Passivation Innovations for Large Format Reduced Pixel pitch strained layer superlattice Focal Plane Array Imagers Operating in the Long Wavelength In

A novel surface passivation technique is proposed for InAs/GaInSb-based strained layer superlattice focal plane arrays with a pitch of 15 µm or less. Buffered oxide and sulfur-based surface treatments prior to dielectric deposition are proposed as the most suitable and chemically stable surface treatments. Both processes result in the removal of elemental oxides, while the latter additionally promotes the formation of stable sulfur-based bonds. The dissolution of the oxide results in a stable surface stoichiometry and avoids the incorporation of any unwanted atmospheric elements in the room-temperature formed oxides. The bare dangling bonds and the sulfur-passivated bonds will be protected with the proper deposition of a dielectric material. ZnS is being proposed for the first time as the dielectric owing to its good thermal match with the superlattice as compared to other previously used dielectrics. The sulfur-rich surface resulting from the sulfur-based surface treatment is expected to yield a highly stable dielectric layer. We will undertake mesa sidewall deposition with a specially designed holder and characterize the resulting InAs/GaInSb superlattice photodiodes. A good surface treatment coupled with the proposed passivation techniques will enhance the performance of these detectors to help them realize their commercial and defense potentials.