A recent review of mid-wavelength infrared type-II superlattices: carrier localization, device performance, and radiation tolerance

摘要

The last two decades have seen tremendous progress in the design and performance of mid-wavelength infrared (MWIR) type-II superlattices (T2SL) for detectors. The materials of focus have evolved from the InAs/(In)GaSb T2SL to include InAs/InAsSb T2SLs and most recently InGaAs/InAsSb SLs, with each materials system offering particular advantages and challenges. InAs/InAsSb SLs have the longest minority carrier lifetimes, and their best nBn dark current densities are <5X Rule '07 at high temperatures, while those of InAs/GaSb SLs and InGaAs/InAsSb SLs are <10X Rule '07. The quantum efficiency of all three SL detectors can still be improved, especially by increasing the diffusion length beyond the absorber length at low temperatures. Evidence of low temperature carrier localization is greatest for the two SLs containing ternary layers; however, the interface intermixing causing the localization is present in all three SLs. Localization likely does not affect the high temperature detector performance (>120 K) where these SL unipolar barrier detectors are diffusion-limited and Auger-limited. The SL barrier detectors remain diffusion-limited post proton irradiation, but the dark current density increases due to the minority carrier lifetime decreasing with increased displacement damage causing an increase in the trap density. For these SL detectors to operate in space, the continued understanding and mitigation of point defects is necessary.