Improved light output power of GaN-based flip-chip light-emitting diode through SiO₂ cones

We formed SiO₂ cones on p-type GaN by using a simple wet-etching process and investigated the effects of the size and the coverage of the SiO₂ cones on the output power performance of GaN-based light-emitting diodes (LEDs). The diameter of two different size SiO₂ cones and the distance between the cones are in a range of 17. 3-21. 1 μm and 32. 7-33. 9 μm, respectively. The coverage of the SiO₂ cones on p-type GaN is measured to be 9. 5-10. 9%. As the SiO₂ cone size increases, LEDs exhibit a slightly higher forwardbias voltage (at an injection current of 20 mA) and somewhat higher series resistance. The light output increases with an increase in the size of the cones; the LEDs fabricated with the cones exhibit 5. 8-8. 4% higher light output power (at 20 mA) than those without the SiO₂ cones.