Passivation of long-wave infrared InAs/GaSb strained layer superlattice detectors

We have investigated various passivation techniques for type-II InAs/GaSb strained layer superlattice (SLS) detectors with p-i-n and PbIbN designs with a 100%-cut-off wavelength of ∼12 μm at 77 K. The passivation schemes include dielectric deposition (silicon nitride (SiNx), silicon dioxide (SiO2), photoresist (SU-8)), chalcogenide treatments (zinc sulfide (ZnS), ammonium sulfide [(NH4)2S]), and electrochemical sulphur deposition. [(NH4)2S] passivation and electrochemical sulphur passivation (ECP) showed the better performances, improving the dark current density by factors of 200 and 25 (p-i-n detector) and ∼3 and 54 (PbIbN detector), respectively (T = 77 K, −0.1 V of applied bias). The specific detectivity D* was improved by a factor of 2 and by an order of magnitude for (NH4)2S and ECP passivated PbIbN detectors, respectively.