Improved Light Extraction Efficiency in Blue Light-Emitting Diodes by SiO2-Coated ZnO Nanorod Arrays

We report on the improved light extraction efficiency of blue light-emitting diodes (LEDs) by SiO 2 -coated ZnO nanorods (NRs) grown on indium--tin oxide (ITO). The optical output power of the LEDs with SiO 2 -coated ZnO NRs, which are grown on the patterned sapphire substrates, increases by 5% at 20 mA, compared with that of LEDs with bare ZnO NRs. This increase is attributed to the improved light extraction efficiency of LEDs because the SiO 2 layer with a refractive index lower than that of ZnO NRs further reduces the Fresnel reflection.