In this work, the dislocation-related efficiency droop in InGaN/GaN blue light-emitting diodes (LEDs) was investigated by comparing the external quantum efficiency (EQE) of GaN grown on c-plane sapphire and free-standing GaN substrate over a wide range of operation conditions. The values of A, B, and C coefficients had been iteratively obtained by fitting quantum efficiency in the rate equation model. Analysis revealed that threading dislocation density was strongly related to the decrease in EQE of InGaN LEDs at elevated currents by introducing a number of acceptor-like levels with the energy EA lying within the band gap.

Ultraviolet (UV) photonics‐based device and equipment have various applications in sterilization, military covert communication, medical treatment, nanofabrication, gem identification and so on. The traditional constituent UV components are bulky, inefficient, expensive and easily aging under UV radiation. An all‐dielectric metasurface offers a promising way to control the amplitude, polarization and phase of light by engineering the size, shape and distribution of its constituent elements. However, UV components based on all‐dielectric metasurfaces are difficult to be realized, due to significant absorption loss for most dielectric materials at the UV region. Here we demonstrate the design of a UV metalens, composed of high‐aspect‐ratio aluminum nitride nanorods. The in‐plane on‐axis, off‐axis and out‐of‐plane focusing characteristics have been investigated at representative UVA (375 nm), UVB (308 nm) and UVC (244 nm) wavelengths, respectively. Furthermore, we design UV router for mono‐wavelength and multiple wavelengths, that is, guiding UV light to designated different spatial positions. Our work is promising for the development of UV photonic devices and would facilitate the integration and miniaturization of the UV nanophotonics.

Naked-eye 3D micro-LED display combines the 3D characteristics and advantages of micro-LED simultaneously. A conventional micro-LED device emission exhibits Lambertian distribution, and it requires stacking of multiple optical components into a 3D display, resulting in bulky systems, low efficiency, and a limited viewing zone and points. We propose and investigate a single-chip micro-LED with unidirectional emission through an in-situ integrated resonant cavity and metasurface, which has great potential to be used for an efficient naked-eye 3D display with a wide viewing angle and multiple viewpoints. This Letter promotes the application of GaN-based micro-LEDs in a display, especially a 3D display.

Augmented reality (AR) is emerging as a next-generation interactive display that promotes the interaction between users, digital content, and the real world. Although micro-LED is regarded as the most promising light engine candidate for AR, its inherent Lambertian radiation characteristics and relatively broader emission spectrum result in low optical coupling efficiency and diffraction dispersion-related “rainbow” phenomenon when combined with a waveguide combiner. Here, we numerically and experimentally demonstrate resonant cavity (RC) micro-LEDs by incorporating SiO₂/TiO₂ distributed Bragg reflectors with chip sizes of 60, 100, and 150 μm. The device has a divergence angle of 78.7° and a narrow spectrum width of 6.8 nm, which is significantly lower than that of the controlled micro-LEDs. The reported GaN-based RC micro-LEDs have the potential to be used in the display panel for AR applications in a variety of scenarios, including AR glasses, and head up display for cars and airplanes.

Visible light communication (VLC) has attracted widespread attention for wireless communications. The popularity of GaN‐based light‐emitting diodes (LEDs) has also laid a solid foundation for the application of VLC. As the light source of VLC, LED's modulation bandwidth directly determines the speed of communication. Herein, reviewing progress on modulation bandwidth improvement schemes of GaN LEDs transmitter is reviewed, covering aspects from epitaxial to devices. Epitaxial approaches include c‐polar facet epitaxial optimization, non/semipolar facet epitaxial growth, and chip scheme such as micro‐LEDs, nano‐LEDs, resonant cavity‐LEDs (RC‐LEDs), plasmon, and metacavity LEDs. In terms of white LEDs, approaches to tackle the slow Stokes transfer and long carrier life for conventional phosphors including new color‐conversion materials (CCMs) and new energy transfer routes are reviewed. This review promotes the development of GaN‐based LEDs as the transmitter for high‐speed VLC.

Solar-blind ultraviolet photodetectors have potential applications in space communication, ozone hole monitoring and missile tracking. Amorphous Ga ₂ O ₃ (a-Ga ₂ O ₃ ) films are deposited by a simple radio frequency magnetron sputtering at different deposition temperatures. Fully transparent devices on a quartz substrate are fabricated with high responsivity, wide detection range and good repeatability. With the increase of Ga ₂ O ₃ deposited temperature, the concentration of oxygen vacancy increases accordingly, leading to a wide detection range from 250 to 325 nm and high responsivity (138 A W ⁻¹ at 5 V bias). The underlying mechanism has been discussed and analyzed. Our results should advance the application of a-Ga ₂ O ₃ -based ultraviolet photodetectors and other relevant devices.