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InGaN red light emitting diode (LED) is one of the crucial bottlenecks that must be broken through to realize high‐resolution full‐color mini/micro‐LED displays. The efficiency of InGaN LEDs drops rapidly as the emission spectra go from blue/green to red range due to the poor quality of high‐indium‐content InGaN materials. Here, high‐performance InGaN red LEDs on sapphire grown by metal–organic chemical vapor deposition through strain modulation are reported. A composite buffer layer is proposed to increase the surface lattice constant of GaN and hence successfully enhances the indium incorporation efficiency of the following InGaN active layers. Consequently, a high‐efficiency InGaN red mini‐LED chip (mesa area: 100 × 200 µm2) with a peak wavelength of 629 nm and an external quantum efficiency of 7.4% is realized. Finally, a full‐color nitride mini‐LED display panel with 74.1% coverage of Rec.2020 color gamut by using the InGaN red mini‐LED chips is fabricated. The study signifies the great potentials of full‐nitrides high‐resolution full‐color mini/micro‐LED displays. [ABSTRACT FROM AUTHOR]

AlGaN‐based ultraviolet‐B light‐emitting diodes (UVB‐LEDs) exhibit great potential in phototherapy, vitamin D3 synthesis promotion, plant growth regulation, and so on. However, subjected to the excess compressive strain induced by the large lattice mismatch between multiple quantum wells (MQWs) and AlN, UVB‐LEDs that simultaneously satisfy the requirements of high light output power (LOP), low working voltage, and excellent stability are rarely reported. Here, a substrate‐dominated strain‐modulation strategy is proposed. By precisely manipulating the strain in AlN grown on nano‐patterned sapphire substrate (NPSS) to a slightly tensile one, the compressive strain in the following Al0.55Ga0.45N underlayer and Al0.28Ga0.72N/Al0.45Ga0.55N MQWs is successfully suppressed. As a result, an outstanding UVB‐LED with a peak wavelength at 303.6 nm is achieved. The 20 × 20 mil2 UVB‐LED chip shows a wall‐plug efficiency (WPE) of 3.27% under a forward current of 20 mA and a high LOP of 57.2 mW with an extremely low voltage of 5.87 V under a forward current of 800 mA. It is more exciting that the LOP degradation is as low as 17% after 1000 h operation under a forward current density of 75 A cm−2, showing excellent stability. The here‐developed UVB‐LED, with a high LOP and excellent reliability, will definitely promote the applications of AlGaN‐based UVB‐LEDs. [ABSTRACT FROM AUTHOR]

The use of light‐emitting diode (LED)‐based photodynamic therapies in the treatment of periodontitis is increasing because these modalities are effective, safe, and painless. They are not subject to acquired drug resistance or environmental issues and are associated with no complications when used appropriately. These light sources have also been used in combination with pharmacological measures to synergize their effects and optimize therapeutic outcomes. This review focuses on optical devices used in treating periodontitis and delineates the current applications of various methods, including their utility and efficacy. The application of LEDs in periodontology is described. [ABSTRACT FROM AUTHOR]

Ultraviolet‐C light‐emitting diodes (UVC‐LEDs) have great application in pathogen inactivation under various kinds of situations, especially in the fight against COVID‐19. Unfortunately, its epitaxial wafers are so far limited to a size of 2 inches, which greatly increases the cost of massive production. In this work, a 4‐inch crack‐free high‐power UVC‐LED wafer is reported. This achievement relies on a proposed strain‐tailored strategy, where a 3D to 2D (3D‐2D) transition layer is introduced during the homo‐epitaxy of AlN on the high temperature annealed (HTA)‐AlN template, which successfully drives the original compressive strain into a tensile one and thus solves the challenge of realizing a high‐quality Al0.6Ga0.4N layer with a flat surface. This smooth Al0.6Ga0.4N layer is nearly pseudomorphically grown on the strain‐tailored HTA‐AlN template, leading to 4‐inch UVC‐LED wafers with outstanding performances. The strategy succeeds in compromising the bottlenecked contradictory in producing a large‐sized UVC‐LED wafer on pronounced crystalline AlN template: The compressive strain in HTA‐AlN allows for a crack‐free 4‐inch wafer, but at the same time leads to a deterioration of the AlGaN morphology and crystal quality. The launch of 4‐inch wafers makes the chip fabrication process of UVC‐LEDs match the mature blue one, and will definitely speed up the universal application of UVC‐LED in daily life. [ABSTRACT FROM AUTHOR]

Strain evolution of AlN grown on hole‐type (HT) and pillar‐type (PT) nanopatterned sapphire substrates (NPSSs) during the epitaxial lateral overgrowth process is comparably studied. It is found that, after complete coalescence, the residual strain of AlN on HT‐NPSS is tensile, whereas AlN on PT‐NPSS is almost strain free. The different strain states are associated with different behaviors of crystal merging during the lateral overgrowth process, depending on the type of pattern. Then, ultraviolet‐C (UVC) light‐emitting diode (LED) wafers are grown on two types of AlN templates with the distinctive strain states. It is confirmed that AlN on HT‐NPSS with tensile strain offers the advantage of producing a high‐quality AlGaN layer with a fairly flat surface, which is the key point for fabricating high‐performance UVC LEDs. [ABSTRACT FROM AUTHOR]