Development of device fabrication process for strained layer superlattice IR detectors

We report on progress in the development of a device fabrication process for type-II strained layer superlattice IR detectors, composed of InAs/GaSb or InAs/GaInSb. Steps of the process include etching the mesas, cleaning up the surface, and applying a surface passivation treatment. Certain etchants have been evaluated and calibrated. The surface has been studied with single wavelength ellipsometry and results have been compared with modeled ellipsometry values, revealing effects of surface residues and surface roughness. An initial investigation of ammonium sulfide treatment for surface passivation has been made. Initial measurements of the IR transmission of the GaSb substrate have also been made to determine how much thinning is needed for back side illuminated operation of the IR detectors.