb material system emitting at wavelengths of λ = 19 μm and λ = 21 μm. The maximum operating temperatures are 291 K and 250 K, and the threshold current densities at 78 K are as low as 0.6 kA/cm2 and 1.3 kA/cm2 for the lasers emitting at λ = 19 μm and λ = 21 μm, respectively. These values represent the best performance to date for quantum cascade lasers operating above λ = 16 μm. Although the devices employ metal-metal waveguide geometries, the diffraction effects which typically hinder the output beam of THz devices are not observed.We thank Nathalie Isac for help with the wafer-bonding process. We acknowledge financial support from the French National Research Agency (No. ANR-11-NANO-020 “DELTA”) and by the Collaborative Action (No. 8748RA12) between the CEA and the University Paris Sud. The device fabrication has been performed at the nano-center CTU-IEF-Minerve—part of the French RENATECH network—which was partially funded by the Conseil Général de l'Essonne