Improved performances InAs/AlSb Type-II superlattice photodiodes for eSWIR with L_diff of 2.4 µm and QE of 38% at 300 K

We studied InAs/AlSb superlattice photodiodes grown on a GaSb substrate, for the extended short wavelength infrared range. Reducing the majority carrier concentration from 2 × 10¹⁶ cm⁻³ to 2 × 10¹⁵ cm⁻³ caused the carrier diffusion length, L_diff, to increase from 1.4 µm to 2.4 µm, respectively. This, in turn, increased the front-side illuminated quantum efficiency, without anti reflecting coating, at 300 K, λ = 2.18 µm and −0.1 V from 19% to 38%. At 200 K the 50% cutoff wavelength was 2.45 µm, the dark current density at −0.1 V was 2.4 × 10⁻⁵ A/cm² and the detectivity was 2 × 10¹¹ cm-Hz^1/2/W. Using a gating technique on the mesa sidewall surface enabled the reduction of the dark current density.