Performance comparison of flip-chip blue-light microLEDs with various passivation

In this study, arrays of mu LEDs in four different sizes (5 x 5 mu m2, 10 x 10 mu m2, 25 x 25 mu m2, 50 x 50 mu m2) were fabricated using a flip-chip bonding process. Two passivation processes were investigated with one involving a single layer of SiO2 deposited using plasma-enhanced chemical vapor deposition (PECVD) and the other incorporating Al2O3 deposited by atomic layer deposition (ALD) beneath the SiO2 layer. Owing to superior coverage and protection, the double-layers passivation process resulted in a three-order lower leakage current of mu LEDs in the 5 mu m chip-sized mu LED arrays. Furthermore, higher light output power of mu LEDs was observed in each chip-sized mu LED array with double layers passivation. Particularly, the highest EQE value 21.9% of mu LEDs array with 5 mu m x 5 mu m chip size was achieved with the double-layers passivation. The EQE value of mu LEDs array was improved by 4.4 times by introducing the double-layers passivation as compared with that of mu LEDs array with single layer passivation. Finally, more uniform light emission patterns were observed in the mu LEDs with 5 mu m x 5 mu m chip size fabricated by double-layer passivation process using ImageJ software.