Two-dimensional (2D) Ruddlesden-Popper perovskites with bulky organic cations have attracted extensive attention in light-emitting devices and photovoltaics due to their robust environment stability, tunable luminescent color, strong exciton binding and promising efficiency. A quantum well (QW) structure is spontaneously formed by sandwiching PbBr₄ layers into bulky organic cations. However, some intrinsic excitonic mechanisms in these materials still need to be elucidated. In this study, the exciton–phonon interaction of quasi-2D (PEA)₂(CsPbBr₃)_n−1PbBr₄ with different PbBr₄ layer numbers (n) was analyzed by temperature-varied photoluminescence (PL), scanning electron microscopy (SEM) and powder X-ray diffraction (PXRD). The mechanism of bandgap shifting with temperature was found to be dominated by the thermal expansion effect in the large-n 2D and bulk perovskite, and gradually switched to exciton–phonon interaction in the n = 1 (PEA)₂PbBr₄ phase, indicating enhanced exciton–phonon interaction in the thinner quantum well structure. Further analysis showed that the enhanced exciton–phonon interaction originated from the longitudinal optical phonon-exciton Fröhlich interaction rather than acoustic phonon-exciton coupling. We believe that our results will benefit the further optimization of light-emitting devices based on 2D perovskites.

An optically pumped AlGaN-based vertical-cavity surface-emitting laser (VCSEL) in the deep ultraviolet (DUV) range (<; 280 nm) is demonstrated. The lasing wavelength is 275.91 nm with a threshold power density of 1.21 MW/cm ² and a linewidth of 0.78 nm. The lasing is believed to be benefited from high internal quantum efficiency (IQE) of the AlGaN-based multiple quantum wells (MQWs) and improved fabrication processes.

Gallium oxide has gained significant attention due to its exceptional material properties, including an ultra-large bandgap of 4.9 eV, a high breakdown electric field of 8 MV/cm, and availability of large size bulk crystal grown by using the melt method. These merits enable Ga2O3 to be a promising material for high power electronics and solar blind UV optoelectronic applications. In recent years, substantial progress has been achieved in the single-crystal substrate growth, thin film epitaxy, and device fabrication. Thin film epitaxy is a particularly crucial step for harnessing the full potential of Ga2O3-based devices, as it enables precise control over carrier doping concentrations, interfaces, and defect minimization. This review presents recent advancements in the epitaxial growth of Ga2O3 thin films using molecular beam epitaxy, metal-organic chemical vapor deposition, hydride vapor phase epitaxy, and other growth techniques. We will first discuss the important material properties of Ga2O3 for electronic device applications, followed by a brief review on the status of bulk melt growth of single crystal substrate. Then, we will focus on the latest advancements on the thin film epitaxial growth technologies, with emphasis on the doping controlling over electrical properties, defect minimization and controlling, and progress in the development of (AlxGa1−x)2O3/Ga2O3 hetero-interface for two-dimensional electron gas.