Dynamic of Junction Temperature and Heat Flow in Light-Emitting Diodes

Since the field of light-emitting diodes (LEDs) has been an important industry in Taiwan, applying LEDs to the backlight of liquid-crystal displays seems to be the driving force of the revenue soon. After that time, LEDs are expected to penetrate the worldwide largest market –general lighting. Due to the ability of cost down and mass production, now, Taiwan’s LED manufacturers have the chance to compete or cooperate with the largest lighting companies such as GE, OSRAM, and PHILIPS. Therefore, it is necessary to understand how to dissipate the heat generated in the device. The thermal energy in a crystal is carried by phonons. The heat flow can be equivalently described by the phonon diffusion. However, there is a vierity of different nanostructures in an LED. The phonons generated in the active layer should pass through all the nanostructures to dissipate the heat. The purpose of this project is to build up a method to monitor the dynamic of the heat flow. It can be used to extract the thermal parameters of the device such as the thermal conductivity, heat capacity, light output power and the parasitic thermal resistance by applying this method at room temperature. While applying this method at low temperature, it can be used to understand the influence of the nanostructures on the phonon transport. Therefore, this method will be a powerful tool for developing high-power semiconductor lighting devices. Furthermore, the estimatation of light output from thermal analysis and the method for measuring the dynamic heat transport in the vertical direction are innovative. In case of successful observation of phonon transport in the nanostructures, this study could pave the way for new field of nanotechnology and solid-state physics.

Project ID:PB9709-3565
External Project ID:NSC97-2221-E182-011