Abstract
Light emitting diode (LED) has many advantages such as long lifetime, high efficiency and reliability, directional, insensitive to vibration and shocks, compact forms. In the recent years, high efficiency white LEDs have gained much interest because the replacement of fluorescent lamps will be realized in the near future. Nowadays the high internal quantum efficiency of LED has already been obtained because of the matured growth of epitaxy technology. However, the light extraction efficiency of LED is always less than 40%. In addition, when LEDs are applied to various applications especially in the field of solid-state lighting, the far-field radiation patterns of LEDs becomes a very important issue.In order to enhance the light extraction efficiency of a flip chip LED, we design the different rough surface structures between the sapphire layer and GaN layer. The roughed surface structure can reduce the total internal reflection (TIR) inside the LED and increase the probability of light escape from the chip. In order to predict the far-field radiation patterns of LEDs, we also design the optical model for practical packaged LED.After the optical simulations, we can get a higher light extraction efficiency LED chip. We also can design the various form of LED packages for any kind of lighting applications. All of the optical models and simulations in this thesis are built by ray-tracing software (TracePro)