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 InAsSb/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 InAsSb bulk and AlAsSb/GaSb superlattice layers was introduced to allow complete substrate removal and a shorter wavelength cut-on. Test pixels exhibit 100% cutoff wavelengths of ∼2.30 and ∼2.48  μm 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 8.75×10  A/cm under -400  mV applied bias, providing specific detectivity of 2.82×10  cm·Hz/W at 1.78 μm. At 300 K, the dark current density reaches 4.75×10  A/cm under -200  mV bias, providing a specific detectivity of 8.55×10  cm·Hz/W 1.78 μm.