Effect of Beveled SiC Substrate on Light Extraction of Flip-Chip Light-Emitting Diodes

Abstract

We fabricated GaN-based flip-chip light-emitting diodes (FC-LEDs), which were grown on both conventional and high purity SiC substrates. The influence of beveling, thickness, and absorption of the SiC substrate on the light extraction efficiency (LEE) of the FC-LED was investigated by simulation and experiment. From the simulation results, the LEE of the FC-SLED with a 60°beveling angle is higher than that on a rectangular substrate. The experimental results demonstrate that about 15% enhancement of the LEE was achieved by increasing the thickness of the high purity SiC substrate from 120 to 470 µm. A sample with an X pattern on the top face exhibits the highest light output power. The LEE of the FC-SLED can be efficiently enhanced by suitably beveling the substrate with no degradation of the electrical properties.

Analysis of the light-extraction efficiency of SiC substrate-based flip-chip vertical light-emitting diodes with embedded photonic crystals

“…So most methods used to enhance the LEE of SiC substrate-based LEDs are modifying the geometry of LEDs. Xu et al 17) have beveled the SiC substrate and achieved a 15% enhancement of LEE. Recently, Ou et al have used the e-beam lithography to fabricate antireflective sub-wavelength structures on the SiC substrate and achieved more than 91% enhancement in a very large emission angle range.…”