Type-II band-engineered infrared detectors: III-V T2SLs, 2D junctions, and mixed-dimensional hybrids.

Type-II band engineering spans several physically distinct infrared-detector platforms: periodic epitaxial III-V type-II superlattices (T2SLs), atomically layered 2D/2D type-II junctions, and mixed-dimensional structures in which a 2D layer serves as a barrier, contact, gate, or sensitizer for a T2SL or another absorber. This review separates these categories rather than treating them as interchangeable. We examine interface bonding and passivation, carrier transfer and gain, and optical or barrier-based enhancement across SWIR, MWIR, and LWIR detection. True T2SL/2D demonstrations remain limited, but matched-control studies show that MoS2 barriers can reduce T2SL dark current by about two orders of magnitude and that graphene coupling can enhance LWIR detectivity by 217-fold under the conditions of a single study. Reported figures of merit are compared only with their wavelength, temperature, bandwidth, bias, device area, and noise-extraction context; cross-study values are not treated as a rank order. We also place these platforms beside colloidal-quantum-dot, QWIP/QDIP, and nBn technologies, explain the gap between idealized calculations and measured devices, and assess chemical interface engineering, scalability, reliability, and commercial readiness.