THz quantum well photodetector based on LO-phonon scattering-assisted extraction

Abstract

We present a design for a quantum photodetector operating in the terahertz range, at 3.45 THz (15 meV, 87 μm). Our device relies on biased GaAs/AlGaAs heterostructure, designed to exploit LO phonon scattering as an extraction mechanism. In our design, the external potential due to the applied bias forms an extraction miniband and allows accommodating an LO phonon transition (36 meV) and use it as an extraction mechanism, even though its energy exceeds the detector's absorbing transition at 15 meV. Spectral-resolved measurements performed on arrays of patch antenna microcavities reveal a peak photocurrent at the designed photon energy with a responsivity of 80 mA/W at 20 K. The maximum operating temperature of the photodetector is found to be 40 K. Detector characterizations were performed both with a black-body source as well as with a terahertz quantum cascade laser emitting at 3.5 THz.