Ultra-small InGaN green micro-light-emitting diodes fabricated by selective passivation of p-GaN

Here, we proposed fabricating ultra-small InGaN-based micro-light-emitting diodes (µLEDs). The selective p-GaN areas were intentionally passivated using a H₂ plasma treatment and served as the electrical isolation regions to prevent the current from injecting into the InGaN quantum wells below. Three kinds of green µLEDs, two squircle shapes with widths of 5 and 4 µm and one circular shape with a diameter of 2.7 µm, were successfully realized. The current-voltage characteristics indicate that the series resistance and the turn-on voltage increase as the dimension of the µLED decreases. This originates from the diffusion of the hydrogen atoms into the unexpected conductive p-GaN area. The light output power density and the calculated external quantum efficiency of the µLEDs from a 5-µm-squircle to a 2.7-µm-circle were enhanced by 10-20% when compared to 98×98µm² µLEDs that were fabricated using mesa etching.