The next generation infrared (IR) detection technology demands for very-large-format focal plane arrays (FPAs) with
high performance. Semiconductor up-converters can convert IR photons to near-infrared (NIR) photons, and can be
potential candidates for large-format IR imaging since the mechanical bonding with the read-out circuits can be avoided.
However, previously reported up-converters and corresponding up-conversion systems suffer from low detectivity
because of the trade-off between responsivity and dark current. To solve this issue, a cascade infrared up-converter
(CIUP) is demonstrated in this work. Based on a quantum cascade transport mechanism, high IR responsivity is achieved
while the dark current is maintained fairly low. A 4-μm InGaAs/AlGaAs CIUP has been fabricated, and both the CIUP
and up-conversion system are under background-limited infrared performance (BLIP) regime below 120 K. The upconversion
efficiency is 2.1 mW/W at 3.3 V and 78 K. Taking shot noise as the main noise in the up-conversion system,
the BLIP detectivity of the system is 2.4×10<sup>9</sup> Jones at 3.3 V and 78 K, higher than the semiconductor up-converters at
similar wavelengths reported so far. To further improve the CIUP performance, an AlInP hole-blocking layer is
introduced taking place of the AlAs layer. AlInP/GaAs has larger valence band discontinuity than AlAs/GaAs, showing
the advantage of tightly confining injected holes into the emission quantum well. By adopting the AlInP hole-blocking
layer, the quantum efficiency and detectivity of the up-conversion system can be enhanced.