The utilization of the P+-π-M-N+ photodiode architecture in conjunction with a thick active region can significantly improve long wavelength infrared type-II InAs/GaSb superlattice photodiodes. By studying the effect of the depletion region placement on the quantum efficiency in a thick structure, we achieved a topside illuminated quantum efficiency of 50% for an N-on-P diode at 8.0 μm at 77 K. Both the double heterostructure design and the application of polyimide passivation greatly reduce the surface leakage, giving an R0A of 416 Ω cm2 for a 1% cutoff wavelength of 10.52 μm, a Shot–Johnson detectivity of 8.1×1011 cmHz/W at 77 K, and a background limited operating temperature of 110 K with 300 K background.

The dominant dark current mechanisms are identified and suppressed to improve the performance of midwave infrared InAs/GaSb type-II superlattice photodiodes at high temperatures. The optimized heterojunction photodiode exhibits a quantum efficiency of 50% for 2 μm thick active region without any bias dependence. At 150 K, R0A of 5100 Ω cm2 and specific detectivity of 1.05×1012 cm Hz0.5/W are demonstrated for a 50% cutoff wavelength of 4.2μm. Assuming 300 K background temperature and 2π field of view, the performance of the detector is background limited up to 180 K, which is improved by 25 °C compared to the homojunction photodiode. Infrared imaging using f/2.3 optics and an integration time of 10.02 ms demonstrates a noise equivalent temperature difference of 11 mK at operating temperatures below 120 K.

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