Developing aluminium gallium nitride deep-ultraviolet (UVC) micro-light-emitting diodes (micro-LEDs) with sufficient power has been a challenge, which particularly limits these devices to various applications. However, advanced fabrication processes have been developed to enable the demonstration of highly efficient 270 nm UVC micro-LEDs and large-format UVC micro-LED displays with high resolution for maskless photolithography. Optical and electrical characterizations were performed on UVC micro-LEDs with sizes ranging from 3 µm to 100 μm to evaluate these emerging devices. The 3 μm device achieved a record-high peak external quantum efficiency of 5.7% and a maximum brightness of 396 W cm^–2. Moreover, 2,540 pixels per inch parallel-connected UVC micro-LED arrays featuring rear-side reflection layers exhibited emission uniformity and collimation. UVC micro-LED displays, with a resolution of 320 × 140, were explicitly designed for maskless photolithography applications utilizing a customized integrated circuit driver for optimal performance. The UVC micro-LEDs and UVC micro-displays provide sufficient doses to fully expose the photoresist film within seconds, owing to their enhanced current spreading uniformity, improved heat dispersion and superior light extraction efficiency. This work may open a path to maskless photolithography, potentially leading to revolutionary developments in the semiconductor industry.

In this paper, the GaN-based green micro light-emitting diodes (Micro-LEDs) with various sizes (from 3 to 100 μm) were fabricated and electro-optically characterized. Atom layer deposition (ALD) passivation and potassium hydroxide (KOH) treatment were applied to eliminate the sidewall damage. The size dependence of Micro-LED was systematically analyzed with current-versus-voltage and current density-versus-voltage relationship. According to the favorable ideality factor results (<1.5), the optimized sidewall treatment was achieved when the device size shrank down to <10 μm. In addition, the external quantum efficiency (EQE) droop phenomenon, luminance and output power density characteristics were depicted up to the highest current density injection condition to date (120 kA cm⁻²), and 6 μm device exhibited an improved EQE performance with the peak EQE value of 16.59% at 20 A cm⁻² and over 600k and 6M cd cm⁻² at 1 and 10 A cm⁻², indicating a greater brightness quality for over 3000 PPI multiple display application. Lastly, the blue shift of 6 μm device with elevating current density was observed in electroluminescence spectra and converted to CIE 1931 color space. The whole shifting track and color variation from 1 A cm⁻² to 120 kA cm⁻² were demonstrated by color coordinates.

Deep-ultraviolet (Deep-UV) micro light-emitting diodes (Micro-LEDs) array greatly benefits various future applications. In this letter, we fabricated Deep-UV Micro-LEDs with different geometries from $10 \times 10\,\,\mu \text{m}$ ² to $200 \times 200\,\,\mu \text{m}$ ² , and investigated its application on tristimulus quantum dots converted display. As the Micro-LEDs scaling, the smaller-sized devices provided higher brightness under the same injection current density due to the enhanced current spreading uniformity and heat dissipation. For a $10 \times 10\,\,\mu \text{m}$ ² device, the maximal optical power density was up to 185 W/cm ² at 5 kA/cm ² , and the peak external quantum efficiency reached 3.43 % at 30 A/cm ² . The device exhibited a minor blue shift phenomenon as the current density increased. Deep-UV Micro-LED stimulated quantum dots display obtained 121% of the Rec. 2020 standard in the CIE 1931 color space. This ultra-wide color gamut indicated it as a competitive candidate for future display technology.

Ultraviolet band C (UV-C) micro light-emitting diodes (micro-LEDs) provide a high energy light emission of 200–280 nm, which are brilliantly utilized in optogenetics, communications, and fluorescence. However, the limited device efficiency notably restricts the grand potential application field. In this work, three types of 20 × 20 μm² UV-C micro-LEDs with the peak wavelength of 269 nm are fabricated by different etching strategies, including an inductively coupled plasma (ICP), post-ICP tetramethylammonium hydroxide, and a hybrid scheme combining plasma and chemical treatment. By enhancing the radiative recombination and light extraction, the hybrid scheme improves the peak external quantum efficiency of UV-C micro-LEDs to 3.45%, an elevation of 57.5% compared with ICP. A step advance in the forward injection current and ideality factor is also found on the devices fabricated by the hybrid scheme due to better contact on the AlGaN surface.

This work explores the pivotal role of laser lift-off (LLO) as a vital production process in facilitating the integration of Micro-LEDs into display modules. We specifically investigate the LLO process applied to high-performance gallium nitride (GaN)-based green Micro-LED arrays, featuring a pixel size of 20 × 38 μm on a patterned sapphire substrate (PSS). Scanning electron microscopy (SEM) observations demonstrate the preservation of the GaN film and sapphire substrate, with no discernible damage. We conduct a comprehensive analysis of the optoelectrical properties of the Micro-LEDs both before and after the LLO process, revealing significant enhancements in light output power (LOP) and external quantum efficiency (EQE). These improvements are attributed to more effective light extraction from the remaining patterns on the GaN backside surface. Furthermore, we examine the electroluminescence spectra of the Micro-LEDs under varying current conditions, revealing a slight change in peak wavelength and an approximate 10% decrease in the full width at half maximum (FWHM), indicating improved color purity. The current–voltage (I–V) curves obtained demonstrate the unchanged forward voltage at 2.17 V after the LLO process. Our findings emphasize the efficacy of LLO in optimizing the performance and color quality of Micro-LEDs, showcasing their potential for seamless integration into advanced display technologies.