Type-II strained-layer superlattices have theoretically predicted advantages that make them an attractive material system for use in infrared technology. However, the influence of structural disorder has been demonstrated to negatively impact the performance of these materials. A recent development in infrared technology is the use of curved focal-plane arrays which promise improved uniformity of sensitivity and a reduction in the optical complexity of the device. Curving of the wafer introduces mechanical strain into the absorber layer which can also impact the vertical carrier mobility. This work reports on an analysis of the influence of external strain and disorder on the vertical hole mobility in curved focal-plane arrays utilizing a mid-wave InAs/GaSb absorber layers. A series of quantum transport calculations is performed over a range of strain configurations for two different structures: an ideal superlattice and a superlattice with graded interfaces and disorder. Finally, the impact these effects have on the quantum efficiency of a hypothetical curved-FPA is approximated, and a potential avenue for improved device design is suggested.
High resolution, wide field-of-view, infrared (IR) imagers find use in defense and civilian applications. The most demanding of them desire uniform sensitivity across an image’s field of view, while maintaining a small and light-weight optical design. These attributes can be achieved by curving of the focal plane array to reduce the need for field curvature correction. Using experimental and numerical methods, we investigated the spherical curving of hybridized arrays to demonstrate mechanical feasibility and opto-electronic performance. Each hybridized array comprised a 4k x 4k, 10 μm pixel pitch, midwave IR (MWIR) detector hybridized to a 67 mm diagonal fanout chip. We curve an array to 139.2 mm radius of curvature, resulting in a pixel area coverage of 0.086 sr. Measurements across the curved array revealed minimal variation in bandgap (<0.1 μm) and no appreciable difference in dark current.
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