Breaking the interband detectivity limit with metasurface multi-quantum-well infrared photodetectors

Since their initial demonstration, metasurface quantum-well infrared photodetectors (QWIPs)—intersubband detectors integrated with plasmon cavities—using only a single quantum well (Nw = 1) have been considered the highest performance design. However, experimental confirmation via comparison of detectors with different Nw has not been performed. Here, we systematically compare Nw = 1 and Nw = 3 metasurface QWIPs with identical cavities and reveal the clear superiority of Nw = 3 detectors. While signal (responsivity) decreases with additional wells as predicted, the signal-to-noise-ratio (detectivity) increases due to drastically reduced noise. Thanks to the narrow spectral linewidth unique to metasurface QWIPs, our detectors can reach detectivity beyond the theoretical limits of interband detectors; our best detectors show maximum detectivities of 6.4×1010 cm Hz1/2/W at 7.0 μm, exceeding the interband limit of 5.3×1010 cm Hz1/2/W at the same wavelength.