Electrical Characteristics of a Ga-free T2SL Mid-wave Infrared nBn Detector Based on an InAs/AlAsSb/InAsSb Barrier

Ga-free InAs/InAsSb type-II superlattice (T2SL) has been used as an absorption layer of a high-operating-temperature mid-wavelength infrared nBn detector because it has a long Shockley–Read–Hall limited minority carrier lifetime (~10 μs). In the Ga-free T2SL nBn detector, the ternary barrier was easily oxidized, and then the oxidized barrier contributes to a surface leakage current. Also, since the ternary barrier forms an unavoidable valence band offset (VBO) with an absorption layer, the nBn device has a high turn-on voltage. The high turn-on voltage induces an electric field in the absorption layer, which increases the dark current of the device. In this work, we studied an InAs/AlAsSb/InAsSb T2SL barrier instead of a ternary barrier, having a minimal VBO and a turn-on voltage close to zero. As a result, the fabricated nBn device with the T2SL barrier exhibited a dark current density of ~1.57×10 −8 A/cm 2 at 130 K, which is 20 times lower than the dark current density of the nBn device with the ternary barrier.