High-power GaN LED chip with low thermal resistance

Abstract

The recent breakthrough in high power GaN LED's efficiency makes the adoption of these tiny solid state light emitting devices into general lighting application earlier than expected before. However, heat management is still an important issue for these white high power GaN LEDs. So far, the most popular driving current for 1mm square die is about 350mA but there is a trend to increase the driving current up to 1A or even higher. In order not to degrade the LED performance at such a high current operation, it is very important to reduce the thermal resistance and keep the junction temperature below 60 degree centigrade. In the past, GaN flip chip, thin GaN LED, or GaN on SiC or GaN substrate are some typical structures used to make high power LEDs with low thermal resistance. However, all of these methods need very complicated chip process or using very expensive substrates and are difficult to meet general lighting dollar per lumen target. In this study, we proposed a cheaper way to make a high power LED die with lower thermal resistance. We will report how we can achieve the thermal resistance of high power GaN LED die less than 1°C/W.