Type-II InAs/GaSb photodiode array pixel isolation by femto-second laser anneal

• Pixel isolation in SL photodiode array is demonstrated using fs laser anneal technique.
• A two fold improvement in the inter-pixel isolation is observed for fs laser annealing.
• fs annealed SL diodes showed a seven fold reductions in surface leakage dark current.

A 775 nm, 150 fs laser anneal technique for increased inter-pixel isolation in type-II InAs/GaSb superlattice photodiode arrays (5.5 μμm cutoff wavelength) without mesa etch, is presented. With only p+p+ inter-pixel etch and fs laser anneal, a greater than two fold improvement in the inter-pixel isolation is observed at 70 K. A similar reduction in the dark current of p+p+ etched + fs laser annealed p-i-n photodiodes is observed at 70 K over un-passivated mesa etched photodiodes of 400 μμm pixel sizes, whereas in 55 μμm pixels a seven fold reduction in the surface component of dark current over un-passivated mesa etched diodes is achieved. An increased band gap of the inter-pixel region (∼∼10 meV) due to fs annealed intermixing has been calculated to be a possible reason for the improved inter-pixel isolation.