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6 October 2017 The development of the room temperature LWIR HgCdTe detectors for free space optics communication systems
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There are many room temperature applications to include free space optics (FSO) communication system combining quantum cascade lasers sources where HgCdTe long-wave (8-12 micrometer) infrared radiation (LWIR) detector reaching ultrafast response time < 1 ns and nearly background limited infrared photodetection (BLIP) condition are implemented. Both nearly BLIP detectivity and ultra-response time stay in contradiction in detector’s optimization process. That issue could be circumvented by implementation of the hyperhemispherical GaAs immersion lens into structure to increase optical to electrical area ratio giving flexibility in terms of response time optimization. The optimization approach depends on voltage condition. The generation - recombination (GR) mechanism within active layer was found to be important for forward and weak reverse conditions while photogenerated carrier transport is significant for higher reverse bias. Except of applied voltage, the drift time strongly depends on thickness of the absorption region. Reducing the thickness of the active region, the short drift times could be reached, but that solution significantly reduces quantum efficiency and lowers detectivity. Taking that into consideration a special multilayer heterostructure designs are developed. The p-type absorber is promising due to both high ambipolar mobility and low thermal GR driven by the Auger 7 mechanism. Theoretical simulations indicate that depending on bias condition and T = 300 K the multilayer barrier LWIR HgCdTe structure could reach response time below < 100 ps while biased and ≤ 1 ns while unbiased. Immersed detectivity reaches > 109 cmHz1/2/W. Since commercially available FSO could operate separately in SWIR, MWIR and LWIR range - the dual band detectors should be implemented into FSO. This paper shows theoretical performance of the dual band back-to-back MWIR and LWIR HgCdTe detector operating at 300 K pointing out the MWIR active layer influence on LWIR operating regime.
© (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Piotr Martyniuk, Waldemar Gawron, and Janusz Mikołajczyk "The development of the room temperature LWIR HgCdTe detectors for free space optics communication systems", Proc. SPIE 10437, Advanced Free-Space Optical Communication Techniques and Applications III, 104370G (6 October 2017);


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