GaN-based light emitting diode (LED) is a very hot topic these years for their diverse applications, such as liquid crystal displays’ backlighting, vehicle lamps and both indoors and outdoors illumination. However, the wall plug efficiency of GaN-based LEDs is still not high enough; the heat produced by the chip will gradually degrade the chip’s efficiency as well as life span. And the light extraction efficiency is limited by total internal reflection inside the chip, originated from the large refractive indices difference between GaN and air.

Photonic crystals (PHCs) have the ability to control and couple the trapped light and enhance the light extraction efficiency of LED. But the poor interaction between PHCs and low order modes becomes the bottleneck for further extraction...[ Read more ]

GaN-based light emitting diode (LED) is a very hot topic these years for their diverse applications, such as liquid crystal displays’ backlighting, vehicle lamps and both indoors and outdoors illumination. However, the wall plug efficiency of GaN-based LEDs is still not high enough; the heat produced by the chip will gradually degrade the chip’s efficiency as well as life span. And the light extraction efficiency is limited by total internal reflection inside the chip, originated from the large refractive indices difference between GaN and air.

Photonic crystals (PHCs) have the ability to control and couple the trapped light and enhance the light extraction efficiency of LED. But the poor interaction between PHCs and low order modes becomes the bottleneck for further extraction efficiency improvement. The p-GaN surface PHCs on patterned sapphire substrate (PSS) LED structure is proposed for the first time and shows its potential by combining PSS’s scattering effect and PHCs diffractive capability to extract these low order modes.

The p-GaN surface PHCs on PSS LED has an 18% wall plug efficiency and exhibits 4.3-5.5% higher radiometric power as compared to the conventional PSS LED. Moreover the extraction efficiency improvement is even as high as 14%.