Electrical Characterization of Different Passivation Treatments for Long-Wave Infrared InAs/GaSb Strained Layer Superlattice Photodiodes

Silicon dioxide (SiO2), silicon nitride (Si x N y ), and zinc sulfide (ZnS) with ammonium sulfide [(NH4)2S] as a prepassivation surface treatment were compared as passivants for InAs/GaSb strained layer superlattice detectors with a 0% cutoff wavelength of ∼10 μm. SiO2 did not show significant improvement and the zero-bias resistance-area product (R 0 A) was 0.72 Ω-cm2 at 77 K. Si x N y passivation showed a nominal improvement with an R 0 A value of 4.1 Ω-cm2 at 77 K. ZnS with (NH4)2S treatment outperformed others significantly, improving the R 0 A value to 492 Ω-cm2 at 77 K. Variable-area diode measurements indicated a bulk-limited R 0 A value of 722 Ω-cm2. ZnS-passivated diodes exhibited maximum surface resistivity with a value of 2500 Ω-cm.