Enhanced light-extraction efficiency of GaN-based light-emitting diodes with hybrid Photonic Crystals

The light-extraction efficiency (LEE) of GaN-based light-emitting diodes (LEDs) is strictly limited by total internal reflection (TIR) and Fresnel reflection. In this paper, we sought to utilize hybrid Photonic Crystals (PhCs) with different etched depth to increase the LEE of GaN-based LEDs. The results showed that the structure proposed here could decrease not only the TIR but also the Fresnel reflection. Three-dimensional rigorous coupled waves approach was employed to calculate the total transmission efficiency at different incident angles, and numerical simulations based on finite-difference time-domain method were carried out to explore mechanisms by which hybrid PhCs can effectively improve the LEE. This improvement is related to the grade-refractive-index effect and diffraction properties of the hybrid PhCs. And the structure proposed here provides a train of thought for the design of high efficiency LEDs.