A GaN/AlN quantum cascade detector with a broad response from the mid-infrared (4.1 μ m) to the visible (550 nm) spectral range

We report on a GaN/AlN quantum cascade detector operating in an extended spectral range going from the mid-infrared to visible wavelengths. This broadband detection is achieved thanks to the design of active quantum wells supporting five bound-to-bound intersubband transitions. The photodetector exhibits a broad signal between 4.1 μm and 550 nm. The photocurrent persists up to room temperature. The calibrated responsivity at 77 K under irradiation through a 45° angle polished facet amounts to 7 μA/W at a wavelength of 633 nm and is peaked at 14 μA/W at a wavelength of 720 nm.