Control Of Characteristic Performance By Patterned Structure In Light-Emitting Diodes

Various types of nano-to-micron scale patterned structure have been employed into nitride light-emitting diodes (LEDs) in order to investigate the optical performances of device. The patterned structure was formed on top of the LED epitaxial structure or was embedded between epitaxial layers and sapphire substrate. The patterned structure affected to the LED performances in terms of light distribution and anisotropic increase of light extraction as well as increase of external quantum efficiency. The controllability of light extraction by forming a patterned structure with different index material is applicable to flip chip devices or chips on board in which light is supposed to be extracted toward a certain direction with the straight forward directionality. The index matched nano-patterned AlN template played such a role of anisotropic directionality of light extraction in the device. Periodic (photonic band gap) and non-periodic (random hole) patterned structure also showed different extraction efficiency and characteristics of light distribution. The experimental result was well matched with the simulated estimation.