2.7 <b> <i>μ</i> </b>m quantum cascade detector: Above band gap energy intersubband detection

Abstract

Quantum cascade detectors (QCDs) are mid-infrared and far-infrared, low-noise, photovoltaic detectors utilizing intersubband transitions. This Letter presents an InAs/AlAs0.16Sb0.84 based QCD lattice matched to an InAs substrate. This material system exhibits properties like a low effective electron mass of the well material of 0.023 m0, beneficial for higher optical absorption strength, and a high conduction band offset of 2.1 eV, allowing the design of QCDs in the mid-infrared and near-infrared region. The presented QCD has a peak spectral response at 2.7 μm (0.459 eV), the center of a CO2 absorption band. To enable top side illumination, a grating was implemented. This additionally bypasses absorption by the narrow bandgap 0.345 eV (3.54 μm) InAs substrate material. The QCD has a peak responsivity at a room temperature of 5.63 mA/W and a peak specific detectivity of 1.14 × 108 Jones.