Effect of the Joule heating on the quantum efficiency and choice of thermal conditions for high-power blue InGaN/GaN LEDs

The heat model of a light-emitting diode (LED) with an InGaN/GaN quantum well (QW) in the active region is considered. Effects of the temperature and drive current, as well as of the size and material of the heat sink on the light output and efficiency of blue LEDs are studied. It is shown that, for optimal heat removal, decreasing of the LED efficiency as current increases to 100 mA is related to the effect of electric field on the efficiency of carrier injection into the QW. As current further increases up to 400 mA, the decrease in efficiency is caused by Joule heating. It is shown that the working current of LEDs can be increased by a factor of 5-7 under optimal heat removal conditions. Recommendations are given on the cooling of LEDs in a manner dependent on their power.