Long wavelength InAs/GaSb type-II superlattice digital focal plane detector passivated by atomic layer deposited Al2O3

The dangling bond and unsaturated bond introduced by mesa isolation etching and the native oxide of detector material formed during the focal plane process introduce serious surface leakage current and finally deteriorate the performance of long wavelength (LW) InAs/GaSb detector. Eliminating the surface etching defect and suppressing the leakage channel can be particularly significant in passivation technology. In this paper, the atomic layer deposition (ALD) with good conformality to pixel side wall, controllable thickness and deposition rate, high compactness was applied to passivated the 640×512 (15μm pitch) format LW InAs/GaSb type II superlattice (T2SL) focal plane array (FPA). The complete passivation process composed of the chemical surface pretreatment, the ALD deposition and inductive coupled plasma chemical vapor deposition (ICP-CVD). Eventually, the 640×512 FPA detector, treated with HCl solution, passivated with 40nm Al₂O₃ deposited at chamber temperature 200^◦C and 100nm SiO₂ deposited by ICP-CVD, obtained the best performance with effective pixel rate >99.9%, NETD≤40.7mK.