Discussion around IR material and structure issues to go toward high performance small pixel pitch IR HOT FPAs
Résumé
In the last decade, infrared imaging detectors trend has gone for smaller pixels and larger
formats. Most of the time, this scaling is carried out at a given total sensitive area for a single
focal plane array. As an example, QVGA 30 µm pitch and VGA 15 µm pitch exhibit exactly
the same sensitive area. SXGA 10 µm pitch tends to be very similar, as well. This increase
in format is beneficial to image resolution. However, this scaling to even smaller pixels
raises questions because the pixel size becomes similar to the IR wavelength, but also to the
typical transport dimensions in the absorbing material. Hence, maintaining resolution for
such small pixel pitches requires a good control of the modulation transfer function and
quantum efficiency of the array, while reducing the pixel size. This might not be obtained
just by scaling the pixel dimensions. As an example, bulk planar structures suffer from
excessive lateral diffusion length inducing pixel-to-pixel cross talk and thus degrading the
modulation transfer function. Transport anisotropy in some type II superlattice structures
might also be an issue for the diffusion modulation transfer function. On the other side, mesa
structures might minimize cross talk by physically separating pixels, but also tend to degrade
the quantum efficiency due to a non-negligible pixel fill factor shrinking down the pixel size.
This paper discusses those issues, taking into account different material systems and
structures, in the perspective of the expected future pixel pitch infrared focal plane arrays.
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Gravrand et al. - 2023 - Opto-Electronics Review - Discussion around IR material and structure issues to go toward small pixel pitch IR.pdf (1.96 Mo)
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