Dual regulation of band asymmetry via GaSb layers for high-performance InAs/GaSb long-wavelength infrared nBn detectors

We demonstrate a strategy to resolve the inherent trade-off between electron blocking and hole transport in InAs/GaSb type-II superlattice nBn structures by precisely tuning the GaSb layer number in the barrier. The underlying dual regulation mechanism of the band structure was investigated using 8-band k·p simulations. A series of superlattice barrier structures (4InAs/XGaSb, X = 5, 7, 9) were designed and fabricated into devices for electrical characterization. The effectiveness of our band-engineering approach was confirmed, as increasing the GaSb monolayers from 5 to 9 suppressed the dark current density at 77 K by two orders of magnitude (from 2.21 × 10−2 to 7.19 × 10−4 A/cm2), concurrently reducing the turn-on voltage from 400 to 100 mV. The optimized device exhibits a quantum efficiency of 30.04% and a specific detectivity of 2.37 × 1011 cm Hz1/2 W−1, demonstrating high performance for long-wavelength infrared detection. This work provides a general band-engineering strategy for developing high-performance long-wavelength infrared focal plane arrays.