Enhancement of Light Extraction Efficiency of Gallium Nitride Flip-Chip Light-Emitting Diode With Silicon Oxide Hemispherical Microlens on its Back

Silicon oxide (SiO
₂
) hemispherical microlens with the density of 8.2 times 10
⁸
cm
^-2
has been formed on a sapphire substrate of gallium nitride (GaN) light-emitting diode (LED) by liquid phase deposition to enhance the light extraction efficiency. For flip-chip LED, the SiO
₂
microlens exhibits 1.25 times enhancement of optical output power. In comparison of the conventional LED, there is 61% enhancement for flip-chip LED with a SiO
₂
microlens.