Broadband Response and a Transformation between Dual‐ and Single‐Wavelength Detection in Coupled Doped‐Well Quantum Cascade Detector

Abstract As a third‐generation infrared detector, the quantum cascade detector (QCD) exhibits an accurately adjustable wavelength, low noise, and ultrafast response characteristics. By introducing an additional doping layer, QCD also shows excellent application prospects in the broadband response. Herein, a coupled doped‐well QCD with an array structure located at very long‐wave infrared (VLWIR, ≈15 µm) is prepared. Based on the energy levels interaction and carrier distribution, the regulatory mechanism of the applied bias on the response characteristics is explored. At zero bias, the detector exhibits dual‐wavelength detection owing to the splitting of the energy levels, then transforms into single‐wavelength detection with the bias increasing. Simultaneously, the QCD device exhibits a broadband response (≈13–16 µm) from 15 to 300 K and an excellent detectivity of 1.52 × 10 12 cm Hz 1/2 W −1 at 15 K. A high R 0 A (>10 6 Ω cm 2 ) and robust detectivity (>10 9 cm Hz 1/2 W −1 ) are obtained at room temperature. The results of the response characteristics presented in this work provide a strategy for the flexible application of QCD in infrared detection.