Ammonium sulfide passivation of Type-II InAs/GaSb superlattice photodiodes

We report on the surface passivation of Type-II InAs/GaSb superlattice photodetectors using various ammonium sulfide solutions. Compared to unpassivated detectors, zero-bias resistance of treated 400 μm×400 μm devices with 8 μm cutoff wavelength was improved by over an order of magnitude to $\text{∼20\hspace{0.5em}}\mathrm{k}\Omega$ at 80 K. Reverse-bias dark current density was reduced by approximately two orders of magnitude to less than $\text{10\hspace{0.5em}}{\mathrm{mA/cm}}^2$ at −2 V. Dark current modeling, which takes into account trap-assisted tunneling, indicates greater than 70 times reduction in bulk trap density for passivated detectors.