Effect of Patterned Sapphire Substrate Shape on Light Output Power of GaN-Based LEDs

An optical simulation including reflection and refraction is used to simulate the light illumination intensity of gallium nitride (GaN)-based light-emitting diodes (LEDs) on varied patterned sapphire substrates (PSS) with different slanted angles and fill factors (f ). It is found that a micro pyramid array with a slanted angle from 25° to 60° is able to effectively improve illumination intensity which reaches to summit as the slanted angle is around 33°. And illumination intensity enhances monotonously as f increases. In addition to the mentioned work, epitaxial growth of GaN-LEDs on PSS is investigated for comparison. The output power of GaN-LEDs on PSS increases with simulated light illumination intensity increasing. The experimental results prove the simulation.