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Traditional LEDs emit light that exhibits incoherence and displays a Lambertian distribution. To achieve linearly polarized (LP) light and control the emission direction, a variety of optical components are required to be stacked, which is unsuitable for compact applications and results in low deflection efficiency. Here, we propose and and numerically simulate a novel single-chip micro-resonant cavity LED (micro-RCLED) device that generates directional LP light by integrating a continuous metasurface. This device includes a bilayer grating at the GaN layer's bottom, providing high transverse electric (TE) reflectivity above 89.5% and an extinction ratio exceeds 57 dB at 500 nm. The top distributed Bragg reflector (DBR) and the bilayer grating together constitute a TE mode Fabry–Pérot resonant cavity. This not only promotes the emission of the TE wave, but also guarantees its collimation with the appropriate phase, thereby enhancing its spatial coherence. A functional metasurface above the DBR layer precisely controls the TE wave's deflection angle. It maintains a low aspect ratio while enabling efficient, large-angle deflection. The simulation results demonstrate that this device provides an effective solution for generating highly spatially coherent directional LP light, with broad potential applications in fields such as polarized light imaging and advanced 3D micro-LED display systems. [ABSTRACT FROM AUTHOR]

In the pursuit of developing high-performance low-dimensional spintronic devices, two-dimensional van der Waals heterostructures comprising non-magnetic nitride and ferromagnetic materials have emerged as a crucial area of investigation. This paper proposes a novel structure that employs hexagonal two-dimensional semiconductor GaN flanked by two half-metallic two-dimensional CrN layers. The stability of the proposed structure is verified via first-principles calculations, which indicate good thermodynamic and magnetic stability. The transport characteristics of electrons in the structure are analyzed through the Band structures and density of states. Specifically, the study examines the spin polarizability of parallel and anti-parallel magnetic configurations of the CrN/GaN/CrN vdW heterostructure, and the results demonstrate a significant spin valve effect. Overall, the study establishes the potential of the CrN/GaN/CrN vdW heterostructure as a candidate for the development of innovative spintronic devices. [ABSTRACT FROM AUTHOR]

In this study, α-Ga2O3 nanorod arrays (NRAs) were grown using a simple and low-cost two-step hydrothermal method. Subsequently, a photoelectrochemical ultraviolet photodetector (PEC-UV PD) based on the α-Ga2O3 NRAs was fabricated, which can operate at zero bias and has a performance far superior to that of PEC-UV PDs based on the one-step hydrothermal method. Under 2 mW/cm2 illumination at 254 nm, the device achieved a responsivity of 26.59 mA/W, an external quantum efficiency of 12.98%, and a rise/decay time of 53 ms/7 ms without external bias. These results demonstrate outstanding detection performance compared to previously reported devices. The superior performance can be attributed to the better crystallinity which provides a larger absorption area for the device, the solution contact area, and a faster channel for carrier transport, the space charge region at the solid/liquid interface which also allows efficient separation of photogenerated carriers. Furthermore, it also benefits from the positive effects of moderate oxygen vacancy (VO) concentrations for NRAs. The α-Ga2O3 NRAs PEC-UV PD with two-step hydrothermal method is undoubtedly a promising candidate for future solar-blind detection. [ABSTRACT FROM AUTHOR]

High‐sensitivity photodetection capability has become an indispensable requirement for detecting feeble solar‐blind ultraviolet (UV) light. Micro‐nano metallic metasurface structures are employed to enhance the detector photoelectric performances. However, existing approaches are confronted with bottlenecks of structure simplification and efficacy mediocrity. Here, a distinctive diamond solar‐blind UV photodetector with a synthetic multistage‐concentric‐annulus (MCA) architecture metasurface is reported, which is prepared through a facile and peculiar Fraunhofer diffraction technique. The detector achieves an excellent photo‐to‐dark‐current ratio of 2.4×108 and maintains an extremely low dark current on the order of pA magnitude. The intrinsic response peak and resonance absorption phenomenon in solar‐blind UV are evident from the optical properties. Moreover, the surface potential distribution intuitively reveals that plasmon resonance enhances the UV scattering and absorption cross sections, thus facilitating the photogeneration of carriers. Meanwhile, it expressly demonstrates that multi‐level dipole interaction in the MCA structure accelerates the separation and extraction of electron–hole pairs through enhancing the localized electric field intensity. In addition, a wide range of variable temperature measurements further prove the device possesses capacity for working in extreme environments. This photodetection technology by virtue of a delicate and viable diffraction metasurface is anticipated to provide a leap forward for future applications in wide‐band‐gap semiconductor UV detectors. [ABSTRACT FROM AUTHOR]

Amplification of weak ultraviolet signals has always been a challenging issue to design and fabricate high-performance ultraviolet photodetectors. Here, we observe a distinctive microplasma breakdown behavior in AlGaN-based ultraviolet avalanche photodiodes with artificial mesa architecture. At 107 V breakdown voltage, the photocurrent increases sharply whereas dark current intriguingly remains at the extremely low level of 0.1 nA as the applied voltage increases. Simultaneously, a significant blue luminescence phenomenon is observed at the mesa edge of photodiode at breakdown voltage, indicating the occurrence of microplasma breakdown. Ultimately, the microplasma avalanche photodiode achieves a record-high avalanche gain of 3 × 106 with light–dark current ratio readily exceeding 107. Kelvin probe force microscopy was employed to reveal the physical mechanism of localized avalanche breakdown induced by photoelectric effects and elaborate the microplasma discharge process, which is related to surface states. The unprecedented detection mode of photocurrent triggering avalanche events while remaining low dark current is anticipated to effectively shield the background noise and amplify ultraviolet signals. It is worth further research to explore its possibility on high-sensitivity ultraviolet photodetection. [ABSTRACT FROM AUTHOR]

In this work, temperature-dependent transient threshold voltage (VT) instability behaviors in p-GaN/AlGaN/GaN HEMTs, with both Schottky gate (SG) and Ohmic gate (OG), were investigated systematically, under negative gate bias stress, by a fast voltage sweeping method. For SG devices, a concave-shaped VT evolution gradually occurs with the increase in temperature, and the concave peak appears faster with increasing reverse bias stress, followed by a corresponding convex-shaped VT recovery process. In contrast, the concave-shaped VT evolution for OG devices that occurred at room temperature gradually disappears in the opposite shifting direction with the increasing temperature, but the corresponding convex-shaped VT recovery process is not observed, substituted, instead, with a quick and monotonic recovery process to the initial state. To explain these interesting and different phenomena, we proposed physical mechanisms of time and temperature-dependent hole trapping, releasing, and transport, in terms of the discrepancies in barrier height and space charge region, at the metal/p-GaN junction between SG and OG HEMTs. [ABSTRACT FROM AUTHOR]