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.

In recent years, rare-earth metals with triply oxidized state, lanthanide ions (Ln³⁺), have been demonstrated as dopants, which can efficiently improve the optical and electronic properties of metal halide perovskite materials. On the one hand, doping Ln³⁺ ions can convert near-infrared/ultraviolet light into visible light through the process of up-/down-conversion and then the absorption efficiency of solar spectrum by perovskite solar cells can be significantly increased, leading to high device power conversion efficiency. On the other hand, multi-color light emissions and white light emissions originated from perovskite nanocrystals can be realized via inserting Ln³⁺ ions into the perovskite crystal lattice, which functioned as quantum cutting. In addition, doping or co-doping Ln³⁺ ions in perovskite films or devices can effectively facilitate perovskite film growth, tailor the energy band alignment and passivate the defect states, resulting in improved charge carrier transport efficiency or reduced nonradiative recombination. Finally, Ln³⁺ ions have also been used in the fields of photodetectors and luminescent solar concentrators. These indicate the huge potential of rare-earth metals in improving the perovskite optoelectronic device performances.

Nanowire photodetectors, which have the advantages of fast response and high photoelectric conversion efficiency, can be widely applied in various industries. However, the rich surface states result in large dark current and can hinder the development of high-performance nanowire photodetectors. In this paper, the influence and mechanism of sulfur surface passivation on the dark current of a single GaAs nanowire photodetector have been studied. The dark current is significantly reduced by about 30 times after surface passivation. We confirm that the origin of the reduction of dark current is the decrease in the surface state density. As a result, a single GaAs nanowire photodetector with low dark current of 7.18 × 10 ⁻² pA and high detectivity of 9.04 × 10 ¹² cmHz ^0.5 W ⁻¹ has been achieved. A simple and convenient way to realize high-performance GaAs-based photodetectors has been proposed.

Integrated mixed-dimensional (MD) van der Waals (vdWs) heterojunctions for self-powered photodetectors have attracted intense attention. Performances of these photodetectors are highly dependent on the interface properties, including the semiconductor–metal interface and the semiconductor–semiconductor interface. To date, how to balance the interface properties remains to be explored. Here, we explore a straightforward strategy to balance the interface properties of the MD-vdWs heterojunction photodetector, by tuning the Fermi level of ambipolar two-dimensional material with a gate bias. The effectiveness of gate-tunable interface properties is verified by a GaAs-WSe₂ MD vdWs heterojunction self-powered photodetector with different metal contacts. Under the gate biasing, the responsivity is enhanced from 122.55 mA/W to 510.98 mA/W in the GaAs–WSe₂ heterojunction photodetector with the Au/Cr electrodes, which is better than the state-of-the-art GaAs-based self-powered photodetectors. This work provides a simple and effective method to fabricate high-responsivity, self-powered heterojunction photodetectors by gate-tunable interface properties.

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).

As a typical wide bandgap semiconductor, ZnO has received a great deal of attention from researchers because of its strong physicochemical characteristics. During the past few years, great progress has been made in the optoelectronic applications of ZnO, particularly in the photocatalysis and photodetection fields. To enable further improvements in the material’s optoelectronic performance, construction of a variety of ZnO-based composite structures will be essential. In this paper, we review recent progress in the growth of different ZnO–graphene nanocomposite structures. The related band structures and photocatalysis and photoresponse properties of these nanocomposites are discussed. Additionally, specific examples of the materials are included to provide an insight into the common general physical properties and carrier transport characteristics involved in these unique nanocomposite structures. Finally, further directions for the development of ZnO–graphene nanocomposite materials are forecasted.