Enhancement of light extraction efficiency of gallium nitride flip-chip light-emitting diode with silicon oxide hemispherical microlens on its back

Silicon oxide (SiO2) hemispherical microlens with the density of 8.2 x 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 Si02 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 Si02 microlens.