Pixel isolation in Type-II InAs/GaSb superlattice photodiodes by femto-second laser annealing

Abstract

A 775 nm femto-second laser annealed approach for the inter-pixel isolation, without mesa etching, to reduce dark currents of type-II InAs/GaSb superlattice photodiodes is presented. A greater than two fold improvement of the pixel isolation and a corresponding reduction in the dark current are observed for laser annealed superlattice photodiodes with a 5.5 µm cutoff wavelength, operating at 10K. A higher band gap barrier material from the superlattice structure in the inter-pixel region is expected to form after femto-second laser annealing, which has been explained on the basis of a superlattice inter-diffusion model. The increase in inter-pixel barrier height at 10K is estimated to be ∼ 4 meV in the laser annealed superlattice photodiodes.

InAs/GaSb Type-II superlattice photodiode array inter-pixel region blue-shift by femtosecond (fs) laser anneal

“…Finally, the group-III and group-V inter-diffusion rates in these intermixed samples II and III are quantified by an interdiffusion model [7,8]. As the group-III (In, Ga) and group-V (As, Sb) atoms have different concentration gradients, the inter-diffusion may occur in both the sublattices.…”