Relationship between light efficiency and juction temperature of high power AlGaInP light-emitting diode

Abstract

One of the main problems of high power AlGaInP light-emitting diode (LED) is the heat generated seriously at large working current, which is caused by the weak current spreading, the photon blocking and absorbing of p-type or n-type electrode, and the critical reflection at the interface between the device and air. The heat inside can lead to the restriction on light output, and gives rise to low light efficiency and the low luminous intensity. In this paper, we introduce a new LED structure which is composed of compound current spreading layers and compound distribute Bragg reflector (DBR) layers. For the new structure LED, the injected current spreads adequately and the reflectivity is improved by the compound DBR layers. The testing results show that the performance of new structure LED is much better than that of the conventional LED, and that at a working current of 350 mA, the output powers of the two kinds of LEDs (which are unpackaged) are 17 and 49.48 mW respectively. At the same time, the heat testing results show the relationship between LED light efficiency and juction temperature, and the consistence between the juction temperature ratio and the ratio of light efficiency for the two kinds LEDs, which implies that LED light efficiency can be improved by reducing heat generated inside and reducing the juction temperature.