We presented the mid-wave single (λ_50% cut-off = 5.2 μm) pixel mesa PIN T2SLs InAs/GaSb detector with ∼1.1 mm GaAs substrate converted into immersion lens to increase detectivity by ∼10.

At T = 230 K reached by thermoelectrical cooling, presented detector exhibits detectivity, D^* ∼ 2 × 10¹⁰ cm Hz^1/2/W, under reverse bias 200 mV.

At T = 300 K presented detector exhibits detectivity, D^∗ ∼ 4 × 10⁹ cm Hz^1/2/W at 300 K, under 500 mV.

Presented results are higher than PIN architectures with the same and lower cut-off wavelength grown on GaAs without immersion lens and grown on GaSb substrates.

Detectivity for MWIR (λ_50% cut-off = 5.1 μm) multi-layer MCT Auger suppressed, unbiased heterostructure with comparable λ_50% cut-off = 5.2 μm, GaAs immersion lens is one order of magnitude higher than PIN T2SLs InAs/GaSb due to SRH defects.