Type-II superlattice-based extended short-wavelength infrared focal plane array with an AlAsSb/GaSb superlattice etch-stop layer to allow near-visible light detection

A versatile infrared imager capable of imaging the near-visible to the extended short-wavelength infrared (e-SWIR) is demonstrated using e-SWIR InAs/GaSb/AlSb type-II superlattice-based photodiodes. A bi-layer etch-stop scheme consisting of bulk InAs0.91Sb0.09 and AlAs0.1Sb0.9/GaSb superlattice layers is introduced for substrate removal from the hybridized back-side illuminated photodetectors. The implementation of this new technique on an e-SWIR focal plane array results in a significant enhancement in the external quantum efficiency (QE) in the 1.8 -0.8 mu m spectral region, while maintaining a high QE at wavelengths longer than 1.8 mu m. Test pixels exhibit 100% cutoff wavelengths of similar to 2.1 and similar to 2.25 mu m at 150 and 300 K, respectively. They achieve saturated QE values of 56% and 68% at 150 and 300 K, respectively, under back-side illumination and without any anti-reflection coating. At 150 K, the photodetectors (27 mu m x 27 mu m area) exhibit a dark current density of 4.7 x 10(-7) A/cm(2) under a -50 mV applied bias providing a specific detectivity of 1.77x10(12) cm . Hz(1/2)/W. At 300 K, the dark current density reaches 6.6 x 10(-2) A/cm(2) under -50 mV bias, providing a specific detectivity of 5.17 x 10(9) cm . Hz(1/2)/W. (C) 2017 Optical Society of America