nBn extended short-wavelength infrared focal plane array

An extended short-wavelength nBn InAs/GaSb/AlSb type-II superlattice-based infrared focal plane array imager was demonstrated. A newly developed ${\mathrm{InAs}}_{0.10}{\mathrm{Sb}}_{0.90}/\mathrm{GaSb}$ superlattice design was used as the large-bandgap electron barrier in this photodetector. The large band gap electron-barrier design in this nBn photodetector architecture leads to the device having lower dark current densities. A new bi-layer etch-stop scheme using a combination of ${\mathrm{InAs}}_{0.91}{\mathrm{Sb}}_{0.09}$ bulk and $\mathrm{Al}{\mathrm{As}}_{0.1}{\mathrm{Sb}}_{0.9}/\mathrm{GaSb}$ superlattice layers was introduced to allow complete substrate removal and a shorter wavelength cut-on. Test pixels exhibit 100% cutoff wavelengths of $\sim 2.30$ and $\sim 2.48\mathrm{\mu m}$ at 150 and 300 K, respectively. The devices achieve saturated quantum efficiency values of 59.7% and 63.8% at 150 and 300 K, respectively, under backside illumination and without any antireflection coating. At 150 K, photodetectors exhibit dark current density of $8.75\times {10}^{-8}\mathrm{A}/{\mathrm{cm}}^2$ under $-400\mathrm{mV}$ applied bias, providing specific detectivity of $2.82\times {10}^{12}\mathrm{cm}·{\mathrm{Hz}}^{1/2}/\mathrm{W}$ at 1.78 μm. At 300 K, the dark current density reaches $4.75\times {10}^{-2}\mathrm{A}/{\mathrm{cm}}^2$ under $-200\mathrm{mV}$ bias, providing a specific detectivity of $8.55\times {10}^9\mathrm{cm}·{\mathrm{Hz}}^{1/2}/\mathrm{W}$ 1.78 μm.