Advanced infrared optoelectronic devices fabricated using antimony-based type-II superlattices have progressed significantly in recent years. However, fundamental challenges remain in the understanding of the exciton recombination mechanism associated with these superlattice structures and in the exploration of efficient methods to suppress the effects of native defects and thus prolong carrier lifetimes. We have investigated the optical properties of high-quality InAs/In0.5Ga0.5As0.5Sb0.5 type-II superlattices in the long-wave infrared band (6–9 μm), where a significant carrier localization phenomenon was observed via temperature- and excitation-power-dependent photoluminescence measurements. The carrier distribution with respect to temperature, including the anomalous temperature dependences of the peak energy, the full width at half maximum, and the integrated intensities, were identified and explained using the localized-state ensemble luminescence model. We also observed a large radiative to nonradiative recombination ratio (∼42.6) by analyzing localized-state ensemble equations in type-II superlattices. Finally, the InAs/In0.5Ga0.5As0.5Sb0.5 superlattice showed long minority carrier lifetimes of up to 847 ns. These results show that the prepared InAs/In0.5Ga0.5As0.5Sb0.5 superlattices have excellent optical properties compared with existing type-II superlattices and have great potential for infrared optoelectronic applications.

High-quality III–V quantum structures, advanced epitaxial technologies, and characterization methods are essential to drive the development of infrared optoelectronic materials and devices. As an important component of type II superlattices, InAs/InxGa1−xAsySb1−y would play an important role in the field of high-performance infrared detectors due to their excellent luminescence efficiency and high crystal quality. However, their interfacial characteristics and the associated minority carrier lifetime are still difficult to identify. In this paper, an atomic imaging technique was used to identify the arrangement and distribution of elements of the InAs/In0.5Ga0.5As0.5Sb0.5 superlattice. Our results confirm the epitaxy mechanism that the quaternary alloy consists of two kinds of ternary alloy in one monolayer. Moreover, by separating the cation and anion columns in the elementally resolved atomic images of the InAs/In0.5Ga0.5As0.5Sb0.5 superlattice, we demonstrate that the interfacial atomic intermixing is less than one molecular layer thickness. Therefore, benefiting from excellent interface quality, InAs/In0.5Ga0.5As0.5Sb0.5 superlattice exhibited high radiation recombination efficiency in the long-wave infrared band (∼8.5 μm), and longer minority carrier lifetime (∼810 ns at 90 K).

This work demonstrates a significant advancement in the minority carrier lifetime of InAs/In0.5Ga0.5As0.5Sb0.5 type-II superlattices (T2SLs) designed for long-wavelength infrared (LWIR) detection. The superlattices were grown using the fractional monolayer alloy epitaxy method on GaSb substrates and subsequently integrated into nBn device architectures to suppress dark current. High crystalline quality and strong photoluminescence efficiency were confirmed. Furthermore, time-resolved microwave photoconductance decay measurements revealed a record-long minority carrier lifetime of 20.31 μs at a photoluminescence peak of 9.4 μm and a temperature of 77 K. This value surpasses those of other common LWIR T2SL materials and reached the Auger-limited lifetime for mercury cadmium telluride. The fabricated 1024 × 6 format nBn photodetectors, incorporating a 2.5 μm-thick absorber, exhibited a low dark-current density of 4.45 × 10−6 A/cm2 at 77 K. A quantum efficiency of 37.7% was achieved at 8 μm. Additionally, the detector demonstrated a noise-equivalent temperature difference below 25 mK up to 95 K, using a 7.7–10 μm bandpass filter and f/2 optics under a 300 K background. These results underscore the strong potential of InAs/In0.5Ga0.5As0.5Sb0.5 superlattices for next-generation LWIR imaging applications.

A novel InAs(Sb)/In_xGa_1−xAs_ySb_1−y superlattice with high‐indium‐content In_xGa_1−xAs_ySb_1−y in the immiscibility gap has been designed and fabricated through the fractional monolayer alloy growth method by Peng Du et al. (article number 1900474). Compared to the InAs/GaSb superlattice, this neoteric superlattice InAs(Sb)/In_xGa_1−xAs_ySb_1−y exhibits a flexible miniband engineering ability and high luminescence property, which would have great potential applications in infrared optoelectronic devices.