MTF enhancement in LWIR InAs/GaSb Type-II superlattice nBn detectors via sidewall optical blocking

Abstract

As pixel pitch in type-II superlattice (T2SL) infrared detectors decreases, lateral photon propagation through pixel sidewalls becomes a major source of inter-pixel optical crosstalk, degrading the modulation transfer function (MTF). Even in mesa isolated pixel arrays, this lateral propagation can persist and limit spatial resolution. In this work, we demonstrate a sidewall-modified pixel architecture to suppress pixel-to-pixel optical interference in T2SL detectors. A 70-nm-thick Ag nanoparticle film was deposited on pixel sidewalls, and optical measurements show an extremely low transmittance of approximately 1% in the long-wavelength infrared region. By blocking photon transmission between adjacent pixels, the proposed structure yields a 18% improvement in MTF compared to uncoated reference devices. These results confirm that suppressing sidewall-induced optical crosstalk is an effective and practical approach to improving spatial resolution in next-generation T2SL infrared focal plane arrays.