Highly efficient top-down processed blue InGaN nanoscale light-emitting diodes

Demands for high-performance displays with high pixel density and picture quality are ever increasing. Indium gallium nitride (InGaN)-based micro-LEDs (μLEDs) are suitable for meeting such demands owing to their high efficiency, brightness, and stability. However, the poor yield of the pick-and-place technique, defect repair, and visibility of edge lines between modules limit the applications of μLEDs. Furthermore, the external quantum efficiency (EQE) decreases (<10%) when μLED size is reduced to less than 10 μm for high pixel densities, thereby limiting the luminance. Here, we demonstrate a top-down-processed blue InGaN/GaN multiple-quantum well (MQW) nanorod-LED (nLED) can be made highly efficient as well as become an enabling technology for reducing manufacturing cost of large-screen displays. A pixel array comprising of horizontally-aligned nLEDs between pixel electrodes can be cost-effectively fabricated by applying the dielectrophoretic force to the inkjet-printed nLEDs dispersed in ink solution. To overcome size-dependent EQE reduction problem, we studied the interaction between the GaN surface and the surface passivation layer via various analyses and found that minimizing the point defects created during the passivation process is crucial to manufacturing high-performance nanoscale LEDs. Notably, the sol–gel method is advantageous for the passivation because SiO2 nanoparticles are adsorbed on the GaN surface, thereby minimizing its atomic interactions. The fabricated nLEDs exhibited an EQE of 20.2±0.6%, the highest EQE value ever reported for the LED in the nanoscale. This work opens the way for manufacturing self-emissive nLED displays that can fully meet the industry requirements of high efficiency and brightness and low-power consumption, contributing to energy saving, carbon neutrality and mitigating climate crisis.