The antimonide material system consisting of the nearly lattice-matched semiconductors of InAs, GaSb, and AlSb (and their alloys with InSb, GaAs, and AlAs) has recently emerged as a highly effective platform for the development of sophisticated heterostructure-based mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) detectors, as exemplified by the high-performance double heterostructure (DH), nBn, XBn, and type-II superlattice infrared detectors. A key enabling device design element is the unipolar barrier, which is used to implement the barrier infrared detector (BIRD) architecture for increasing the collection efficiency of photogenerated carriers, and reducing dark-current generation without impeding photocurrent flow. The effective use of unipolar barriers in heterostructure III-V MWIR and LWIR detectors has resulted in substantial reduction in generation-recombination (G-R) dark currents and enhanced detector performance. One example is the InAs/GaSb type-II-superlattice-based complementary-barrier infrared detector (CBIRD), which has already demonstrated very good performance in LWIR detection. In this chapter we describe a modified CBIRD design that incorporates a new bottom contact structure intended to facilitate material growth and device processing. The reduction of the turn-on voltage in the new device structure is explained with the aid of drift-diffusion simulations. Another example of the effective use of the unipolar barrier is the MWIR nBn detector. The standard nBn detector is based on the InAsSb absorber being lattice matched to the GaSb substrate. We show that by incorporating self-assembled InSb quantum dots (QDs) into the active detection area, we can extend the detector cutoff wavelength from ~4.2 μm to ~6 μm. The quantum-dot barrier infrared detector (QD-BIRD) shows infrared response at up to 225 K. Sections 17.2 and 17.3 of this chapter, respectively, describe the LWIR CBIRD and MWIR QD-BIRD in more detail. Section 17.4 concludes with a brief summary.
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