Type II InAs/GaSb superlattices for high-performance photodiodes and FPAs

The authors report the most recent progress in Type II InAs/GaSb superlattice materials and photovoltaic detectors developed for focal plane array applications with a cutoff wavelength of ∼8 μm. No turn-on of tunneling current was observed even at a reverse bias of-3 V for a 3 μm thick p-i-n photodiodes. The thermally-limited zero bias detectivity under 300 K 2 π FOV was 2 ∼3 × 10 ¹¹ cm.Hz ^1/2/W at liquid nitrogen temperature, with a current responsivity of 2 ∼3 A/W and a mean quantum efficiency of ∼50%. Initial passivation using SiO ₂ has shown to decrease the dark current by ∼30% at a reverse bias of -1 V. The same detector structure was used for focal plane arrays with silicon readout integrated circuit. Concept proof of imaging was demonstrated with a format of 256 × 256 at liquid nitrogen temperature.