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 GaxIn1-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 2.6×10-5 Acm2 at -3 V reverse bias at 77 K. At this temperature the photodiodes have R0A of 9300 Ω cm2 and a thermally limited zero bias detectivity of 1×1012 cm Hz12W. 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.