High-performance type-II InAs/GaSb superlattice photodiodes with cutoff wavelength around 7 μm

We report the most recent result in the area of type-II InAs/GaSb superlattice photodiodes that have a cutoff wavelength around 7 μm at 77 K. Superlattice with a period of 40 Å lattice matched to GaSb was realized using ${\mathrm{Ga}}_x{\mathrm{In}}_{1-x}$ type interface engineering technique. Compared with significantly longer period superlattices, we have reduced the dark current density under reverse bias dramatically. For a 3 μm thick structure, using sulfide-based passivation, the dark current density reached $2.6\times {10}^{-5}\mathrm{A}∕{\mathrm{cm}}^2$ at −3 V reverse bias at 77 K. At this temperature the photodiodes have $R_{0}A$ of $9300\mathrm{\Omega }{\mathrm{cm}}^2$ and a thermally limited zero bias detectivity of $1\times {10}^{12}\mathrm{cm}{\mathrm{Hz}}^{1∕2}∕\mathrm{W}$ . The 90%–10% cutoff energy width was only 16.5 meV. The devices did not show significant dark current change at 77 K after three months storage in the atmosphere.