Study of patterned sapphire substrate and SiO2 array in GaN LED

Epitaxial lateral overgrowth can be implemented using patterned sapphire substrates (PSS) and SiO₂ nanorod arrays (NR). Both PSS and SiO₂ arrays are fabricated using nanoimprint lithography. In this paper, we study patterned sapphire substrate width and period and SiO₂ nanorod array z position to optimize GaN LED light extraction and improve the device efficiency. First, we compare our simulation with pervious experimental data from other group. The simulation results match the experimental results in the trend. Second, we investigate PSS design and optimization, and find that by setting the period and width of PSS to 2μm and 1.3μm respectively, the light extraction can be increased by 47.9%. We also optimize the z-position of the SiO₂ nanorod array to 7.1μm increases the light extraction by 51.8%, which is much better improvement prediction compared to the published experimental data. Finally, we find that the appearance of the reflection layer has major effects on light extraction. Ag layer can increase or decrease the light extraction efficiency. From these simulations we find a maximum increase in light extraction of 128% for a l LED with an Ag reflection layer compared to a conventional LED.