Delayed luminescence in sub-5 μm InGaN/GaN fin-LEDs with efficiency enhancement by UV-induced moisture adsorption

High costs and efficiency degradation from surface defects in small-chip top-down fabrication impede micro-light-emitting diodes commercialization. To address this, we introduce Ultraviolet-irradiated moisture adsorption as a novel top-down approach, integrated with defect-reducing etching, to enhance ultra-small micro-light-emitting diodes. Ultraviolet-irradiated moisture adsorption is crucial: it effectively reduces surface strain caused by dangling and oxidized bonds through moisture adsorption, thereby facilitating significant delayed luminescence via detrapping from shallow trap states. This mechanism profoundly improves the internal quantum efficiency of ultra- micro-light-emitting diodes and the external quantum efficiency of light-emitting diode devices. Our approach, including defect-removal and strain-alleviation, yielded highly promising results for sub-5 μm fin- light-emitting diodes, achieving an internal quantum efficiency of 70.9 % and an external quantum efficiency of 16.5 %. By actively leveraging delayed luminescence through Ultraviolet-irradiated moisture adsorption, these methods offer a cost-effective and highly efficient solution, holding great potential for future micro-light-emitting diodes display commercialization.