Significant reduction in sidewall damage related external quantum efficiency (EQE) drop in red InGaN microLEDs (∼625 nm at 1 A cm−2) with device sizes down to 3 μm

Abstract

Ultra-small (10 μm) InGaN-based red microLEDs (625 nm at 1 A cm−2) are necessary for modern displays. However, an increase in surface-area-to-volume ratio with a decrease in the micro-LED size resulting in higher surface recombination causes a drop in efficiency with device size. In this letter, we demonstrate microLEDs from 60 μm down to 3 μm with significantly reduced sidewall-related efficiency reduction using a two-step passivation technique using Al2O3 and Si3N4. The peak on-wafer EQE changes from 0.21% to 0.35% as the device size reduces from 60 to 3 μm, possibly due to improved light extraction efficiency for smaller mesa-widths.