Enhancement of the light-extraction efficiency of light-emitting diodes with SiO2 photonic crystals

In this paper, we proposed a method of using SiO2 photonic crystals (PhC) to improve the light-extraction efficiency (LEE) of light-emitting diodes (LEDs). Numerical simulations based on the finite-difference time-domain (FDTD) algorithm were performed to reveal the mechanism of using SiO2 PhC to improve the light extraction of LEDs. The effects of several critical parameters, including the depth, the filling factor, and the radius of SiO2 PhC on the enhancement of LEE were investigated. The rigorous coupled-wave analysis (RCWA) method was utilized to verify the variation trends we got from the FDTD simulations. The LEE of the LEDs with normal air-hole PhC structures and the conventional planar LEDs were also studied for comparison. According to our calculations, more than 37% improvement has been achieved in the LEE of the SiO2 PhC LEDs in comparison to that of the conventional planar LEDs. And SiO2 PhC LEDs obtained more light extraction than normal air-hole PhC LEDs. The influences of the SiO2 PhC on the current density and the temperature distributions in the active layer of LEDs have also been discussed in this paper. Results demonstrated no noticeable degradation in electrical and thermal characteristics under high current injections.