Modelling metastructures for quantum efficiency enhancement in long-wavelength infrared InAs/GaSb type-II superlattice detectors: A case study

We present a modelling study regarding the impact of metastructures on the quantum efficiency (QE) of long-wavelength infrared (LWIR; 8-12 µm) InAs/GaSb type-II superlattice (T2SL) detectors. The approach is based on finite-element-method modeling of the electric-field distribution in the detector volume and deducing the QE. The optimization procedure consists of identification of a best-adaptive absorber thickness for a topside gold-coated photodiode, iterative optimization of the metastructure parameters, and adoption of a suitable anti-reflection coating. The modeling results indicate the potential to increase the average integrated QE for a 2.1-µm thick absorber layer from 35% to 73%, which corresponds to an improvement of 108%. For a detector with a thinner absorber of 0.9 µm, the average integrated QE improves from 21% to 59%, which corresponds to an increase of 180%. With this case study, we demonstrate the overall potential of employing metastructures for QE enhancement in LWIR T2SL detectors.