Improved the light extraction efficiency of GaN vertical light-emitting diodes using 3D sphere-like arrays

The formation of the micro-patterned structure in the vertical light-emitting diodes (VLEDs) is a practicable solution for light extraction enhancement. In this study, the Monte Carlo ray tracing method was used to investigate the effects of the absorption coefficient of GaN material and structural parameters of 3D sphere-like arrays on the light extraction efficiency (LEE). The simulation results showed that a maximum LEE change of about 17 % can be achieved when the absorption coefficient (alpha) varies between 0 and to 10 mm(-1). The 3D sphere-like arrays can effectively improve the LEE of GaN VLEDs. The LEE decreases as the period of the 3D sphere-like arrays increases. The LEE for close-packed convex hemisphere arrays with R = 3 mu m and alpha = 0/mm(-1) is about 4.5 times greater than that for planar VLEDs. For the close-packed convex hemisphere arrays, the LEE of the GaN VLEDs is inversely correlated with their diameter. However, for the close-packed concave hemisphere arrays, an opposite trend was observed. In addition, for the VLEDs with the concave sphere-like arrays, an increase in array height leads to an improved LEE. These results provide theoretical guideline for the design of the GaN VLEDs with high LEE.