Analysis and evaluation of uniformity of SWIR InGaAs FPA – Part II: Processing issues and overall effects

The contribution of processing related issues on the uniformities of latticed matched and wavelength extended InGaAs focal plane arrays (FPAs) were analyzed based on practical evaluations. Nonuniformities of response and dark current of different types of InGaAs FPAs were measured experimentally. In conjunction with the material issues investigated in our previous work, the overall effects of those issues have been discussed qualitatively and quantificationally. Results show that the material issues especially the composition fluctuation still plays the most important role on the nonuniformities of dark current and detectivity regardless of lattice match conditions, whereas response uniformities of practical devices are most possibly determined by stochastic defects or dislocations. For lattice matched In0.53Ga0.47As FPA with 50 μm pixel pitch, relative nonuniformities within 2–3% could be expected. For wavelength extended In0.8Ga0.2As FPA, the demonstrated relative nonuniformities of response increase remarkably, and the dark current and detectivity nonuniformities reach around 20%. The reasons have been analyzed in detail.

► An image sensor based approach was developed for geometrical fluctuation test.
► Geometrical fluctuation on the uniformities of FPAs were analyzed.
► Overall uniformities of FPAs are estimated and measured.
► Nonuniformities of lattice matched or wavelength extended FPAs are compared.
► Dominating issues on uniformity of FPAs are discussed based on practical status.