The limit of quantum cascade detectors: A single period device

In this work, we demonstrate a 4.1 μm quantum cascade photodetector with external quantum efficiencies of 40% at 80 K and 25% at 300 K. Such high efficiencies have been made possible by using a single period active region embedded in a facet coupled low-loss dielectric ridge waveguide. This emphasizes the relevance of enhancing the optical interaction for this type of detector in a different manner from increasing the number of periods. Low noise operation was achieved by using photovoltaic operation at zero bias and an elaborate band structure design to prevent undesired scattering paths. A noise equivalent power of 10 pW / Hz and a corresponding specific detectivity of 7 × 10 7 cm Hz / W at room-temperature, as well as background limited operation below 124 K with a detectivity close to an ideal photodetector, are demonstrated.