Extended Data Fig. 9: Synthesis of SiO₂ passivation layer using the sol–gel method.

a–c, Transmission electron microscopy images of nLEDs passivated with sol–gel SiO₂ at reaction times of 15 min (a), 30 min (b) and 60 min (c). d–f, In addition, the reaction was repeated twice under the same synthesizing conditions to increase their thicknesses. g, The thickness of the SiO₂ layer was saturated at 23 nm after reaction for 60 min. h, PL intensities of the nanorods. We obtained the PL spectra from three different positions on a 4-inch wafer. The variation in the PL intensity with respect to the position is small. Furthermore, the PL intensity increased with an increase in the thickness of the sol–gel SiO₂ layer.